Speed secret # 5

[jim_howard_pdx]

Ultraflow,

What I can tell you about rod ratio is this, every race engine I have ever built to run 180 mph or faster had a minimum of 2.05 rod to stroke ratio, and most had 2.1 to 2.2. After 2.2, you actually do better adding extra displacement since the burn event is pretty much over in about 40-50 degrees of crank movement.

So for the Chevy crowd running 1.5 rod ratios, my 351 at 1.78 comes out of the hole much faster and revs faster too. They have trouble building the low torque, in fact their torque curve tends to be highly peaked.

Like I said, most speed shops do not know how to build a world class race engine. When Trans Am cars were limited to 302 cubic inches, we were well into the 178 mph range on these cars. When NASCAR set their limits to 355 cubic inches, almost every team was hitting 190-210 mph in the straight aways with a two barrel 500 cfm carburetor. You gotta know they were running long rods.

Hope this helps...

My 428, when it made the finals, only lost two races. One was to a 500 cubic inch chevy, and the other race was to a 426 Hemi. Both beat me by less than 48 inches at the finish line. At this proximity, it is launch quality and reaction time that determines the winner. I ate a fine cuisine of short rod big blocks in my time, and they came up wanting..... Even the 427 Fords couldn't hang with me in my bracket. (short stroke, short rod, huge pistons, this design is called "over square". It does very well on track courses where the rpm capabilities of the 427 allowed it to dominate until the 428 and then the 429 replaced it.

The 428 was a little bit of magic with its 1.88 to 1 stock rod to stroke ratio. There are very few engines before or since with these types of ratios.

Building a 10 second car is getting relatively easy. Like I said in different thread, it is getting to be like building with lego blocks.

[7000rpmisheaven]

This is new to me but I think I understand what you are saying. Would it be possible to run a 302 crank in a 351 block and just use longer rods.

It sounds like a cool idea and even something that I might want to try out. But the 15k motor you suggests is well out of my reach. Using a 302 crank in a 351 block sounds much more practical. In comparison would a long rod 302 make more power than a regular 351.

[Eric4Nitrous]

Big Block?? bwahaha who needs a big block to go fast? My motor is just a little ol windsor. Tranny is a liberty clutchless five speed, and if the parachutes don't stop it..then i'm hoping my strange brakes will.

[drtbiker]

or u could try to put your feet out lol na maybe safer to jump out

[Eric4Nitrous]

haha i think i'd rather jump

[vetteeatr]

Ok I got 2 questions.

1. Ok This seemingly is jsut plain ingenouis even if you didnt officially think of it. Too good to be true. Not that im saying oyur lying a bit though. I jsut woudl think there would be come downfalls to all that great power gain and efficiency. Any you can think of?

2. As someone metioned earlier 15k is pretty pricey for oyur average car guy or at least for me at the moment it is. What woudl be a budget buildup on a 351 form a 69 or 70 stangf with the stronger block to get a longer ratio what about a 5.0 Block?.

Using any rod pistons and crank from any make of car.
Doesnt have to be optimal but if you could maybe somehow work something out with a few forged pieces that are allready slightly diffrent for other motors allready forged it would be alot cheaper then machining everything.

Thanks

[vetteeatr]

Is there a reason that you do not try to make a longer ratio or is it the limitation of the block design?

Also how can nascar do those high ratios do they got special blocks with diffrent dimensions?(Sorry know not a thing about NASCAR)

[jim_howard_pdx]

No

a 302 crank and a 351 crank have different main journal diameters. The 351 uses a 3 inch main journal which puts enough meat on the crank to support 1000 hp or so.

What you do is offset grind the 351 Windsor crank, usually a forged crank, to get down to the destroked point where you can add the length back to the rod. On a stock crank, I usually go for a 332 cub inch engine. With a custom forged crank blank, I can get it down to a 306 or 312 and hit the 2.2 rod ratio I desire.

On a 351 piston, it is relatively easy to get a forged piston with a .5 inch taller pin location. Then take a quarter inch off the 351's stroke, and you end up with a 6.695 rod. I just bump the rod to 6.7 iches and measure to maintain a minimum .39 quench on the deck. Some modern race engines are building zero deck engines, so the piston actually pokes up through the head gasket space, but this is very dangerous, and I do not recommend it for us common folk.

With any rod, over time the rod bearing cap will elongate into an oval, and when you put that .001 inches back into a zero deck height race engine, you get catastrophic failure.

I believe a stock 351 crank, nodular iron can be cut to 3.2 safely. Perhaps lower, but I really like 332 engines, so this is where I destroke a nodular cast iron crank. Then go with the longest rod, shortest piston you can fit. 1.98 rod ratios are easy, 2.05 to 2.1 come at a price, the oil control ring land will be machined in the pin's boss, so you lose oil control. Ok with racing, not as ok on a street engine.

My extra secret to you is this. At 5,000 rpm the spark plug is firing some 30-36 degrees before top dead center, so as the mixture is compressing, the spark creates preignition, a kernal that must get the air fuel mixture to burn as fully and completely as possible. With a long rod, the piston is higher in the bore at 36 degrees btc. See why you build more torque? You have more cylinder pressure, greater quench, and less chance for detonation because the mixture has been compressed more at 2.2 than at 1.5.

Plus the longer rod accelerates the piston faster up the bore during the compression stroke. This creates more mixing of the air and fuel in the cylinder. Then at the top of the stroke, the long rod slows down and "dwells" the piston LONGER than those short ratio engines.

I should have told Ultra flow this in my response, but I wanted someone to say WHY would your 428's 1.88 rod ratio almost double the torque of that 350 small block engine with only 78 more cubic inches????

This is the reason. When the spark ignites, the piston is higher, quench is tighter, cylinder pressure is higher and THEN we get the cherry on top.

The cherry is that the piston "dwells" longer at tdc than the short rod ratio engines. So the fuel is burning and the piston is parked there as cylinder pressure goes astronomical. The pressure exerts far move leverage against the piston and crank.

See why a NOS or charged engine would put out 1700 horsepower with 420 cubic inches (like Eric 4 Nitrous's Missle Car!) Only his rod ratio is short, so he has to use three stages of NOS to compensate!!!

And the best part is yet to come. Now as the piston falls away during the power stroke, more cylinder pressure is being exerted BUT the long rod engine pulls the piston away slower at top dead center, then very quickly as you move to center bore. Since your pistons are firing 45 degrees apart, this means that the extra torque is multiplied by a factor of 8. So if you are building 10% more torque in one cylinder, it gives you 80% more torque at the flywheel or pressure plate.

You get all this for FREE, other than the cost of admission.

You use less fuel to get more torque. You get a lot more torque at every rpm range. You get mind altering results with NOS, Turbos, or Super Chargers, and you get less chance of detonation to boot.

That is why the 302 Boss ran 224 mph at Bonneville. It had a 351 Windsor block, and it had a custom forged crank that let us offset grind to a 3 inch stroke. Titanium rods and pistons kept the reciprocating energy low. Compression ran 11.5 to 1 and for the bonneville run, my Pantera buddy ran gasoline only. Later he added direct port injected NOS, and eventually went to dual turbos. I helped him with the destroked block, piston shape, head work and bolting everything together. I also helped him with the direct port NOS injection.

I am glad he had some money, cause it cost 100 grand to build this race car. 25 grand in the engine alone.

So if anyone tells you the jury is out on whether long rods are better than extra displacement tell them both sides are right. BOTH methods work. I can build a 10 second car either way. But the long rod engine will have a broader and taller torque curve, it will consume less fuel to build the target horsepower you need, and it will run without detonation. It can tolerate more advance and can take it sooner also adding to the torque levels of your engine.

So now you know the physics. Next time you build an engine, set about to maximize that rod ratio. You will be happy that you did. 1.9 is the minimum rod ratio I would want to run on any of my race engines. Next time I rebuild by 358, or build a new engine, I plan on building a 2.2 ratio engine. It may be a 460 block, or it may be a Windsor. I just want something to play with that when boosted by a Vortec or Novi blower will make 700-800 horsepower, idle like stock, get 16-18 miles per gallon, and run like a triple crown winner.

You can have your cake and eat it too, if you take the time to make it a long rod engine.

[jim_howard_pdx]

To build a 400+ horsepower engine, plan on spending at least 2,000 to 2,500 dollars on a block. To do a long rod, tall deck Windsor, you might not spend any extra money, but you will need to measure everything twice, check clearances and the like.

A 1970 351 Windsor core would be about 50-75.00 A full shortblock around 250.00. You do not need the full shortblock.

Have the engine decked for straightness and to square all 4 corners. (150.00). Take the minimum material necessary to accomplish this. Usually about .002 to .01 inches will need to be removed.

When the bore is enlarged, try to center the bore down the cylinders. Most blocks are bored off center. Try to get these centered if possible and reject any block that can not tolerate a .030 bore with a minimum of .18 cylinder wall thickness. I have punched holes through thin cylinder walls on an engine before.

Bore and cross hatch with a deck plate. Cost about 250.00.

Line hone the mains. Cost about 75.00 to 150.00 Have then chase all the bolt holes with a bottom tap, or do this yourself. Have all oil gallery plugs tapped for screw in plugs. NO PRESSED IN PLUGS.

Have all oil return holes chamfered for easier oil return. Some of my buddies swear by painting the inside surfaces for oil return. I am still on the bench on this one. I cannot see any difference on the dyno or at the track. I leave this one to you.

If using a stock crank, have the main journals cut .010 undersized to what ever they are. Maximum is .050. I just cut the minimum to keep it straight. Chamfer the oil holes. Have them offset grind the crank to 3.2 or 3.25 depending upon your pistons. I like to use extreme light weight Probe pistons or J&E custom slugs with .5 inch higher pin location and ring lands sized for thin racing rings. I like the Child and Alberts zero gap units. Slugs and rings will run about 700.00 The crank will run between 500 and 700 dollars for a stock nodular iron, and 1,000 to 1,500 for a forged steel crank. Check Summit out, they may have some ready to rumble for a great price.

I use an Aluminum Chrysler rod with Chevy journal and pin dimensions. 1.64 inches to 1.7 inches and alter the stroke to match the deck height. So I do try to get the most cubes I can with the cheapest parts I can. With good ARP wave lock bolts you will pay about 700.00 with pin and mounting to the pistons.

I like to get the pop top or dome piston 12.5 or 13.0 to one compression pistons. I then smooth them out completely aiming for .060 quench. .080 max along the top. I go 0.12 near the spark kernal to get a great preignition event. Coat your piston tops yourself (about 125.00, or pay up to 40.00 per piston to have it done (320). Or leave it raw. I like them coated but let the RULE BOOK decide this. Many classes do not allow custom pistons, or domed pistons, or coatings........

Use studs and a girdle, windage tray, crank scrapper, and high volume oil pump. 300.00.

Bolt it together yourself. With a good 400.00 harmonic balancer and new pressure plate or flyweel your short block will come in at about 3,000.00. Not bad for a set up that should deliver safe power to 800+HP with only a cam change.

The cam I leave up to you and your driving ambition. I like Cloyes true roller timing chains. They have an infinite adjustible model but I usually buy their street roller set up. Replacement chains every 100,000 miles cost you 17.95. Cannot beat that guys.

These are available in under size chains to take up the slack from the line honing. I have them aim the line hone for .010 crank to cam shortening, then order a .010 shorter chain!!!! This maintains your timing!.

Bolt on some Trick Flow street heat or R heads, a good intake set up, a good distributor and MSD or Crane ignition box and you are set to go. All together the engine will run less than 5 grand, and with a super charger it will run under 8 grand.

I have built 8 grand engines for kids to run Honda's at the 12 second et bracket. Here is an 8 grand engine that will build 650-700 hp and run easy 10's with slicks on a 3300lb Mustang.

Put some money in the transmission, clutch, and rear end. Set up the suspension for bite, and 9's can be yours from the very same engine. Plus you drive it home from the track dusting off unsuspecting turbo porsches JUST FOR THE FUN OF IT.....CAUSE YOU CAN!

[Eric4Nitrous]

My rod isn't short I don't use more nitrous to compensate for having a short rods. I use more nitrous to make more hp and to keep up with the competition.

[Moxie]

No flames or disrespect meant here. Pasted below is a viewpoint from Richard Iskendarian of Isky Cams. This article, and the charts mentioned can found at www.iskycams.com, under the Tech Info section.


Rod Lengths/Ratios: Much ado about almost nothing.

Why do people change connecting rod lengths or alter their rod length to stroke ratios? I know why, they think they are changing them. They expect to gain (usually based upon the hype of some magazine article or the sales pitch of someone in the parts business) Torque or Horsepower here or there in rather significant "chunks". Well, they will experience some gains and losses here or there in torque and or H.P., but unfortunately these "chunks" everyone talks about are more like "chips".

To hear the hype about running a longer Rod and making more Torque @ low to mid RPM or mid to high RPM (yes, it is, believe it or not actually pitched both ways) you'd think that there must be a tremendous potential for gain, otherwise, why would anyone even bother? Good question. Let's begin with the basics. The manufacture's (Chevy, Ford, Chrysler etc.) employ automotive engineers and designers to do their best (especially today) in creating engine packages that are both powerful and efficient. They of course, must also consider longevity, for what good would come form designing an engine with say 5% more power at a price of one half the life factor? Obviously none. You usually don't get something for nothing - everything usually has its price. For example: I can design a cam with tremendous high RPM/H.P. potential, but it would be silly of me (not to mention the height of arrogance) to criticize the engineer who designed the stock camshaft. For this engine when I know how poorly this cam would perform at the lower operating RPM range in which this engineer was concerned with as his design objective!

Yet, I read of and hear about people who do this all the time with Rod lengths. They actually speak of the automotive engine designer responsible for running "such a short Rod" as a "stupid SOB." Well, folks I am here to tell you that those who spew such garbage should be ashamed of themselves - and not just because the original designer had different design criteria and objectives. I may shock some of you, but in your wildest dreams you are never going to achieve the level of power increase by changing your connecting rod lengths that you would, say in increasing compression ratio, cam duration or cylinder head flow capacity. To illustrate my point, take a look at the chart below. I have illustrated the crank angles and relative piston positions of today's most popular racing engine, the 3.48" stroke small block 350 V8 Chevy in standard 5.7", 6.00", 6.125" and 6.250" long rod lengths in 5 degree increments. Notice the infinitesimal (look it up in the dictionary) change in piston position for a given crank angle with the 4 different length rods. Not much here folks, but "oh, there must be a big difference in piston velocity, right?" Wrong! Again it's a marginal difference (check the source yourself - its performance calculator).

To hear all this hype about rod lengths I'm sure you were prepared for a nice 30, 40, or 50 HP increase, weren't you? Well its more like a 5-7 HP increase at best, and guess what? It comes at a price. The longer the rod, the closer your wrist pin boss will be to your ring lands. In extreme situations, 6.125" & 6.250" lengths for example, both ring and piston life are affected. The rings get a double whammy affect. First, with the pin boss crowding the rings, the normally designed space between the lands must be reduced to accommodate the higher wrist pin boss. Second, the rings wobble more and lose the seal of their fine edge as the piston rocks. A longer Rod influences the piston to dwell a bit longer at TDC than a shorter rod would and conversely, to dwell somewhat less at BDC. This is another area where people often get the information backwards.

In fact, this may surprise you, but I know of a gentleman who runs a 5.5" Rod in a 350 Small Block Chevy who makes more horsepower (we're talking top end here) than he would with a longer rod. Why? Because with a longer dwell time at BDC the short rod will actually allow you a slightly later intake closing point (about 1 or 2 degrees) in terms of crank angle, with the same piston rise in the cylinder. So in terms of the engines sensitivity to "reversion" with the shorter rod lengths you can run about 2-4 degrees more duration (1-2 degrees on both the opening & closing sides) without suffering this adverse affect! So much for the belief that longer rod's always enhance top end power!

Now to the subject of rod to stroke ratios. People are always looking for the "magic number" here - as if like Pythagoras they could possibly discover a mathematical relationship which would secure them a place in history. Rod to stroke ratios are for the most part the naturally occurring result of other engine design criteria. In other-words, much like with ignition timing (spark advance) they are what they are. In regards to the later, the actual number is not as important as finding the right point for a given engine. Why worry for example that a Chrysler "hemi" needs less spark advance that a Chevrolet "wedge" combustion chamber? The number in and of itself is not important and it is much the same with rod to stroke ratios. Unless you want to completely redesign the engine (including your block deck height etc.) leave your rod lengths alone. Let's not forget after all, most of us are not racing at the Indy 500 but rather are hot rodding stock blocks.

Only professional engine builders who have exhausted every other possible avenue of performance should ever consider a rod length change and even they should exercise care so as not to get caught up in the hype.

[jim_howard_pdx]

Ha

I used to have Ed, Richard's dad, build me custom length pushrods and solid lifters. I wouldn't buy one of his cams though, because they were old hat back in the 70's. Not one of the world class engines I ever wrenched on had an Isky cam. I mean no disrespect, but if you understand the engineering, then you either believe in Richard's voodoo scenario, or you believe the world records you produce throught proper engineering.

Each part in and of itself is totally meaningless. Running a long rod on s h i t heads gives you the same torque as the short rods. So Richard is right in saying that rods alone are never the single answer.

As I said in speed secret number one, it is the burn event that dictates how much horsepower you can make. It is the rod ratio that determines how long the piston is held at tdc and that effects torque. Since horsepower is a MEASUREMENT of torque at rpm divided by a constant, then you cannot get horsepower WITHOUT Torque.

This is what I mean by a speed secret. Guess we will never have to worry about Richard building a world record engine........

[Moxie]

Funny, Jim Oddy and Fred Hahn seem to be doing just fine in IHRA Pro Mod with Isky components, including cams.

[jim_howard_pdx]

Have them send me their cam numbers and I bettcha a dollar to a donut that comp cams was building the same cam over 20 years ago.

Just to let you know, when you race brackets, the closest to their dial in wins. It was extrememly important to me to run within one tenth of a second. So it didn't bother me that the Hemis were crossing the finish line 10-20 mph faster than I was. It didn't matter. I took home the trophies. So I could have run 5 or 6 different cams each season. I usually just ran one or two. And mostly that was to keep up with valve geometry improvements in the "ramps" and so forth.......

Richard's dad, Ed was an interesting guy, but like Smokey Yunich he believed in low valve lift, high duration engines with lots of overlap. Cause back in the 50's, 60's, and 70's, there were a lot of short stroke engines running very high rpms to get to their horsepower peaks. And these cams built big power even though the torque curve was poor.

Like Eric 4 Nitrous said, "who needs a big block anymore" to run 6's and 7's. Now it is high lift, low duration, big flow head engines that take the trophies.

The one thing that Richard said in his article that shows how poorly he understands engineering is that "an extra 5 to 10% power is not worth the engine lasting only half as long." Does an LT1 last half as long as a low power chevy? NO! Because as the engine goes up in power, the reciprocating pieces go up in strength. Often, it is the high power engines that last longer unless they are raced professionally.

A long rod engine typically puts LESS stress on the bearings, rings and piston skirts. WHY, because the burn is more controlled. Less predetonation and detonation makes for longer lasting parts.

You know that the sbc crowd started making a 6 inch rod for the 350's about 15 years ago, because they were being dominated by the 5.0 Liter Ford engines. The 302 has a 3" stroke, a 5.09 inch rod for a 1.699 rod ratio. The 350 chevy had a 5.4 rod, a 3.5 stroke for a 1.54 rod ratio, and IT COULD NOT KEEP UP!.

So in came a 6" rod for the Chevy guys JUST so they could stay EVEN!!!!. So tell Richard to take some engineering courses, take some physics courses, build some engines, and try lengthening the rods by .25 ratio increments. Keeping a tight quench and high compression he will not get a 5% increase in torque, he will get a second off his elapsed times.

Just going from 1.54 rod ratio to a 1.714 rod ratio in an LT1 Impala, we took the et times from 14.3 to 13.3 with NO OTHER CHANGES. No cam work, no intake work, and no ignition work. Just a rod and piston change.

Hope that sheds some light on long rods.

[Moxie]

Jim, I'm not trying to discount your automotive knowledge. Open forums like this just lend themselves to healthy debate. Good reading, no matter what opinions people take. Thanks for your contribution to the board.

[jim_howard_pdx]

No problems Moxie,

If I put 15 engineers in a room to discuss long rods,....
7 would say, "I would rather have more displacement"
7 would say "I would like to study the effects of rod length vs torque on a standard engine" (CLUE LESS).....
and ONE guy like me would stand up and say

"to take advantage of long rods, you need a proper package. This would include 11 to 11.5 to 1 compression, tight quench of .039 to .060 at the deck, and no more than .08 at the wedge and a kernal carrot of .10 to .12 inches.
Light rods and light pistons.
Pistons with low friction rings
and zero gap rings on top of that.
A cam with low overlap, but very high lift.
A dual sequential, MAS controlled EFI set up.

And some beers for the testers!!!

That last point was the most important in this entire thread.
If we are not having fun building speed, then we might as well take up knitting or basket weaving.

Moxie, I like to debate long rods with everyone I know, cause few cars keep up with mine, and everyone wants to know why.

Tight quench, high compression, light reciprocating parts, and LONG RODS. These are things I know make superior torque on any platform.

Let's have a beer sometime!!!!

[gofastmercury]

Originally posted by jim_howard_pdx
g rods.

Hope this helps...

My 428, when it made the finals, only lost two races. One was to a 500 cubic inch chevy, and the other race was to a 426 Hemi. Both beat me by less than 48 inches at the finish line. At this proximity, it is launch quality and reaction time that determines the winner. I ate a fine cuisine of short rod big blocks in my time, and they came up wanting..... Even the 427 Fords couldn't hang with me in my bracket. (short stroke, short rod, huge pistons, this design is called "over square". It does very well on track courses where the rpm capabilities of the 427 allowed it to dominate until the 428 and then the 429 replaced it.

The 428 was a little bit of magic with its 1.88 to 1 stock rod to stroke ratio. There are very few engines before or since with these types of ratios.

Building a 10 second car is getting relatively easy. Like I said in different thread, it is getting to be like building with lego blocks.

Just looked it up.

428
6.488 rod
3.98 stroke
1.630 rod stoke ratio

427 ford
6.488 rod
3.78 stroke
1.716 rod stroke ratio

[jim_howard_pdx]

THANK GOD for go fast mercury.....and moxie.....

Thank you, thank you, thank you.....

I am sorry to bait all of you like this. I am not trying to mislead anyone. And I am not trying to b u l l s h i t anyone. I am trying to get you all to think through the steps to successful power building so you will make good engine building decisions.

Lets really discuss this thread logically, and see why rod ratio does or does not build any extra power. When you see where I end up, the light will click on and you will understand WHY certain engine configurations make hot rod magic, while others just simmer.

My real Speed Secret Number 5 should have read like this.... "If you increase your dynamic swept length, you will increase your horsepower."

Both of Moxie and go fast mercury deserve BIG bonus points on this thread.

I was wondering how long it would be before someone looked up the 428 numbers and called me out on this discussion point. I think some 300+ views took place and GO FAST MERCURY took the prize....at the end. (Like any good racers!!!)

I am not retracting anything I said about the benefits of a long rod ratio.......I am only going to explain the missing link that Richard "Isky" could only hint at!

So HERE is the entire point to my thread......, this is what you need to know when you engineer a world class engine....

Like anything about a basic engine the length of the rod divided by the length of the stroke alone does NOT tell you what horsepower you will derive from your engine. This is also true of static compression ratios. The compression ratio alone does not build horsepower or torque. That is because NO SINGLE FACTOR of your engine is responsible for ALL the horsepower you create.

Looking at static compression ratio as an illustrative example, (something I discussed on a different speed secret) I told you that to win a bracket, you match the maximum static compression ratio of the engine you are running, and then you use overlap and valve lift to create the cylinder pressure you need to power down the strip.

This is what Richard weakly pointed out in his discussion of cam timing, and how 2 degrees more intake event made more horsepower than running a longer physical rod length. SO THE DYNAMIC SWEPT LENGTH Plus proper cam timing combine to create the maximum available horsepower.

I just wondered who could explain to me why he is right???? And thank you Moxie for getting this discussion into this thread......

To simplify this information, just take the total stroke length and add the total rod length together. Compare this new sweep length against where you started. This total swept length is a great prognosticator for maximum power, but it is the rod length that most controls the piston dwell at TDC and this is where an excellent burn event combined with piston surface and stroke and rod length all add together to build the total torque and ultimately the horsepower curve of your engine.

For all of you trying to build the next killer engine, just take the total cylinder height you can play with inside your block. Then plan a way to maximize the total swept length of the stroke and rod together while maintaining the longest possible rod.

Remember Richard's warning about putting the piston pin into the oil or compression ring lands. When you reduce the blow by's ability to push out against the rings you lose piston seal and this dramatically reduces the cylinder pressure and torque production.
You need a good ring land to get good cylinder sealing.

Now look at the cam timing. You may or may not already know that your crank shaft spins the rod cap and bolts extremely close to the crank case on stroker engines. Many times we have to clearance these to clear the reciprocating parts. Did you know the same rod bolt and cap swing dangerously near your high lift, high duration camshaft????

The point Richard made was that there is a maximum lift and duration you can fit in the block with the rod and bolt combination you use. Knowing how to fit in the best cam timing, with the longest rod and the overall longest swept length will help you maximize what you can generate in horsepower.

So I am right, and Richard is right, and this points out why rod length arguments exist in the first place. Just remember that there is no one single factor of an engine that gives it all its magical power. It is really a combination of a lot of small contributing pieces that builds a racer's advantage.

Just to completely finish this thread and I promise you I am done now, unless someone really throws me something I did not expect.....this does in fact happen......Let's take all this new information I have shared and plug it into our first example.

Looking at the STOCK small block chevy we find a 3.5 inch stroke plus a 5.4 inch rod equals 8.9 inches. 8.9 inches is the dynamic swept length of the piston and rod. Now also examine the dynamic stroke ratio of 8.9 inches divided by the 3.5 inch stroke which is 2.5428!

Now look at my 351 Windsor STOCK. 3.5 stroke + 5.95 rod equals 9.45 inches of dynamic swept length, divided by 3.5 yields a 2.700 dynamic stroke ratio. So is it just the 0.16 dynamic stoke ratio that accounts for me taking every chevy 350 off the line? No it is really the 17 percent difference in the total DYNAMIC swept stroke that accounts for my coming out faster...... As long as I am not sleeping at the tree......

Now lets look at the 428 STOCK. 3.98 stroke + 6.488 rod equals 10.46. Divide by 3.98 and you get a 2.68 dynamic stroke ratio.
My favorite Ford engine is the side oiler 427. It has a combined dynamic swept length of 10.268 vs the 428's 10.46. That is why the 428 replaced the 427 wedge in Nascar racing. It was a more effective torque producer!!! The 428's dynamic rod ratio is a little shorter 2.628 to the 427's 2.7164.

That is why we liked to use a 427 side oiler block, add a 428 crank. This ended up supplying 454 cubic inches and I never frankensteined one of these that did not produce in excess of 500 flywheel horsepower with the stock 425 hp 427 cam!!!!!

In summary, it is the rod length PLUS the stroke length of the mill between you and your competitor that you should work to increase. Then make sure you are not giving up too much piston surface because that also effects ET times. Crank throw, plus rod length, plus piston surface area AND DYNAMIC COMPRESSION all combine to deliver your torque curve and horsepower curve. He with the most area under the curve generally wins.

I am sorry if I kept all these details out until the bitter end, but I really expected someone to call me on the hard numbers right away.

I am glad that Moxie and Go Fast Mercury are interested in looking over the details. Thanks guys!!!! Now we can all see how rod length works in the overall scheme of things.