351????

[MiracleMax]

Originally posted by NO SLO PK:
Regarding that "legendary 454", it BETTER be making some decent torque...after all, it's got 454 cubes for crying out loud. What it lacks in rod ratio it makes up for in size.

Just illustrating a point , the 347 gets a bad rap for a short R/S ratio and I just wanted to show an engine that was considered highly successful and one that had a shorter R/S than the 347 with a 5.4" rod. I think that BOP 455's had even crappier R/S ratios? but were pretty successful as perfromance engines.

[Five0]

There is a gut here in jacksonville fl that has a supercharged 347 making just over 700 hp and I have seen the print out from the dyno. I don't know if it's safe or if it will last long but there are people doing it.

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James Cox
nochevy@hotmail.com
1991 Mustang LX
12.565 @109.38mph 1.764 60ft

I'm looking at it from a street legal, AFFORDABLE, emissions legal, 50-state dyno pass standpoint. I'm happy many of the people in this discussion don't have to worry about emissions. I DO! For MY money, it's much easier (and cheaper) to take a '69 Windsor out of a '69 Cougar, break it down, buy heads and EFI, roller valve train, Cartech fuel system, etc., bore it, hot tank it, balance and blueprint it, possibly stroke it, throw it in a gorgeous red 93GT with 60K on the dash that is set up to do 9's, and hit the street on a dialy basis. I agree that it all depends on the application. It cost WAY more to stroke a 302 than to find a 351 bare bones ready to rebuild. The cubes are already there. And so is the STRONGER BOTTOM END. The original reason for this discussion was to help someone decide on what to do with the limited amount of $$. Stroking motors costs big $$. I also read that to make good HP out of a 347 you a specially prepped shortblock. Most people don't have the $$ for that.

[Ron1]

I think to dip into the 10's you need roughly 500 HP at the rear wheels in a 3000 pound car. Low 10's will take about 575 HP. You might look at the 392 (351W based) stroker that Ford Motorsport now produces. Just ad carb.

Ron

[DirtKing]

Just to correct some 411....

Motors with better rod ratios WILL make more torque due to more time spent at TDC and less friction losses to the piston/cylinder wall angle. They WILL handle higher compression better than the low ratio motor(302 and most strokers)

Strokers make more power due to more CI (inches are everything) and the use of the longer lever(stroke). They suffer from higher piston speed and friction/reliability issues caused by (relatively) poor piston/bore angles. Blowby is increased....seal is decreased. For a street application strokers will not last as long as a COMPARABLY built high ratio motor. That's why they build bulletproof strokers....they need to be that way. Any motor needs to be built for the ponys it's making! For the most part this is philosophy...most strokers aren't going to need to see 100k. The stock 351 has a much better rod ratio than a 302. It will also take money to convert that mustang. If you are worried about long term durability the 351 is better than a 347 stroker...how much? Too many variables to say, but apples to oranges the 351 WILL last longer. The longest ratio you can have in ANY application is desirable whether it's stock, stroker or long rod motor...stroker builders spend alot of time trying to get the best ratio out of their combinations. A racer planning a rebuild every season just doesn't care.

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88LX notch, Speedpro EFI Procharged!

[This message has been edited by DirtKing (edited 03-09-2001).]

[macx]

Hey, lots of good points! One option nobody mentioned is the 393 stroker (of course also a 351 block)- crate or shortblock. Personally, I'd do the shortblock (has a GREAT cam already in it) and add AFR 185 heads - the heads it comes with are too small for that motor and cam. NOW - I've got that article on the long rod 351 - with the smaller street tw heads, it made 380hp at 5000 & 430 torque at 4000 with only a 220 @ 050 & 498 lift hydr roller cam and efi. With the R heads and same cam, it made 20 more of each at the same rpms. With a bigger cam, the R heads would be probably 20 more again of each. The engine ran shelf JE forged pistons with the Yates style valve reliefs that matched the comb chamber shape for very good quench. It used slightly modified 400 rods which are over 1/2" longer than stock 351, but wasn't up too far into the ring pack because the 351W is the tallest deck of all small blocks so has the most room for long rods. It was able to run 11 comp ratio and ran best at only 32 max advance - shows very efficient combustion - and did it on 87 octane even. The article referenced a similar build on a 350 Chev with similar results. I can email that article if anyone wants. The long rod 351 made very close to the same torque and not much less hp than the crate 393, with a smaller cam, did it on 87, and I'll bet with a heck of a lot less gas. With the same cam as the 393, I'll bet it would come very close to the same output on both torque and hp and run a heck of alot cheaper. Not saying that the 393 with AFR 185's wouldn't be a blast, though! As to tranny, how about a tremec, or a Richmond 5 or even 6 speed - either would handle just about any motor.

Now those are #'s I like! I'm still figuring out if I should get my brand new Edlebrock heads worked for the stroker kit and if it would effect my emission's, or return them to Summit for a set of Tricflow's 50 state legal head. That particular cam you talked about sounds like the Ford Motrsports SVO E-303 cam that most run in street legal 11 and 12 second cars. I had a buddy who dumped 10K into a 89GT just to have it sit in the driveway b/c he stupidly used the B-cam that is much more beefy and never could pass that evil emissions dyno devil.

[MiracleMax]

Originally posted by DirtKing:
Just to correct some 411....
Motors with better rod ratios WILL make more torque due to more time spent at TDC and less friction losses to the piston/cylinder wall angle. They WILL handle higher compression better than the low ratio motor(302 and most strokers)

Yes, they can especially with slow burning racing fuels which can take advantage of the dwell time a long rod motor spends at TDC. However a stroker motor with what seems to be considered a less than Ideal R/S ratio is more comfortable on street or pump gas since this type of fuel burns more rapidly than race fuel. Once you've extracted whatever heat is available from the fuel mixture and it has began to cool down there's no advantage to maintaining the piston's dwell time. As for high compression tolerability with pump gas in a dynamic state I don't see how a long rod engine would reduce the tendancy to knock or detonate. Give me a solid argument in this paticular case and I'll relent . All of this is academic I suppose since just about any engine can be made to perform sucessfully . I can clearly see the advantage of using a 351 as a racing engine, it has every advantage to using it, but for the street (at least to me) a 302 based stroker seems more attractive.

[MiracleMax]

Hey macx, that engine was run in an old hotrod then recycled in an old carcraft (or vice versa)

[nosfed]

I was planning a 351 swap, and even bought some parts for the swap, when an opportunity to get an a4 came along. I understand that the A4 is significantly heavier than a production 302. Is this correct? For the money- $700 for a block that needs machine work- and the small weight difference between an A4 and a 351, the 351 may again be the best option.


Incidentally, how will a 10.9:1 stroker run on the street with a .060 overbore? That's what this block needs now.

[DirtKing]

I'd use the 351 if you're gonna stroke it, but the a4 IS a great block. 10.9:1 will run fine with aluminum heads, especially with the 351's better rod ratio.

hey miracle, I think the very article you referred too built a 400hp 450ftlbs torque using a long rod 351....11:1 compression on 87 octane! 32 degrees of total advance tell ya how efficient the motor was. That was with what would now be a stock 5.0 efi cam.
The reason ratio handles more compression is due to the more efficient combustion. so- `called bad ratios rely on faster pison speeds to promote better cylinder filling...

anyway, I'm building a 12.5:1 version, so I'll let ya know what gas I have to run. I'm looking for about 550hp@6500! I'll post the dyno numbers too.

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88LX notch, Speedpro EFI Procharged!

[MiracleMax]

Sir, This could turn into a lengthy discussion, so I'm going to do two things, at least for now. I'll make a couple of comments and then I will suggest areas for your further thought. Then, if you want/need to discuss the matter further, just let me know. Much has been written/practiced about the benefits of square, over-square and under-square engines. Actually, each has advantages and disadvantages depending upon application, method of aspiration and fuel type. Simply stated, piston motion approaching and leaving TDC {as you are obviously aware} changes the conditions observed during "constant volume combustion" at TDC. Your reference to combustion rate, based on fuel type, is valid...if no other changes are made that affect net cylinder pressure {mechanical compression ratio, spark timing, valve timing, etc.}. While currently available unleaded premium fuel has a quicker flame rate than a "racing" fuel, an engine's tendency toward detonation would increase {all else being equal} as a function of rod length increase. However, and here is an area for your thought process, I suggest to you that a quick flame rate can be advantageous in optimizing IMEP or "net" positive torque. Do you not have an opportunity to delay spark timing, as flame travel increases, and correspondingly reduce negative torque? The fact a "long rod" engine's piston is also leaving TDC {under positive torque conditions} slower than an engine of "short rod"? Perhaps this is an opportunity that could lead to a benefit for street engines of increased connecting rod length. Of course, as in the case of most "absolute" situations, there are other parts that govern the whole. Bottom line is I suggest you stay focused {as it appears you are} on factors that affect net cylinder pressure as a function of crank angle, working toward minimizing pre-TDC combustion pressure and maximizing post-TDC pressure. I hope this provides some clarification for you. But if it doesn't, my offer still stands. Jim McFarland

Hey Dirt I knew I wasn't entirely off base with the L vs. S rod thing on a street motor. I guess it depends on how you digest the information. This is the reponse I got to a question regarding the matter.

The site is http://www.n2performance.com/

[DirtKing]

Awesome tech! I know they have been debating this topic since smokey yunick. All I can say is I'll post my dyno sheets when I've got her done. should be in a month..cross my fingers! anyway, I appreciate the info.

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88LX notch, Speedpro EFI Procharged!

[BilLster]

I went with the stroked 351 and now im looking for a used miata to drop my 302 into.

As far as longditivity is concerned i think proper care is more important than what you go with i just had my heads off and everthings is still fairly clean and slick a friend has alot more money into his car and had to change a valve and there was tons of carbon simple things like oil changes can make a diffrence . PS lent my van to my dad and he wrote it off so i drove my stang all winter here in calgary . gald i got a block heater when i had the short block done.


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89 with 395 single stage n2o and 373's need suspention upgrade

[drag79stang]

Originally posted by MiracleMax:
Sir, This could turn into a lengthy discussion, so I'm going to do two things, at least for now. I'll make a couple of comments and then I will suggest areas for your further thought. Then, if you want/need to discuss the matter further, just let me know. Much has been written/practiced about the benefits of square, over-square and under-square engines. Actually, each has advantages and disadvantages depending upon application, method of aspiration and fuel type. Simply stated, piston motion approaching and leaving TDC {as you are obviously aware} changes the conditions observed during "constant volume combustion" at TDC. Your reference to combustion rate, based on fuel type, is valid...if no other changes are made that affect net cylinder pressure {mechanical compression ratio, spark timing, valve timing, etc.}. While currently available unleaded premium fuel has a quicker flame rate than a "racing" fuel, an engine's tendency toward detonation would increase {all else being equal} as a function of rod length increase. However, and here is an area for your thought process, I suggest to you that a quick flame rate can be advantageous in optimizing IMEP or "net" positive torque. Do you not have an opportunity to delay spark timing, as flame travel increases, and correspondingly reduce negative torque? The fact a "long rod" engine's piston is also leaving TDC {under positive torque conditions} slower than an engine of "short rod"? Perhaps this is an opportunity that could lead to a benefit for street engines of increased connecting rod length. Of course, as in the case of most "absolute" situations, there are other parts that govern the whole. Bottom line is I suggest you stay focused {as it appears you are} on factors that affect net cylinder pressure as a function of crank angle, working toward minimizing pre-TDC combustion pressure and maximizing post-TDC pressure. I hope this provides some clarification for you. But if it doesn't, my offer still stands. Jim McFarland

Hey Dirt I knew I wasn't entirely off base with the L vs. S rod thing on a street motor. I guess it depends on how you digest the information. This is the reponse I got to a question regarding the matter.

The site is http://www.n2performance.com/

I'm sure EVERYONE has seen/heard it a couple hundred times by now, but my 351W (Eagle stroker kit), 418 made 572.6 HP @ 6400 and 517 ft lb. tq. @ 5200, carbureted. Plenty reliable motor. I'd stroke the 351!

[MiracleMax]

So drag what is the stroke on your 418 and what is rod length?

I think this started out as 351 vs. 347? I'll reserve the 418 arguement for 418 vs. 428 when it comes up