Speed Secret # 7

[jim_howard_pdx]

Speed Secret # 7

First lets sumarize our speed secrets.

One was keeping the quench very tight, allowing you to run more static compression ratio without detonation.
Two was to reduce parasitic horsepower loss (reduce the weight of anything spinning or rotating in your drive line, from crank, pistons, and rods, to flywheel, to transmission, to driveshaft, to rear end, axles, to your wheels and tires.
Three was optimizing your static compression ratio to the highest your class allows, and then increasing the dynamic compression ratio by using the proper overlap and valve lift to get extra cylinder pressure.
Four was to reduce the intakes dillution effect by using advanced cam technology.
Five was to use as long a rod as you can on your stock or stroker engine. Look to have the longest swept length of stroke + rod length you can create.
And six was to get your spark advance curve set up for optimum ets. Use the right heat range plug, good cap and rotor, good wires, a magnetic trigger duraspark, and an ignition box and high quality coil.

Now for Speed Secret # 7.

Would you like to get a free 5% increase in torque. Lets say you have a 400 ft lb of torque engine. That would make it a 420 ft lb of torque engine. That would make about 35 extra horsepower for you at the track--FOR FREE.

How can you do this.... Switch to a zero gap piston ring set, and keep a tight piston to wall clearance next time you build.

When I was still in diapers, I build a 500 hp cleveland engine. Everyone told me to run a wide clearance of .005 to .006 so my forged pistons would have less friction and rev faster. At the time, chrome moly ring sets were the rage. So in went a trw 11.5 to 1 compression forged piston, wide clearance and chrome moly rings. The results were ok, 500 hp is always fun. But the blow by was really bad with the chrome rings. They were so hard it took nearly 5,000 miles for them to seat completely. Then the wide wall clearance allowed a lot of cylinder pressure to slide under, behind, and through the ring lands. Blow by was a harsh 7.3 percent! OUCH

Lets look at an example so you can see why this is bad. On a stock 351 cleveland, blow by is 4% for a new engine, and they recommend rebuilding when you exceed 6-8 percent.

What is blow by?

During the compression stroke, your piston squeezes the intake mix, the spark preignites an ignition kernal that starts a flame that propogates from the plug to the pistons edges. This wave front releases high cylinder pressures that exert force against the piston and drives it down the cylinder.

But at the very top, as the pressure builds during the combustion process, hot charged gas flows around the edge of the piston and into the top of the first ringland. It then exerts pressure against the back of the ring pressing the ring hard against the side of the cylinder wall. At the same time, pressure leaks past the bottom ringland and moves right on to the second ring. The same process is continued. Then on to the oil control rings, now the gas escapes into the crank case where it increases pressure and forces air and oil mist out the valve cover baffles.

A 4% blowby means that 4% of the total combustion cylinder pressure is lost past the rings and enters the crank case. This is 4% power that cannot produce torque during the power stroke of your engine. It is lost horsepower.

In the 70's, we used to buy ring sets that were "cut to fit" We then modified them for a "half slide" edge. This is exactly what Childs and Alberts provides for you today with their zero gap ring sets. At the conjoining ends, each is shaped like an "L" and the two "L"s fit together to make an zero gap I. The "L"s slide past one another as they heat and expand, or as they contract.

Use zero gap rings and you will be rewarded by just a 1% blow by. On a 426 Hemi race engine, we pulled a 35 horsepower increase at the rear wheels with just a ring set change. On my 351 cleveland, we pulled an extra 17.5 hp at the rear wheels.

I expect a bunch of engine builder guys to sprout off that ET times will not increase that much from a ring change. But 17.5 rear horsepower was good for a tenth second on my car. More importantly, less blowby means FEWER contaminants reach your oil. It stays cleaner, and provides more lubrication under extreme racing conditions.

Now why run a tighter cylinder wall to piston clearance???? A .0022 to .0035 is where I like to run my forged pistons. .0012 to .002 is where you want to be with hypereutectic pistons. The tight clearance reduces piston rock and that will reduce friction. The tighter wall clearance also seems to concentrate the pressure effect of the combustion gas on squeezing the top ring tightly. This also enhances better cylinder sealing.

If you are doing a rebuild now, or if you are planning one, check your rule book. If it allows you, run a modern light weight racing piston that uses the thinner racing ring sets. You do not have to go microscopic here. Just get them at least a full size thinner than the old thick stock rings. If you have a choice of oil ring control pressure, stay standard. The light pressure oil control ring may do a poor job on your street/highway car. And that is not a good thing.

Here is a historical fact you all may or may not know about. Honda car company was formed because Ford, GM, and Chysler turned down an engineer with a superior piston design. That guy was the founder of Honda motor car company. He had created an improved piston ring that reduced friction, improved sealing, and increased horsepower. He took this new ring technology to Ford, Chevy, and Dodge, and each of the big three decided to use their old thick, heavy, standard rings....

Honda was born as its own car company.

Today, Honda has dominated Cart racing for three years straight. Not by a little, but by a wide margin. So maybe Honda had a better idea.....

The point of the last paragraph is not to allow some Ford "expert" to tell you to run thick, heavy, standard ring set. Run the light, thin, racing rings on a good forged racing slug and you will make MORE Horsepower. Just make sure you chose the racing ring set to have a zero gap ringset TOO.

So let the discussion begin.

I am sure someone will disagree with me.

But remember that all motor, 2.5 liter Honda engines, are running 10's this year, and will run 9 second times next year. I can tell you first hand that the rings and cylinder clearances play an integral part to making that magic happen.

So take advantage of the same great engineering and gain some FREE horsepower.

If you don't, your competitors will!

[MEDIK418]

I went with gapless rings on the last 306 I built and I really like the things. I used the Total Seal two piece rings. The two top rings are both gapless. Each ring is a two piece design with each piece having to be gapped same as standard rings. All you do is stagger each set just as you would for the top and second ring. It's a little more tedious than managing the gap placement of a standard set of rings but worth it I believe. I was kinda leary of stacking two rings in one land but it was really easy to install and I haven't had any problems with them for a year of hard running and they seem to have every bit as much "pop" to the cylinders as always. I wish I had something to compare them with but the engine was all new and lots of changes took place during the rebuild but oh well, maybe next time.
FYI, I am putting them in the 351-C I'm building for my next project. This one will be pretty much the same as the previous one but with a roller cam and roller rockers. I'm shooting for 400-450 horses but time will tell. (400 should be easy to come by but I don't know about the last 50)

[jim_howard_pdx]

A 2V Cleveland head, Australian closed combustion chambers would be my choice, and a cam about the same as the E roller should put you at 400 hp with 11 to 1 compression. Stepping up to about 575 lift at 255 degrees at .030 will put the 2V at 475 hp with the same compression.

Just do the pop up trick I outlined in speed secret 1 keeping a very tight quench throughout the combusion chamber.

Using the 4V cleveland head with the 575 roller cam will put you about 520 hp. I use those port plates they make for the heads, both intake and exhaust to improve the flow. They work GREAT. If you can afford the SVO cleveland aluminum heads, these will easily put you at 525 hp with the 575 roller cam.

Hope this helps.

What were you going to do for the intake side of your cleveland project?

Hey, keep me informed on the 351 C. I am going to do a 302 Boss engine for a Miata with 180 mph in mind. About 500 horses at 8,500 rpm is what I am hoping to hit. I am going to use the 351 Block, a destroked crank and 6.45 length aluminum rods and probe or Ross light weight pistons. The rod ratio will be 1.195 but the swept length will be 9.45 inches which is much more than a small block chevy ( 3.5 + 5.4 = 8.9 inches). This will be a torque beast as well as a good upper rpm performer....perhaps a perfect engine....if I can get it to fit in the engine bay? I expect over 400 ft lbs of torque on the engine from 3,500 to 5,500 rpm, and over 300 ft lbs of torque at 7,000 rpm!

Now I need to cut the weight on that Miata, cause it weighs 3,300 lbs with the aluminum 4 cylinder engine. With the 351 windsor block I will weigh as much as a new Mustang!

I really want a MAS EFI for this application, but will probably have to go single plane and a throttle body speed density FI system. I just have to find a friend that will smog certify me when I am all done. Luckily I have one or two that will help me if I beg and do some favors in return.

[ultraflo]

Low tension, zero-gap rings (placement of the zg ring(s) depends on application) are the way to go... just be sure to use a vacuum pump, which alone is worth 20hp, with low tension rings

[jim_howard_pdx]

Ultraflow is referring to a crank case vacume system. (This was going to be a part of a future speed secret of its very own, but everyone will need to wait for the full blown secret.....)

Ultra good job there guy, even if you did spoil a future thread.....

(just kidding)

I would recommend a low tension oil control ringset ONLY for a racing application. Use the thin race, zero gap ringset with a standard tension oil spring for a street/highway engine.

But with the vacume system, I think even a street/highway engine could get away with this low tension spring......

I will have to give this some thought, but I think Ultraflow just taught me something important today!

[RPM427]

If you are spraying nitrous, won't the zero gap rings expand and ruin the engine?

Someone please clarify.

[MEDIK418]

Here's the deal. I have two Cleveland engines to make this thing out of. A 71 4-bbl and a 72 2 bbl. I am going to use the four barrel heads mostly because they have been rebuilt completely and all I need is port fillers. The pistons are flat top TRW's as this is going to be a street engine and past experience with this same engine, shows me it detonates at will if the timing is pushed too high with pump gas as it is. Quench or no, this thing needs good gas. As for intake, I'm thinking single plane and a road demon, not sure what size yet. The 575 shows promise but I believe there's one a bit larger with the same design that will let it breathe better.

I'm hoping to keep rpm down to the 6000-6500 range. THis is a toy that I want to drive to work if I want but still have a high fun factor. No effort to set any records with this one.
THe last Cleveland I built has a hydraulic cam of 512/509@224deg. (.500) and it was a stump puller. I was hoping to improve a little on it with the roller cam and a few other items I didn't so last time. THis is my winter project and I have to rebuild a transmission first so it may take a while but I hope to finish by April.

[HotRoddin]

Originally posted by jim_howard_pdx
The tight clearance reduces piston rock and that will reduce friction.

Tight pistons reduce friction ??? Not only does that go against everything i've ever heard but its not logical either.

[jim_howard_pdx]

Tight pistons, lose pistons, what is the difference friction wise????

Nothing, because lose or tight, the piston should never have metal to metal contact with the cylinder wall. The only friction is the ringset's drag along the cylinder wall. Even then they primarily just scrape away the oil, and provide spring tension against the oil film.

However, if the piston rocks in the bore, then you get physical contact of the skirt to the bore and that IS FRICTION.

So the key to getting good cylinder sealing, is keeping the piston tight to the bore, so that you can use a racing ring set with minimum friction, but maximum cylinder sealing.

Hope this makes more sense.

I am a big proponent of zero gap rings. Zero gap rings are a risky business with NOS unless you run a water injector to eliminate detonation and to reduce the combustion temperatures.

Our 500+ HP Honda and Wankel engines all run NOS, TURBO's, and zero gap ring sets. They run really well into the 9's and 10's without problems.

Now for any Cleveland 4V engine, if it detonates, you know the quench is too lose. You really need to keep the combustion space TIGHT. Use a 12/1 pop up and smooth it out completely to 11/1. No more than 0.08 clearance at top dead center except you want a kernal space of about 0.12 at the plug. You want 10 degrees at idle, and no more than a total of 32 degrees at full advance. If you run a vacumn advance, limit total advance to 40 without load, 32 under load.

You should be good on 92 pump gas, just run a water injector if you want to keep things a little cooler under pressure.