Cheap compression

[JVMopar]

Doing some thinking on my race 318. I can't deck the block and have to use stock pistons, stock bore, and heads can only be milled 0.010". So I was talking to a long time friend. He said he remembers reading an article about grinding the crank 0.010" and using a 0.020" upper bearing and a standard lower bearing. To raise the piston 0.010" in the hole.

What are your guy's thoughts experiences etc. Seems plausible.

The pistons I have are flat tops and measured -0.066" from the deck at TDC. Heads CC'd at 64 before milling them.

I just want all the compression I can get.

[bulldog426]

also you can get some steel shim head gaskets, they are a little thinner, and will give you a little more, also what kind of heads are you running?? and what kind of heads can you run??

[John Kunkel]

The different size bearing idea won't work because each bearing is made for a specific journal diameter, you would have a mismatch at the parting line.

If you want to raise the piston in the bore you could have the small end of the rod bushed and raise the pin hole in the rod or have rods built to your desired length if money is no concern.

[JVMopar]

Just stock 302's for heads. I'll be using the thinnest head gasket possible.

I know the bearings are different diameters, but at the parting surface their isn't ever any wear anyways. And I could scrape the babbit down with a bearing knife.

I thought about the small end. I'll have to look into that. Sounds more reliable.

[Stoga]

One other thing to keep in mind is the condition of the valve seats and heads and if they have sunk or been ground into the head. Also, the amount of the valve head that sticks up into the chamber can also change the volume in the combustion chamber. I remember changing valves to get compression just right for stock class NHRA class work. Seeing that stock 318 heads are somewhat cheap, just some checking and mixing and matching of several sets could find the best set of heads with the least amount of volume in the compression chambers.

[cudabob496]

I think these days you make a lot more power with a cam change, than you do with just a compression change. Also, if you change compression, you have to have the right cam shaft profile for that compression. I think going from 11:1 to 13:1 compression on a 426 Super Stock engine only gave you a 20 hp boost.

[Ray Bell]

Effectively giving you longer rods... yes, that would work...

Or, seeing as you haven't mentioned that you need to retain the original stroke, you could grind the crank 0.020" and make that 0.015" offset to give you a stroke 0.030" longer and the piston is 0.015" further up the hole as well.

[bulldog426]

what was it that gave the late 60s 318s higher compression? was it the pistons or the heads?? just find whichever one of them it was and put it on your motor..

[adodgemann]

How do the officals check the deck height or only .010 off the heads ??? Sounds to me like rules that can't be or won't be enforced. What is the max compression you can have ???

[stroker mike]

Is there a way to raise the dynamic compression to acceptable heights without making disqualifying modifications? With a static compression near stock? I had a 360 .060 over with speed pro h405's , .058 in the hole, with 587 heads with the smog holes plugged, a felpro .039 head gasket and with a crane energizer 272 it had 155-160 cranking psi warm, but when I put a hughes HMC cam in it the psi went up to 175-180. I believe because the reduction of overlap, from a 112 lsa to a 107, and significant advance, made it pop like a dragster. Cackle, cackle! The intake closing early made it seem like alot more compression... But I'm not expert, here, by any means, but I hope this is valid input.

[JVMopar]

Stroking it isn't an option cause they can pump the motor to check the displacement.

Raising the piston in the hole on a 318 by 0.010" is a 2cc reduction in combustion chamber volume. So like milling the heads an extra 0.020"

There is a measurement for cylinder head. And a spec on how much they can be milled. I've had some heads done and to clean up the surface they were taked down to the maximum according to the machinest. I don't know exactly how they measure it.

I'm trying to stay within the rules, but maybe bend them just a bit. Of course it all depends on how well the car does. If I don't ever make the top 3 they'll never check it. But if I mop the floor every time out they'll surely tear it down.

[bulldog426]

what kind of class u running?
In 68 the 318 piston was 0.020" taller than 69 and on. So if you can find pistons from one of these 318s that can also give you compression.

[Ray Bell]

Yeah, I think you really need to tell us the whole of the rules...

Then it's easier to work out ways around them.

[JVMopar]

Pure stock. Stock pistons, stock rods, stock crank (can be ground 0.010), stock displacement. No grinding of the block. Heads can be milled 0.010". 4bbl Thermoquad, 0.420" cam lift, stock exhaust manifolds (got the big magnums), 1.78 1.50 valves no porting. Pretty much gotta stay stock.

Next time I'm up to Napa which will be tomorrow. I'll ask the machinist about how they measure the heads.

As for the '68 318 pistons anything that is used is gonna be wore out and NOS is gotta be hard to find.

Just toying with all possibilities. If I could mill the block it wouldn't be a big deal. But I'm trying to stay within the rules. Just push them to the limit.

[stroker mike]

Isky makes lift rule cams that are .420 lift but more duration and set to rev, tight lobe sep and all that. Are those legal?

[Ray Bell]

Okay... you say 'stock'... do you mean 'stock for that model' or 'stock parts from the manufacturer'? Or, more to the point, do the rules mean one of those?

[bulldog426]

most of the pure stock rules around here as far as pistons are say dished or flat top only, and no forged pistons, because stock pistons would mean that you had to use the original pistons and you couldn't overbore, and it would be hard as heck to find a buildable block that didn't require boring to an extent. and i'd reccomend a set of magnum heads, they typically give you more compression than most la style heads, especially the r/t heads, and you can run the rocker arms off the magnum series v6s which were 1.6 ratio and would help you on the lift as well, i know a guy around here that's real big into dirtrack and he taught me that.. at most dirtracks they mostly run all chevys so you can get away with a little more on a mopar because the tech guy hasn't been lookin at em all day everyday... whats the cubic inch rule? can you post a copy of the engine rules?

[JVMopar]

It's pretty much stock for the make. They aren't gonna know what to think when I roll up there in a mopar. As long as it came on a stock mopar it'll be ok.

No boring. The car I got had 45,000 on it. Bores look real good.

Only cam rules are hydraulic and 0.420" lift.

Can't use magnum heads. Valves are 1.78, 1.50.

http://www.abcraceway.com/user2/imag...lesrevised.pdf

[Ray Bell]

Looks like they've got you pretty well fried...

1. 307 Olds, 305 Chev., 302 Ford, and 318 Mopar. All motors must be stock OEM. No intermarriage.
2. No fuel injection/turbo.
3. No HP stamped motors (HP=228.305).
4. Stock or stock replacement, cast dished pistons.
5. No performance enhancing work on heads and block. Heads and crank may
be trued .010 only. Maximum one (1) time only.
6. No grinding of castings, including block. Exceptions see ENGINES #5.
7. No vortex heads/intakes.
8. No interchanging or rocker arms, ratios.
9. No boring, shaving or grinding of engine block.
10. No degreeing of cams. No offset key in crank.
11. No double roller timing chain.
12. No screw in studs. No pinning of studs.
13. No roller cams
14. No balancing motors.
15. Cast iron or aluminum intakes only. Must match CID of motor. Quadrajet
GM, Motorcraft FORD, Thermal Quad MOPAR.
16. Stock OEM ignitions only.
17. Stock replacement steel or aluminum radiators allowed.
18. After market gaskets allowed.
19. After market air filters allowed.

You might have to push the flat top pistons as you don't want to have to run dished ones.

So your options don't even include blueprinting, you have to find a block that's close to minimum deck height (according to manufacturing tolerances) if you want to go any further with that.

And you can't change the rocker ratio, that idea's blown.

[toad490]

Originally Posted by Ray Bell

, you have to find a block that's close to minimum deck height (according to manufacturing tolerances) if you want to go any further with that.

I'd deck the block to the specs, would still be within the rules. You just happened to find a block right on the button. You can bet your running against blocks just like that.

How about gapless rings?

[Ray Bell]

No, even if it's oversize, the rules say 'No boring, shaving or grinding of the engine block.'

These are really unusual rules...

[JVMopar]

It's strictly a budget class. But the one rule I can't figure out is the no roller chain rule. The damage done when a chain breaks is very expensive. And you can get a roller chain for cheaper than a stock silent chain.

So that's why I was thinking outside the box with the bearings.

[Ray Bell]

There's a clause in there that says, basically, that they can be approached about 'bending' the rules...

Why not put the case with the chain? Show the logic, they should see it, there's no performance advantage is there?

I'd also reckon that other competitors have also approached them about 0.020" overbores because they can't find good enough virgin blocks.

[pishta]

get yourself a cheater cam. .420 lift but has about a 250 @.050 duration. Nothing about duration. You might even use long reach plugs that dip into the chamber and gobble up a few mm of course. You got an edge with the TQ though, great velocity carb getting out of the corners.

[adodgemann]

The rules sound like they want ya to throw in a junk yard engine and race it. I can see those rules evolving quickly in the future. I don't get the 1 1/2 .095 tubing around the driver, should be 1 3/4 .095 then 1 1/2 out from the main cage. Also the 1/2 inch plate the size of the drivers door, wow that must weigh a ton. 1/8 is what we have to run, Even the Frank Kimmel enduros are lighter at 1/4 inch door plate and those cars are fast. How long has this class been running ??? Have you raced yet or hung out in the pits ??? I would be asking a lot of questions at the track. The guy who builds his car exactly to the rule book will be running at the back. Guys who get creative, bending the rules will be running up front. I think it is like that every where ya go... I would lobby the track for some "saves the racers money" rule changes for the future. The way they are wrote now, will cost more money to go fast. Allowe the engines to be rebuilt, .030 over, defined compression 9 or 9.5 to 1 the cam rule is OK but cheater cams can be bought to make up for the low lift but aren't cheep. No roller chain, come on who thought up that one. Main thing is to keep the rules simple and easy to enforce.

[Ray Bell]

There's nothing in there to prevent you putting a spacer under the carb, is there? Maybe that would help?

[bulldog426]

i don't see where it says no magnum heads, and with the magnum heads, you can use stock 1.6 ratio v6 rockerarms and nobody would know.
stainless steel valves would also help raise compression

[JVMopar]

Valve size keeps me from running magnum heads.

I'm gonna have a cam ground for it. Might as well it's only money right.

My cage is mostly 1 3/4 12ga. all of the main pieces are. Then there is some 1 5/8 mixed in there. And no 1/2" plate on the drivers side for me. Heck what's on there now is 14 ga. I got the cage used. There are cars going threw tech without any plate on the drivers side at all.

I think I'm gonna be using a roller chain just for my own piece of mind if nothing else. Heck the '86 1 ton I have had a roller chain in it. Grandpa bought it new off the lot.

There was a buzz last year about a 0.030 overbore rule comming. But it's not here. Someday they'll figure it out. Heck the 305 has been out of production for 10 years. So they'll have to make some changes to keep people doing it.

[adodgemann]

Give Racer Brown a call for a cam. If it was me I would deck the block enough to clean it up and square it. Then I would mill the heads enough to get to 10 to 1, go racing and keep my mouth shut.... Whats to most they gonna do, DQ ya. You could throw some stock heads back on to be almost legal... LOL

[JVMopar]

Yup I think your right. Just enough off the block to square it up. Then go from there.

I guess I don't want to "cheat" but I don't want engine problems. And decking the block to insure a flat smooth surface is a good idea.