Advice on Compression Ratio needed

[451Mopar]

I did not run the numbers, but the compression and cam timing is close to what I have in the 505" stroker.
When I was first working on the tuneup I did hear some pinging, but it now runs fine on pump.
Keeping the air inlet temps reasonable really helps, compared to sucking in hot under hood air. I also took the 195 degree thermostat out and went with a 180 degree thermostat.

 

[67belvedere/225]

Maybe get some other opinions here on the board but based on this information I am completing my build with this setup and plan to run the some 92 with a couple gallons of race fuel. I will only drive the car about 15 miles a month tops

My six is 9.5 And run pump gas and I add some VP racing fuel for a extra thump

 

[69Bee]

How do I go about changing the piston/head clearance? Thicker gasket or different pistons?

A little extra deck height = more piston/head clearance

 

[69Bee]

.035 minimum piston to head clearance? Only if you are running aluminum rods. I've done engines with much less using stock type or aftermarket steel rods. I will say that .019 is too close for using laughing gas Axe me how I know that lol

0.045" min for aluminum rods, and 0.035 min for iron rods. Sure, sure, people say the run less all the time, but I won't do it on a customers engine.

 

[BSB67]

I would go with what you have. You are close imo. The details will probably make the difference

 

[lewtot184]

0.045" min for aluminum rods, and 0.035 min for iron rods. Sure, sure, people say the run less all the time, but I won't do it on a customers engine.

last time I played with any bill miller rods their literature said .055" min.

 

[wyrmrider]

so are those versions of Performer open or closed chamber?
if open you need to rethink your combustion chamber (piston plus head)
I go with threewood
lewton those 84 cc open or closed chambers?
good piston with closed chamber head but I though the CR would be higher

 

[66Satellite47]

My 500" motor has 10.5 CR with a cam very close in valve timing (less lift), EDE Perf RPM 84cc open chamber, 35* total timing. Ran fine on pump 92 (no alcohol). Absolutely no signs of detonation. BTW back in the day I ran .010 deck, .020 steel shim, steel LY rods, 915 heads at 7000+ rpm. Was enough piston to head for that.

 

[lewtot184]

so are those versions of Performer open or closed chamber?
if open you need to rethink your combustion chamber (piston plus head)
I go with threewood
lewton those 84 cc open or closed chambers?
good piston with closed chamber head but I though the CR would be higher

84's are closed, 88's open

 

[wyrmrider]

Thanks lewton copying your build would be a good plan
or threewoods it's the combination that works
note that Edelbrock wants the reverse deflector pistons- step deck- with the 88 cc heads to get some quench
I have run 915 heads, 6 pack pistons (sometimes with machined D-dish like a SBC "turbo" piston) rebuilt LY stock rods with DC bolts .030 piston to head also- no problems
very fuel tolerant and take less timing than open chamber

 

[threewood]

I have an almost identical build...
Same 3842 cam
KB237 pistons .010" in the hole
Stealth aluminum heads 80cc
.030" Cometic gasket
.040" quench, 10.4:1 CR, dynamic is around 8.4
I run 91 pump gas without issue with the cam drgreed straight up, 24 degree initial / 36 total.
Edit---I'm running stock rods with ARP rod bolts, floated wrist pin.

I just confirmed, my dynamic is 8.65:1 with dynamic cranking pressure at 173.2

 

[Cranky]

0.045" min for aluminum rods, and 0.035 min for iron rods. Sure, sure, people say the run less all the time, but I won't do it on a customers engine.

The .019 was and accident. Was helping a friend build an engine and we both thought the other had checked. So much for getting in a hurry. It ran very well until he decided to hit it with the gas. Anyways, .030 with good rods doesn't bother me any with good rods so long as the pistons don't weigh a ton.

 

[wyrmrider]

440 pistons have such long skirts that you do not get much piston rock even with loose clearance
I've run .025 with a 3 7/8 bore motor
One thing when you look at the two builds, lewtot and threewood a very important step is trans, converter, gears, weight and how they drive theirs
In another thread we had tow posters who love the HE284HL or 29X cam but then they were 3.91 stick shift cars

 

[threewood]

440 pistons have such long skirts that you do not get much piston rock even with loose clearance
I've run .025 with a 3 7/8 bore motor
One thing when you look at the two builds, lewtot and threewood a very important step is trans, converter, gears, weight and how they drive theirs
In another thread we had tow posters who love the HE284HL or 29X cam but then they were 3.91 stick shift cars

Good point. Mine is a 727, shift kit with 3500 PTC converter, 3.55 gears sure grip, ss leaf springs, 3700 lbs. Street driving but I do get on it. Plenty of low down torque.

 

[BSB67]

Thanks lewton copying your build would be a good plan
or threewoods it's the combination that works
note that Edelbrock wants the reverse deflector pistons- step deck- with the 88 cc heads to get some quench
I have run 915 heads, 6 pack pistons (sometimes with machined D-dish like a SBC "turbo" piston) rebuilt LY stock rods with DC bolts .030 piston to head also- no problems
very fuel tolerant and take less timing than open chamber

Cutting a step in the 2355 piston when used with the 915 head was not uncommon.

 

[BSB67]

I just confirmed, my dynamic is 8.65:1 with dynamic cranking pressure at 173.2

Consider easing up on the four significant figures when using a formula that is plus or minus 10%.

 

[threewood]

Consider easing up on the four significant figures when using a formula that is plus or minus 10%.

That went right over my head lol.

 

[66Satellite47]

84's are closed, 88's open

Guess I could be mistaken on mine. They have a 6091 casting number and are open chamber. Thought that would correspond to the EDE 60919 part number. Sure could be wrong & then mine are 88 cc opens.

 

[BSB67]

Guess I could be mistaken on mine. They have a 6091 casting number and are open chamber. Thought that would correspond to the EDE 60919 part number. Sure could be wrong & then mine are 88 cc opens.

They have three different combustion chamber configurations. 88cc, 84cc and 75cc. Only the 88 is an open chamber. 84 and 75 are closed. The 60919 is the 84cc closed chamber. Don't know how that corresponds to casting numbers. Would be interesting to know.

 

[lewtot184]

as the 440 piston is lightened up skirt length becomes shorter. usually clearance is reduced for shorter pistons. any piston with a straight pin will make noise when cold; especially if the oil ring groove is drilled vs slotted. I fired up my 65 coronet with the Icon pistons last week (about 40 degrees F) and they'll talk to you. I prefer staying on the tighter side of clearances for drivers. people freak out at piston slap especially with a solid cam.