When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Having a really tight quench is probably one of the most over rated factors when building an engine and nothing to get over excited about. On your engine if it is excessive and I'd say over .060 probably is then usually a KB piston will reduce it to something reasonable without having to machine the block. Their CD is usually pretty high.
If you can get forged pistons made to your specifications, great !
I suggested hypers because they are cheaper, and would be suitable for your proposed build.
A 'zero deck' is an absolute must, and adding 12cc pistons and 72cc heads would give the engine a static compression ratio (SCR) of exactly 10 : 1.
13cc pistons would provide an SCR of 9.9 : 1.
The squish would be perfect (efficient) also.
Mention an SCR of 10 : 1 when talking to the piston supplier.
It wouldn't hurt to speak to cam manufacturers for their grind suggestions, and I for one, wouldn't mind knowing what results you get.
A custom ground cam could also be a consideration, but you can't choose a cam accurately until you know the EXACT engine specs. (10 : 1 etc could be used as a good example though.)
A zero deck isn't an absolute must who told you that nonsense?
I’m no expert, just trying to get an engine together that does what I want. I’ve always heard the .40-.100 range is prone to detonation. 10:1 sounds like a pretty high starting point, not aiming for a big cam, big heavy truck.
Aim to spend some time south of the border, there is no premium fuel available. My bike does not do well with 10.5 static, unsure of dcr, but it’s healthy cam.
have reached out to a couple piston outfits, see where it gets me. Will do the same on cams soon.
I’ve always heard the .40-.100 range is prone to detonation.
10:1 sounds like a pretty high starting point, not aiming for a big cam, big heavy truck.
Aim to spend some time south of the border, there is no premium fuel available. My bike does not do well with 10.5 static, unsure of dcr, but it’s healthy cam.
When you say the .40-.100 range, are you talking about squish ?
10 : 1 is a combustion efficient starting point for 'closed chamber heads', and a big cam wouldn't be required at all.
The DCR will play the major role in your cam choice.
Given the context of the OP's build, what would you suggest instead of a zero deck ??
The engine must have clearance between the flat portion of the piston and the flat portion of the head. What you can get away with as a minimum is anybody's guess but I can tell you with absolute certainty that it is far better to have a little more and have carbon build up to get that minimum than having it too close and a piston slamming the head. So far this year I've torn down 3 engines where the previous builder had it too close, zero and a .040 wasn't enough.
In this guy's case .010 in the hole with a .040 gasket would be superior to zero and a thicker gasket for the same amount of clearance.
I've had to build for a class where you had to run a flat top piston, 358 inches and the piston could not come above the deck. When trying to get the best running combination and the most compression possible which gives more compression, a piston that's at zero with a .050 gasket or a piston that's at -.020 with a .030 gasket?
The clearance between the flat portions is 'squish'.
The general consensus for a minimum squish is 0.035'' - 0.06'', but I think that is in the context of detonation.
I am surprised that 0.04'' wasn't enough for those three engines.
My engine runs 0.035'' with a 0.041'' gasket, and the only reason I have a negative deck height is because I trusted the machine shop to adhere to my specs when milling the block. They didn't !
That said, no problems in 80,000 miles, and the engine gets red lined on quiet empty roads.
A zero deck and 0.04'' compressed gasket for the Op's engine would (should !!!) be just fine.
The compressions in your example would be very close, but I'd choose a zero deck any day. (I'd want the combustion fully in the chamber with none in the cylinder.)
.040 isn't enough if you're going to turn 6000 or more RPM. Especially with a forged piston it will hit the deck. Your engine is hitting if it only has .035 and you're turning it over 6000 rpm.
Having a really tight quench is probably one of the most over rated factors when building an engine and nothing to get over excited about. On your engine if it is excessive and I'd say over .060 probably is then usually a KB piston will reduce it to something reasonable without having to machine the block. Their CD is usually pretty high.
Amen to that !!
I think this obsession with quench, squish etc. is more of an inline valve head thing.
Haven’t had anyone get back to me on pistons yet. Did come across Dss racing which shows a few options available for 400s. Including 13cc dish 1.71 comp height
For a Cleveland piston? Isn’t the compression height still way off?
No. The compression height of a 351C piston is the same as a piston for a 400. The only difference is the 351C uses the .912 pin diameter like the other small blocks whereas the 400 uses a .975 pin. A bushing for a Y block Ford works perfectly to make the rod full floating.
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Slideshow: The VelociRaptor Expedition gains a lift, upgraded suspension, Brembo brakes, and trail-ready equipment while retaining the stock 440-horsepower EcoBoost V6.
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Slideshow: Called the Fortress, the 850-horsepower pickup combines Raptor underpinnings with military-inspired features, survival equipment, and a starting price of $285,000.
