[Formulajones]

Originally Posted by Cliff R

#My own engine is 11 to 1 compression, and has been fine now on pump gas coming up on 10 years. I even run 87 octane in it and it doesn't grumble much and still has great oil pressure and non of the pistons have ended up in the oil pan yet!

Just some things to think about when rounding up everything for your new engine build........Cliff

Originally Posted by skullbucket

Goes against every magazine, TV show, build book in existence.
You must be running a cam that acts like a huge vacuum leak all the time its running?

11:1 isn't terribly difficult to live with on pump gas with aluminum heads. Fairly common in builds today that run pump gas, especially with these modern chambers today. Some push it further.

Iron heads is a different deal, with chambers that aren't efficient, needs more ignition lead, iron that holds heat to boot, can be a tricky deal if not careful.

[STEELCITYFIREBIRD]

Things got lost in the 70's with real low CR's ~7.8:1 and such.
Looking at my daily driver,
production 2013 Taurus,
3.5L non turbo,
10.8:1,
288HP, from a V6! .....not a hot rod model buy any means
Yes the modern engine has huge benefits helping it... EFI, VVT and computer controlled timing control.

I agree, 11.0:1 aluminum headed modern chamber engine, the norm.... not the impossibility.

[Will]

My 2006 WRX only had 8.4:1 compression...

[bendutro]

Originally Posted by Cliff R

Unless the project is "max effort" and requires iron heads, I don't recommend it.

I'll also add this, we did one 455 to date with dished piston and small chamber heads compared to all the others having larger chamber heads and flat top pistons with very tight quench. Using basically the same parts the dished piston engine didn't make the grade on the dyno. It still made acceptable power, but down considerably from the other engines we did with similar cam specs, head flow and close in compression just using flat top pistons instead.

Thanks Cliff - do you recall how much was lost with reverse domes?
I'm ordering the rotating assembly and was planning on running a set of Dave's 260+ ported #48s but I'll need a -19cc to hit 10:1. If this is gonna handicap me I'll order FTs and just go with aluminum heads.

[Cliff R]

Can't remember the exact numbers and I lost the dyno sheets when my last hard drive took a dump.

I think the dished piston engine was off about 30hp and at least 40ft lbs torque from what we typically make with them using flat top pistons and larger chamber heads......Cliff

[BB69judge]

Did you ultimately use the 48 heads or go with aluminum heads,. If you still have the 48s, I’m interested.

Thanks,
Bruce

[Cliff R]

The 48 heads ended up being cracked so we used 295cfm CNC ported KRE heads. Despite having plenty of cam in it and just over 10 to 1 compression power was off some from similar builds we've done with flat top pistons and larger chamber heads.

530hp and 550ft lbs torque still make for a pretty formidable pump gas street engine, so I wouldn't stick my nose up at a dished piston combo with smaller combustion chamber heads on it if I ended up going that route to use up some parts I already had laying around or had to change the game plan after finding out my iron heads were cracked as with the engine mentioned above....etc............

[BB69judge]

Thanks cliff