what the heads are made of makes absoulutly no difference at all. i thought weve been thru this

 

OK, lern me sump'n... Why not?

 

Ferrea have a web site ??

 

Really? Tell us why. Im all

 

http://www.ferrea.com/

 

cast iron heads can make MORE power than aluminum heads because cast can retain heat better than aluminum, which dissipates the heat. the more heat in the chamber, means higher potential power. the ONLY gain you get from aluminum is wieght savings over the cast and maybe easier porting. the higher compression issue is debateable. ive heard both sides of the story. and i have built many a engine with cast heads and high compression and have NEVER had a pinging issue other than a timing/ cheap gas issue. so other than the massive wieght saving, your not gaining anything, but are actually losing some power potential. which means nothing because youve gained all the wieght with the cast head. IMHO and the experience i have, the pysical material that a head is made of makes little or no difference. inside a combustion chamber, that flame has NO idea what material it is being squished against. then you can get into other issues w/aluminum like gasket failure due to expansion rates, overheating and cracking failures, headbolt torque loss. electrolosis of the different metals.

 

And that is why you can run about a full point higher on DCR with aluminum than cast before you run into detonation issues.

 

never had an issue. i think this is rumor started so they can sell more aluminum heads. hell, old cars came with that much comp. stock! they didnt seem to have a problem either....hmmmm

 

yes, those old cars did have high compression engines...
but they also had lead in their fuel.


I've heard this debate before..... iron heads can make similar/better power, but need a higher octane fuel to prevent detonation.

 

Those old higher compression iron head engines had higher octane back in the day they were being produced. Citing them isn't pertinent to today's situation.

Besides, of any two equally prepared, equally powered C3's, the one with aluminum heads is always going to corner better and get to the other end of the straightaway first due to the roughly 75 lb. advantage. So it kinda makes this debate moot.

 

http://www.holley.com/60212.asp This might be something you would consider. It is for 9.75 or higher compression, 3.70 gears and could be custom ground on a 112 LSA and should keep you out of detonation. Your big block will have plenty of low end torque and this cam is done at 5800 RPM. It is a little bigger but should be very streetable with 3.70 gears and a 4 speed. Here is another Lunati. More duration, Less lift. 114 LSA It says EFI but not nessesary. http://www.holley.com/50268.asp These have a cam card that will help you determine DCR.

 

Thanx 63mako I checked out those two cams and I like the looks of the second one with the little lower lift.

Upon further searching and reading I have found a custom ground cam with 218/224 @.050 with a 112 lsa and lift of .605in/.600ex. Recommended Beehive springs. I'm concerned that this will be too much lift for the pistons. What think you? TIA

shmoky

 

That won't have enough duration. The lift shouldn't be an issue. CHECK DCR ON ANY CAM YOU ARE CONSIDERING!! The 454 has low end grunt. Really check out that second lunati. The working RPM looks good for your gearing and as you notice the working RPM range is wider! More LSA does that, flatter torque curve. Don't want to go bigger on LSA though I has bigger duration numbers but I think you might need that with your compression. You might want to start a thread and ask for someone to run DCR numbers for you on these. My computer won't download the DCR calculator.

 

I can run it on empirenet's calculator. Stand by and let me check to see if all of the numbers to plug in are here...



edit - Better give me the specs all in one place so I've got it right. I'll need advertised (seat timing) duration, sinse this calc doesn't extrapolate from @ .050" data, and installed ICA or installed advance. Engine specs needed are bore, stroke, rod length, head cc, gasket thickness, gasket dia, deck height, and piston dome/dish volume.

 

Skunkworks I have all the #'s except the deck height. When I get it from my engine builder I will post everything or start a new post.



shmoky

 

I'll check for your post...

BTW, with all the cam talk over the past month or so, I did some more modeling on my 496 and I've decided to change my own specs recently - different firing order and going one step larger down both the intake and exhaust lobe charts. Now it's so close to 2008 that I'm waiting to see if any new profiles come out that may interest me.

 

Okay here goes. Let me know if any #'s don't make sense or if you need anything else.

Adv. dur. 282/290
dur. @.050 231/239
LSA 110* ICA 106*
link to cam specs http://static.summitracing.com/globa.../lun-60212.pdf

Engine Specs.
bore: 4.2817
Stroke: 4.00
rod length: 6.135
Head cc: 104
gasket thickness: .040 compressed? (FelPro)
gasket dia: .4370
deck height: .025 (guestimate)
Piston head volume -13.80cc

Hope these are the numbers you need.

shmoky

PS here's another cam
http://www.holley.com/data/Products/Technical/50268.pdf

 

I figure the actual intake closing point @ 67 degrees abdc on the first cam and 73 degrees abdc on the second cam. First cam has a faster ramp rate. If you go with the above specs .025 deck and .040 gasket your quench is a pretty sucky .065. Zero deck with that gasket or leave the deck cut there and go with the .015 shim gasket to get ,040 quench.

 

Sorry I haven't looked at this before now, but family time has taken priority the last few days during Thanksgiving.

Anyway, without beating around the bush, I'm not going to start advocating lousy quench clearances for even the mildest of perf engines, so let's skip those scenarios as moot.

If your current CR is 10.3:1, bringing the quench down to .040 - .045" is going to raise your CR to between about 10.75 - 10.85:1. With the Lunati 282 installed at 106* ICA or even retarded to 110* (straight up), the resulting DCR's (in the 8.5:1 range) are much higher than I recommend for your combo on pump gas.

Installing a cam with more duration which closes at 73* ABDC would yield a DCR of between about 8:1 - 8.15:1. That sitll leaves you a bit higher than I'd personally be comfortable with, given the iron heads, w/o assurances from a real expert. And, keep in mind that longer duration valve timing increases the likelihood you could encounter streetability issues, and that as you shift the power band upwards cylinder pressures at higher rpm's can increase significantly. Suggest 112* LSA, if not wider, should you head this direction.

IMHO, on the street with those heads you need to reduce that static CR by decreasing piston dome volume and/or increasing combustion chamber volume, correcting the quench in any event. Kind of a pickle... BTW, a set of aluminum heads with 110cc chambers (i.e.: Edelbrock Performer RPM 454-O's) would actually put your DCR's on the low side with that 282 stick, and if you can swing a set you'd be looking to earlier IVC timing, bigger domes or some milling to get it back up. (10.25 - 10.5:1 would look to be about golden with those heads and that cam.) That's the safer side of this curve to be on.

I know it's not all good news, but FWIW I hope it helps you get your build optimized.

Charlie

 

If you are @ 10.3 actual comp and .040 quench looks like this cam http://www.holley.com/data/Products/Technical/50268.pdf which has an intake closing point of 73 degrees ABDC and an LSA of 114 is a great choice. Bigger quench or higher compression makes you have to move up in duration to maintain correct DCR. The above cam will be very streetable with your drivetrain and a 454 but looks like you have 2 options to attain that. Different pistons or different heads. Don't go with more quench to drop compression. The other way to go is more duration which will affect streetability although with your setup you might be able to go 1 step bigger and still be happy with streetability. Go back to the drawing board. Those heads are originally 109 CC. Have they been surfaced .030?. In stock configuration they would be alright with your setup.