[shoebox1.1]

“Bump the compression up to 10 to 1,
224/234/112
or even move up to a Crower 60243 (
228/235/112
) cam, add high ratio rockers, Rhoads lifters and guess what. It will idle with plenty of vacuum for power brakes, great street manners, but closer to 400-430hp. Ours actually made 424hp on the dyno and 465 ft lbs torque with umported heads. Vacuum at idle speed 12" at 750-800rpms.

So a 1 point bump in compression opens the door for a larger cam with less negatives and considerably more than a 4 percent power increase.......Cliff“

I’ll take door number three for 300 bob!....

[Jay S]

Originally Posted by ponjohn

And...how well did they dyno OR run at the track?

I'd rather exchange compression for head flow.

Hard to beat head flow.

Good running 454 for 8.2 scr. I have read that article before. Did good for what it was.

Just got the cam last week for that engine mentioned earlier Ponjon.. So I don’t know hp or e.t. yet. Shooting for around 530 hp with the ported stock intake, qjet and ra manifolds. 6x heads are 190cc. I don’t have final flow numbers yet though. Hoping it kind of keeps up with our 510 cid pump gas 69 Charger with 10.50 scr, ported cast iron heads and a big flat tappet mech cam. The Trans Am needs to come close to 11.50 to match my brothers et in the Charger. I think it has a shot. My brother and I have had the charger since 1988.

The dished icon with the 2802 or 60243 Crower looks like a good combo to me transam474. IMHO, no reason to do the flat tops unless the heads cc’s are larger than expected.

[Stan Weiss]

Originally Posted by Jay S

Hard to beat head flow.

Good running 454 for 8.2 scr. I have read that article before. Did good for what it was.

Just got the cam last week for that engine mentioned earlier Ponjon.. So I don’t know hp or e.t. yet. Shooting for around 530 hp with the ported stock intake, qjet and ra manifolds. 6x heads are 190cc. I don’t have final flow numbers yet though. Hoping it kind of keeps up with our 510 cid pump gas 69 Charger with 10.50 scr, ported cast iron heads and a big flat tappet mech cam. The Trans Am needs to come close to 11.50 to match my brothers et in the Charger. I think it has a shot. My brother and I have had the charger since 1988.

The dished icon with the 2802 or 60243 Crower looks like a good combo to me transam474. IMHO, no reason to do the flat tops unless the heads cc’s are larger than expected.

What is the max lift from the Summit 2802? How much of that head flow is above that max lift? After looking at the head flow numbers you might want a cam for more lift.

Stan

[TransAm 474]

The 2802 has .465"/.488" lift with a 1.5 rocker. The heads that will be used are the numbers matching #12 heads, and will be completely bone stock except for hardened exhaust seats, valve job, Crower 68404 springs, and Ferrea F5143/5144 stainless valves. We are thinking if this engine comes out in the 9.6-9.8-1 area, we will probably use either the Summit 2802 or the Crower 60916.

[Jay S]

Originally Posted by Stan Weiss

What is the max lift from the Summit 2802? How much of that head flow is above that max lift? After looking at the head flow numbers you might want a cam for more lift.

Stan

All the stock D ports we have had on our flow bench seemed to go turbulent at very close to .5. I have never flowed a 12. Only a 48 for the ra 3. Stan I noticed you had a ram air 3 head listed on your compiled head flows that had a little left after .5. Not sure what it is though, just says ra 3.

Stan has the best head flow compilation across brands I know of.

http://users.erols.com/srweiss/tablehdc.htm#Pontiac


The 2802 does look better with 1.65s. It would be a good candidate for 1.7 rockers too. Not sure how bad it needs them with stock heads. I am pretty sure Summit has the rating wrong, suppose to have 298/308 for the SAE rating, not 298/303, someone got a 8 and a 3 confused somewhere.

[Jay S]

Adding 12 degrees to the crower advertised ratings will get you close to the SAE numbers if you want to compare the crowers to the 2802. The advertised 2802 numbers summit lists are generally numbers someone in sales picked to sell more cams. IRC, subtract 14 degrees on the 2802 SAE numbers to get to Crowers rating at .006. Summit is a lazier cam.

Looks like you have the right idea. See where the compression lands and pick a cam from there.

[TransAm 474]

Ok guys, I recieved my CC'ing kit today, and even though I haven't had the heads rebuilt with hardened exhaust seats and a valve job yet, I played with them this evening, and put our new Ferrea valves in them and checked them 3 different times. The first time came out at 70cc, the second time came out at 69.5cc, the third time it came out at 70.5cc, so I am gonna call them 70cc. Now like I mentioned earlier, this is before the heads are rebuilt, but I was just curious what they measured. Calculating Compression with the 14cc Icon piston, .039" gasket, Zero decked, it comes out 9.82-1. I feel that it will be much more managable for pump gas than the Flat Tops 10.6-1. If may come out even a hair less than than that if the heads gain a couple cc after being rebuilt?

What do you all think? Would you feel safe?

[pastry_chef]

Originally Posted by TransAm 474

it comes out 9.82-1.

Good.

[MUSLCAH]

I have the original motor and tranny and rear end in my 67 GTO..670 heads ..matching intake and a 1969 Service carb...Q -Jet.....just put 93 octane in it....no problem.

[TransAm 474]

Just as a side not, I used the Diamond Pistons Compression Calculator....

[chiphead]

I like that calculator. It even accounts for top ring land volume, which adds about 1 to 1.5 CC to piston dish size.

[TransAm 474]

So... Y'all think 9.8 compression will work out good for this on pump gas? If so, which camshaft for this compression? Crower 60916 or Summit 2802? The look on paper, it seems the 2802 would make it even more pump gas tolerant, do too its later Intake Closing, but it may be a bit more soggy down low in normal driving conditions over the Crower 60916, but then again, even the specs of the 2802 doesnt really look that big for a 400 CI motor with it's 114 LSA.

[John Milner]

Originally Posted by TransAm 474

So... Y'all think 9.8 compression will work out good for this on pump gas? If so, which camshaft for this compression? Crower 60916 or Summit 2802? The look on paper, it seems the 2802 would make it even more pump gas tolerant, do too its later Intake Closing, but it may be a bit more soggy down low in normal driving conditions over the Crower 60916, but then again, even the specs of the 2802 doesnt really look that big for a 400 CI motor with it's 114 LSA.

I ran that same exact combination once. It was a 400, 62 heads and a 2802 cam. It never overheated, never pinged and ran fine on 91 octane. The engine really pulled hard too.

[Formulas]

I ran a cam very similar to the 2802 in a otherwise stock 1968 GTO 400 TH400 3.08 gear it was noticeably softer just off idle than the original 067 camshaft but it was so much more fun everywhere else

[Jay S]

Personally I would rather tune the 2802 than the 60916 at that 9.8 compression. Mid nines I would rather work with the 60916.

The 2802 with the wider lsa and 4-5 degrees of advance is a pretty nice combo with ra manifolds. The bigger exhuast spread with that size of cam usually means the cam needs a couple more degrees of advance. The extra advance the 2802 needs cancels out some of the dynamic compression differences between those two cams. The much earlier exhaust opening from the advance spreads the power out more on the 2802. Which makes it easier to tune at 9.8, also has some advantage with exh manifolds, IMO.

[unruhjonny]

Originally Posted by John Milner

I ran that same exact combination once. It was a 400, 62 heads and a 2802 cam. It never overheated, never pinged and ran fine on 91 octane. The engine really pulled hard too.

keep in mind, your heads had larger combustion chambers.

[TransAm 474]

Thanks guys, I assume the centered pins, instead of offset, in the aftermarket pistons wont present any problems? I noticed most all aftermaeket piston pins are centered.

[Jay S]

Originally Posted by TransAm 474

Thanks guys, I assume the centered pins, instead of offset, in the aftermarket pistons wont present any problems? I noticed most all aftermaeket piston pins are centered.

It is fine. IRC, It actually increases the piston velocity some at tdc and helps the quench speed. More quench velocity is a good attribute. So is less contours on the piston top compared the the 4vr oems. FWIW, being that this is the high compression thread, our 510 cid 10.5 iron head engine I run on pump gas has flat tops with no valve reliefs and a small dish. The solid cam iron headed Pontiac we pushed compression on had oem forged piston reverse hung with the crank offset ground with a really tight quench. It was 10.4:1. It it probably had a higher piston velocity for the quench than an normal oem.

OEM’s do the offset to quiet down the engine noise some and moves the biggest forces past TDC slightly. It changes the dwell some as the piston is coming up on top dead center, moves the largest forces on the rod and crank over so the piston has more leverage on the crank. Seen different opinions on what it does with friction for what the engine is being used for.

The 2618 alloy of the icons takes more pistons to wall clearance. Engine will be noiser when cold than an oem forged or a forged 4340 alloy. 4340 (hope I have the number right) is a better alloy for your project imo. Builders run the icons all the time for projects like this though. They do have the best quench with out a lot of decking. Autotec can move the piston comp height in a 4340 alloy, so can Ross. More money though, can only say we did it.

I have built a couple engines that we reverse hung the oem pistons. Years back, was supposedly good for a couple horsepower and make pitch of the exhuast higher and louder. Lol, trying to intimidate the competition. I do not recall it changing much of anything though.

Better experts on here for piston than me, if I missed something somewhere feel free folks, correct it..

[Stan Weiss]

What the offset does it make it so the piston and the crank rod journal are not at TDC at the same time. On a 400 ci Pontiac with 0.06" offset it is about 1/2 degree difference.

Stan

[TransAm 474]

Thanks guys, y'all have been a big help, and I'm sure I will have more questions along the way. We are going to go ahead and go with the Icon IC891-030 pistons, and "probably" the Summit 2802 camshaft. I definitely want to use the camshaft that makes it more pump gas tolerant for sure, which sounds like the 2802 is, but I also want to be careful not to cam it so that it loses low end and makes it feel mushy. Looking at the specs of the 2802, I wouldn't really think that would be a problem, as we have ran bigger cams in 383 sbc's with great results.