I thought the LQ4 and LQ9 blocks share the same heads...?

 

I have a question about the 72cc version of the LS6 style heads. Is the combustion chamber on the 72cc heads left alone or is it welded up like the smaller cc combustion chambers and then machined to 72cc?

The reason that I ask is that I would like a 72cc combustion chamber that is correct for a 3.9" bore instead of correct for a 4" bore.

 

I've been really happy with my PP 5.3 heads! Very nice people to do business with and order was shipped very quickly although I never got my free headgaskets and my subsequent calls never got them shipped either. For $1295 and no core charge I was pleased with the power I picked up. No problems after install and 5K miles. I'm making 416 rwhp thru cats with a baby cam by todays standards.

 

Thanks for the info and help. it looks like i'm going with the AFR 225 heads or the ap engineering. sofar AFR's are leading.

 

I'm going to do a few things different. Are you going to help me out?

 

i have 8000 miles on mime and lovem. great air and i ran 11.17 at 123mph on nittos!!!!!!!!!!!! i did all my mods myself except rebuild tranny and saved as ton i am sure those vette guys on the other board spend double what i did

 

thanks for the help. the AFR 225 heads sound good to me.

 

He's going to be another big player in the LS1 head world very soon. It's going to be big.

 

I'd like to know you plan on "doing a few things different." And if I'm off work/available I'm definitely willing to lend a hand, as always.

 

The key term here is "sound" good to me. You better wait for something other than a few shop cars to come out. I have no problem with AFR and have considered swapping my Patriots for the 225's, but with no real world tests out to date, it's hard to make a decision. I hope they are better than there LT-1 castings.

 

From what Craig at GTP was showing me about the heads, they should be awesome. He's super excited about working on them. We should have a pair on the G-Force Motorsports shop C5 in the next week.

 

I felt the same way untill i saw a dyno graph on a 1-1 swap AFR 205 VS LS6 head on a Z06 vette at LAPD.

Before swap 385rwhp dyno tuned run then 409rwhp dyno tuned run with AFR's. That showed me the potential of these heads. BTW I had LT1 AFR heads and was dissapointed, but LS1's are a different ballgame. Every company has a flop. Otherwise we wouldn't own any American car

 

I will be bolting on a set of 243's in a week. I wish i could find someone that would lend me a set of PP heads so we could see the dif. I know there will be a power dif but how much. I have heard lots of good things about PP and only a couple of bad but that was when they where getting started. I do think that most people look at peak flow numbers when buying heads. You need to look at the under the curve numbers. Yaa 300cfms is a lot in all but at .600 lift. I dont think the ls6 intake will flow that much. O and for the record i did not spend 2k plus for the heads. $1,200 with 918's and Ti retainers. I got them used.

Special #2 CNC Ported LS6 Heads
Once in a lifetime opportunity! Earlier this year we bought truckloads of bare LS6 cylinder heads for our engine customers and for our own R&D programs. What does this mean to you? A one-time special price on bare LS6 CNC ported heads. And here is the really cool part, we have not milled anything off of the deck surface so you can set the chamber size to your specification. A big plus for you LS1 guys who are trying to kill a little compression ratio or you just simply need a larger chamber for those big cubic inches.
These are fully CNC-ported new LS6 castings (243). The seat area is hand finished and they have a high performance valve-job. Wash and assemble! The valve seats are prepared for the stock LS1 valve sizes of 2.000” and 1.550” --- another big plus, because you can take your stock heads and just switch the components for bolt-on horsepower. No need to buy new valves, just match your valve springs to the camshaft, decide what chamber size you require, mill if necessary, lap the valves and assemble! Customers have reported a 30rwhp gain on stock ZO6’s with absolutely no other changes.
The combustion chambers are approximately 70cc with the stock GM valves. Larger valves can be installed, of course you will need to have the seats cut for the increased diameter, though we have not seen any gain on the stock bore with the combustion chamber remaining in this configuration when larger valves are installed.
For an additional $92.00, you can send us your valve train components and we will back-cut the intakes, lap the valves, set the spring heights, and assemble the heads for you. Completely painless! This price is for the stock diameter valves only and does not include any additional components or labor that might be required for proper assembly, i.e.; valve seals, shims, etc. Think about it – no core charge, new LS6 heads, CNC ported, use your stock valves --- it’s a no brainer! Don’t wait too long, ‘cause when their gone – they are long gone!
Flow Figures 0.100 0.200 0.300 0.400 0.500 0.550 0.600
Intake 66 140 210 255 291 304 307
Exhaust 55 112 163 213 218 222 225
SF1020 - 28”H2O, stock valve size 2.00/1.550, SDPC back-cut intake valve.

 

The 72cc chamber is the O.E. chamber. These are designed for the big bore motors. The largest chamber we have for the 3.9" bore is the 68cc chamber.
Of course, you can use the 72cc head with no problems. We have had customers with forced inductions use these on the small bore motors with great results!

 

Yep you just need to make sure you use the 6L gaskets

 

Thanks for the info. That's what I was looking for.

 

I thought that the small shelf (for lack of a better term) created at the top of the clyinder from using 6.0 heads was not an ideal situation from a quanch and air flow standpoint.

 

As I mentioned before, we have several guys that use the big cc head on the small bore motors, and all have been very pleased. The "small step" does not seem to disrupt the airflow.