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I would say that part of me regrets opening up the entire motor $$$$ and the other doesn't, as I want to put this motor in and not touch it again.
Would milled 823 heads plus right gasket get me to that 10.5:1 range and be a better head than the stock 706?
The extra cost with switching from cathedral to rectangular is just really starting to add up. I do not have the offset rockers yet, I've been told by many local guys that while i'm doing that I might as well do the bronze trunion kit in them. I'm just starting to question if all that extra money is worth the power difference in this motor combo?
Clean them up, put decent valve springs and new valve seals in them and send it. I wouldn't even waste my time lapping the valves. In the future, you can get them CNC ported with a 7 angle super radiused valve job for more power.
Well after doing some research is the 706 castech head a problem to worry about is it just random what years have them. Would 862s be better or if you can find a set that is not cracked just go with it. I want to run these on a 6.0 with a cam
Well after doing some research is the 706 castech head a problem to worry about is it just random what years have them. Would 862s be better or if you can find a set that is not cracked just go with it. I want to run these on a 6.0 with a cam
Some heads had a problem leaking coolant, most didn't. There was a recall so many of the bad ones were replaced by their original owners under warranty, I doubt there are many "bad" 706 heads left
stockA4 I believe i remember reading a thread of yours a few years ago, you were delivering pizzas in that camaro correct? your build was one of the first to start pushing me more towards a torque instead of peak power build! still may do an eagle 10.7:1ish 402 inside the otherwise stock lq4 and be well aware i have power on the table, but i think for the time being a truck cam and some more compression will be alright.
Ive also wondered about whether the castech issue is as prevalent as the internet makes it out to be....as to the recalls thats interesting because castechs sometimes have that battery looking symbol but ive seen what looks like a "CT" or more looking like "CJ" in the same spot... wonder if theres a correlation to replacements or?
Here is a picture of the different casting logos on the 706 heads. Not all of them crack and it is possible for the 862 castings to crack as well. None of this stuff is low mileage any more so I would suggest having them pressure checked any way.
706 with Castech Battery logo
706 Non Castech Logo
Last edited by 1FastBrick; 05-28-2021 at 08:32 PM.
I THINK only the top pic with the "battery" casting mark are the Castech heads.
Not all 706's are Castech, and not all Castech heads crack.
Just a LOT of them....
I THINK only the top pic with the "battery" casting mark are the Castech heads.
Not all 706's are Castech, and not all Castech heads crack.
Just a LOT of them....
Yes, the battery logo is the Castech casting logo. The other one is cast at a different foundry.
706 chamber on top, 317 chamber on the bottom 706 head, The chamber on the left has a 2-in valve just stuck in it
I tried the heads completely stock with the stock sized 1.89" valves on a 4.0662" bore after mocking this up and thinking, How bad could it be? lol
An inexpensive option is T.E.A.'s competition valve job. Coupled with a 2.040 intake valve, they go fairly deep into the venturi area and can swap the springs over and whack the heads .030 while you're at it. These changes can provide 80% of the gains of a full cnc'd stock casting head at a considerable savings.
We believe there are several options. Valve job is the most basic with steep bottom angle. Then Bowl Hog which is sending a tool in there vertically below the valve jobs bottom angle...but still not hand blended. Then finally a bit of a bowl blend. They do it all! We can check and get current pricing perhaps.
Talking 6.0s here I never understand the conversation between 706 862 and 243 799 heads.
Take the PRC 2.5 5.3 head or similar work. Folks are often recommending taking a 706 factory casting and porting it out and adding larger intake valves. So the larger valve is going to negate any of the benefit of the lighter weight 1.89 valve and this will also do away with any of the coefficient of discharge conversation.
If an aftermarket ported 5.3 head flows equal to or more than a 243 Casting and has similar size and weight valves, then mainly what is left is the compression. So in that regard wouldn’t a 243 head milled to have a 61.5 combustion chamber (ptv aside for now) perform better than any stock 706 head (on a 4.0 bore) and more so towards that of a high end aftermarket ported 706? Not talkin every last ounce of power but say in increments rounded to the nearest 10 whp.
Is it that the factory runners and valves of the 706 are better at lower rpm torque, but then once prc’ed become again more inline with a 243 albeit higher compression?
Though a lot of us have read the hotrod articles and seen the holdener videos it seems most times when people post of a 6.0 with 706 heads and a 22x cam theyre in the 325 rwhp area while when you look at LS2 243 or aftermarket head guys with similar boltons theyre often around 400 rwhp.... 243 used prices have come down and 706 prices have ticked up closing the gap.... thoughts!?
Definitely like quick response down low but I don't want to be ran down on the big end because I lack the HP though. If cathedral heads and runners would have been the cats meow on a 4.065 bore then the engineers would have made a bigger/better cathedral intake and cylinder head but they didn't. This topic has got me curios to know how a FAST92 intake for 243/799's would perform over a stock LS3 intake and heads with a NW92 on a 4.03 bore utilizing the same camshaft 238/246 .633SL 111+3 with a 4500 stall and 4.30 gear?
Definitely like quick response down low but I don't want to be ran down on the big end because I lack the HP though. If cathedral heads and runners would have been the cats meow on a 4.065 bore then the engineers would have made a bigger/better cathedral intake and cylinder head but they didn't. This topic has got me curios to know how a FAST92 intake for 243/799's would perform over a stock LS3 intake and heads with a NW92 on a 4.03 bore utilizing the same camshaft 238/246 .633SL 111+3 with a 4500 stall and 4.30 gear?
Most comparo's that I've seen show the cathedral port benefits are with throttle response, and power below 4000 rpm or so. With your converter, I don't know how much of that would really matter.
The 4500 stall is for an LS3 top end but you can toss that out of the equation if you go with manual trans. I'm thinking the LS3 top end would make more across the board on an engine dyno but perhaps not.
05-27-2021, 08:52 PM
