Originally Posted by blakethechop
thanks for replies the car is for street and i would like to port heads myself could anyone give me what they would do with the 4x heads what pistons what gaskets how much to mill of heads would they reshape combustion chamber changing heads is not an option i am going to put an xe 268 comp cam and a edelbrock rpm intake 750 carb .would love some ideas
If the heads are from a 455, the chambers are too big. If it was me, I'd find a set of smaller chamber heads like the well known 6X-4 or 4X heads from a 400. I used a set of these on a 455 in a '81 Camaro and was very satisfied w/the results.
I didn't go w/the 1.77" exhaust, either. Stock valve sizes. Much is made of using the bigger exhaust valve, and that's fine if the budget allows. But my way of looking at it is, every penny you spend on a set of iron production heads is a penny better spent on a set of aftermarket heads. Not saying you cannot get good results from iron heads- but keep the expensive mods out of the picture.
The best results are sometimes the cheapest: owner bowl work and porting, careful attention to quench
, as well as other areas of the valve train
Cleaning up the bowls by removing the lip just below the last angle of the valve seat (see image below) will help as much as anything. The valve guides have to be right before doing the valve job. The guides, valve job (three angle, but do not be tempted to change the intake seat from 30 to 45 degrees), and milling the heads to help compression are the only things I would recommend outsourcing. Everything else you can do yourself.
Choose a head gasket to raise after
you've measured the piston deck height (as well as the actual combustion chamber volume) during the mock-up phase of the build.
Rods are bound to come up any time a performance Pontiac build is mentioned. If you have the budget, buy a set of forged rods for peace of mind if nothing else. But an iron head 455 is not going to make power past about 5200 unless you've done a lot of porting and have the cam to match. FWIW the stock cast iron rods are what I used- with ARP bolts and resizing- and they worked just fine. And according to Hand, he also thinks the cast iron rods are OK at that level.
From a recent post:
...(my 455/Camaro) was the tamest, easiest to drive anywhere, everyday, regular gas, 3.31 rear gear, 650 DP, all steel, full interior, 12 second vehicle you'd ever want to see.
I mean, how many cars w/those specs can stage in Drive, mat the gas from an idle and let the tranny shift out on its own (no governor work) and still run 12's on street tires? With a 10-bolt 3.08 run the same way (in Drive) it went 13 seconds flat in the quarter. Oh, and it had a 4777 Holley on a Performer intake (not the RPM, it hadn't come out yet). It was a ball.
The engine shifted out at about 4400 rpm by itself. For the best ET I shifted it at 5000 rpm.
Some Pontiac info:
• Pontiac engine info