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9.7K views 11 replies 9 participants last post by  SDDL-UP  
#1 ·
I'm in the process of building a Pontiac 400 +.030 with a TRW forged flat top piston. I'm looking for a decent performance OEM Pontiac head. I'm confused with all the dam casting part numbers. Some heads come with small and large valves. Press or screw in rocker studs and different chamber volumes. Do all OEM Pontiac heads share the same port volumes and shapes? What is considered the Best all around head-casting number to use? The Ram-Air stuff is out of the question. I can do the grinding-porting and valve job myself. So, what do you Guys recommend, casting number, valve job, bowl percentages, valve job angles 30 deg or change to a 45, etc?

Thanks for looking,
 
#4 ·
I would look at 48, 62, 12 or 13 casting #'s. Those heads are about 72 cc's, screw in studs, nice preforming d port heads. All but the 62 were on RA 3 motors, so they bring alittle bit more money. Just change out the valves to some decent stainless with longer RA 4 length for more lift, and a good cleanup , stock valve job , should be good to go. You could always call Butler or Kauffman to get info also, they are good people.
 
#7 ·
Ron,

What are your goals? HP? RPM? CR? A lot depends on how much power you want to make and what fuel you run.

Pontiac did pretty much all of their CR in the head using flat top pistons... so depending on the CR you need or want that will inform your decision. It also changes how you port the head as the short turn is radically different in a run of the mill 72cc D-port head vs the 6X series which can be made to flow better at high lifts but needs a dome piston to get any CR in a 400.

In any case, using a more cost effective D-port like the 62 (which essentially has the same ports as a RAIII and can make good power) be prepared to eat a lot of iron. There is a ton of metal to remove unless your goals are very modest... hence the questions.

Valve angle depends on the cam lift and the head chosen. Pontiac used a 30° seat due to the flat machined chamber, it flows better at low lifts and was designed around .400" lift. Basically you have to be a bit careful on the heads with deep chambers if you get a 45° seat too low it can hurt until the very high lifts.

As far as TRW flat top factory replacement pistons, they aren't that heavy if you put a proper pin in them. I've gone 10.65 @ 125 @ 3400# (455 +.030) with the Sealed Power version (same piston) from 40 years ago... hooked to cast rods even ;)
Of course there are way better pistons out there if the budget allows.

All depends on the goals.
 
#9 · (Edited)
69 Judge said:
Ron,

What are your goals? HP? RPM? CR? A lot depends on how much power you want to make and what fuel you run.

Pontiac did pretty much all of their CR in the head using flat top pistons... so depending on the CR you need or want that will inform your decision. It also changes how you port the head as the short turn is radically different in a run of the mill 72cc D-port head vs the 6X series which can be made to flow better at high lifts but needs a dome piston to get any CR in a 400.

In any case, using a more cost effective D-port like the 62 (which essentially has the same ports as a RAIII and can make good power) be prepared to eat a lot of iron. There is a ton of metal to remove unless your goals are very modest... hence the questions.

Valve angle depends on the cam lift and the head chosen. Pontiac used a 30° seat due to the flat machined chamber, it flows better at low lifts and was designed around .400" lift. Basically you have to be a bit careful on the heads with deep chambers if you get a 45° seat too low it can hurt until the very high lifts.

As far as TRW flat top factory replacement pistons, they aren't that heavy if you put a proper pin in them. I've gone 10.65 @ 125 @ 3400# (455 +.030) with the Sealed Power version (same piston) from 40 years ago... hooked to cast rods even ;)
Of course there are way better pistons out there if the budget allows.

All depends on the goals.
Click to expand...
69 Judge,

Thanks for the reply and Great info. I will start with my goals. I'm Not building a all out drag race engine. I want to assemble a Good Street/Strip engine that can possible make around 500 to 550 HP @ 5800 to 6000 rpm or less. This short block has the TRW piston L-2262-F .030. The piston to deck is around .023. This block has never been decked. I'm thinking I want .005 in the hole. I would like to keep the compression ratio around 10.0 No more than 10.5 using pump premium fuel. The connecting rods are Pontiac re-sized with a ARP rod bolt. Factory cast .010/.010 crank.

One Member mentioned that the TRW piston & pin is heavy. Everything I see in comparison weight wise. They are almost the same weight as factory + or - a couple of grams.

Getting back to cylinder head discussion. I have worked on a set of 6X -8 heads. Oh my God what a casting mess. I never seen a factory GM head casted so poorly. Their was so much casting flash-slag in both the intake & exhaust ports. How in the Hell did this engine run. Talk about port choke. So, the only experience I have with the Pontiac head is the 6X casting. You sound like you been around a Pontiac head more than once. What are the suggested porting mods? Valve seats angles, bowl percentages, etc? As you commented valve lift dictates valve angles. So, is safe to say that all D port heads, 670, 62, 48 have the same port shape? Are the intake ports similar? Intake wise, what would you suggest for this kind of build?

Cam wise, I have considered a hydraulic roller cam. But haven't picked-bought a cam yet.

Thanks again for your reply and information, (y)

Ron
 
T
#11 ·
500 out of a 400 will be a chore.The rods won’t be up to the task,you will need 250-260 Flo on the heads and will need a lot of cam that won’t be very street friendly.Might look into a stroker rotating assm.500 out of 455s is pretty EZ.I would not waste porting money on iron heads,gets set ofKRE D ports.Speed costs money,how fast do you want to go?Tom
 
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