[cobalt327]

Originally Posted by actmobmar

i pulled the head off the pass side, piston to deck is .006-.008, so block has been decked. there are no numbers on the pistons, i think they are kb hypereutectics? they have a dish w/ 2 valve reliefs. i am thinking about porting the heads and putting the engine back together- everything inside looks perfect. what do you guys think? i just have alot of money to spend on other parts of the car

Someone put some thought into the engine. The D-shaped dished pistons are the best type of dish to have- they optimize the quench effect.

The KB 346 piston has a D-shaped dish, 17cc volume. That piston volume, combined w/a 0.040" quench will get you the 9.5:1 CR you were told the engine had. Unfortunately, the KB piston has the ID on the side of the piston (shown below), so you'd need to pull a piston and rod to see.

The forged Icon KB p/n 891 is 14cc IIRC. It has an intake valve relief of:
.199” deep x 2.140” diameter. Exhaust relief is .201” x 1.830"

You can still use the same procedure used to CC the combustion chambers to see what the dish volume is, by using some grease around the outside diameter of the piston to keep the measuring fluid from seeping out. Then using a clear cover made from scrap plexiglass w/a couple holes in it (one to add fluid, the other hole to release the trapped air) or use an old CD w/the plating removed (the center hole is big enough so you don't need another hole) sealed to the block deck w/grease, you can add fluid using a graduated burette or a large syringe (get them from a pharmacy or vet.

It'll take a little math to subtract the volume above the piston at TDC from the dish volume, but it's not that hard to do. If you choose to go this route and want more info just ask.

[cobalt327]

Seeing as how this engine seems so far to be assembled correctly (no small deal!), check the ports real close to see if they've already been worked over.

One fairly quick/easy way to tell is to measure the port throat diameter right below the seat's last angle. See how close to 80% of the intake valve's diameter this area is (around 1.7" would be about 80%). That would indicate serious effort had been made, not just a brush w/a sanding roll to smooth things a little. This does require a valve be removed, obviously.

You can also look for evidence of the chamber being relieved to remove shrouding of the valve. Sometimes you will be able to see some scribing left from where the ports were gasket matched, as well as seeing how the gasket port opening compares to the head/intake port opening.

[actmobmar]

one thing that bothers me about the whole thing after studying it for awhile is the lack of a crosshatch in the cylinders, the motor maybe has an hour or 2 of run time, but yet no crosshatch? something doesn't make sense. i need to post pics of the combustion chamber, it is pretty thin(where the head gasket fire rings are) between the cylinders. i pulled an intake valve and see no evidence of porting there, but wonder if the chambers have been played with

[cobalt327]

That is odd that there's no crosshatch. Even honed w/400 grit, a cylinder will still show of c-h even after break-in. It might help to get a good light source in there and hold the light at a shallower angle to see the crosshatching better.

Is there any ridge at the top of the cylinders? I'd want to get a bore gauge on it to see if there's any taper and to get the bore diameter. Was there any smoking or fouling plugs, or any other signs of oil consumption (might be an optical illusion but the bottom piston looks pretty sooty)? If the cylinders were glazed or the hone too fine or nonexistent, the engine would be using more oil than it should.

Have the bores been chamfered (arrows)?


Below is a #48 chamber for comparison.

[actmobmar]

yes, they have. i cc'd the heads last nite and came up with 70 cc? also, i measured across the the bridge between 2 combustion chambers and came up w/ .256" across. look at the imprint of the fire rings on the head, doesn't seem like much sealing area, headgasket was a fel pro blue

[cobalt327]

You want about 0.030" between the chamber and fire ring. ATM I do not have a single Pontiac head to compare to your 0.256" measurement. Hard to judge by the photo. The photo shows a lot of oil is reaching the chambers, though.

On the chamfer, I should have said notches (arrows below), not the small taper right at the top of the bores to help the pistons and rings to fit. The notches I was asking about are there to help flow. If that's also what you meant, disregard this.

[actmobmar]

my engine has those. if you look close at the pic of the head the fire ring from the head gasket is barely touching the head between cylinders, and the ring is actually partially in the combustion chamber. why couldn't i go with a head gasket with a slightly larger bore size, as i would think it would make the rings larger in diameter and move it away from the edge of the chamber? here are some examples of felpro head gaskets PONTIAC 6.6L/400 Head Gaskets - SummitRacing.com

[Mr. P-Body]

Any "stock replacement" head gasket has the appropriate "reliefs" for the chamfers. We prefer the Victor/Reinz, but of course, Felpro is very popular. Unless static compression is over 12:1, there is no need for "special" head gaskets. Stock ones hold up fine. Just be certain you use the correct octane rating for the compression you have. You will have better service and good parts available at your local parts outlet. No need for "mail order". Pontiac parts are NOT rare. If they don't have them "on the shelf", they can get them in one day, as ALL the "big" warehouses stock them.

The chamfer in the block is to "unshroud" the intake valve. 396 and 351C also use the technique. The small loss of compression is far offset by the improved flow. In olden times, we would actually sleeve all the cylinders to rid them of the chamfer (for a "class" race car). Today, we make it a little wider... Due to the necessity of lower compression ratios for street engines in recent years, we've learned "flow trumps compression".

The 1/4" between the cylinders is no big deal. The aftermarket blocks, with their 4.350-4.4" bores, have nothing more to "leave", yet seal fine under "race" conditions. While it's true, the Pontiac has "only" ten head bolts, consider that those ten are 1/2", not 7/16", and they're located in the best possible locations. Note the center bolt on the lower row is "closer" to the middle of the block than the "outer" bolts. This is where the clamping force is necessary, and also what makes the Pontiac different from other engines using ten head bolts.

FWIW

Jim

[actmobmar]

i talked to butler yesterday and was advised against using the felpro gaskets, said the pattern was all wrong for the pontiacs, and he described it to a t. he offers his own line of gaskets w/ the correct pattern, but the victor may be a good way to go as well. i'm finding out the stroker kit will be around 2k for this engine, not the 1300-1500 advertised price, apparently i need custom dished psitons because of the head volume.

[69 widetrack]

Those guy's at Butler are fantastic...From the first time I spoke to one of the guy's, it was obvious that they knew their Pontiac's to a T. Anytime I've called they had the answer to any question I've ever had. Things might cost a bit more (machining etc) but I trust them and their judgement and that's worth the extra cost to me.

Did I say it right Uncle Dave...LOL.

Ray

[h0trod]

the Butler boys, hands down, are some of the most awesome and helpfull folk ive ever had the pleasure of dealing with.

if you really want a stroker kit, you can buy it piece by piece.
i have not completed my engine yet. however i have purchased a
Eagle 4.25" stroke rough machined for the pontiac 400.
6.800 Eagle forged H beams.
i went to butler to purchase my ross pistons (good gawd at the .030 clearence between the wrist pin and the oil ring)
ive spent around 1400 dollars so far however i do not have bearings and rings.
im a budget builder, so i had to do it this way. also the eagle crank is unfinished, so a reputable pontiac engine builder is a must.

the only part of ths post that i didnt like, in my unprofessional opinion, was the demon carburator! they make great oil lamps, but i wouldt use one on any of my yacks!
455 blocks are great for towing, but stick to the 400 if you ar going for power.

HEI distributors??? i dont trust those ICM's but the HEI makes a great shell for a MSD 6 AL

[69 widetrack]

Originally Posted by h0trod

the Butler boys, hands down, are some of the most awesome and helpfull folk ive ever had the pleasure of dealing with.

if you really want a stroker kit, you can buy it piece by piece.
i have not completed my engine yet. however i have purchased a
Eagle 4.25" stroke rough machined for the pontiac 400.
6.800 Eagle forged H beams.
i went to butler to purchase my ross pistons (good gawd at the .030 clearence between the wrist pin and the oil ring)
ive spent around 1400 dollars so far however i do not have bearings and rings.
im a budget builder, so i had to do it this way. also the eagle crank is unfinished, so a reputable pontiac engine builder is a must.

the only part of ths post that i didnt like, in my unprofessional opinion, was the demon carburator! they make great oil lamps, but i wouldt use one on any of my yacks!
455 blocks are great for towing, but stick to the 400 if you ar going for power.

HEI distributors??? i dont trust those ICM's but the HEI makes a great shell for a MSD 6 AL

I agree with much of what you say...especially the competence of the Butler boys. It does sound like your on a great Pontiac build and I was informed recently that they don't make Demon Carb's anymore...I'm a big fan of the Pontiac engines, I've had a few, even a 326 in the mid 70's that ran fairly strong. The 326 had a Holley 650 Carb and every Spring I'd get to replace the rotted out gaskets...I don't know if they've improved them over the years or if it was because the car was parked all Winter but my last Pontiac build was a 428, 30 over, ported heads, decent cam, balanced and Torker intake etc. ...running an 850 Demon. It ran like a champ...that was a few years ago and still haven't had to touch the inside of the Carb...maybe I got lucky...I don't know, but I was happy happy with the Demon.

Ray

[cobalt327]

Originally Posted by actmobmar

i talked to butler yesterday and was advised against using the felpro gaskets, said the pattern was all wrong for the pontiacs, and he described it to a t. he offers his own line of gaskets w/ the correct pattern, but the victor may be a good way to go as well. i'm finding out the stroker kit will be around 2k for this engine, not the 1300-1500 advertised price, apparently i need custom dished psitons because of the head volume.

A big X3 on the crew at Butler. Highly qualified and I've never felt like they were trying to "sell" me on anything I didn't actually need- they answer questions/state the facts and the rest is basically up to you.

[actmobmar]

super nice people at butler and very knowledgeable! i'll buy the head gaskets from butler and be done w/ that part of it. i'm still waiting on a couple of price quotes for the stroker kit. as far as your unmachined crank on the kit you put together, when you buy a normal kit i would assume everything is ready for assembly other then possibly balancing the whole thing? if that is the case it sounds like by the time you are done buying rings and bearings and having it machined you'll be at almost 2k$ plus?

[h0trod]

Originally Posted by actmobmar

as far as your unmachined crank on the kit you put together, when you buy a normal kit i would assume everything is ready for assembly other then possibly balancing the whole thing? if that is the case it sounds like by the time you are done buying rings and bearings and having it machined you'll be at almost 2k$ plus?

pretty much. so if you got the coin, spend it on a complete kit, less headaches.

however, i would not use the stock block.
the only reason i say that, is because thats a high dollar car,
always nice when the #'s matching is a virgin.