Pontiac 6X Heads, Advice Needed (pontiac masters)

[72blackbird]

I was more referring to a stock long block 350P. To start with you're not really talking "shelf" pistons in a "good light weight forging." All I found was cast, not too surprised at that since it seems most "odd ball" engines are that way. This means you're on the hook for a few pistons if you ever need a replacement, and that you're looking at custom lead time too if you want forged not to mention the extra cost (which isn't horrid considering.) On the flip side though anyone ever rev the snot out of one of these using a set of cast slugs and decent rods?

One of the guys on Turbo Mustangs a long time ago was running low 11s/high 10s in a 3800lb car with a stock rebuild fully cast 455. It ran mid 10s using ARP rod bolts and prepped Armasteel rods. While I wouldn't expect the same results out of a 350, I wouldn't expect it to be a slouch either. If it puked it would simply be a matter of building a 400 up, throwing a slightly larger set of turbos on then letting it do what it does best except with better breathing and 50 more CID.

I'm curious why you would go through the trouble of installing an engine in your car along with turbos with the plan of making at least double or triple the factory output and not upgrade the internals in your 350P. Forged Pontiac rods are so cheap these days, and they go a long way towards keeping the engine from tossing a rod. And as far better breathing goes, just upgrade the stock 1.96 intake to a 2.07- that upgrade alone will make your small-valve heads flow just that much better. Upgrading to stainless valves will also keep you from sucking a valve and grenading the motor.

Upgraded 326's and 350P's seem to do well, even with cast pistons- with the addition of forged rods they will happily buzz to 6500 rpm. Whether or not you have the heads that will flow enough to make power at higher rpm is another matter (I guess the turbos will take care of that).

Geno

[paul s.]

I was more referring to a stock long block 350P. To start with you're not really talking "shelf" pistons in a "good light weight forging." All I found was cast, not too surprised at that since it seems most "odd ball" engines are that way. This means you're on the hook for a few pistons if you ever need a replacement, and that you're looking at custom lead time too if you want forged not to mention the extra cost (which isn't horrid considering.) On the flip side though anyone ever rev the snot out of one of these using a set of cast slugs and decent rods?

One of the guys on Turbo Mustangs a long time ago was running low 11s/high 10s in a 3800lb car with a stock rebuild fully cast 455. It ran mid 10s using ARP rod bolts and prepped Armasteel rods. While I wouldn't expect the same results out of a 350, I wouldn't expect it to be a slouch either. If it puked it would simply be a matter of building a 400 up, throwing a slightly larger set of turbos on then letting it do what it does best except with better breathing and 50 more CID.

Alrighty then.... I see where you are coming from.

Turbo charging, when done right, can make a guy look like a real hero by using barely adequate parts (when talking N/A), pressurizing the intake tract and not requiring much rpm.

As far as "reving the snot" out of a 350... not necessary. Remember, the Pontiac 350 is an internal combustion engine just like any other but it is NOT a 455 where you can make 450hp by 5,000 rpm while falling off of a log.

'Blackbird is right, I wouldn't worry about a slight flow deficiency, even with a smaller bore. Just open up the intake throat, put some lift into it and let the turbo do what it does.

Regarding a custom piston, there is a much smaller chance of grenading one of those than a cast one so the "wait time" for a replacement is pretty much a moot point... besides, there will be other problems if a piston lets go.

Just my opinion. Good luck with whatever you decide to do!

[Nicks67GTO]

Generally speaking, for anything under 400hp, why not go smaller? I could see a smaller, higher reving engine for a guy with a 1st gen 'bird and a 6 speed. No it wouldn't be the fastest, but it would be fun.

I agree if MORE output is the goal then more cubes are always a good idea. But for a good running, SOMEWHAT fuel efficient cruiser.... I say go for it with a smaller engine.

Simply because the power is so cheap, easy to make and readily available at absolutly no cost to driveability. In fact with the tq increase from CI increase it might make the car that much more driveable. There is no downside to a larger factory bore when comparing engines of the same stroke/rod length JMO. Regardless im happy the guy is staying with poncho power.

[paul s.]

Simply because the power is so cheap, easy to make and readily available at absolutly no cost to driveability. In fact with the tq increase from CI increase it might make the car that much more driveable. There is no downside to a larger factory bore when comparing engines of the same stroke/rod length JMO. Regardless im happy the guy is staying with poncho power.

Believe it or not, I understand what you are saying, but when we are talking about a mild 400 ci engine that puts out under 1hp/ci, then there will not be ANY torque advantage from the extra cubic inches. Torque is a function of displacement, VE, and compression so if you ignore VE and compression, displacement by itself can be underwhelming.

There is something else to consider: On a higher hp build, if you are cylinder head limited, those extra cubic inches will choke out alot sooner than a smaller engine.

Slightly different topic but it is definitely related: Have you seen some of the 600hp Pontiacs engines out there? Have you noticed a number of the larger displacement ones have vacuum pumps installed... on so-called STREET ENGINES?

It's not always because of thin ring packs...

I agree 100%, I too am glad he's staying with a Poncho!

[Nicks67GTO]

Believe it or not, I understand what you are saying, but when we are talking about a mild 400 ci engine that puts out under 1hp/ci, then there will not be ANY torque advantage from the extra cubic inches. Torque is a function of displacement, VE, and compression so if you ignore VE and compression, displacement by itself can be underwhelming.

There is something else to consider: On a higher hp build, if you are cylinder head limited, those extra cubic inches will choke out alot sooner than a smaller engine.

Slightly different topic but it is definitely related: Have you seen some of the 600hp Pontiacs engines out there? Have you noticed a number of the larger displacement ones have vacuum pumps installed... on so-called STREET ENGINES?

It's not always because of thin ring packs...

I agree 100%, I too am glad he's staying with a Poncho!

Enlighten me on the vacum pump thing. Im planning the standard 400 based 455, Kauffman 290's, old faithful, RPM, and forged assembly. Thats supposed to be good for 550hp and a broad, flat, 600tq I think. No need for a vacuum pump on that combo is there?

[paul s.]

Nah, you'll be fine. The builds I am referring to are bigger displacement utilizing heads with small cross sectional areas for the displacement and rpm.