[ponyakr]

This pic was just posted on another forum. It's of a '75 350 block which came with 5c-4 heads. Even tho it had 2.11 intake & 1.66 exhaust valves, the factory cyl chamfers are on the exhaust valve side only.

The '69 350HO had 2.11 intake valves & did have chamfers on the intake side.

Anybody know why the later big valve blocks didn't have 'em on the intake valve side, and/or why they do have 'em on the exhaust side, even tho 1.66 valves were used & the cam was very small ?

[Formulas]

My guess would be since valve reliefs are gone it was to achieve a desired compression with a multi use 400 head and perhaps the exhaust was retained for emissions

[PRC]

I seem to recall that there was an article in HIgh Performance Pontiac magazine about a 350 build. I think it was done by Racecrafters in Lancaster, PA. It was installed in a 1st gen. Firebird. I don't remember if it was a stroker or not. I searched for that article but could not find it online. My guess is that this was about 15 years ago. Anyone else remember that?

[STEELCITYFIREBIRD]

I have a 76 and had a 77 400...neither had ANY valve chamfers in the bores. The 76 is a 75 casting date.
Also the #48 Heads I am using on my 400 I 'believe' are from a 350HO.
Any way to positively ID them as such??

[ponyakr]

Originally Posted by STEELCITYFIREBIRD

I have a 76 and had a 77 400...neither had ANY valve chamfers in the bores. The 76 is a 75 casting date.
Also the #48 Heads I am using on my 400 I 'believe' are from a 350HO.
Any way to positively ID them as such??

Your '76 was a 350 ? Don't think the late model 400's would have needed any chamfers, near as much as 350's, due to the larger bore size of the 400.

I have a '77 350, but haven't taken the heads off yet.

Don't know of any way to ID 350HO heads. Some sites list 'em with smaller chambers. But obviously, 400 heads could have been machined down, at some point.

[Jays76bird]

Thought I would revive the old thread. So no one ever built a stroked 350 on here from I gathered. I have been told it would be a waste of time due to the small bore of the 350 Pontiac. I do have a set of Probe forged pistons identical to the ones Ace Brewer used. Just wonder if there is any value to rounding up a 4 inch crank and trying this ? I have a 76 Bird and was planning on 3:23 gear with a TH350. I have a set of #16 heads with the 2.11s. Other than Steve Magnate's original 2007 article there ain't squat about anyone building one of these 383 Pontiac's. A Google search you end up with basically 383 Chevy's someone stuck in a Pontiac.

[Sirrotica]

Tom S, has built a 383 from a 3.75 crank in a 301 block, comes out to 383 cubes. I believe it dynoed at 475 HP. I realize this isn't what you have planned, but he's done it once, and is currently building another one, The way Tom has done it is closer to how they arrive at a 383 chevy, but uses Pontiac parts.

Link to 301 stroker build: https://forums.maxperformanceinc.com...d.php?t=710524

Link to current 301 stroker build:

https://forums.maxperformanceinc.com...17#post6148917

[tom s]

Im in the planning stage right now if I get a block i have been stalking to build a 4X4 RA V.Tom

[Baron Von Zeppelin]

They have all been great builds Tom
4.00 by 4.00 sounds like a Really good one to go for next.
Best wishes and Good luck to you.

[Baron Von Zeppelin]

Originally Posted by Jays76bird

I do have a set of Probe forged pistons identical to the ones Ace Brewer used. ...
... building one of these 383 Pontiac's.

Sounds like you have the main ingredients in hand , being those are the parts that cause the most expenditure - that most want to avoid in the "down-sizing" department.

Shame to see these 350 blocks wasted, but a lot of guys can grab a 400 shortblock/complete engine for less than the "upgrade/downgrade" conversion of a 350 - and be 17cid ahead from the go - plus overbore cid.

If you don't have that good of a cost option on another 400 shortblock - i would definitely do the 383 Stroker.
Chrysler did good with that number (383), and its pretty close to 389cid.
It will have to make good power even if just built to Ram3'ish type specs.

Keep us posted if you do it

76 Bird and was planning on 3:23 gear with a TH350. I have a set of #16 heads with the 2.11s.

I do know for sure a 400 with #16 Heads - with TH350 and 3.23 will make those cars scoot and a lot more fun to drive.
The 383 will likely be just as much Night&Day difference from a 76 350cid/350thm 2.73 - as most were born.
We did a 76 Formula that started life as a 350-2bbl Auto 2.73 , it made it into like driving a 70 T/A

[ponyakr]

It's my casual observation that every time a question is asked about building a 350 Pontiac, there are ALWAYS lots of guys telling the OP to forget the 350 & use a 400, 428, or 455 block.

I suppose it mostly depends on how much low rpm torque you insist on. 500 @ 3000-3500 is real easy with a very mild 455. Would take a pretty strong 350 to make 500, at any rpm.

BUT, if you can live with less low rpm torque, & reasonable horsepower, a 350 can be a real nice engine.

I just can't help it. Every time this comes up, I immediately think of all the quick low compression 350 Pontiac drag cars. Lots of '74 Vents have been record holders, thru the years, & there is still one that runs real low 11's, in legal Stock Elim form. Then there are the '74 & '77 Super Stockers that have run mid 10's.

With high compression, member Adam Strang has run high 10's with his 350 powered '68 Bird Stocker. My Pontiac friend won LOTS of dirt races against some pretty stout 350 sbc powered cars.

And all these were with the 3.75" or slightly larger stroke crank. So, with a 4" stroke & reasonable pump gas CR, a nice 350 block stroker can be built, IMO.

But, I realize that in this modern era, horsepower in the 400's is just not deemed enuff for a respectable street car. Hey, I'm just old school. Well, I reckin now I'm just old.

[Jays76bird]

Originally Posted by ponyakr

It's my casual observation that every time a question is asked about building a 350 Pontiac, there are ALWAYS lots of guys telling the OP to forget the 350 & use a 400, 428, or 455 block.

I suppose it mostly depends on how much low rpm torque you insist on. 500 @ 3000-3500 is real easy with a very mild 455. Would take a pretty strong 350 to make 500, at any rpm.

BUT, if you can live with less low rpm torque, & reasonable horsepower, a 350 can be a real nice engine.

I just can't help it. Every time this comes up, I immediately think of all the quick low compression 350 Pontiac drag cars. Lots of '74 Vents have been record holders, thru the years, & there is still one that runs real low 11's, in legal Stock Elim form. Then there are the '74 & '77 Super Stockers that have run mid 10's.

With high compression, member Adam Strang has run high 10's with his 350 powered '68 Bird Stocker. My Pontiac friend won LOTS of dirt races against some pretty stout 350 sbc powered cars.

And all these were with the 3.75" or slightly larger stroke crank. So, with a 4" stroke & reasonable pump gas CR, a nice 350 block stroker can be built, IMO.

But, I realize that in this modern era, horsepower in the 400's is just not deemed enuff for a respectable street car. Hey, I'm just old school. Well, I reckin now I'm just old.

Actually Don a lot of your old post have come up when researching the Pontiac 350. The 350 I have is a 74 block and came with the car, I know the 350 can run, my cousin ran a 70 LeMans with a 350 in circle track and did well with it. I don't want to put a 400 or 455 in the car. Just don't know if it is worthe the added expense to by the 4 inch crank. I already have the pistons and the rods I would replace anyway.

[maxpowerta]

Originally Posted by ponyakr

http://forums.maxperformanceinc.com/...17&postcount=8

From the info posted in that thread, it appears that we MIGHT could say that MOST '68-'74 350's had double chamfers. Has anybody here seen a '68-'74 350 block with none or only 1 ?

One guy posted that he knows of 1 block that didn't have any.

So, has anybody else seen one from ANY year that had none or 1 ? If so, do you know what year or at least the casting number.

"... I believe the chamfers were there to unshroud the valves, not for valve deck clearance since Pontiac used a flattop no valve relief piston in the 350 that would have hit the valve before the valve hit the deck. The unshrouding may not have been needed in the later blocks with deep chamber heads and eliminated when the casting changed in 1975-76..."

I'm trying to think about this. Ya'll help me here. When the valves are fully open, the pistons are not at TDC, therefore would logically hit the deck(if any part of the valve would contact the block on the way down) before they could possibly hit the pistons. I assume the valve reliefs are need mostly for larger, longer duration cams, which might have the valves open a bit more at TDC or very near TDC.

I suppose that's why engines with really big, long duration cams need deeper reliefs.

I think the no relief pistons began in '74. All '74 350 heads had small intake & exhaust valves, and the deeper chambers, actually slightly larger than the 6x-4 head chambers used in the last 350's. At least that's what this Wallace info says. The biggest cam used that year was an 066, in the GTO. All others were smaller.

http://wallaceracing.com/head1.htm

But, a guy posted that he had a '74 that had both chamfers.

The 6x-4 heads had 2.11 intake valves. So, did the '75-'77 350's have just 1 chamfer ? I have a '77, but haven't pulled the heads yet.

A Pontiac friend told me that what he did was to bolt the head to be used, to the bare block, then turn it over an look down into the cylinder, to see which valves might hit the block, and exactly where, then grind the chamfers there, if needed.

The pic below is of a block with only 1 chamfer. But, I don't know what year or casting number.

Here is a pic of a 1973 that I just finished putting together, Just one chamfer on it.

[HO Kenny]

My 68 350 HO had chamfers for both valves even though the 68 used smaller valves. It was an SR block and had the larger 400 style crank weights.

[Jays76bird]

Still surprised that no one has stroked one using the PPR kit or Butler kit. The big difference in the kits seems to be Ace Brewer's kit was using the 6.800 rod and Butler is using a 6.700 rod, maybe because of piston difference ? I keep hearing about the bore being too small. But on a street engine not sure how much of an issue that is ? The Probe pistons I have are supposedly the same ones Brewer used. I don't see the sense of junking a perfectly 350, I would like to use it.

[Jays76bird]

Originally Posted by maxpowerta

Here is a pic of a 1973 that I just finished putting together, Just one chamfer on it.

Yes my 73 block has one chamfer too