350CI - 11 Second Build - Pontiac GTO Forum
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post #1 of 3 (permalink) Old 01-22-2018, 08:44 PM Thread Starter
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350CI - 11 Second Build

So who says the Pontiac 350 doesn't have potential? I know most want a 400 or 455 because these engines have a reputation, but as they get harder and $$harder to find, the 350 is still easy to get and relatively cheap.

It does not take too much to get one to perform if you are willing. This would, in my opinion, be a good engine with a 5-speed to take advantage of the lower gear ratio's coupled with a set of 3.90's or 4.11's out back.

The engine in the article is built around a 350HO which is the 350CI with the #48 big valve heads. What to note is the cut-outs in each side of the block's top bore to provide clearance for the bigger valves - this is factory. Not all 350 blocks will have this, but the scallops can be added by a competent machine shop. From what I have read, and as you can see, the 350 blocks (which I think are the 1968-1970 years) have the scallops on each side whereas the later blocks don't. If you use the smaller 1.66" exhaust valve versus the 1.77" valve, you don't have to have the exhaust scallop for clearance. Again, choose a block/engine that is 1974 or earlier as I have read that they too were made lighter/weaker.

I don't see anything real trick with this build seeing it is aimed as a Super Stock entrant. The key in my opinion is the roller cam which will allow the engine to really breathe, but is certainly not crazy at .512" lift. The rods are the factory cast rods along with the factory crank. The RPM limit of the engine was 6,000 no doubt to the cast rods.

So, the 350 can be made to perform without a lot of trick items and externally, it looks like a 400CI so no one will know the difference except you.
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post #2 of 3 (permalink) Old 01-22-2018, 08:46 PM Thread Starter
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Here is a good pic of a 1970 350 block with the scallops at the top of the cylinder bores.
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post #3 of 3 (permalink) Old 01-23-2018, 11:17 AM
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Yeah, a Pontiac 350 can be built to make power, even with small valves & fairly low compression. Bill Rink has proven that, with his '74 GTO. He did very well with it in NHRA Stock Elim, and is now running 10's with the same car, in Super Stock. Mike Morgan also runs 10's with his 350 powered '77 Formula Super Stocker.


Bill Rink won the SS/MA class at last year's US Nationals.


Adam Strang is planning to try a 350HO in his '68 Bird 4-speed Stocker. He has already got some good forged pistons approved by NHRA, for Stock Elim. These will be legal for all 350's which came with pistons which had valve reliefs. The '74-'77 pistons had no reliefs.

One reason that many don't try to build a performance 350 is because there are no cheap forged pistons for them. The TRW L2339F forged pistons were discontinued several years back. So, the only source for 350 forged pistons is custom pistons. The cheapest I've been able to price are made by Auto Tec. They use a shelf piston blank, actually made for some other brand of engines, in an appropriate size, then machine it for a 350 Pontiac. The shipped price will be a little over $500. But, that's cheaper than most any other brand. I assume that most of the big name brands will run well over $700, with pins & shipping.

The price quote I got for the Auto Tec customs was from Shannon's Engineering.


Obviously, if you are not bound by any rules, you can go with alum heads & any cam. So, 450-500hp is easily attainable. I had one with #48 heads, a HFT cam, & a 750 Q-jet that made 434hp on the dyno.

An easy way to make more power, using a 350 block, is with a stroker assembly. Butler sells 4" & 4.25" stoker assemblies for 350 blocks.


Small-Bore Pontiac Performance Engine Build - Revenge Of The 350 - Hot Rod Network
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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