[stuman]

A few months ago, I posted a question on the options I had of increasing the compression ratio of my ’77 Pontiac 400cid to approximately 9:1. I thank you all for your ideas and opinions. The engine is now being machined and will be assembled late summer early fall. One thing I have noticed about this site that the drag racing information is just super plentiful here, but I’m having trouble finding circle track racing information.


Now I have a few more ideas that could use some comments. (AKA: the Pontiac project)

As a hobby I am involved in dirt track racing. The track is a .375 mile medium/high banked black dirt/clay surface and the sanctioning body is IMCA (www.imca.com). After a few years of success, the driver/owner/etc. is considering installing a Pontiac 350cid engine (after I talked him into it). The reason for the 350cid is imca has an engine size limit of 360cid on general motor engines, so no 400’s (also no 400cid parts). Please keep in mind that imca has an engine claim where the top 4 finishers in the feature has a chance that a racer that finished in 5th on back could purchase their engine. (Hobby stock class is $325.00) You will see me try to save every penny at every point in this project.


- Not too much information too early, I need to keep everybody interested.

- The short block-

I would like to leave completely stock (almost used condition). That means maybe polishing the crankshaft, turning it if I have too. New pistons might be too expensive, try to use the existing ones if I can, unless I have to bore the cylinders oversized. New bearings (of course), new oil pump (any affordable high pressure ones available?), timing chain (still looking for information on how to adjust the camshaft degree, Chevrolet no problem Pontiac has a keyway, so I’m assuming an offset key?), new camshaft (this requires its own paragraph), factory windage tray – 1973 style, homemade crank scraper, oil pump pickup will be looked at and modified. Etc. etc. etc.

- The camshaft-

The single most influence on an engine (in my opinion). I have studied a few camshaft choices and will continue to do so. I don’t expect to find the best camshaft first but at the same time I don’t want ten camshafts that didn’t work. Before the engine is completed I see I need to contact some cam grinders.

- Heads-

What we have now (as we only have one 350cid Pontiac engine) are #46 heads w/screw-in studs and guide plates. Damn, already we have a problem, rules state – no porting, no polishing, and no shouldered (big hex on the bottom) screw-in rocker arm studs. The first rules – porting, polishing are no problem, but the rule regarding the rocker arm studs causes some concern. Can we find non-shouldered rocker arm studs? If so can we still use factory guide plates with them, or can a Pontiac push rod survive without guide plates? Back to the number #46, I have not measured them yet, so valve sizes and chamber volumes will be added to this post later, I did see the cylinders are machined to “un shroud� both intake and exhaust valves. Lastly would the #46 head be a good choice or should I be looking in more junkyards for different numbers.

- Intake/Exhaust manifolds-

The intake manifold on this engine is a stock cast iron 2bl with egr provisions. The rules state no porting no polishing, which is not a problem. I see issues when trying to use different intake manifold with different heads so I might have to live with the egr. The manifold seems heavy, has anyone cut the egr passageways off the bottom of the manifold (just to save weight)?

The exhaust manifolds are stock cast iron dual type (the exhaust pipes combined together after the transmission). Rules state the exhaust manifold go with the engine when claimed, so porting polishing cutting and welding is allowed. But with such huge manifolds compared to Chevrolets is anything necessary?

-Quick facts-

• building a Pontiac 350 to test feasibility of use
• .375mi medium banked dirt track
• 3000# car weight w/driver
• currently using a stock (and I mean stock, excluding Cam and springs) Chevrolet 350 engine turning 7000 rpms – will be changing gears to decrease rpm’s an appropriate amount for the Pontiac
• also considering an Oldsmobile (but that’s a different project)
• Can’t wait to see the tech inspectors, or the claiming drivers expecting to see a Chevrolet, ask us what the heck engine is that? Oooohhhhh

THANK YOU FOR YOUR TIME

Lastly – opinions needed…. (And I know everyone has at least one)