The Break Down of a '69 Pontiac OHC inline six

Had one of the overhead cam engines that was in my firebird back in the early eighties. It got a lot of attention, especially since it had a Q jet. Good luck with it and keep us posted. I for one would really like to see it running, mine never really ran that good.

 

If you're not already, check out inliners.org. I used to be a very active memeber their when I had my Nova and first Skylark, both of which had the Chevy 250.
Clifford Performance to Inline engines is like TA Performance for Buicks, so might want to give them a look as well.

 

Nice project. I've always been intregued by the Pontiac cammers. My Dad had a 292 in a pickup when I was a teenager, lots of torque and would out drag 352 Ford truck but kept colapsing pistons. I quess that with that looong stroke it didn't like the hi revs I would wind it to beating those Fords lol.
If you want a high revver you might be happier using the 250 crank.

 

Thanks. I'm defiantely going to keep the 250 crank and not go the stroker route. I'll let the turbo do the work instead of the stroker. I'm still sourcing some forged pistons, and looking into cam avaliabilty. I have to play with some math, but it may go with an aftermarket connecting rod and a stroker 5.3L LS forged piston.

 

What size turbo are you plannig to use? Always nice to see unique projects!

 

I'm still very early in the planning stages with this engine. I'll probably see what the Turbo Buick guys run for 600-800HP, then pick accordingly to shoot for 500-600HP. Also I think will depend on the camshaft I end up using. Available camshafts are pretty limited, so may play a factor in turbo selection. This engine has larger valves than the Turbo 231 engines, though to me it "appears" the ports are smaller, which might be ok from a velocity stand point, at least on the intake.

 

I had to go and pick up another OHC Pontiac. This one is a 215HP 1967 230cid Sprint engine. So sporting a higher compression head, 4bbl carb and dual exhaust. This engine has slightly less stroke than the '69 250cid.

Yup, that's a factory Q-jet.




And factory dual exhaust manifolds.




In the basement ready for disassembly.

 

4barrell. split exhaust manifold. Cool

 

I was going to ask you if the block had the BOP bellhousing pattern or the chebbie. Looks like the 3`rd pic answered that.

 

Yup, BOP pattern. I've only gotten as far as pulling the accessories and cam housing off this engine. It has eaten it's cam too, much worse than the first engine, several lobes. Also it's a sprint in disguise, it's actually a low compression engine (okay for my purposes) with the fancy intake and exhaust bolted on.

 

I don`t know if those cams are a victom of today`s oils or just lack of maintenance. My buddy had a `69 sprint that we ran the piss out of. No problems. We couldn`t kill that thing. And really, we both have been mechanics since the late `70`s. These engines were still around and I don`t remember them even breaking timing belts, at least to a large extent like modern engines.

 

Im not sure, but i read somewhere 230 and 250 stuff is unique...in other words some of the 230 stuff doesnt interchange..like the intakes and exh mannis....not sure but thought i read it somewhere...like on the PY board...

neat build...

if your not on this site you need to be...lots of theory and real world info on turbos......ive got about 20 hrs of reading done...and i discover more and more.you can never get this much info by talking to people, or in books its an amazing place...anything you need to know about turbo'n anything is there..check out the blow thru section..people are making a ton of power on bone stock cams...theres alot of cam theory...it doesnt take a radical camshaft to make power..it takes a properly matched turbo that fits your plan...

http://www.theturboforums.com/smf/index.php

takes all the crap and stero types out of the mix...

use the search button...they haze a person for not trying a search..if you can find it..then start your post with...i tried a search and cant find what im looking for and they will help..

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lots of old timers here...they where doing this stuff in the 60s and 70s...lots of unique builds..if ya search some really wild turbo builds...

http://www.jalopyjournal.com/forum/search.php?searchid=8582546&pp=25&page=5

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ive found some cool stuff here too..dedicated to the OHC6

http://sohcsix.yuku.com/

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look here too..they offer chevy 6 turbo mannis..with very little work and an adapter plate the work on OHC6...my uncle did a swap years ago...if anything..it gives you and idea how they are mounting the turbo...steal the idea if it works..lol
search spaturbo

http://www.ultrarev.com/

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check this seller out..has spa turbo stuff too

http://cgi.ebay.com/ebaymotors/194-...r_Truck_Parts_Accessories&hash=item2c5ad7acbc

 

I think it's probably a break in proceedure issue. Could be an excessive oil pressure issue as well, the oil pump regulator is set at 30psi!! Because if too much oil pressure gets to the lash adjusters it loads up against cam. But since the lash adjusters don't spin, I'm thinking this engine will really like slippery synthetic oil. Might take longer for the rings to seat, but the cam should be happy.

I'm also looking at methods to have an external oil pressure line, with a bypass regulator, ran to the lash adjuster oil galley in the head and block off the feed coming from the block, so I can up the main oil pressure to 60psi or so and maintain a constant 15psi or so the lash adjusters want. The modification is really simple, I just need to find an adjustable bypass pressure regulator for oil pressure. Similar to a fuel bypass regulator but good with 200*+ oil temps.

 

There are a few interchangable issues. Now that I got a 250 and a 230, I guess I'll find them out! But from what I can tell, most the stuff is interchangeable as long as you pay attention to various design differences and account for them (like compression ratio, etc).

I'll check out the turbo site, I'm already on the sohcsix site. I plan on keeping it pretty simple on the build by not over thinking things too much. With a turbo it seems to easy to make enough power to really break things, so just enough thought to get me to 400-600Hp, as opposed to 800-1000Hp. I'll never be the fastest with anything I own, but definately should get enough "Huh, hadn't seen that before." responses while still being reasonably quick and deadnuts reliable.

 

I read an article once about using a Chev 292 crank in one of these. I don't remember much, but it had to be in a Hot Rod Engines mag. Dave Zeuchel did one once also. We used a stock pump in our race car in the late 60's but I'd heard of a mechanical conversion by Somebody for the lifters(?). I don't remember by whom or what. Not much help, I know.

 

I really enjoy seeing such slightly mentally unbalanced creations, and I mean that in the best possible way. I had thoughts of doing this with a Chrysler Slant Six, down to using the stock GN computer and a chip tune. I think it would work well with a MAF translator, coil pack, and a turbo somewhere around a TE-44ish size. You could even use that dual exhaust manifold to gain some spool advantage with a 4 bolt divided tangential exhaust housing.

What are you thinking of for an intake? Is the stocker aluminum or cast iron?

 

The stocker is cast iron, but does have internal dividers for individual runners, which is good for multiport EFI fuel control. I'm looking at making either my own intake or my own exhaust headers, then using the factory complement manifold. Slight chance I'll use both the intake and exhaust because I really don't want the exhaust heating the intake manifold. So I can separate them by using one or the other and fabricating the rest.

I need to get back to pulling this thing apart....

 

hey just saw your thread about the ohc let me know if you need some help on this i got a 68 bird with that motor check out some birds at sema on the google search the firsrt one is mine joseph

 

I picked up the cleaned up OHC Pontiac engines from the machine shop a week and a half ago. The heads checked out with no cracks and it was clear which block I should go with for my build.

So what do you think about an oppose 12 cylinder engine? :grin:




It could almost work! 7 main boxer? :Brow:


The machinist said the thinnest cylinder wall on both blocks was the front side of cylinder 2. The '67 block's thinnest cylinder wall is almost a tenth of an inch thicker than the 1969's thinnest wall.


The cylinder heads cleaned up real nice. No cracks or any surprises. The machinist said the seats all appear to be good, but need harden valve seats.

 

nice