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Two Feathers

42 Posts

Posted - 13 Jun 2016 :  11:11:17 PM  Show Profile  Reply with Quote
I picked up a 1970 350 Pontiac engine today for $150.00. 255 hp Engine code YU, Head code 11, Block casting 9799916. Engine turns freely and does not appears to have any major issue's. Look like the original intake, no carb or distributer. I also have a 76 Pontiac 400 which is in very bad shape internally but everthing else is good like fuel pump, HEI, edlebroke intake and edelbroke 75cfm. My question is what part will interchange seamlessly, between these. I don't have much money and a 350 is better than no engine for now.

1. will the 400 flex plate work on the 350. I have a th350 trans.
2. engine mounts/brackets
3. fuel pump
4, starter etc.
5. Headers swap. My 400 has 6x head, the 11 70 heads look pretty much the same d port so I think they headers will fit right on also.

Looking for some guidance.

If all fails I'm only out $150 bucks. will lube the cylinders tomorrow
w and do a compression test to see if I really want to pull the heads.

Just looking for cheap solution to get the car running right now, until I can find a 400 or 455 to slap in down the road.

Sitting Bull

160 Posts

Posted - 14 Jun 2016 :  3:03:26 PM  Show Profile  Reply with Quote
1. there are two sizes for the output shaft but I think it changed in the 60's, so you should be fine
2. they're the same
3. same
4, same
5. Headers are teh same.400 has 6x head, the 11 70 heads are exact bolt up only difference is the size of the combustion chamber.

Everything else is pretty much interchangeable.

71 Formula 455

Edited by - js292 on 14 Jun 2016 3:07:40 PM
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404 Posts

Posted - 24 Jun 2016 :  02:45:16 AM  Show Profile  Reply with Quote
Here is a interesting 350 build but it requires $$.

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The Great White Buffalo

7293 Posts

Posted - 25 Jun 2016 :  09:02:28 AM  Show Profile  Reply with Quote
Crank register hole on the 76 flexplate (smaller) won't fit on the 70 crank (larger). You'll need an earlier flexplate, or a new one, or have it machined to fit.

Have you checked your #11 heads to ensure they have been tapped for all 6 exhaust bolt holes? All of the ones I've seen weren't tapped at the ends which presents a problem if you want to run those headers.

Those 70 350's actually run quite well and would easily outperform a stock 76 400 btw.

Bowties are for Pee-wee Herman. LS swaps in Pontiacs should only apply to Fieros.

Edited by - Phil on 25 Jun 2016 09:03:03 AM
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