SP code 350 does it have smaller head ccs?

back then, nhra had no clue whatsoever on buick stats. there was maybe 10 cars at most running stage1 or 455's nationwide. 350's were non existitent. still maintain buick gave them the specs.

 

Something you have not mentioned is the distance the factory pistons are down the hole at TDC. Most factory 350's I've taken apart the piston is .060-.080" down. You will NEVER get the factory advertised compression ratio that way. The advertised ratio is at near zero deck.
I believe the 48cc number is the blueprint/designed size. With manufacturing variation and leaving room for rebuilds they end up with mid 50's cc as manufactured.
Best bang for the buck is to zero deck the block.

 

I agree Johnny, Buick did provide those specs to NHRA. All the manufacturers did.

But they are not representative of what the production engines were, rather they were the specs that the Buick engineers wanted the guys to be able to run to be competitive with the other makes.

Every early 350 head I have seen, including the SP 70 ones, are typically about 57-59 cc stock. I have a set of 72 castings on the bench now, and after oversized valves were installed with a very small relief cut, they measure in at 58.2 cc, which is typical. No way any factory stuff was near 48cc.

And as underdog said, I have yet to see any factory Buick motor be near the advertised compression ratio, because the factory allowable variation in the deck height was so large. Even the vaunted STG 1 motors were typically half a point low, in production form.

This is one of the things that the boys in the backroom "massaged" when they blueprinted the motors for the test cars that went to the mags for evaluation back in the day.

To my knowledge none of the later hi performance Buick V-8 engines had specific head castings, or any specific extra machining work such as cutting the decks for compression increase.

The only exception to that rule would be the oversized valves in the 455 STG 1 heads, and of course the Stage 2 stuff, that was available over the counter, or as a dealer installed option.

 

amazing.......nobody believes that the manufacturers lied. besides, nhra wasnt that smart. they were bias, but not smart.

 

i've already explicated my point if that were the case. 48cc is the chamber size that the NHRA will permit you to mill the heads down to for rebuild purposes, not the production size.

Yes this is correct. 48 is the minimum not the starting size.

Also I could only find the 2 casting numbers and they are 70 only.

It would be interesting to find a virgin old motor to find out.

How much would you have to pay for one just to find out?

The minmum deck hight is .010 for stock so mine are .011.

There would not be any factory motors built on the minimums or maximums from the factory. These are numbers that the factory recomends as the limit before a repacement part should be used. I would guess if a head was milled less than 48cc on the chamber it sould be replaced. These are the numbers that Buick gave NHRA for that 70 motor.

It is a thrill to get the drill on this web site.

When some one askes I try to help but I can just go away.

Dan

 

Please keep posting! I knew what you meant it was just a miss understanding...

 

When some one askes I try to help but I can just go away.

no one is trying to make you go away, not me, not Jim not anybody.

but the question was very specific and you're trying to use NHRA specs to describe a production piece. that's misleading to the person you're trying to help. Sean could have wasted a lot of time looking for and testing for 48cc factory heads and never found them.

better to nail down exactly what's going on so no one is confused.



Also I could only find the 2 casting numbers and they are 70 only.
It would be interesting to find a virgin old motor to find out.

yes, one production piece and one service replacement piece. these heads went on everything from the factory "spec" 10.25:1 'SP' code motor to the 9:1 'SB' and 'SO' codes.




How much would you have to pay for one just to find out?

Buick 350's tend to go cheap. not much demand for them. i wouldn't pay over $400 for an old runner. if you just want to look at the heads you can probably find a whole non-running car for $500 and play to your hearts content.

 

I did buy a SP code 350 BUT the heads turned out to not be the correct ones anyway so I was never able to get my hands on a set to measure them. I really would like to measure the cam, and check for other minor different things that may have been different for the SP code engines just to know....

 

Dan,I hope that you don't feel as if I was beating on you when I posted earlier on the thread,that was not my intent and if any ofense was taken I respectfuly apologize to you.
I read the original post as a question on the volume of the stock castings as offered in the cars to the general public hence my comment of why the NHRA spec was not applicable to what Sean was looking for.

Please don't go on not posting in here on account of anything that I say,I don't know much myself and a racer's feedback is always welcome.:beer

I still think that we need to start some kind of log for measured virgin casting volumes in order to have a ready reference for all years sbb 350 heads.

 

Buick did not change the casting for the 350 head throughout the entire run.:Smarty:
They all started in the 56-59cc range. That's how precise they were back then.
What happened during the assembly stage may be a different matter.
A quick milling to a few pieces to boost the numbers is possible but undocumented.

 

Except the extra cooling scallops in the 72 and later heads, the runners look different on the late heads as well compared to the early ones not sure which flows better stock though.

 

I still think that we need to start some kind of log for measured virgin casting volumes in order to have a ready reference for all years sbb 350 heads.

Gessler's casting number list continues to get more detailed every year. and this is a very good thing for the small block guys as 350, and even earlier, casting numbers seem to be quite hard to come by for us.

i would be surprised if he wasn't also taking some stock measurements.

 

Bump to the top.

 

My heads for my new motor are from the original sp motor I had in the car from the factory. I am the second owner ( was grandmas car ) and I can tell you that my heads have been ported twice....this last one adding 192 - 155 manley valves and new guides, new springs and roller rockers.
I measured the heads when they were factory virgin and there is no way that 48cc would be a number from the factory. They were then 56cc's and they are now 52cc's. The casting # 1233472 dated june 19

 

Thanks, any chance that you checked the cc of the SP pistons? I am trying to figuer out how the SP code engine got the extra .25 of compression over the regular 70 high compression engine....

 

Pistons...

 

Sean,

There were only two advertized compression ratios available on the 350 in '70, either 9:1 or 10.25:1. There is no 10:1 350, the SP is the only Hi-compression 350 offered in '70 and was available in the Skylark Custom, GS, LeSabre, and Sportwagon.

Please read the post Jim Weise made earlier in this thread, it pretty much explains everything.

 

Thanks, had a few beers and got confused LOL....

 

As a matter of fact....I just sold those pistons but have not sent them yet. I will go pull them out of the box and measure them.....I believe they are 14cc's, Bu t I will confirm it

 

Cool, any chance you could also post the depth of the dish. I believe mine were .070" deep, but that was two years ago. I'd like to know for sure.