SP code 350 does it have smaller head ccs?

I have never measured them but have read that they have smaller head ccs (47 cc) vs the regular 58 cc. Has anyone measured?? As far as I know the other 350s (68,69,70 4 bb) that are high comp are 10:1 and not 10.25 the way it is advertised in the books.

 

They have 48CC.
Dan

 

Thanks!

 

Interesting info, I don't believe I've seen anyone mention that anywhere else before.

 

Ok so if this is the case then the I am pretty sure that all the other high comp 350s are actually 10:1 and not 10.25 and only the GS (SP code engine) is actually 10.25 due to the smaller head cc. As far as I know there is only two 350 pistons, high comp and low comp and the variations between are deck height of the block other than the SP code that has the smaller cc heads.

 

They have 48CC.

where does this number come from?

 

there would be a different casting number for that head if that is the case.

 

there would be a different casting number for that head if that is the case.


mmmm, not necessarily. i can see it being like the Stage 1 heads, taken off the mass production lines and machined to spec.

of course over the last ~40 years, it would have been really easy for various GS350 engines to have had their heads get shaved in the aftermarket and then have someone come along later yet and cc the chambers and pronounce that GS350s have smaller chambers than other SP code engines. o No:

 

Bob
wouldn't they have all been cast with the smaller chambers and then machine work done to the low compression versions if there was only one casting number? the stage ones had millwork done to unshroud the valves. it was the valves that made the combustion chamber have less CC's not the actual chamber

 

No, they would cast them with the larger combustion chambers, then plane the heads down which would reduce chamber size. Maybe Buick did this, but I wonder why they wouldn't list the GS 350 as having higer comp than the standard 350-4

How would valves affect the combustion chamber size?

 

the larger valve heads took up more space in the chamber and raised compression. if the factory shaved the heads more on the sp engines which were available on other cars besides GS350 then they would have had to use a different push rod to make up for the difference.

 

70 350 sp

315hp 350 10.25 1-4 Roch 4MV-7040245/SM 7040244/AUTO 48.0cc

315hp 350 .010 Dished .075" 17.3 cc's 1880/1505val 382/398 cam

315hp 350 .020 1233472,1240143 head castings.

Here ya go guys. The casting are different and the head gasket is .020 the pistons are the same.

Dan

 

the larger valve heads took up more space in the chamber and raised compression. if the factory shaved the heads more on the sp engines which were available on other cars besides GS350 then they would have had to use a different push rod to make up for the difference.


1880/1505valves

The valve size is the same 68-74

the exaust increased in75 to 1550.

The head gasket was .020 on the 70 sp motor only. All the rest is .041.

Did the .021 make the 10.25 diffence? 10.00 with .041 head gasket.


DAn

 

The valve size is the same 68-74

the valve size question is in relation to my example using the 455 Stage 1 head.



1233472,1240143 head castings.

3472 appears to be the standard casting for 1970 and 0143 looks to be the service replacement.
http://www.gesslerheadporting.com/m...8464cf4d587de6d085256e47001720b1!OpenDocument

you haven't shown that these heads weren't used only on 'SP' code ( and the SP code was the hi-comp small block 4v motor for all Buick car models in 1970 ) engines, must less be specific to the GS350.

where are your numbers coming from? the NHRA? if that's from the NHRA, those are the specs they will permit in competition not what you would expect to see from the factory.




wouldn't they have all been cast with the smaller chambers and then machine work done to the low compression versions if there was only one casting number?

while this is a possibility, i think it would be odd of them to put the added production expense into the standard application 350 head.




it was the valves that made the combustion chamber have less CC's not the actual chamber

i am aware of this. and actually, the valve seats have to be enlarged to fit the larger valve head.




if the factory shaved the heads more on the sp engines which were available on other cars besides GS350 then they would have had to use a different push rod to make up for the difference.

good point.

 

where are your numbers coming from? the NHRA? if that's from the NHRA, those are the specs they will permit in competition not what you would expect to see from the factory.

Yes NHRA what is your point?
Dan

 

Yes NHRA what is your point?

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.

also, more generally, the NHRA info is not particularly accurate for Buick. i've long since given up referencing them.

 

This is why I brought this up, trying to find out the REAL ccs of a SP code head.

 

racing my 73 back then, the pistons dish specs were 71's. where did the specs come from......buick

 

This is what allows the 73 and 74 ect racers to run over 11:1 compression because they can use the stock high comp pistons and deck the block some. The head cc is limited by ccs and they are allowed to stroke the engine a tiny bit which also helps compression.

The real secret with the Buick 350 seems to be angle milling the heads to the exhaust side from what I have heard..... 1 or 2 degrees seems to work magic.

 

This is a good discussion,it has been brought up before but the certainty of what was offered keeps eluding us.Short of having some paperwork from the factory documenting the specs for the heads,it will be up to us to start cc'ing chambers of known virgin castings and recording the findings.

One does not have to invest on expensive equipment to measure the volume of the chambers.A very inexpensive irrigation syringe can be bought at a drug store for a couple of bucks and a small piece of plexiglass or lexan is all that is needed in order to make the measuring kit.Maybe we can start a thread and encourage other members to get involved and we may be able to put the question to rest and have a nice reference for all to go to in the future.

Dan,I'm with Bob on the issue of the NHRA specs being what it is allowed to run on the classes sanctioned by them,not what was offered from the manufacturers.There's no way that the Buick 350 in my '79 came with the 9.x:1 scr that the NHRA specs call for,they also claim over 10.x:1 scr for a '79, Chevy 350 equipped Buick,we all know that just didn't happen in 1979.Since there's not a chart or table showing casting #'s and corresponding volumes in cc's for our cars out there,most people find and go by the NHRA's list.I don't believe that to be the answer to the stock volume question.I could be wrong but that's how I see it but I welcome the discussion and hope that we see more threads and topics like these on this board.