65cutty

WHERE WOULD ONE GO ON THE WEB TO FIND THE COMPRESSION RATIO ON 1975 OLDS 350 4BBL?

Wireman134

Lots of info. in these pages. http://oldsjunction.classicoldsmobil...0of%20Contents

65cutty

have decided which way to go as to use pump gas of 87 oct, 1975 olds 350, no boring just rebuild with rings ect.low miles motor, from mondello, thin head gaskets, roller tip rockers, studs and guide plates w/pushrods, 130 lb's 245 valve springs retainers and keepers 3 angle valve job, tall valve covers, cam 20-22 496/512 lift. 266/274 duration@50 226 intake 230 exhaust 110 lobe seperation, 1400-5800 rpm, elderbrock performer rpm manifold, 750 carb, melling stock oil pump, off course hei dist. trans is tci 350 with 2600 stall convertor, rear is posi 355 w/ 27in tall tires, have hooker super comp header's, am looking for bumpy idel little bit of go and dependelity, thinking of spectra's forced air induction, what do you think?

Oldsguy

Sounds like a pretty good plan you have. By he way, most valve jobs are 3 angle and I don't think you will need tall valve covers with those rockers(Comp Cams kit?).

captjim

Too much cam IMO for what will end up being low-mid 8.xx to 1 Cr. The gear will help a little, but again, IMO you will not be happy with it.

88 coupe

Assuming the factory 8.5 (or 8.0, depending who you believe) compression ratio, and a matching advance curve, it looks like a good combination.

If you raise the CR you will raise the Octane requirement.

If you use a smaller cam, you will get less power.

Norm

65cutty

ok then could I go with the 65 330 heads and bump up to 8.9 or 9.0 and still be ok on pump fuel? keeping the above list of items from mondello!

cutlassefi

I have a 72 350. Stock compression is much closer to 8.0 to 1 than 8.5. If you raise it to 9.0 with a bit more cam you should be fine. I would think it would run fine on 89 octane, maybe even 87 if you're real careful and smooth everything out inside. I have EFI but have no problem running 89 with a measured 9.7 and the stock heads. But I smoothed everything out very carefully.

Norm- you can't make the blanket statement "if you raise your cr you'll raise the octane requirement, i.e. if you went from 8.0 to 1 to 8.5 to 1 I'm pretty sure you wouldn't have to do a thing. Like I said, can't make that blanket statement, other things come in to play.

Wireman134

Yea, the 65 heads at 62cc would work better. For 9-9.2:1CR

65cutty

OK, then thats way I'll go, Ive also purchased there quite gear drive and the cam has four degree advance built in, but will degree it in as I read else whre on this forum, thank you all very much and really enjoy reading everything on this site....jim

captjim

I have no personal experience but have read and heard of pretty bad experiences with those gear drives, so do your research. FWIW, I have never had any kind of issue with a Cloyes double roller.

88 coupe

Fuel injection and carburetion, are not a legitimate comparison.

At the risk of over generalizing: In a given application, FI will tolerate higher compression and more cam than a carb.

The statement is accurate. You read something into it, that I did not write.

Did I say anything different?

Norm

Bunser

"If you raise the CR you will raise the Octane requirement." I have to agree with Norm on this!

65cutty

I'd better stay with the 350 all the way, heads ect, what am wanting is good sounding, lumpy idel , run on 87,91 oct be able to drive goodguy's nationals, olds club national's and be dependable, the gear drive is a concern but will research this, all parts are from mondello and len and jr are very helpfull, they think 330 heads are the way to go but Iam not wanting a 11 sec car , no intention's of drag racing it, have lots of bling for under the hood, whats your thought on this?

Wireman134

I believe 9.2:1 cr is do-able with pump 93 easily. I'm running the stock cam in my 350 with around 9.5:1 cr . You might have to limit the amount of mechanical advance the distributor puts out. Along with reducing total vacuum advance and rate with a adjustable unit. The smog engines used more advance to make up for EGR and low compression ratios. A distributor with 16-18 mechanical, with 12-14 initial, for 28-32 total in by 3200rpm is real close to the factory performance curves for the 68-70 model engines using higher compression ratios. Maybe a 13 sec. car and very streetable.

cutlassefi

I agree with Wireman, 9.2 to 9.5 should be fine. Still disagree with Norm, can't make that blanket statement, I guarantee you that you wouldn't need to go to a higher octane if you were to increase your CR from 8.0 to 8.5, with all else being equal. There are still other things that come in to play.

380 Racer

Like overlap.

88 coupe

At the risk of beating the dead horse, here it is again:

I am finished with your thread hijack.

Norm

88 coupe

Here is another thread, dealing with the same subject:

https://classicoldsmobile.com/forums...rminology.html

Perhaps, you would like to join in.

Norm

cutlassefi

Norm - Yes you did say something different. You made a blanket statement that said if you change CR it will change your octane requirements. Not true. Admit you were wrong and we'll move on. I admitted my mistake on another thread. Apparently you can't do the same.

380 Racer

Norm, have you ever used a bigger cam? How about a RV style? Leave the quote button alone and just tell me.