I have a recently rebuilt 1970 Oldsmobile 350. It was rebuilt to stock performance. The heads are #6, It has a newer HEI distributor, eddlebrock performer intake, headers, and 750 cfm carb. I have a high stall torque converter and 373 gears in the rear end. Its going in a 1987 cutlass 442. I can not afford the aluminum heads from eddlebrock just yet but would like to increase my hp more with a cam swap. I thought I would be over 300 hp with the extras I already have done but its at 280. Can anyone recommend a proven cam match to boost my hp up with the combo I have? And what should I expect the increase to be?
HP increase
- Thread starter ksmitty
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You can't pick out a cam unless you know for sure what your compression ratio is. It can be anywhere from 10.25:1 to as low as 8:1. I'll bet you my car it's most likely lower than you think it is...
Bullit/Ultradyne, Lunati, and Engle are cams that are proven to work well in Oldsmobiles. Many say Comp is one of the worst for an Olds. I personaly don't know for sure, but I can tell you no matter what brand you go with, picking out a good cam without knowing your CR can cause you some serious problems. It happens all the time; someone thinks ( or assumes ) they have X:1 CR when really it's much lower. They install a big honking cam and their engine is a complete turd and they don't understand why.
If it were me, I'd pull the heads and measure everything so you know for sure what you got. Do some headwork while they're off too.
Bullit/Ultradyne, Lunati, and Engle are cams that are proven to work well in Oldsmobiles. Many say Comp is one of the worst for an Olds. I personaly don't know for sure, but I can tell you no matter what brand you go with, picking out a good cam without knowing your CR can cause you some serious problems. It happens all the time; someone thinks ( or assumes ) they have X:1 CR when really it's much lower. They install a big honking cam and their engine is a complete turd and they don't understand why.
If it were me, I'd pull the heads and measure everything so you know for sure what you got. Do some headwork while they're off too.
Pump her up! Find out your static compression ratio. Stock rebuilt 350 rocket from what year? if it's from the later 70's it's likely somewhere around 9:1, that's just a well informed guess i could be wrong.
DoubleV put it best, a cam that works best with your setup will provide better results than just pushing for as much lift as possible.
DoubleV put it best, a cam that works best with your setup will provide better results than just pushing for as much lift as possible.
well you cant go bigger then a .500 lift with stock heads at least on the sbc not sure about the olds but im sure its around the same.
Your carb is a little big. You should be around a 600 to like 650 cfm.
I would say if your compression is in the low to mid 9s around a 480 to 490 lift cam will do you good.
If you are going to pull the heads. check the casting numbers and find out the CC of the head and see if you can get a head with a smaller cc. that will bump up your compression. either way. do a little porting and polishing.
Your carb is a little big. You should be around a 600 to like 650 cfm.
I would say if your compression is in the low to mid 9s around a 480 to 490 lift cam will do you good.
If you are going to pull the heads. check the casting numbers and find out the CC of the head and see if you can get a head with a smaller cc. that will bump up your compression. either way. do a little porting and polishing.
I did verify the numbers and it is a 1970 motor with matching #6 heads. According to Oldsmobile Faq the compression ratio is 10.25:1 and the heads are 64cc. The heads have had machine work done already. Comp cams recommended a cam that has a 490 lift 280 Degree duration rpm range 2000 to 6000. According to eddlebrock build sheet that is the correct carb to use with those heads and that intake.
ksmitty said:
I can guarantee that you cr is not that high. Aftermarket stock replacement pistons come with bigger dishes and I believe they sit lower in the cylinder so that will kill your cr right there. If regular felpro head gaskets were used, they are thicker than factory ones, so there is another thing that will hurt the cr. Also, that 10.25 cr was for the high performance 4 bbl carb version of that engine and even that rating is not going to be accurate. Your engine most likely started out as a 2 bbl version which had a lower compression ratio and lower power rating.
You really need to take the heads off and measure everything to get an actual compression ratio. Like what was said before, you will most likely be disappointed if you are going off of what you think the cr is to base the cam choice off of. Do not go off of cam choice recommendations from them. They are usually generic, crappy grinds that will not give the engine it's full potential. Talk to an Olds engine builder after you get all the needed info and they can recommend a cam that will work great with what you have. I have heard really good things about Cutlassefi on Oldspower.com. He can have custom grinds done and knows his stuff when it comes to picking cams. I would recommend joining that forum and contacting him.
Ksmitty, my bet is legit; I'll bet you car for car your CR is lower than 10.25:1. :wink:
CR needs to be measured. You can't assume anything. If you really had 10.25:1 CR and were running the lame stock cam, you'd most likely be pinging pretty good with todays low octane gas.
CR needs to be measured. You can't assume anything. If you really had 10.25:1 CR and were running the lame stock cam, you'd most likely be pinging pretty good with todays low octane gas.
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