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Biggest cam?

R

ramses

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What is the biggest cam I can put in my 350 before I have to modify any thing else like valve springs, ect.? I think the one I have now is a 432/45? dual pattern cam and I want to go a little bigger but not too big to where it causes any problems.
 
My Comp cams has a lift of 443/465 and my machinist says he wouldnt recommend going larger without modifying valve springs etc.
 
muscle said:
My Comp cams has a lift of 443/465 and my machinist says he wouldnt recommend going larger without modifying valve springs etc.
Click to expand...
How does this idle? Does it have a noticable "lope"? What rpm range is it designed for? Does it pull enough vaccume to work your brakes.
Sorry for my noob questions.
thanks,
James
 
It isn't just the "size" of the cam that matters. Opening and closing rate also have a big effect on the springs. Even a seemingly mild cam can create harmonics that will wreak havoc on the valve springs. It's really a good idea to spend the extra $100 or so for the springs recommended by the cam manufacturer. Mountainexplorer has some pics of what happens when the wrong springs are used. :(
 
Ive never changed valve springs before, what all is involved in doing it? If its only about $100 more and its not too difficult I wouldnt mind changing the springs. The cam im wanting to go with is a dual pattern with lift in the 460's on the intake and 470's on the exhaust, with a duration around 272 I think, I cant remember the exact numbers right now. Would I have to change my springs to run a cam that size? I want a little more power and lope than my current cam.
 
HarryH3 said:
It isn't just the "size" of the cam that matters. Opening and closing rate also have a big effect on the springs. Even a seemingly mild cam can create harmonics that will wreak havoc on the valve springs. It's really a good idea to spend the extra $100 or so for the springs recommended by the cam manufacturer. Mountainexplorer has some pics of what happens when the wrong springs are used. :(
Click to expand...
If you do the springs, think about new valve stem seals (unless you know that's been done recently), since you'll already have the keepers, springs, and retainers removed so that you can put the new springs in. Easier to do then than later on! Seals are only about $20-25 for the whole set of 16.
 
Check with the cam manufacturer for the correct springs. If you read all the fine print, you'll find that cam companies will NOT honor the cam warranty unless you can show them the reciept for the correct springs that got installed with it.

There are tools available for around $20 that will let you remove and install the springs with the head on the truck.

There are a couple of ways to hold the valves closed while changing the springs. You can use compressed air and a fitting that fits into the spark plug hole, while some folks just slip some rope into the cylinder and then rotate the engine a bit so that the piston and hose are pressed against the valves.

One thing is certain, you don't want to drop a valve into a cylinder with the piston down while swapping springs or you'll get to pull the head. :(
 
Last edited:
78Suburban said:
How does this idle? Does it have a noticable "lope"? What rpm range is it designed for? Does it pull enough vaccume to work your brakes.
Sorry for my noob questions.
thanks,
James
Click to expand...

Has a mild lope at idle. RPM is 2100 to 4900. I noticed when im WFO it comes in at about 1900. I now run 4:10 gearing with a TH400. This made the truck come alive. Its a hunting rig so i felt going more than 4:10 would ruin my highway mileage. as it sits now i run 3100 rpm at 60 mph. But my cam is actually in the street/strip category. as i drive at normal speeds more than crawl around, this is what i chose.

I agree with using the springs to match your cam spec. My springs are new and match the cam specifications. also they are very easy to change.
 
What heads are you running? What valve springs? You can run a lot of lift with flattops, but need the valve train to support it, and over .450 maybe some porting work would help the potential of the combo. Head flow can be more beneficial than more cam.
 
I still have stock heads and valve springs. I dont want to change the heads, thats too major of a job for what I want.
 
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