L31 crate- what kinda cam?

[63frankintruck]

How big of a cam can a person put into a L31 350 SBC crate motor can handle without major mods?
Lunati - Vuddo

[fleetsidelarry]

what I've always seen is .470 lift is where you might want to start checking retainer and seal clearances. I've also seen .480. for reference, the cam used in chevy's Vortec-headed RamJet motor gives .481 lift with the 1.6 ratio rockers that engine uses.

that cam is the one I used in my L31, but with the 1.5 rockers (.451 lift)

[63frankintruck]

Originally Posted by fleetsidelarry

what I've always seen is .470 lift is where you might want to start checking retainer and seal clearances. I've also seen .480. for reference, the cam used in chevy's Vortec-headed RamJet motor gives .481 lift with the 1.6 ratio rockers that engine uses.

that cam is the one I used in my L31, but with the 1.5 rockers (.451 lift)

thanks for the info.
I have looked at some of the Lunati Voddo Cams and others but it appears they all have around .500 lift or more

[Willi2ds]

Originally Posted by 63frankintruck

thanks for the info.
I have looked at some of the Lunati Voddo Cams and others but it appears they all have around .500 lift or more

I just had my heads done & just with a spring change they are good to .525. He did recommend I install screw in studs with that lift though. Cost me $250 and 2 days. I'm going with the Voodoo cam as well.
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[Warrens69GMC]

Call the cam company of your choice and have what you want made. a 230/230 (@.050) cam with .460/.460 lift won't be a problem- nor any other...

[fleetsidelarry]

I did a lot of assuming when I read your post. I assumed this was a new, "in-the-crate" engine and I should have asked what you meant by "major mods". I drew the line on my new crate at simply swapping the cam.

Willi2Ds has a good point about the studs

if your definition of "major mods" is different than mine, there is a simple "mod" you can make to the spring retainers to increase lift (see the last part of this post: http://www.nastyz28.com/forum/showpo...35&postcount=2 )

and, although I didn't check it out, here is a cam someone suggested a couple of years ago: http://67-72chevytrucks.com/vboard/s...54&postcount=2

**you might want to ask the moderator to move this thread to the Engine and Drivetrain section, you may pick up a lot more replies

[panhandler62]

Moving thread to correct section.

[Project86]

Brian tooley. No questions asked.

[Rickysnickers]

I just installed one of these in my truck, http://www.lunatipower.com/Product.aspx?id=4578&gid=289 FWIW

[Captainfab]

Just swap in a Ram Jet 350/HT 383 cam with a set of 1.6 rockers. Check the pushrod clearance going thru the head with the 1.6 rockers. Even if you have to stay with 1.5 rockers, that will make a strong running engine. Both Comp and Lunati make roller cams with less than .500 lift.

[Project86]

I ended up putting a xe268 cam in my 357. No other valvetrain mods. As long as you stay near .490 lift and don't go over on factory heads to will be ok

[Marshy]

Originally Posted by Project86

I ended up putting a xe268 cam in my 357. No other valvetrain mods. As long as you stay near .490 lift and don't go over on factory heads to will be ok

I went with Comp Cams XR258HR roller cam (P/N 12-408-8) which has 0.480/0.487" lift and 206/212 duration at 0.05" lift. It makes the same amount of torque as your xe268 cam just at 100 rpm lower. Peak HP for my cam is 325 @ 4400 RPM where as yours is 342 @ 5000 RPM. Those cams are close in performance with the edge in low end torque going to my cam.

I can say I am happy with the response and power I get from my engine with this cam. When I chose my cam I asked the machinist to make sure there was enough clearance to the seals and he clearance them enough to cover a cam with 0.500 lift in case I decide to go a little bigger in the future. Bottom line is check the clearance, don't assume you have enough to run a 0.480/0.490 lift cam. There's enough articles on the vortec heads to suggest that they only have enough clearance for about 0.470 lift.

[63frankintruck]

Originally Posted by Captainfab

Just swap in a Ram Jet 350/HT 383 cam with a set of 1.6 rockers. Check the pushrod clearance going thru the head with the 1.6 rockers. Even if you have to stay with 1.5 rockers, that will make a strong running engine. Both Comp and Lunati make roller cams with less than .500 lift.

Thanks for all replys. Captain, I would like a mild lumpy idle, and curious as to how your cam selection would sound and what type of horse power it would produce.
Thanks again

[fleetsidelarry]

I don't know if this is going to work (I have to click on the "options" buttons on the upper right and tell it to download). taken with my phone, sound quality is terrible. this is the ramjet cam with stock L31 1.5 rockers:
https://photos.google.com/share/AF1Q...4xOXhINlFhYVNn

[63frankintruck]

That sounds pretty healthy! 👍

[fleetsidelarry]

Thanks frankintruck, it might be the 109 degree lobe separation
or maybe the Sweet Thunder mufflers

I do wish the sound was better from the cell phone

as far as the hp possibilities go, compare the components of the L31 with the RamJet cam to say, the GM 350 HO which is rated at 333 hp with a dual plane manifold and 600 cfm Holley.

both are 350 cu in 1 piece rear main seal blocks with nodular iron cranks powdered metal rods and cast dished pistons

the L31 is rated at 9.4:1 compression ratio, the HO at 9.1:1

both have vortec heads with regular vortec 1.5 ratio rockers

the only real difference I see is the cam

the HO is flat tappet hydraulic with .435 in. intake lift and .460 in exhaust lift with duration at .050 in. for intake is 212 and 222 for exhaust with a 112.5 lobe centerline. (I'm assuming they are referring to LSA)

the lift is similar to the Ramjet (.431/.451) but because the RamJet is roller, you really can't draw a conclusion about the duration values since the roller lobe profile should/could be more aggressive.

lobe separation angle on the RamJet is 109 which is considered "tight" from what I understand. on two cams with otherwise identical specs, the one with the tighter LSA would have more overlap.

another comparison, FWIW, would be the GM 383 (9.1:1 compression ratio, dished pistons) which also has vortec heads and the Ramjet cam. rated at 323 hp

so, who knows? 300+?

[63frankintruck]

Originally Posted by fleetsidelarry

Thanks frankintruck, it might be the 109 degree lobe separation
or maybe the Sweet Thunder mufflers

I do wish the sound was better from the cell phone

as far as the hp possibilities go, compare the components of the L31 with the RamJet cam to say, the GM 350 HO which is rated at 333 hp with a dual plane manifold and 600 cfm Holley.

both are 350 cu in 1 piece rear main seal blocks with nodular iron cranks powdered metal rods and cast dished pistons

the L31 is rated at 9.4:1 compression ratio, the HO at 9.1:1

both have vortec heads with regular vortec 1.5 ratio rockers

the only real difference I see is the cam

the HO is flat tappet hydraulic with .435 in. intake lift and .460 in exhaust lift with duration at .050 in. for intake is 212 and 222 for exhaust with a 112.5 lobe centerline. (I'm assuming they are referring to LSA)

the lift is similar to the Ramjet (.431/.451) but because the RamJet is roller, you really can't draw a conclusion about the duration values since the roller lobe profile should/could be more aggressive.

lobe separation angle on the RamJet is 109 which is considered "tight" from what I understand. on two cams with otherwise identical specs, the one with the tighter LSA would have more overlap.

another comparison, FWIW, would be the GM 383 (9.1:1 compression ratio, dished pistons) which also has vortec heads and the Ramjet cam. rated at 323 hp

so, who knows? 300+?

thanks Larry! I''m pretty sure that is the route I will go. ( I may go with 1.6 roller rockers also) Thanks for the help!

[63frankintruck]

Just thought I would update ya'll
I ordered my L31R last night from Jegs. Should be here Friday. Now need to get cam.