What cam for propane?

TwistedTiTan · Apr 14, 2013

Looking for some help deciding which cam to order .
Heres what I have....

93 SBC TBI short block ( standard pistons)
98 SBC Vortec heads 202 valves 60.4 cc chambers , springs good up to .500 lift
Comp Cams 1.6 Magnum Roller Rockers
Impco 425 single mixer

compression should be about 9:1 to 9:5:1

I'm wanting to keep a standard torque converter and looking for as much power and torque as possible under 4k rpm's.

halcat · Apr 14, 2013

Call comp cams in Memphis , I had a big block chevy they took my info and ground me one for propane and gave my motor 50 more hp

Fire Freak · Apr 14, 2013

i have a 383 with dual mixers with a comp 454 lift cam. I love it ,lots of power stock converter

REVELATION · Apr 15, 2013

I had a 355 with a 488 cam that had 9:1 ratio now I'm running a 406 with 12:1 ratio and a 525 cam.

95yj · Apr 15, 2013

Comp 305h

TwistedTiTan · Apr 15, 2013

95yj said:
Comp 305h

that would be a good cam " IF " I was looking for hp after 4k rpm's and if I was running a 3500 stall

TwistedTiTan · Apr 15, 2013

been thinking about this one .
http://www.compcams.com/v002/Pages/396/XR276HR-10.aspx

JRH · Apr 15, 2013

Erson
ERSE110046K
Dur Adv [email protected]" Valve lift Lobe Center
292°/300° 232°/234° .488"/.488" 108°

drivermod · Apr 15, 2013

Careful with those 1.6 rockers. Look closely at the what rocker ratio was used to calculate the lift of the cam. Most of the sbc cams I've looked at were figured with a 1.52 ratio. So if thats the case with the cam listed above the .488 lift would actually be .513 lift with the 1.6 rockers.

TwistedTiTan · Apr 15, 2013

drivermod said:
Careful with those 1.6 rockers. Look closely at the what rocker ratio was used to calculate the lift of the cam. Most of the sbc cams I've looked at were figured with a 1.52 ratio. So if thats the case with the cam listed above the .488 lift would actually be .513 lift with the 1.6 rockers.

You are right. I need to choose another cam and change that link

Pumpkin · Apr 15, 2013

I have the 262/270 Comp Extreme 4x4 cam. More then happy with it. Its in a 406 with (about 10 to 1) stock 400 heads. Have the valve springs for that cam, a 450 mixer and stock converter. Makes great power off idle to where the mixer maxes out about 5,000 rpms. Just wished I had the coin for better heads. http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=96&sb=2

REVELATION · Apr 16, 2013

Yep On the 488 cam I ran 1.5's.

big ford · Apr 16, 2013

Do ur homework u need a good bit of vacuum to crank a propane motor , I just put a 1000 dollar custom cut roller cam n my big block ford and it does not like to crank, putting the comp cam 270 back n it my loss, stay around a 260 270 duration. Comp cam 4x4 best choice.

Fire Freak · Apr 17, 2013

Oh and my 383 has 12 to 1 compr. With stock rockers

altfuel1991 · Apr 17, 2013

big ford said:
Do ur homework u need a good bit of vacuum to crank a propane motor , I just put a 1000 dollar custom cut roller cam n my big block ford and it does not like to crank, putting the comp cam 270 back n it my loss, stay around a 260 270 duration. Comp cam 4x4 best choice.

We have a start valve that opens when you hit the starter and primes the fuel system for engines with large plenums or big cams. It pulls propane vapor from the secondary side of the vaporizer and has a hose going to the manifold to send the fuel under the throttle blades. It is simple it install.

Buddy Gamel
Precision Sales & Service, Inc.
451 64th Place South
Birmingham, Ala. 35212

877-403-7827, shop
205-591-2267, fax

[email protected]
[email protected]
www.alternatefuel.com
www.workhorseservice.com

big ford · Apr 17, 2013

I have one and it still hard to crank, can a cam be to big for propane 288/296 @ 0.20 with 722 lift

billstoy · Apr 17, 2013

I was told in cam selection choose a low over lap and allow more time for burn and get full gain from the octane. need vacume and lowrange! don't over cam and consider one from a turbo or super application

BUG-E J · Apr 17, 2013

What kinda power numbers you think its gonna make. I got a stock tbi on pane now and was looking into some "cheap" bolt on power. I been huntin some vortec used heads somebody can lay on me for a deal and just buy a good cam. I already got 1.5 roller rockers. It would be much easier to build a little stroker motor and slap some good heads on it but for that kinda money I'd rather go LS and ditch the grill gas.

billstoy · Apr 17, 2013

Propane has great benefits , average 107-110 octain, "I buy in bulk for 1.70$ per gal" allows for max total timing of up to 40 deg. most people would say propane motor tuned properly should gain 10% just on LP fuel. , no leaking fuel on hills or upside down! I have heard " not seen" people are running liquid propane thru stock fuel injector systems? propane has a pressure of up to 250 psi and in liquid form and with proper computer tuning It could work , it would also cool cylinders on this type system. The motor should be built to same specs as a motor on 110 octain fuel . motor will run hotter than stock also much cleaner. I studied the same stuff!! My next idea is a liquid propane regulated to 10 psi liquid NO2 system. using standard soloniods.
We'll see!

matth_85 · Apr 17, 2013

The Erson JRH posted made great power in his cab truck with a stock bottom end 350 and worked set of Vortecs. The heads were decked some and thats really about it I think. Made good power from idle-6K. He was running TH350 with a 2500 stall 203/205 doubler and 4:56's. Worked great on 39" Krawlers. Not the most HP but good HP and TQ all the way through. You could do this set-up for $500 or less.

An LS motor it going to be more HP but more on the top side than a SBC (figuratively speaking). To make the most power your gonna give up the low end. I am putting some more converter in mine to make up for this. I am very pleased though. But, an LS swap is going to be $1500-2500 depending on what you do. Obviously if you want big power then that price range is much more.