propane camshafts

[cleanburner]

does anyone have any suggestions on a cam for my 496 chevy.
it's a 13 to one on full time propane hooked to a 2500 stall turbo 400 transmision, running 4;10 gears.
at this point i have a comp cam marine grind but the package is a bit slower than the previous 454.
i know a close match is an alcohol grind
the streetability is an issue as i do drive the car on the street as well as tow a small travel trailer on the highway

 

[patprimmer]

At a SWAG, go 10 deg more duration than the 454 had at the same lobe centres.

Towing a small trailer with your combo should not be the slightest problem so should not come into consideration for cam selection, unless your definition of small is a tonne or more and you already have something like 280+ duration at 0.050" lift.

You might want extra lift, but you give no indication of current cam specs, car weight, or port flow at various lifts.

What is streetable to one guy is a wild untameable beast to another, so decide on how it compares to your current cam and what difference in power curve you want.

If you have a flat tappet cam, you can get the best of both worlds by going to a roller, but at the significant cost of a steel cam, bronze dizzy drive gear, roller followers, suitable aftermarket rockers and pushrods and much stronger valve springs and retainers, and the machine work and labour to fit them.



Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[turbocohen]

Same cam profile as for gasoline works good but generally you can enhance low rpm torque rise with lpg by advancing the intake lobe a few degrees and slightly reducing exhaust duration. In my experiments lpg seemed to favor a slightly advanced mild cam centerline but my work was with emission certifiable oem centric engines.

 

[patprimmer]

My experience is LPG will tolerate a slightly bigger cam before the idle quality becomes a problem.

With LPG you lose slightly with VE so you need a little more airflow to maintain power.

My experience is limited to 2 engines.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.