cardo0

Where can i get full duration numbers for Chevy hyd roller cams? GMPP catalog lists just the 0.050" duration numbers for duration. GM uses a odd lift value for the open/close valve lift to determine full duration. I recall GM cams have real long/slow rise initial ramps - for longer cam life - and are hard to compare to most aftermarket cam full duration numbers.
Looking at GMPP "hot cam" for the 350 but can't figure overlap without full duration numbers.

Anyone have a source for full duration on Chevy hyd roller cams?
cardo0

mr.beachcomber

Here's a link to the best info I've found on the LT4 Hot Cam; however, it really doesn't have the information you're looking for.

Based upon my experience with Chevy racing cams in the 70's and 80's, you wouldn't be able to discern much information even if you had their full cam specs as Chevy uses clearance ramps in their valve timing calculations. These ramps lift the affected valve gently off its seat. While looking good in overall duration, there is little flow hence the use of the industry standard lift @ 0.050" to determine actual cam duration for comparison with other aftermarket cams.

I, too, would be interested if anyone has actually measured the intake and exhaust lobes of the LT4 Hot Cam to see how much meaningful area there is under the cam's intake/exhaust profiles. So far, I haven't found a reliable source yet.

Curveit

The figures I got from my older GMPP are different than what mr . beachcombers' site lists, to further confuse things. Mine says...279/287- 218/228 @ .050, .525" w/ 1.6 rockers, and 112* lobe centerlines. If you're good at Math and my numbers are right, you might be able to figure it out. It is a fairly slow acting Cam, and I think you could do better at Comp Cams. For the same .050 numbers, a smaller "total" Duration number will idle better as well as picking up the bottom-mid range power, without losing any top end.

cardo0

Thx for the Hot Cam info - that just what i wanted. I read 'bout 53* overlap for the "Hot Cam" which ain't a whole lot. I don't think i can use the same intake ramp duration (62*) to 0.050" and exh ramp (53*) to 0.050" and just add it to other GM hyd roller 0.050" duration to get even a representative/useful number.
I would like 0.006" lift info for the "stock" LT4 cam and the "stock" LT1 cam(s) 0.006" info would also be nice but not totally nessesary. Trying to get an idea of how much overlap i can use and still pass smog. Yes i know the "Hot Cam" is not street legal.

Sorry for the late reply,
cardo0

cardo0

From this link: http://www.grandsportregistry.com/lt1vslt4.htm
Numbers are a bit suspect as they list LT1 & LT4 cams with larger intake durations than their exhaust duration (typo i hope) and i don't agree with what they have for overlap numbers either - only 41* for the LT1 and 46* for the stock LT4 cam. Also, their LT4 full duration numbers are larger than the LT4 "HOT CAM" duration numbers so i don't know where they got their cam info or whether they use 0.006" lift for full duration?

Still looking,
cardo0

ellewood

mr.beachcomber the link provide by you gave me the information
as much as possible about Where can i get full duration numbers for Chevy hyd roller cams.
Thanks a lot.
http://www.limos-la.com