Matthew1821

Hey guys. I had an lt4 hot cam swap a while back but it didn’t sound like a hot cam. Whenever I tore down the valve covers, the ls6 beehives and comp retainers were never installed either. They gave my “stock” cam and springs back but I wanted to make sure this is the actual stock cam that came with the car before I tear it down completely. It’s from a 1992 z28 5.7 TPI

The only numbers on the cam are GMPT•BC•15•••705

Does this look familiar?

TheFryer

1995-’97 350 WITH ALUMINUM HEADS - In 1995, the aluminum-headed motors got the late, pin-drive distributor, so there’s a second version of the H.O. cam with the big pilot hole (.500" x 1.0625" ) and the long (.685" ) dowel pin. Look for a cam with the long pin and either "242" or "705" stamped on the barrel in front of the first lobe.

The 92-94 can be identified by the number "241" stamped on the barrel in front of the first lobe.

hope this helps. i found this info on a few different sites and they all seem to agree about the numbers and years.

LT1/TA

You can measure the stock cam lobe and get the lobe lift.Here is a video below.


The hot cam is designed to run 1.6 rockers,if you are still running 1.5 rockers that could be why it does not sound like it it should.
The lobe lift is .525 w/1.6 rockers and .492 w/1.5 rockers.

Matthew1821

yep, it has the long dowel pin and the "705" on the barrel. so definitely not the cam from my car

KyleF

Am I missing something? The above information pertains to a LT1. In 95, they changed the Opti design and this is what is being referenced above.

No 92 Camaro came with an LT1 optispark style cam.

TheFryer

i know but his cam number match's the LT1 HO cam. he wanted to know if it was the stock cam for his 92 and it was not. 92-94 would of had 241 stamped on it.

KyleF

That's pretty ballsy for a shop to supply that as a "Stock" Part. It's not even from the same generation of engine.

Fast355

iTrader: (2)

IT IS HOWEVER ENTIRELY POSSIBLE THAT IS THE CAM THAT CAME OUT OF HIS CAR!!!

241 would also be a LT1 cam, not a TPI cam. The L98 TPI cam should be stamped 049.

KyleF

Interesting statement. I have not pulled a cam out of an LT1. So this may be a dumb question, but I am going to ask it so I have this knowledge moving on. I thought since between the L98 to LT1 GM switched from using an conventional distributor to the Optispark. the Conventional was ran by a gear on the cam and the opti by the pin on the front of the cam. To me, the LT1 would not have the gear and the L98 would not have the pin. Any give profile is available for both styles I am sure but wouldn't a stock cam in an LT1 not have the gear and the one in the L98 have it?

Fast355

iTrader: (2)

The L99/LT1 and LT4 cam for that matter all still have a distributor gear. The oil pump on those engines is in the same location it always has been and is driven by a stub shaft that bolts in the valley under the intake. GM also did the same oil pump drive setup on the L18 496 8.1 Vortecs as well even though they have 24x crank signal and coil packs. The pin is also on all small blocks. Its just longer on the LT1 based cams. Its just a longer dowl pin on the optisparks. Easily tapped into the cam or cut shorter for older engines.

KyleF

Thanks for the info. Saved me some time looking it up. Fun thing is I am planning on doing a Cam swap in a 96 LT4 in the next year or two. So, this is all useful.

RBob

iTrader: (1)

If the cam they returned to you still has the long pin sticking out. It wasn't in your L98 as the pin would have cut a hole in the timing chain cover. The ensuing noise and oil leak would be signs that something is wrong.

RBob.

KyleF

I was also thinking about this, but it you have never really seen the difference, both have pins. Might not raise a red flag initially.