I'm helping a friend of my son rebuild his engine using a long block we purchased from a rebuilder. His is a '95 LT-1, with the vented Opti.

The BDBHs (Brain Dead Booger Heads) that built this long block up used a cam set up for the non-vented Opti (which I guess is either a '93 or '94 cam).

Question: other than the vented/non-vented Opti, is there anything else different about the cam? The reason I ask is one of the options I'm going to press them on is to just send me the right cam, I figure that'll be faster than having them send me another long block.

And, on the subject of cam installs, is there any way I can keep the lifters up so I don't have to pull the intake manifold? Or should I just pull the manifold back off?

TIA, and have a good one,
Mike

 

Intake has to come off, we have that retainer plate that actually pushes down on the lifters. I have never tried but I suppose there is a tiny chance you could do it like the ls1 swaps.

I think there is a tiny tiny difference in the cam specs. Getting the opti/timing cover right will make the car run. If you plan on a complete stock replacement I don't see a need to worry about the spec difference.

 

No chance at all you can hold the lifters up. None.

The difference in the cams is the dowel pin length. Cam needs to come out, a 94 cam's dowel is too short to drive a vented opti. Worst case you can have a new dowel put in by a machine shop.

Any difference in specs will be negligible, completely unimportant.

 

The '95 - '97 cam has a bigger recess in front for the vented opti. A '93 - '94 cam does not have the extra recess and will not work with a vented opti. You can use a '95 + cam or an aftermarket cam in any year for a vented or non-vented opti. Need the correct dowel pin length also.

 

The pilot hole in the nose of the cam is also a differnt diameter.



The cam sprocket is also different:



The timing covers are different:

 

Ah, I stand corrected! Didn't realize the center hole was different too!

 

Additionally, you can't just hold-up the lifters with the intake on like traditional SBCs and slide the cam out, because you also have the LT oil pump drive shaft down in the valley.

WD

 

To all,

Thanks for the info. After my first post I figured out that I could pull the intake as easily as I could come up with some way of trying to hold them up (thinking about 16 telescoping magnets). As far as the oil pump drive was concerned, I was thinking I could rotate the cam as it engages the gears, but that might not be wise considering the bearings.

So, the intake manifold comes off.

Fred, found out about the pilot hole the hard way. I guess a '94 Opti could fit (since it's pin is smaller diameter), but for sure not the other way 'round.

Y'all have a good one,
Mike

 

FYI. The rear bearing journal on the cam (which is behind the 90 degree oil pump drive gear) would preclude you from rotating the cam to disengage it from the oil pump drive shaft. So, better get to work on pulling the intake manifold, the only way to get-er-done!

WD

 

The 93/94 Opti splined driveshaft "ends" in the cam sprocket - doeasn't go into the cam. The 95-97 Opti shaft has no splines, and passes through the cam sprocket and rests in the hole in the cam, functioning as a pilot shaft.

 

An update: the engine builder is sending us a complete new long block assembly. Probably the best solution, as long as they get it right this time.

Thanks for the assist (this post went a long way towards showing the builders what they'd done wrong), and have a good one,
Mike