KLJZBQEEHE

[Jay Magness]

In my recently acquired '81 C3 I am replacing the extremely tired and worn L81 with a GMPP 350/330HP vortec long block. With very few modifications everything bolts up and is working just fine -- with one exception. The GM dual plane intake manifold I purchased to match the vortec heads is nearly one inch higher than the intake on the L81. All indications are that the stock air cleaner atop the quadrajet will not clear the closed hood. Have any of you run into this problem? If so, how did you remedy it? For the sake of appearance I want to retain the original air cleaner. Thanks.

[Joe L.]

Re: KLJZBQEEHE

Jay-----

First of all, I've never, personally, dealt with this problem. However, I think that your options are going to be very limited and expensive if, indeed, the vortec manifold that you have (likely, GM #12496820) will not allow enough hood clearance.

Consider the following:

1) There is no aftermarket Vortec manifold that I know of that will provide a lower profile than the above-referenced manifold;

2) You cannot machine the carb flange of the above-referenced manifold (or, any other aftermarket manifold) by any significant amount. So, this is not an option;

3) You cannot use or adapt a non-Vortec manifold to fit your Vortec heads.

Therefore, the only option that I see is to replace the Vortec heads with standard heads. You could have your existing heads reconditioned and use them. However, the problem with this option is that your 75 cc heads will drop you down to a very low compression ratio with the long block you'd have. So, your best bet would be to use a set of 58-64 cc heads.

One other thing: irregardless of the "originality" considerations of the air cleaner, if the car is subject to emissions testing, you'll not usually pass with a replaced, non-original air cleaner. You'll probably get by with the replaced engine, but not with a non-original air cleaner.

Perhaps, someone else will have an easier solution than I've indicated. I can't think of anything else, though.

[Chuck S.]

Re: KLJZBQEEHE

"Perhaps, someone else will have an easier solution than I've indicated. I can't think of anything else, though."

Ditching the Vortec heads and rebuilding the original heads seems like an un-attractive solution to me. Here's an idea, but mebbe it's not too appetizing if his mind-set is to keep the original air cleaner...If it were me, I would invest in an aftermarket hood with a big honkin' L88 hood riser or some such. I would keep the engine and hood, and put them back on when I was through driving and ready to sell.

[Joe L.]

Addendum

Jay----

One other thought that I had: some GM cylinder heads are "dual-drilled" for use with both standard and Vortec style manifolds. However, the GM #12558060 heads used for the 330/350 are not. It MIGHT be possible to drill the heads for a standard manifold installation which would allow you to use your original intake with the Vortec heads. The problem is that I don't know if the 12558062 castings (the basis for the GM #12558060 heads) have enough "meat" in the required areas for the standard manifold bolt holes.

You might want to check with a competent machine shop in your area.

[Mark #28455]

when the vortec heads first came out

It was common for the dirt track racers to drill them for the old style bolt pattern and use the stock iron intakes on them. There is a slight port mismatch, but you can deal with this if necessary by having a good welder add a bead or two to your stock intake and re-machine the surface. All in all about a $100-200 dollar job for the intake if the machinist is a friend. The heads you can drill yourself, just use a gasket for the locations - that's how the old Chevy Power manual used to say to do it.

Good luck,
Mark

[Joe L.]

Re: when the vortec heads first came out

Mark-----

The problem is that I would not attempt to drill them with the heads mounted on the engine. And, once the heads are off the engine, it would be worth it to have a machine shop do it to ensure that the holes and the tappings are "straight-and-true".