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Topic: Intake Manifold Fit-Up Question

in Forum: C3 Engines

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Intake Manifold Fit-Up Question (1/8)
8/30/11 2:16am

daveo76
Former Member
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 857

It sounds as if there are two options for intake gaskets for vortec heads/manifolds: a Fel-Pro option (PN 1255) and a GM option. The ones shown in the pic are the Fel-Pro's. They are very thick - about 1/8". This is causing a gap between the manifold and the front and back block edges. The gap measures about .10". Will I be able to sufficiently fill this gap with Silicone or do I need to take other action? These gaskets are supposedly very good and they seem to match the intake ports with the heads very well. The bolts also line up well. I'd like to keep 'em, but I believe the GM gaskets may be slightly thinner. Another thought I had was to actually use those rubber end rail things that most gasket kits come with (these Fel-Pro's did not), but I don't really want to do that since everyone says they invariably leak. Thoughts?

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1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

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Re: Intake Manifold Fit-Up Question (2/8)
8/30/11 6:18am

nosal1
Former Member
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.

Joined: 3/21/2006
Posts: 262

Dave Do not use the rubber front and rear intake manifold gasket as they have a tendency to slip and leak.Use the gaskets you have in place in the picture.If you use them use RTV Black and a bead of 3/16" - 1/4"..After you have the bead in place,with a little extra where heads meet the block,wait about 10 minutes to install the intake,coat the intake bolts with sealant and torque to spec's and sequence..I see you are using the OEM intake(cast iron?)so be very careful to set it in place without shifting the manifold,even if you have to get a helping hand to set it in place..They are not that heavy but clumsy...Good luck and have a great day.. Sal C

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Re: Intake Manifold Fit-Up Question (3/8)
8/30/11 9:10pm

Sal, it's an aluminum GMPP intake. (painted orange since I bought it gently used and it was already painted black). It's very similar in design to an Edelbrock Performer. Two questions for you: 1) what sealant for the bolts? I have a set of ARP bolts for it and was assuming I'd use the ARP lube for 'em. Those bolts don't go into water jackets do they? 2) Do you know what the torque spec is? I've seen 132 in-lbs (11 ft-lbs) but want to be sure.

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1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

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Re: Intake Manifold Fit-Up Question (4/8)
8/31/11 4:35am

Good Morning Dave..There are four bolts( in board bolts)front and back that are above the oil galley and sealant/lube is normally used to seal and improve the threading process(contains anti-seize) and is Permatex #2 a pliable sealant lube in a tube..The ARP lube is also very good especially for SS ARP bolts and should be used if Stainless bolts..The torque for the intake bolts on a Aluminum intake is generally 18-22 ft. lbs.,however I have used 22 ft.lbs in all and have never had a failure and I do this at least 3 times a week on a build..

A note about using an aluminum intake.......We use aluminum intakes to help dissipate heat generated by the engine running,so that we can introduce a colder fuel to the cylinders to produce higher HP and performance.Colder fuel enhance better performance..Paint on the aluminum intake voids the concept.. Continued luck in your build..Take care.. Sal C

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Re: Intake Manifold Fit-Up Question (5/8)
8/31/11 10:44am

Thanks for the continued info, Sal C. My bolts are not stainless, they're black oxide. So Permatex No. 2 should suffice? Good news if so because I have No. 2 already, but I don't yet have the ARP lube. Good info about paint on an aluminum manifold. Not my first choice to have it painted, but that's what I have available now so I guess I'll use that. May consider changing it out some day, but stripping it seems like it would be a pretty big job. Thanks,

Dave

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1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

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Re: Intake Manifold Fit-Up Question (6/8)
8/31/11 4:31pm

Dave

The Permatex #2 will do perfectly so go with it my friend .. As far as stripping the manifold,you are right that it is a time consuming project..

I have done it many times and was a bit of work..I use Aircraft paint stripper at lest two times and as many as three. After the last time I wash it thoroughly and dry with compressed air,I then spray with carb cleaner the brake clean..

After that is done there still more to do and then I BEAD blast not sand blast to remove all traces of paint..Spray on some Simple Green and rinse with hot water to wash off any beads or bead dust..

Again I wash it down with brake clean and then spray on a Polyphosphoric acid and let set 25 seconds and immediately wash with hot water and blow dry with compressed air.....This is a time consuming project,but rewarding as it opens the pores of the aluminum and allows to dissipate the heat better.. Sorry for being so lengthy and good luck...Sal c

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Re: Intake Manifold Fit-Up Question (7/8)
9/1/11 10:34pm

Thanks for the info, Sal. I think I'm going to pass on stripping this particular manifold. I feel like I'd be better off selling that one and looking around for another gently used one - not painted. But I think I'll just live with the painted one - this motor is going to have substantially more juice than my stock L-48, I probably won't miss those couple few ponies.

The intake bolt info you provided will be very helpful, though....

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1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

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Re: Intake Manifold Fit-Up Question (8/8)
9/2/11 5:31am

You are welcome Dave and good luck on your completion of the build and the running up of your engine.Please do not hesitate to ask any questions,hopefully I can be of help.Have a great day....Sal C

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