I am a C-3 owner(69 big block) and have owned a C-4 LT-1, but never an L-98. I am building a 350 Chevy engine for a friends Jaguar. We are using a TPI from an 85 Corvette.. The engine I built is a 74 4 bolt main "010" block and .194 heads. The problem is when I put the intake plenum on, it does not seat down onto the heads with the rubber end seals in place on the block. It seems to seat fine without the seals in place. Do I just use silicone in place of the rubber seals? It seems to correct the fit problem but this block does not have the grooves commonly found on some later small blocks. Any advise appreciated.

 

I just decked my block and slightly milled the heads and had the same issue. I just used black RTV. Extra dollups in the corners. Works fine so-far.

 

I torqued the intake plenum with the gaskets and seals in place and the removed it. It was appearant that the gaskets were not sealing at the bottom(nearest the valley). I torqued it again without the end gaskets and it looks like it contacts everywhere. Still no sealant front and rear.

 

RTV is the standard for sealing the ends of the intake on an L98. Put down a reasonable bead (not goopy) and let it sit overnight before installing.

As an aside, I have a '90 and there is no "groove" on the ends of the block for a gasket or for sealer. Also, I'm not an expert on what year base fits what year block and head combination, but you may be running up against an angle problem. If you probably decked the block and shaved the heads without angle milling them to match up to the intake base, it could be an issue. BTW, if the base and runners are stock, you will have *much* power bottled up in that hot rod motor because it can't flow enough air into the heads. Even on a stock motor you can pick up ~ 20 horsepower using an Accell base and big tube runners. More with a Superram. On a modified motor, the difference is really huge. I recently drove a hot rod L98 on a roadrace track with worked Brodix heads cam and headers, the thing just stops revving at 5,000. Yea, you can stay on it and make some noise above that rpm, but it's just thrashing. My car with stock internals and just bolt ons, pulls harder and longer with the intake setup mentioned, along with a 52mm TB, headers, no cats. Not trying to rain on anybodys parade, but if the TPI setup is new to you, I would hate for you to invest all kinds of $$ on the heads etc and use a stock TPI. Your buddy would love how it pulled off the line but would readily recognize that the motor is constipated.

 

rtv sealant for me as well you can let it skin then install the manifold hope this helps :crazy: :smash:

 

You're at a very serious point in the assembly that, if not handled correctly, could cause you lots of problems down the road.

If you sit the intake manifold on the heads with only the side gaskets in place there should be a gap at each end of the intake manifold. The gap should be about 1/8th inch, give or take.

More importantly, with the side gaskets in place, each intake manifold bolt hole should align perfectly with the threaded holes in the heads. If not, the ports will not be properly aligned. Best case, all you'll have is a power loss due to the misalignment: Worse case, the intake will suck air on the underside where you can't see or hear it and oil and air will get sucked into the intake port.

Many times if the heads are flat milled a significant amount, the intake manifold must also be milled to insure proper alignment. There is a formula used by machine shops to determine how much metal to remove.

Significant decking of the block decks can also cause/contribute to this.

Take your time and make sure that sucka lines up correctly.

BTW, trash the end seals that come with the intake manifold gasket set and use O2 safe, Hi-Temp silicone sealant on the ends. Use a punch to dimple both ends of the block and the underside of the intake to give the sealant places to 'bite'. Dimples should be spaced about .030/.060 apart. You'll end up with more than 30 dimples at each of the four locations.

Hope this helps.

Jake

 

On my L98, I always have to discard the end gaskets and use RTV. I don't wait to install like some have said. I usually install it right away. Just don't use too much and put the bead towards the outboard side more. The main objective is to not have so much that it squishes into the inside of the lifter valley. I like about 1/8" thickness. I don't mind it squishing outwards some. This is when i wait. Don't start the motor until the next day. Trim excess silicone with an exacto knife back flush. I've had my stock intake off and on a couple times and the Super-Ram off and on 3 times. Always the same procedure. you can take everyone's suggestions and come up with something you feel comfortable with. Good Luck!
:cheers:

 

Can the tpi and do this: http://www.momarefi.com/images/momar017-3.jpg