LS1LT1 Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter #1 (Edited)
I've got a manifold to convert my lt1 from FI to carb and I am getting close to getting it installed. There is a reasonably large gap between the engine block and the intake manifold, it mates up fine to the heads though. Should I just fill it with silicone or does there need to be a gasket there?

Looks like it fits up just right without the intake gaskets. I might just silicone the whole thing.
 

·
Global Moderator
Joined
·
13,430 Posts
If this is at the back of the engine, yes silicon the area. When you put intake manifold ob, just snug the bolts down and wait an hour so silicon can partway cure. Then torque bolts down to specs found in factory service manual.

If you don't have a factory service manual, you can download the 93 , 94 , 95 , & 96 f-body service
at at the following link. www.mediafire.com/?40mfgeoe4ctti

I take it that carb intake has a provision for standard SBC distributor.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #3
If this is at the back of the engine, yes silicon the area. When you put intake manifold ob, just snug the bolts down and wait an hour so silicon can partway cure. Then torque bolts down to specs found in factory service manual.

If you don't have a factory service manual, you can download the 93 , 94 , 95 , & 96 f-body service
at at the following link. www.mediafire.com/?40mfgeoe4ctti

I take it that carb intake has a provision for standard SBC distributor.
Yes, I have an HEI streetfire dist for it. I ended up ditching the intake gaskets since it mated up so nice without them and I used some fuel resistant grey silicone to seal it up. Got a nice little bit of squeeze out all around after I torqued it down so I think it's good to go.

How should I go about setting the dizzy for timing? I've got the optispark block-off plate with the notch on it but I still have the stock crank pully. Can I use the stock pulley and put some type of pin in it if I know where the motor is in relation to #1 TDC? I've got two marks on the timing cover, one at #1 TDC and the other at #6 TDC that the pin on the camshaft points to.

 

·
Global Moderator
Joined
·
13,430 Posts
I do it the old fashioned way. I remove #1 spark plug. Turn the engine over by hand using a socket on crank nut with a long breaker bar.

With my finger over the spark plug hole, I turn engine over until I start to feel compression pressure. I then pay attention to the timing mark for # 1 and turn crank until at about 10 degrees before TDC.

That's when I install dist with rotor pointing at cylinder 1 lug. Any fine tuning can be done by rotating dist. Then tighten it down. I'm assuming here that you are using an sbc type dist with vacuum & centrifugal advance. As computer controlled sbc has no advance mechanism, & depends on computer to advance & retard timing.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #5
I do it the old fashioned way. I remove #1 spark plug. Turn the engine over by hand using a socket on crank nut with a long breaker bar.

With my finger over the spark plug hole, I turn engine over until I start to feel compression pressure. I then pay attention to the timing mark for # 1 and turn crank until at about 10 degrees before TDC.

That's when I install dist with rotor pointing at cylinder 1 lug. Any fine tuning can be done by rotating dist. Then tighten it down. I'm assuming here that you are using an sbc type dist with vacuum & centrifugal advance. As computer controlled sbc has no advance mechanism, & depends on computer to advance & retard timing.
Yes, vac and mech adv. Mech adv is tuned for 22 degrees at 4,000 RPM. and the vac adv can be set to limits.

So 10 degrees before TDC and then point the rotor at the #1 s.plug wire right? This is the first dizzy I have ever messed with.
 

·
Global Moderator
Joined
·
13,430 Posts
You have to make sure that cylinder # 1 is on it's compression stroke. That's why you have # 1 plug out & your finger in the plug hole while hand turning the crank.

For those who have never timed a dist, a little theory. A 4 stroke engine will take 2 full crank rotations for every 1 camshaft rotation. That means that crank will bring piston up to tdc 2 times but cyl # 1 will only fire once for every 2 crank rotations.

So if you simply turned crank pulley to tdc on cyl # 1, you have a 50-50 chance of it being on compression stroke. Again, that's why you check for compression on cyl # 1 as you hand crank engine. This makes sure you get dist timed correctly.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #7 (Edited)
You have to make sure that cylinder # 1 is on it's compression stroke. That's why you have # 1 plug out & your finger in the plug hole while hand turning the crank.

For those who have never timed a dist, a little theory. A 4 stroke engine will take 2 full crank rotations for every 1 camshaft rotation. That means that crank will bring piston up to tdc 2 times but cyl # 1 will only fire once for every 2 crank rotations.

So if you simply turned crank pulley to tdc on cyl # 1, you have a 50-50 chance of it being on compression stroke. Again, that's why you check for compression on cyl # 1 as you hand crank engine. This makes sure you get dist timed correctly.
Yeah, I have the cam gear exposed where the original distributor went on the front so I can see the pin on the cam. It points to the passenger side 90 degrees when its #1 TDC. I made sure to mark the timing cover with it. It's also #6 TDC 180 degrees opposite, 1 crank rotation in other words. I put the pin on the cam just before #1 TDC (about 10 degrees according to the degree circle I printed out) and then got the rotor on the dizzy to point about towards #1 cylinder then lined up the cap with the #1 plug wire right on the rotor point.
32559
32560
 

·
Premium Member
Joined
·
14 Posts
I've got a manifold to convert my lt1 from FI to carb and I am getting close to getting it installed. There is a reasonably large gap between the engine block and the intake manifold, it mates up fine to the heads though. Should I just fill it with silicone or does there need to be a gasket there?

Looks like it fits up just right without the intake gaskets. I might just silicone the whole thing.
If it's the right intake manifold there will be a gap on the front and rear, its referred to as the china wall. That's the only thing that should be siliconed and a 1/2" in up onto the gasket. use a good gasket like Felpro. If you use silicone on the whole manifold some will squeeze into the intake path and interrupt air flow. Make sure you use a good grade of automotive silicone, the gray works the best.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #9
If it's the right intake manifold there will be a gap on the front and rear, its referred to as the china wall. That's the only thing that should be siliconed and a 1/2" in up onto the gasket. use a good gasket like Felpro. If you use silicone on the whole manifold some will squeeze into the intake path and interrupt air flow. Make sure you use a good grade of automotive silicone, the gray works the best.
I used a thin layer of silicone instead of the intake gaskets. I made sure not to use too much and there was just a very small amount of squeeze out. Indeed I did use the gray silicone.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #10
I am pretty close to first crank up I think.

If I want to check for oil pressure, I check at the hole in the back of the block right? If that port is open, should I be getting oil out of it when I turn the engine over and about how long should it take for it to pressure up from a fresh rebuild?

I don't have a manual gauge to put in there for now so my plan was to check for oil flow, then plug it with the original electronic sender. All I want to do for now it get it to start.
 
1 - 10 of 10 Posts
Top