MANIFOLDS

[domn8tr]

So I've been struggling with trying to get my exhaust manifold to stop leaking and i realize the problem is the deck height on the L20b is higher. the bottom of the manifold hits the bell housing (which I trimmed). Is the L20b exhaust manifold off a later 620 longer? Also on the intake side the runners in the intake manifold are much smaller than the ports on the head. Do L20b Intake manifolds have larger diameter runners ?I was thinking of hoggin them out but dont want to hit the water passage and there's quite a bit of difference in size.

[Z-train]

Smaller manifold runners than head ports is a good thing,as long as things are relative.Unless you are going to be twisting that motor to the moon all the time,hogging the intake(manifold) ports will actually hurt performance.

[banzai510(hainz)]

Most L20b exhaust man were shorter and used a O ring type bolt up.

a early L16 squareportexhaust manifold should work if you have a square port head.

If this is a truck the Y pipe part could run different But i dont know why it would hit and mever seen that before. Usually the Y pipe shape will hit the floor when installing a taller L20 on a orginal L18/18 set up.

 

Most run short tube heasders on the L20s and they what I have seen all fit . trucks cars ect....

[datzenmike]

So I've been struggling with trying to get my exhaust manifold to stop leaking and i realize the problem is the deck height on the L20b is higher. the bottom of the manifold hits the bell housing (which I trimmed). Is the L20b exhaust manifold off a later 620 longer? Also on the intake side the runners in the intake manifold are much smaller than the ports on the head. Do L20b Intake manifolds have larger diameter runners ?I was thinking of hoggin them out but dont want to hit the water passage and there's quite a bit of difference in size.

 

No way the exhaust manifold can hit the bell housing, you must mean the down pipe that goes under the car to the muffler.

 

The Later L20B exhaust manifold is a four into one large pipe. The down pipe is a single pipe bolted to it. Try to keep the L16 you have it the best. Take to a shop and have them make one with the proper bends.

 

The intake can be port matched without worry, you won't hit anything. Just port in a couple of inches.... OR get the intake off a '78 or 79 L20B they are already larger. ('77 and earlier L20Bs wont work) They will have a bolt on EGR (sub) manifold. I don't know why people want the early L16 intakes just for looks for. They are smaller than the L20B ones. Just for looks you run a restrictive intake?, c'mon!.

[Z-train]

I don't know why people want the early L16 intakes just for looks for. They are smaller than the L20B ones. Just for looks you run a restrictive intake?, c'mon!.

I'm running a L-16 on my LZ-23.Depending on wht you're after,they can be the best choice.

[datzenmike]

That's the one with the dyno sheet?

 

Find a '78/79 intake and run a comparison.

 

BTW that was some monster torque numbers.

[merlin]

I'm actually going through this tonight on my 521 l20b swap...

 

 

I set up the new Weber 32/36 on the stock 78 L20b intake but it has clearance issues with the top of the exhaust mani, so I'm going to port out the 521 stock intake and use that instead.

 

The 69 510 l16 exhaust mani i have bolted up is fine, but it will need a pretty bendy y pipe collector to weave through the steering and torsion bars as it is much tighter to the engine and has amore swooped back angle than the stock L20b one ...

 

I ported out the outlet side of the exhaust manifold to take a true 1 and 1/2 twin pipe flange which i welded up today.. going to get some 1.5 inch flex pipes tomorrow in the big smoke so i can mock up the right bends, then take them to the exhaust shop for a mandrel bend with real pipe.

[Z-train]

That's the one with the dyno sheet?

 

Find a '78/79 intake and run a comparison.

 

BTW that was some monster torque numbers.

The numbers would be down.Keep in mind that my motor was built for low end grunt.ANYTHING that helps promote low speed cylinder filling(port velocity) will help.Trade off is the motor is all done by 4500.But that's fine for me.

Here's the new FI manifold.They have the same port diamter as the L-16& 18..31mm.THe L-20B is 35mm.

[jon521]

a early L16 squareportexhaust manifold should work if you have a square port head.

 

 

true story. mine is very close to the bell housing, but clears.

[datzenmike]

OOooo, long runners too. Also good for low speed tuned intake.

[Z-train]

OOooo, long runners too. Also good for low speed tuned intake.

Almost got the 413 cross-ram effect going here.....without the "cross" part. :rolleyes:

[domn8tr]

Well I got it done! I had to grind the side web on the block and the bellhousing on the dogleg quite a bit. I now have about 1/4 inch clearance. The head is a race built A87 on a 2 liter block so the rectangular port manifold works well. I also hogged out the intake manifold to match the big port head. I can feel a slight power increase but mostly i'm enjoying the quiet manifold and flange!! AHHH Peace at Last !!

[banzai510(hainz)]

great take some photos

[domn8tr]

 

 

 

 

 

 

 

Hooray no more exhaust leak!

[ggzilla]

How did you resolve the exhaust leak? Did you fit a new exhaust manifold? Or just change the gasket?

[domn8tr]

No the leak was being caused by using the a87 1600 head and exhaust manifold on an L20b block and dogleg 5 speed. The Y pipe hit due to the taller block so the manifold would not seat up on the head. Solution1 ; buy shorty headers. Shadetree mechanic solution #2 : Start Grinding!