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o-ring headgasket 111044-u0825 for my l20b turbo motor


Kulper620

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That's cool you found someone to custom make that gasket. I was thinking of running one back in the early 90's but they were NLA even back then..

 

Friend of mine had a similar problem with his head. Shop that did the valve work didn't realize there is a height difference between intake and exhaust valves and ground seats to all the same depth. He ended up using shorter lash pads on exhaust rather than having shop replace the seats they ground the crap out of. His didn't look as far off as yours though, but it's been over 20 years since we built it now...

 

If you have a FSM take that with you when you drop off head. That way your machinist knows what the specs should be, and can find the mistake easier. 

 

Kinda looks like lash pads are too tall for the retainers anyway. Nissan made 3 different retainers for the lash pads according to lash cap height. The height of the pads where rocker sits shouldn't be much above the height of retainer, or you run the risk of them falling out. Cam in photo looks to be stock lift based on how much material I see on base circle. Measure the base circle and height of lobe and subtract. Then multiply by 1.5 for valve lift. That will give you an idea of which lash pads to use...

 

Interesting your turbocharging a L20B with flat tops. That's a pretty high compression ratio to start with 10;1-11:1 depending on head used. Wont be able to run much boost until detonation takes over. Open heads are detonation prone to begin with. Especially with flat tops. combustion chamber ends up looking like a squished pancake, rather than the ideal hemispherical shape.

 

Would like to see some photos of your turbo setup. Im slowly building a L20b turbo for my 4X4 620 too...

 

IMG_0912_zpsbaf2a457.jpg

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This is my setup, mind you this motor build began in 1983 by another guy, the machine shop says everything in the block looked amazing for how long ago it was done and said it was done rite which gave me a little piece of mind, I wanted to keep it all old school, Gonna have the header blasted at some point and get it ceramic coated, think I'll be running in between 7-15 lbs of boost and have water meth injection to keep it from detonation

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Ahh.. I think I saw this on CL year or two ago.. is a draw through or blow thru?

 

I would limit boost at 3psi to start on pump gas. With racing fuel you can get away with the higher compression ratios and boost. Pump gas, not so much.

 

Is head open or closed chamber?

 

Years ago I had '76 620 with a turbo. That was a pretty fun truck!

 

Had a Rayjay turbo drawing through a '79 mustang turbo carb. L18 with dished L20b pistons. open head, MSD BTM, and water injection.

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Should be interesting if you can get all to work. Turbo might be overkill and actually hurt power. My experience with the flat top / open head combo was not good. My friend used that combo on his truck with 290 cam SU's and tri-y header and it never did run good. His wife made him get rid of it cause it would randomly back fire when he shut it off lol...

 

 

 

I wouldn't be able to run a close chamber head on it, I have the a87 peanut head on my l18 in my truck now with the su's, it's a great runner and good power

 

My truck has a engine my old man built back in the 80's.

 

L20b w/SSS L18 pistons (virtually flat) closed A87 270/.480 32/36 and custom ss tri-y header 2-1/4 back

 

IMG_0884_zps1d2531f4.jpg

 

Been really happy with this engine. Turbo motor got put on back burner for now....

 

 

 

It was gonna be draw but I'm gonna em up doing blow through with r1 carbs now

 

Funny. I was nearing the end of reading the R-1 thread. Sounds like there are tuning issues still. the fact that everyone is running 3-1/2 turns out on idle mix says pilot needs to be bigger. I would think that the vacuum holes that open the slides would need to be opened up to make up for the lower velocity, and higher volume on a 2.0l engine that spins half the RPM....

 

Reversion is a issue with ITB's and affects single carb engines too. This can cause a engine that runs rich at idle to run lean while decelerating causing it to backfire. A good long tube 36" header might help low speed and idle tuning alot.... I let you guys figure it out. If id do change my weber it will be for this...

 

IMG_1040_zpsac6b3117.jpg

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  • 4 weeks later...

That's a Crown turbo manifold so the turbo should clear the box fine. I ran one of those back in the 70's 80's. Their prone to breakage where the exhaust pipe is welded to the flange because the flange is so thin. The flange on the manifold for the turbo is threaded and those can be an issue when removing the turbo I installed threaded studs. My engine was a L16 with L18 rods .100 shorter and stock dished pistons with SSS head and custom turbo ground cam by Moon Equipment and a weber 40mm side draft bolted to the Turbo and water injection coming on at 7psi with a total 12 psi boost running 13.90, 14:00. Stock everything else cept for Muholland lowering kit.

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