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Questions, performance rebuild on my L20?


Rubberman

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OK, everyone excuse my stupidity, but, I gotta guy going to rebuild my L20 out of my 77 620. He has rebuilt many L20 motors but has never done any types of performance modifications and I'm clueless. I plan on getting a 38 weber, header, he said he would be boring it out (to what, I don't know) Is there a performance cam that I can get for it and where? I'm I going in the right direction with this or not? Is there other things I should do or can? I would appreciate anyones input on this. I don't want to change motors. I want to keep the L20 in it, but do what I can to get the most out of it. Thanks.

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that weber will work nicely.. or maybe some dual su's.. a nice header and exhaust always helps.. maybe a a87 peanut head for some higher compression.. as for the bore... Find out what he's doing!! what type of pistons he's gonna run ect. you dont want to low of compression.. but u dont want it to high either.. as for cams.. theres always regrinds.. an maybe search online to find an aftermarket one? altho my a87 works nice.. im sure i could put some bigger valves in do a 3 angle valve job.. maybe open the intake exhaust ports up a little. (port matching) some nice stiff valve springs an retainers is always nice.. you cant expect a bagillion hp from a l20b.. but you can expect some decent performance and reliability.. oh and if u dont already have it.. get an EI dizzy!

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that weber will work nicely.. or maybe some dual su's.. a nice header and exhaust always helps.. maybe a a87 peanut head for some higher compression.. as for the bore... Find out what he's doing!! what type of pistons he's gonna run ect. you dont want to low of compression.. but u dont want it to high either.. as for cams.. theres always regrinds.. an maybe search online to find an aftermarket one? altho my a87 works nice.. im sure i could put some bigger valves in do a 3 angle valve job.. maybe open the intake exhaust ports up a little. (port matching) some nice stiff valve springs an retainers is always nice.. you cant expect a bagillion hp from a l20b.. but you can expect some decent performance and reliability.. oh and if u dont already have it.. get an EI dizzy!

 

Would you recommend a Weber 36? 38? or a new set of dual su's?

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Dual SU's are cool and give nice performance but are hard to tune

 

Weber 38 Synchronus carb is a good performance carb and reliable. (not good for mileage tho)

 

Weber 32/36 cant be beat for reliability and daily driving (good on gas too)

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I would not get to carryed away with the short block much especially if its gonna be just a dd or street driven rig find some one that is capable of doing some good port work all your hp is in the head just make sure ya use a good head to start with the u67 head is a good head closed cambered heads are not the best to use anymore with nowadays gasoline.

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The '78 will be the W-58 head, the '77 will be the U-67. The '75 through '77 used them and they have the intake bolted to the exhaust to provide a warm intake manifold. I don't care for this set up, the head is fine. The biggest difference between the two are, the W-58 has round exhaust ports with steel liners for lowering emissions and two coolant passages for intake warming. The U-67 has square exhaust ports, no liners, no coolant passages. (it's bolted to the exhaust)

 

The EI distributor you want (and all you will ever need) is the 'match box' type and comes on the:

 

'79 200sx (maybe earlier but possibly the remote igniter type)

'79 620

'80 720

'79 HLa10 (new 510)

There may be others. specially on older L series motors that have been swapped. Learn to check and recognize the match box and get one. They look like this: Note the black box that gives it it's name.

 

http://i138.photobucket.com/albums/q251/datzenmike/Eidizzy.jpg[/img]"]Eidizzy.jpg

 

jesusno2 is right, don't get carried away. Maybe a re-grind or mild cam, 32/36 and ED distributor and good to go for a DD. Forget the header, at this stage you won't need it. Don't go more than a 1/4" larger exhaust pipe or you will loose more than you gain. Stock is adequate. If your system is ok, leave it. If it needs a muffler get the largest you can fit on your pipe. Check the catalog at the muffler shop and get creative. This will give a bit more flow and won't sound like a fart can.

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The later L20bs had emissions exhaust manis. Total crap. Get either a header or an older 4 into 2 mani with no emissions crap from a 510,521 or early 620 etc. Run 2 1/4 pipe into a decent turbo muffler. What head do you have? The u67 is just fine since it has the largest intake ports and square exhaust ports. If its got a w58 thats ok too and you CAN run a square exhaust mani on it even though its round port but best off to get a u67. The a87 has small intake ports so unless you get it seriously ported dont bother.

A 77 should have a EI dizzy. If not find one at a JY or get an older single point dizzy and a pertronics.

As for a cam we go over this almost daily. A regrind or aftermarket at .460" lift and under will work with stock springs and lash pad retainers. You will need new or reconditioned rockers and taller lash pads.

I have a .450" cam with .460 lash pads so a 460 would take 470 pads. You can get them from z therapy or let us know if you need the nissan part #s.

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I went down to the Auto Zone and checked on a Elect Dist. for a 79 200sx, they had a new one, looked like the picture above with the matchbox, $139.00 So this should bolt right on, no problems?

I've been checking for a weber at all the auto stores and all they have are remans. They are a couple on ebay for around $275.00 new with adapter, sounds like I'll be getting one of them.

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It is possible that the mounting plate will not allow your rotor to point to the right spot. You can either get the later 79 mounting plate or drop the oil pump and re-clock the position. If you got the $$ go for it and a new weber or wait around for the right used one to show up.

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I went down to the Auto Zone and checked on a Elect Dist. for a 79 200sx, they had a new one, looked like the picture above with the matchbox, $139.00 So this should bolt right on, no problems?

I've been checking for a weber at all the auto stores and all they have are remans. They are a couple on ebay for around $275.00 new with adapter, sounds like I'll be getting one of them.

 

If you got the coin get the dizzy. If not, check the wrecking yards for one of the cars I listed and get one. They never wear out, put it in and forget it. Oh yeah.... you will need a matching EI coil preferably.

 

Weber? New to prevent headaches troubleshooting a used one.

 

If you are using the U-67 head find this manifold:

 

http://i138.photobucket.com/albums/q251/datzenmike/motorL16exhaustmanifold.jpg[/img]"]motorL16exhaustmanifold.jpg

 

This is as close to a perfect exhaust header as you can get for a mild engine. It's from an early L16 and may have the air injection tubes... just remove them and install pipe plugs.

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If you got the coin get the dizzy. If not, check the wrecking yards for one of the cars I listed and get one. They never wear out, put it in and forget it. Oh yeah.... you will need a matching EI coil preferably.

 

Weber? New to prevent headaches troubleshooting a used one.

 

If you are using the U-67 head find this manifold:

 

http://i138.photobucket.com/albums/q251/datzenmike/motorL16exhaustmanifold.jpg[/img]"]motorL16exhaustmanifold.jpg

 

This is as close to a perfect exhaust header as you can get for a mild engine. It's from an early L16 and may have the air injection tubes... just remove them and install pipe plugs.

 

 

You recommend this manifold over the header idea? Where could I locate one of those manifolds? Its off a L16, the bolt holes the same, as long as I have a U67 (which I do)

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It is possible that the mounting plate will not allow your rotor to point to the right spot. You can either get the later 79 mounting plate or drop the oil pump and re-clock the position. If you got the $$ go for it and a new weber or wait around for the right used one to show up.

 

Sounds like getting the 79 mounting plate is the easy way to go. I've got the money, well not really but I'm gonna get all new anyways. I just want tell the wife.

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Sounds like getting the 79 mounting plate is the easy way to go. I've got the money, well not really but I'm gonna get all new anyways. I just want tell the wife.

 

You don't have to look for just the '79 200SX or 620. The mounting plate from a 280ZX with the 6 cylinder version of the matchbox distributor will work as well. The L28 and L20B share a similar design, the L28 is just 2 cylinders longer.

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If you are going to cam your engine, which I recommend, you should probably run the weber. A 280/480 is a very nice cam for the street. The su's are a pain to tune, but once they are dialed I heard they can be very nice. Also they are a bit small. I also recommend you to at least have the exhaust port pocket ported. My builder said most of the power gained by porting datsuns was in the exhaust port. As for the dizzy, I have to disagree. I ran a el dizzy and had problems with it. I now have a sss point dizzy with a msd 6a box running it. When you use the msd box the points become a low voltage trigger making them last way longer. Lastly be very careful about timing. These engines hate a lot of timing. In my case I am not supposed to over 32 deg total. I had to have my dizzy re curved to my engines specs, so I would not go over like I did before. Lets just say I found out the hard way and cracked a piston skirt in half because of too much timing. Hope it helps.

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Some of that makes sense but the other half:blink:???

Too much timing??? What does that mean?? And no one,ever,in the history of datsuns has ever said an EI dizzy was problematic. What could go wrong?? There is nothing that a points dizzy could do that a matchbox could not. I run a un resisted msd blaster 2 with a matchbox dizzy and it works great. Plus you never have to do any thing to it ever?

Too much timing????? Some one please help explain this. And porting the exhaust? Never heard of that either.

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