L20 with a L18 head

[maximo]

Hey, I have an L20 with a bad head and an L18 with a good head. Can I put the L18 head on the L20?? What's going to happen if I do that? Thanks:eek:

[71-521]

it depends on which head you put on it but the open chambered heads don't raise the compression to where you have to run premium to avoid pinging...

you might read this for more info:

http://www.nwde.org/extras/forum/forum_posts.asp?TID=4945&KW=l20+compression

[Bleach]

The L18 head (depending on what type) will most likely just have a slightly shorter duration cam and smaller valves. You'll gain a little torque. It should work fine.

[Jason]

I'm running a stock L20b bottom end with the dished pistons and an open chambered A87 head on it with dual 38mm Hitachi's. It's fine with 89 octane gas and if you back off on the timing you should be able to run on 87 octane regular. It's giving me about 11.5L/100km in the city with the crane cam it has in it....

[datzenmike]

Back in the '70s I had a 521 and eventually put an L20B in it. It had a warped head and I had an L 16 spare from a 510. I phoned the local Datsun dealer and they looked it up and told me that it would absolutely, 100% would not fit. I checked it out and put it on anyway, and went back and showed them. Even a mechanic came out to look at it. It ran fine no pinging, but the gas may have been better back then. I later switched back.

[hang_510]

if you find that it wont work....http://forum.ratsun.net/showthread.php?t=247

[Cookapoop]

Hey, I have an L20 with a bad head and an L18 with a good head. Can I put the L18 head on the L20?? What's going to happen if I do that? Thanks:eek:

 

i've done that several times in the past with an a87 closed chamber head on an L20B,with the cam out of a u67 head, it worked wonderfully. It bumps the compression up a little bit. I was running 89 octane at about 12 degrees static timing. Yours will undoubtedly be different. The engine did become a little snappier. Just my two cents. Just wanted to let you know that it can be done.

 

Have a wonderfully magnificent day!

[datzenmike]

I checked and the L18 had the same open chamber volume (45.2cc) as the L20B, so there would be no compression change with it if you use it.

 

BTW the L16 head I put on my old L20B would have given it a 9.2 to 1 c/r

[pope_face]

I checked and the L18 had the same open chamber volume (45.2cc) as the L20B, so there would be no compression change with it if you use it.

 

So would this be a bad idea, not due to compression ratios but due to shorter cam duration and smaller valves? I don't mean bad as in detonation, but would you lose power due to the above?

[fiveoneohray]

I have a LZ22 with a high comp A87 head with a U20 casting cam in it (same as L20) and its great, lots of torque. I run premium with no problems.

You guys cant really be worried with running premium since you figure its only a couple bucks more when you are done filling up with near 10 gallons. On average its 20 cents more per gallon times that by 10 gallons= $2. You gotta be kidding me.

[pope_face]

Ugh, I was going to make a whole long post, but it was so complicated...

 

I'm one of those people that tends to drive a lot more than others, so for me fuel consumption vs cost can be a big issue. It's been mentioned that higher octane fuel can actually increase performance and fuel economy... The latter I've never really tested, although I agree with the former. However, because of the amount of driving I do, it might not be worth the extra few bucks when filling up as I have to refill the tank so often... Sometimes there's not much point for paying extra for something you don't really need when the benefits aren't that much greater and both last about the same amount of time.

 

It's sort of like buying a combo from Burger King for $7 or buying a comparable one at a restaurant for $12. If you don't eat out much it's nice to get a good burger even if it costs a couple extra bucks. If you're on the road a lot and just need food, you can't always justify paying the extra cash...

[datzenmike]

I think your L18 head has the same chamber volume as the L20B. If so there is no change. If you aren't shure, cc the head. You can do this for next to nothing using my method below:

 

http://forum.ratsun.net/showthread.php?t=367

 

 

If the L18 head has a chamber volume of about 45cc, then this will give a stock c/r of 8.5 on the L20B motor.

 

 

If it works, put it on and get it running. Smaller valves or ports won't slow it down that much, you're on the road, and you can look for a proper head while you drive.

 

Install the intake and exhaust manifold before you put the head on the block, much easier. Don't forget to set at TDC compression and lock the timing chain. No crying later:D

[pope_face]

Something I haven't thought of asking till now, but are the L-Series interference engines or not? I know the Hondas are, so timing belts are something to really keep on top of... just wondering if it's the same deal here...

[fiveoneohray]

Another note on the octane choices. I was looking through my manual for a 510 (the actual manual that goes in your glovebox) and it states that you should run fuel with an octane rating of 90 or higher. Funny since that lets us only run 92 here. Just food for thought. I am a firm believer that you should run what it was meant to run on.

[DanielC]

There is a reasonable chance the way that octane ratings are made has changed since our L-series motors were designed. Octane ratings are maybe different in Canada, and the USA. By adjusting your timing, you can to a degree change the fuel requirements on the engine. Many other things affect the requirements, also. DO NOT LET YOUR ENGINE KNOCK! My Datsun pickup would run regular and not knock in central Oregon, but would knock around Portland. Altitude difference. In Summer, the position of the carb heat lever in the Winter position would cause engine knock more often.

Higher Octane numbers on the gas pump means that with all other things being equal, the fuel air mixture will burn slower. The engine will develop less power. The more expensive gas will give you fewer miles per gallon, and less power, assuming the engine does not knock on the lower grade of gas.

You can adjust your timing more advanced with a higher octane rating gas, and I believe you can get at least the same mileage with the higher octane, you might even be able to get a little more miles per gallon with premium gas, and timing slightly advanced, but I doubt you could gain enough of a mileage increase to offset the additional cost of the premium. Running premium, and advanced timing will give you more power, and to some that is an acceptable trade off for the increased cost of running premium.

 

I think the L-series motor is an interference motor, meaning that if the cam stops turning, and the crankshaft keeps turning, pistons will hit the valves. I am so glad the L-series motor has a timing chain, bathed in oil, to connect the camshaft to the crankshaft.

[pope_face]

Higher Octane numbers on the gas pump means that with all other things being equal, the fuel air mixture will burn slower. The engine will develop less power. The more expensive gas will give you fewer miles per gallon, and less power, assuming the engine does not knock on the lower grade of gas.

 

You can adjust your timing more advanced with a higher octane rating gas, and I believe you can get at least the same mileage with the higher octane, you might even be able to get a little more miles per gallon with premium gas, and timing slightly advanced, but I doubt you could gain enough of a mileage increase to offset the additional cost of the premium. Running premium, and advanced timing will give you more power, and to some that is an acceptable trade off for the increased cost of running premium.

 

Daniel, your post confuses me a bit... are you saying that higher octane fuel reduces mileage? Or that it increases it? Or, does a higher octane simply allow you to run more advanced timing, which in turn increases power and fuel economy?

 

Maybe I'm completely wrong, but I thought higher octanes ignited at a higher temperature, therefore being more resistant to higher pressures and residue heat, which (I thought) causes detonation...