a87 peanut head

[1974datsun]

what is so special about a a87 peanut head?

i have a l 18 bored .50 over, will this help add more horses or no

Edited September 29, 2009 by 1974datsun

[datzenmike]

It has the desirable 'peanut' shaped combustion chamber with surrounding quench area. This head promotes combustion chamber turbulence, or swirl, which helps to homogenize the temperature of the inner surfaces and prevent hot spots that lead to pre-ignition even though this head has a higher compression than the open chamber ones.

 

It has reasonably large valves and square exhaust ports. This would be a good head to use on a later L20B to replace the W58 head so the L16/18 exhaust manifold will fit perfectly.

[1974datsun]

its about to go on a l18. will it produce more horse power

[datzenmike]

Not really enough to notice, but is a good start if adding more or larger carb and bigger cam.

[datsunaholic]

The big thing is it will SLIGHTLY increase compression without increasing the risk of detonation. The bad thing is it doesn't have the largest valves- BUT that helps with the bottom end, hurts on the top. On an otherwise stock L18, the valves are the same size as stock anyway, and MOST L18s (the exception being US-market 1973-1974 L18s) came with that style head anyway. Certanly not a knock-your-socks-off difference. Maybe 2-5% (percent, not HP) difference vs a otherwise identical head and using 89 octane vs 87? Again, MAYBE. Might not be a change at all.

[1974datsun]

The big thing is it will SLIGHTLY increase compression without increasing the risk of detonation. The bad thing is it doesn't have the largest valves- BUT that helps with the bottom end, hurts on the top. On an otherwise stock L18, the valves are the same size as stock anyway, and MOST L18s (the exception being US-market 1973-1974 L18s) came with that style head anyway. Certanly not a knock-your-socks-off difference. Maybe 2-5% (percent, not HP) difference vs a otherwise identical head and using 89 octane vs 87? Again, MAYBE. Might not be a change at all.

 

what would be the best head to put on it. i also forgot to mention i have a l20 cam in it

[datsunaholic]

For an L18 that IS the best overall head, but it's still a compromise. There are better heads for specific needs, then to get any better overall you start doing major modifications. It all has to do with the port and valve sizes. There are 4 intake port sizes and 2 intake/2 exhaust valve sizes in stock heads, and the A87 is pretty much in the lower-middle of port sizes and uses the larger valves.

 

The L20B cam is no big deal. It's nearly or absolutely the same as the JDM L18 cam.