e31 head on l28 block?

[intangible3]

I recently bought a l28 and I was wondering if I should put my e31 head on the l28 block? Or should I leave the n47 head on it? I will be running SU carbs but they are off a 73 240z would those be good? Or should i find different carbs?

 

I'm also thinking about putting flat-top pistons, MSA stage 2 cam, and full twice pipes exhaust. Would that be too much for the SUs?

[BluDestiny]

L28 with dished pistons and the e31 head should be fine in stock form. With the cam and flattops I don't know.

[RedNeckZ]

I have a E-31 head that has been ported and polished. It also has bigger valves in it. Running 45mm DCOES Webers on it with a header. It is on a L-28 block with flat tops. Have a Schneider cam #270-80f in it right now. It runs pretty good on the street. Haven't had any problems with it in that area. Did have some problems with gas and sitting for a time. Had to replace the gas tank and blow out the lines. So you shouldn't have any problems with it on the street. I wish you luck with it. Rich.

[JMortensen]

Just to be the counterweight here, I had an L28 with flattops (no overbore) and cc'd polished chambers and 280 valves with 44s. In CA and WA state with 91 octane oxygenated fuel, I could not get the thing run without pinging. I had to mix pump gas with race gas to make it work with timing in the mid 30s.

 

I ran that head previously on an L28 with dished pistons and I could run 87 in it. If you're not going for the last hp, I'd suggest running the dished pistons. Dropping the compression down a bit and being able to run all the timing you want is a very good trade off. There is nothing worse for a street car than building it on the ragged edge for pump gas and then listening for pinging EVERYWHERE you go. The focus changes from having fun beating the crap out of the car to wondering if you're destroying the engine.

 

I'd also suggest a larger cam. I ran something close to the Stage IV cam with SU's and it worked great with the lower compression pistons, I wanted more cam when I went to Mikunis, and really wanted more when I went to the flat tops. I'd also do a regrind instead of running the Schneider. Search "schneider" or "schneider lobe" and I'm sure you'll see why. Something in the .500/280 or 290 range should work nicely for SU's. Mine was .490/280 with a pretty aggressive profile.

 

Get roundtop SU's.

Edited November 8, 2011 by JMortensen

[intangible3]

Thanks guys sorry it's been awhile. But are the crank and cam gears interchangeable? Or should i be ok with just slapping the whole head on with a new chain and tensioner?

[JacktheRiffer]

Adding to this topic: would an e31 on a flattop bottom end with a large (.490/280) cam be alright with 91? Trying to plan an autocross engine build for my Zx.

[NewZed]

Thanks guys sorry it's been awhile. But are the crank and cam gears interchangeable? Or should i be ok with just slapping the whole head on with a new chain and tensioner?

It's been over 5 years.  OK and "slapping" don't go well together.  The answer to your first question was really "leave the N47 head on".  Seriously, it's got the bigger valves and good compression ration that JM mentioned as important.  You'd be creating problems and ending up with a weaker motor by swapping on an E31 head.