Best Head

[Dan Baldwin]

Originally posted by Royce

I think that makes a good case for the N42! Any L6 head could use a cam and a little polish and port. With the N42 you do that and add the 280ZX intake valves and there you go!

280ZX valves in an N42? You know the N42 already has the larger-diameter intake (44mm) and exhaust (35mm) valves, right? Only the 1974 260Z E88 head had the bigger exhaust but the smaller intake valves. As far as I know, the 280ZX valves are a bit longer than 280Z valves. I know that those who shave the 280ZX heads to get decent compression with them frequently use the 280Z valves. You can't use 280ZX valves with the N42 (280Z) head, they're too long. This fact caused me to miss my first '02 event, as the guys who built up my cylinder head found at the last minute they had the wrong length valves!

This is my understanding of 280Z vs. 280ZX valve lengths, anyway. Someone correct me if I'm wrong.

Dan

[Royce]

Oops!!! Sorry, I looked over you info too quickly and mistook the info as 240, 280, and 280ZX specs, instead of 240,260, and 280Z/ZX! I realize E30,E31 and P79,P90 have better combustion chamber design but I think this is further proof that you can do quite well on a budget when starting with the N42 head!

My bad! Thanks for the quick correction!

[Mudge]

Originally posted by Royce

From what I have heard Rebello Racing builds a 200HP L24 SCCA ITS spec motor using relatively stock bottom end and carbs and mild head work. For the same money they can build you a 250-275HP L28 using modified SU carbs, L28 block, and modified head (using 280ZX intake and exhaust valves). I do not work for Rebello or have any affiliation, they are just well know local Z motor builder that I had build my motor many years ago.

Low friction setup basically, and lack of leakdown yada yada, all machine work. I think they are ~$5k

I'm looking to pull 250-275 in a streetable F54 flattop setup, with N42. I want to believe it can be done, I know a local guy who has a friend with a Robello 3.0 doing 287 crank HP, not alot of people believe it. There is a Robello employee with a 280ish HP daily driver (one of the head porters), so again I want to believe that its possible but I'll see what I can get out of the head, and select one of 2-3 cams that I'm considering. Not sure yet on single or dual pattern.

[Zsled]

Really, $5K for a L28 setup..... Ouch!

I mean for less than a 1K I can get a warmed over 302 v8 / 5 spd cobra tranny setup and even get a 50/50 setup on the car.

I was really hoping to keep it original, but the dollars don't make sense.

Am I wrong?

[Mudge]

Zsled, that price is due to expensive machine work, constantly trying to eek the most out of it by lowest friction/lowest leakdown possible since they have to run a certain cam.

It would make the series MUCH cheaper if they followed the rules like some budget series', be within a certain HP and TQ range at approximately stock points in the curve, and voila. The Camaro Mustang Challenge runs this way, if you go over you have pretty hefty weight penalties, and you can't go over that much. Those that are slightly over might have an advantage on tracks with long straights, and vice versa. This way most of the expense is the racing itself and occasional parts replacement, 5k to dump on a somewhat stock engine but being forced to max it out with with machine work to be competitive sounds a little dissheartening. I just think things could be done a different way.

I'm going to do a budget rebuild, refresh with rings/bearings, top end work, better pan or hack up the stocker myself, new oil pump, fresh seals obviously, so the rebuild itself will be well under a grand, and the rest goes into making horsepower!

[Royce]

I think either motor would range between $4k & $6k depending on what you have done, condition of head/block/etc. they start with and if you are going to give up your original motor or not.

If you build your L28 right you could be in the range. My 2.9L Rebello motor, built in 1990, is basically a smaller bore version of there current 3L motor. Mine is a N42 L28 block with L24 rods and custom pistons. It has my E88 head with 280Z vavles and some machine work. These days they usually start with the F54 block and will use a N42 head if you don't supply one. I have never put my engine or car on a dyno but I am sure it is not there. I put in a stock cam with my stock intake, exhaust, and all the smog equipement (remeber this was 10 years ago). It has a lot of torque but needs some other modifications to get the power.

I have talked to two members from North California that have purchases Rebello L28 motors recently who could probably tell you more.

[Dan Baldwin]

I guess my engine probably has 275hp (235 at the wheels). It's streetable enough for me, though with recent headwork and cam I do have to wind it out a bit more than I used to on the street. Extremely lumpy idle.

I had heard that Rebello were expensive for what they did, but $5k for a competitive ITS engine would be a relative bargain. I would bet a Sunbelt engine would beat it, though.

I spent a total of ~$4500 on my engine over the years. It was built in '94, but the most recent expense was having Sunbelt rebuild, port, and do some chamber work on the head, and install a their custom cam grind that uses lighter than stock springs. That cost $1500 (included in the $4500 above).

If I'm making 276 on a motor that has ~35000 miles and ~50+ track days on it, with a pretty radical cam (.550" lift, 302 duration), then a fresh professional build with total-seal 2nd rings should be able to make that much with a milder cam, I'd bet.

[Mudge]

.550 lift and milder than stock springs? Hmm...

Sounds like a monster cam, is that thing streetable? What rear gears are you using? I've seen your dyno sheet on HybridZ

[derk]

Britney Spears?

[Royce]

Zsled,

Remember, that is $5 for a L24 or L28 with modified bottom end, head, and carbs. You are not talking about your basic rebuilt engine here. They can build you a standard L24 - L28 for less, it just depends on the condition of the parts they are starting with and whay you want to have done to them! A little machine work here and there and some upgraded parts can add up really quick. Sure a small block V8 might be cheaper in some respects, but if you get out of the standard build it will add up quick too! Besides, small block V8's are still in new production and race developement. The L6 hasn't been for a few decades, not to the same degree anyway!

Hope it makes sense!

Derk,

Sorry, no clue what Britney has to do with this!?

[Dtsnlvrs]

Lotsa good info from Dan et al. But also a little misleading info. Dan you are very correct, A Sunbelt eng runs rings around everyone else. Lets see where to start. N-42 head on a L-24....nope would not do it....if the head has been resurfaced even the slightest....the valves WILL make contact with the block IF the valve lash has been adjusted properly and the engine is hot. There are different E-88 heads. My advise.....Call Sunbelt and have him build ya' a E-88 with larger valves and slap it on a fresh L-28

[SCCA_racer]

Anybody know what type of CR to expect with an N42 head on a p54 block? I would use a non-shaved figure as a starting point. I am curious if the CR would be too high to try to get away with using the FI system with a modifier like GREDDY e-manage or some other enrichment/fuel tuner to provide additional fuel and or adjust spark.

thanks

Bryan