Hey All,
I just thought I'd post something really out of the ordinary that I did so maybe some of you could squeeze some extra juice out of your z's also. I currently am running a FULLY ported and polished E31 head on a '83 280zx block using L28 rods and standard sized flat top pistons. No amount has been removed from the head nor block large enough to effect compression at all. Cam is an Isky unit, .475 lift and 282 duration. I had an HKS 2mm metal head gasket laying around which consists of a total of 5 metal pieces. With this set up, according to the z compression calculator, an HKS 2mm head gasket will make 9.43:1 compression and an HKS 1mm gasket will make 10.5:1 compression while the standard Fel-Pro gasket will make 10.3:1 compression. Wanting the 10.5:1, I realized that I didn't have the 1mm head gasket, only the 2mm. SO, I dremeled out the copper rivets that hold the five pieces together, and peeled off 2 of the five pieces which is equivalent to a .8mm head gasket. I figure if it didn't seal, or if i felt anything touching by turning it over manually, that I could yank the head and put the standard gasket back in. I used the copper spray on both sides of the two pieces, plopped it all in, turned it over, and no problem! Though, still not in the clear since i hadn't turned it over, I turned it over, ran it, no problem. Took it to Balanced Performance which is right next to the infamous Sunbelt Performance Engines, had them look, listen, and rev it up-no valves touching or anything! I estimate that the z it pushing 11:1 compression or a little over that, and boy it has some more umph to it! I've had it set up like this for two weeks, no problems, taken it to redlineplenty. Just an idea for some of you out there-Taylor

 

Are you on pumped gas with 11:1? That would be cool. Well, I guess you can with that big of cam. I'm going to bump my a little more this summer. right now little shy of 9:1 with 274 cam

 

Yes, its running on Georgia 93 Octane. No pinging or detonation, I'm running a 180F thermostat from strictlyz.com to help lower the temp. and prevent that. Dual SU Dude's last set up was 11.6:1 compresson and he wasn't detonating during the fall with pump gas.

 

Great to know. May be I'm going to set my car to 11:1 too : )

 

-I checked out your ride-you're killing yourself with that flowmaster muffler. Probably losing around 10-15 hp with it believe it or not. Check out my previous posts, I've done alot of research on exhaust and those flowmasters are one of the most restrictive systems on the market. Sound good, but hold back power. Run with a straight through Borla and bump up the compression and you'll feel some more power coming out of your z.-Taylor

 

Hummm. I heard that before too. The flowmaster is more restrictive because the V shape plate inside of the muffler. Well, I have my muffler is under the car with about a foot of downpipe and seems to be pretty good there. I know they are scavenge type muffler that likes to be close to the header not at the tail of the car. I also heard the by creating pressure the flowmaster is good for N/A car because the muffler helps build torque quicker. Have you ran 1/4 mi with your car? I want to know the difference with mine. I going to run it this weekend. I think I'll be in 15's. If your car runs 14's, I'm definally going to change my muffler! : ) You are in GA right? May be we can meet sometime.

 

Sorry, I just saw your car and your car runs 12's.............disgard my earlier post.

 

Another question. Where did you put your muffler? under the car or the back of the car.

 

Muffler is at rear of car. This allows smooth uninterupted flow for the first 6 feet or so. Your flowmasters depend on baffles to muffle noise which kills exhaust velocity and "scavenging effect". A friend of mine found about 14 hp on a dyno when dropping the flowmaster for a straight pipe which is what a muffler like Borla is equivalent to due to its straight through/perforated interior design.

 

Thanks for the infos. I may try it sometime later after I ran and get some time

 

wow, your car is awesome tyco, how hard is it to get the L28 to run 12 second quater miles- is it expensive, and how driveable is it one the street?

Alan, Australia

 

No, its not that bad at all. I first made it my goal to run a 12 second quarter mile when I heard of Norm the Dual SU dude. I thought that if he could do it with a SU carburated motor, hi compression, the right tuning, and proper gearing then I could do it also. I went for hi compression, large cam, full port and polish-I'm telling you, its all in the head work you have done to the motor, that's the most important source of power. After that, its all about getting the carbs tuned right. I'm surprised more z's haven't gotten into the 12's.

 

If you like at my car I've got L28, E88 head(slightly polished I think) bosch ignition, headers and the SU's, so I guess I'm already on my way. What sort of head work is required, is it possible to do it myself? Is there anything else I need to do? I put premium unleaded in my car which has an octane ratng of 98, will that be enough to run high compression like yours, or will it ping? thanks for the help

Alan, Australia

 

98 Octane is plenty enough. I'm running 93 here in Georgia. The port work you need to do should be done by someone with a flow bench and can matchport each to the same CFM. Most likely you would do more harm than good by greatly changing the flow characteristics across each cylinder. You are running compression in the nine's with the E88 head on the L28 block and would be best off shaving the head a bit to get the compression up into the tens, have some major port work done so the head flows well (restrictive enough as a SOHC), drop in a big cam, open up the carbs a bit and smooth them out, lighten the flywheel, find yourself a 3.9 or 4.11 lsd rearend, 2.5 inch pipes with straight through muffler, healthy ignition system, then tune the carbs right and you should be on your way. -Taylor

 

How driveable is it? I don't really want to lose too much driveability. I'd also prefer to keep the diff for fuel economy reasons. I don't mind I don't get into the 12's, thirteens would be enough

Alan, Australia

 

The z is completely driveable. You have to realize that keeping the SU's will make the difference. If you're running triple carbs then you are going to be eating much more gas, tend to bog a lower rpms, then feel the kick back when the cam comes on. The SU's provide you with more of your low end power which is perfect for street driving. I run a 3.36 rear on the street-its actually better for traction with street tires for stoplight races and lets you run at nice rpms on the highway with your 5 spd tranny. I feel that lower gearing would help nothing but losing more traction since I drop clutch at around 4000. It drives smooth, has crisp throttle response, gobs of power, and that high compression inline 6 is just about one of the best sounding motors in my opinion.

 

amen

 

now all I need is some money... What do you suggest as the first step for my motor? The head work?

Alan, Australia

 

Is your z your daily driver? If not, get the money together, park it, pull the motor and send it to a reputable shop. If she is your daily driver, you may want to find a head and block from an outside source, have the work done, then put it all in at once during a long weekend. I would suggest getting the whole motor squared away. If you're going to get a performance head, you might as well match it up with a nice bottom end.

 

Yeah, it sort of is my daily driver, but I ride my bike to Uni, so I only really drive it on weekends when I need to. I don't think I could afford having the bottom end redone, especially since the motor was rebuilt 2000 miles before I bought it. If I try to source an E31 head and just have this worked, and fit it when its done, will that do the trick?

Alan, Australia

 

Source an E31, have it extensively worked open, have the valves set out a bit, drop a nice big cam in it(I run an Isky stage III cam .475 lift and 282 duration which is about as big as you wanna go for street driving), have them cut out the valve seats and drop in the bigger intake and exhaust valves b/c the E31 has the smaller ones, then have them shave it to the compression setting you need. I would dial it in to 11:1 and not go above that to be safe or maybe a tad less if you can't get 93 octane(91 i think i remember you saying was available) Order some SU needles, smooth out the carbs, tune them, and you'll be on your way.

 

So use the valves from the E88? Thanks for your help, I'll start saving.

Alan, Australia