pjo046

I am going with forged flat tops in my L28ET to raise the compression to about 8.5:1. How hard is this to do myself? Also, I have just installed the timing cover and oil-pan etc with new gaskets. Had gasket cement on the timing cover gasket. I will now of course have to take that of again. But when installing it for the second time, can I just put some more gasket cement on and put it on, or do I need to reclean the surfaces, use a new gasket etc? I only want to swap to forged pistons, don't want to bore or hone the block or anything like that, because that will cost a bit. Can anyone give me a link to somenone who sells good, cheap, forged pistons that will fit in the L28 without boring or things like that? And that will give me a compression of 8.5:1 with the stock headgasket? Is it better with small dishes in the piston than a completely flat one? Will I need to renew some other components when changing the pistons? Like main bearings etc?

I am wondering about the same thing!!!! I think if someone would make a 3" downpipe for the S30, a lot of people here would buy one!!

Well, I guess I just have to bite the dust and realise that forged flat top pistons is my best bet. I know that's what Corky Bell says in his book as well, the only acceptable way to alter the compression ratio is through the pistons. Altering headgasket thickness is also unacceptable according to him. Furthermore he says that "Special headgaskets and O-rings are often cures to the wrong problem. They are only poor excuses for not dealing properly with detonation. If detonation is the problem, cure it, and a stock head gasket will usually perform well." So I think I'll just get myself a new stock headgasket and ARP studs to go with the ported P90 head. What he also says though is that "Unless circumstances are highly unusual, street cars with stock redlines will prove more successful with cast pistons. Forgings should be reserved for the high revvers, while T6 hypereutectic alloys can cover almost all requirements. Rule: Do not rush to the forged pistons store every time a turbo engine needs preparation" But I guess if buying flat top's I will get forged ones. But I don't see that happening in the near future though. I have just assembled the engine with new gaskets etc, and to take it completely apart, resetting the ignition, and going through the trouble it probably is to change the pistons, is not appealing.... Tony, which Ross were you talking about had cheap forged turbo pistons for 450$? Ross at modern motorsports? Because I didn't find pistons on his website. Clifton, you say you went from 8.4:1 to 7.5:1 in your 7M without noticing any difference in off boost power or lag. Well, I think the similar compression altering on a 280ZXT engine is far more noticeable, as the 7M engine is after all a much more modern engine etc. Or is this wrong? If it is true that I won't gain much off boost response and have reduced lag etc by raising the compression on my L28T, then I won't bother with it. But I would think it should make quite a difference. What I have always belived is that the lower the compression ratio, the easier it is to produce a lot of boost without detonation. The higher the compression ratio, the greater the fuel efficiency and nonboosted response, and the shorter the lag.

Refering to what Tony D said: "There is the argument of "low compression" versus "high compression"... Most people use the argument that lower compression allows you to "run more boost" to make horsepower. This is true. But to what extremes are we going to take the argument. An 8 or 8.5:1 compression engine will easily take 20psi of boost. And what are we making by that point? 350, 400HP? E'motive in 1983 with stone age electronics made 580HP at 7500rpm, on 20.6 pounds of boost, using racing gas, and a compression ratio ABOVE the stock ZXT of the day (considerably more if you talk with the people involved). So the question becomes, in my mind at least, "How much money do you want to spend?" If you spend the money on head work and a cam, 580HP is waiting at 20-psi, but ASSUREDLY NOT at 7.4:1 compression ratio! You can get decent performance from a stock compression turbo, but for the money the drivability and spooling capabilities of a higher compression engine seem to win out when you weigh it. There really should be no trade-off in the octane scare between 7.4 and 8.5. I would personally waste my time with anything below 8.0! The naysayers about "higher boost levels" might want to do a reality check and actually ask "how much boost do I terminally want to run?" For someoen going with 45psi, then yeah, I might say 7's would be in order. For someone with an inefficient intercooler? Maybe no more than 8:1. But for someone pushing a hybrid turbo and a decent intercooler on even 90 octane, I would shoot for the stock N/A drivability that 8.5:1 offers off-boost. Nothing is more discouraging to hear than some idiot with a well-tuned stocker say "I got him out of the hole till the boost come on!" Lets' not let those N.A. guys ever have the ability to say that! In a roundabout way what I am trying to say isn't really about boost. It's about total mass flow through the engine. The power is, and always will be, in the HEAD of the L-Engine. A properly ported L-Head running 17# of boost will make more power than an unported engine running 20+. I have an acquaintance that did a before and after dyno test (headwork only). After retuning the TEC2 for the new flowing configuration, the SAME engine using the SAME turbo, and basically the SAME everything save for the portwork and runners in the intake manifold made more HP at 17# than he did at 21# before! (BTW, this was on an engine with 8:5:1 Slugs) So the "More Boost means more power" line of thinking is a bit corrupted. My training has (since I work in Compressed Air and Gasses for a living) always been that "pressure is the resistance to flow! The less resistance you have to flow, the more efficiently you transport air... So in some cases, LESS boost means MORE power! On the test vehicle, it assuredly did!" Tony D, I really agree with what you're saying. I am going to buy a P90 head, and have Spork port and polish it for me, and install a upgraded turbo-cam. But I also want to raise my compression, and much more than what I get by just installing a 1mm gasket. I see from my Lengine calculator that by swapping to flat top pistons instead of the dished turbo-pistons that come stock, I get a compression of 8.52:1. The only problem with this is that forged turbo pistons are expensive, and that I don't know if I am able to do the swap myself. What I was thinking doing instead is let Spork shave enough of the P90 to get me to a compression of about 8.5:1. What do you think about this? Doable? Or would it perhaps be better to go with a E88 head and a 1mm gasket? That would give me a compression of 8.46:1. But this head isn't as good as the P90. Would it be possible to make it as good by heavy porting, installing a aftermarket turbocam and perhaps bigger SS valves? What do you all say? All input on this appreciated. And furthermore, if going with a compression around 8.5:1, how much boost will I be able to use when I have a good intercooler, 3" exhaust, am getting a custom intake manifold, ported exhaust manifold, and have a T3/T04B hybrid? I have TEC3 engine management, so the timing etc can be tuned optimally. You see, I'd rather have a engine that is really responsive and have a broad powerband, than having a low compression slug that needs high RPM's and much lag to wake up. This is going to be a streetcar, not a quartermile-runner. Can I still achieve my goal of 350-400RWHP? Will the turbo I have be to big(Since I will be using lower boost with this higher compression?) Remember, I have 93.5 octane available at the pumps.

Tony D, I really agree with what you're saying. I am going to buy a P90 head, and have Spork port and polish it for me, and install a upgraded turbo-cam. But I also want to raise my compression, and much more than what I get by just installing a 1mm gasket. I see from my Lengine calculator that by swapping to flat top pistons instead of the dished turbo-pistons that come stock, I get a compression of 8.52:1. The only problem with this is that forged turbo pistons are expensive, and that I don't know if I am able to do the swap myself. What I was thinking doing instead is let Spork shave enough of the P90 to get me to a compression of about 8.5:1. What do you think about this? Doable? Or would it perhaps be better to go with a E88 head and a 1mm gasket? That would give me a compression of 8.46:1. But this head isn't as good as the P90. Would it be possible to make it as good by heavy porting, installing a aftermarket turbocam and perhaps bigger SS valves? What do you all say? All input on this appreciated. And furthermore, if going with a compression around 8.5:1, how much boost will I be able to use when I have a good intercooler, 3" exhaust, am getting a custom intake manifold, ported exhaust manifold, and have a T3/T04B hybrid? I have TEC3 engine management, so the timing etc can be tuned optimally. You see, I'd rather have a engine that is really responsive and have a broad powerband, than having a low compression slug that needs high RPM's and much lag to wake up. This is going to be a streetcar, not a quartermile-runner. Can I still achieve my goal of 350-400RWHP? Will the turbo I have be to big(Since I will be using lower boost with this higher compression?) Remember, I have 93.5 octane available at the pumps.

Yes, that is correct. They are 30mm!

I have gone with one Walbro 255 pump. That will do! I am hoping to achieve the same power output as you are. Think I'll just use the stock gas tank myself. Will have the pump just after the outlet of the tank, and run -6AN lines to the engine and probably -6AN return line as well. Think I'll only use one inline filter though.

Hmmm.. Okay. Never thought of that. But, looking at that link you gave me, if I use what is called 98 octane here in Norway, that would be the same as 93.5 octane in the US. So that is a bit higher then what you guys normally have available at the pumps. Or? Because Norway, is one of very few countries in Europe that has 98 octane. Most other countries only have 95 octane and downwards. At gas stations in Norway, you find 98 and 95 octane unleaded, but in for example Germany, Holland, Denmark etc you find 95 and 92 octane at the pumps. So, isn't 93.5 octane a bit higher than what you have available most places in the states?

Oh, and James, you do realise that here in Norway we have 98 octane at the pumps? Hehe. 8) That lets me run higher compression without fear of detonation. What compression would you recommend when my car is basicly going to be a streetcar, and I want the best possible respons of the line etc withoug having to rev the car to 3500 or more on launches.

Spork(James) have you received the e-mails I sent you? Haven't heard anything from you regarding that. If you could set me up with a ported head, then you could perhaps also alter it so that the compression would be raised to 8.0:1 with a stock headgasket. Isn't it true that it would be better to have a stock headgasket than a 1mm steel unit? (IF detonation, god forbid, should occur?) Because then it would be more likely that the gasket is the thing getting blown, not my stock pistons. Right? Also, people have more trouble getting the metal gaskets to seal properly than the stock gasket. If you could get back to me today regarding the questions etc in my e-mails, that would be great, as I need to know wether or not I shall tell a Z friend of mine that he can buy my P90 head if he wants to.

I would be interested too. I could pay you 20$ for it as well. Seeing spark280ZT already got the other one, why not give this one to me, as I need a new center section with wheels for my housings? (I have polished the compressor housing and high temp painted the turbine housing. But managed to mess the center housing up on installment)

Yep, you are right! By installing a thicker headgasket you decrease the compression, thus enable the use of more boost without detonation.

Well, found out that cam was wrong for a turbo application, and besides, if I am aiming at maximum 400hp, the stock head will do fine. I have been thinking about installing a 1mm HKS headgasket though. This would raise the compression from 7.38:1 to 7.52:1. I was thinking this might help on the low end power and off boost characteristics of the engine? Will this be noticeable? Will it make much of a difference as to how much boost I can make? I know it will be less bost, more off boost power. Do you think it would be a good trade of for a street car? Also, if I install a 1mm headgasket, will this cause a retardation of the timing, as the timing chain then would be a bit slacker? Noticeable? Bad?

Scottie, what is a WB02? I am planing on using pump gas yes. But here in Norway, we have 98 octane at the pumps. 8) Hehe. Well, I will be using 17x7 rims with 225/45 tires, I have a 3.54:1 R200 with C/V's and Ross' adapters, I have a freshly rebuilt T5 tranny, Fidanza aluminium 12lbs flywheel and a SPEC Stage 2 clutch. I have Ross' coilovers, and Illumina inserts, I have Toyota 4x4 front brakes, Green stuff performance brake shoes in the rear and stainless steel lines all around. Have strut bars front and rear, urethane bushings all around, blitz supersound BOV... Hmm. Might be forgetting something, but think I have covered everything now. What else do you recommend using the money on instead if overall performance is my goal? Mind you, it's for the streets, not track or drag.

Well, it's only that I have a chance to buy a P90 that is freshly rebuilt with that exact cam kit in it, and it is ported and polished, and decked. Comes with stock valves. I would have to pay a total of 900$ for it. It has not been installed after the rebuild, so the cam kit is brand new. Is this cheap or what? Remember, those heads are hard to get at hold of here in Norway. And is that cam with those specs not any good at all for my engine? It's not better than the stock cam? A new cam kit alone costs 400$, and the machining job here in Norway would cost 500$ easily, maybe more. And, if I buy it, I can take the P90 I have now of my engine and sell it for probably 300$ here in Norway. So then my total for the above mentioned P90 head would be 600$. What do you guys say? Take it or leave it?

And with all this, would you go with a 1mm HKS headgasket, or keep the compression as low as it is?

Yes, I already have a 60mm TB from a 240SX. How does a SCHNEIDER 274F performance cam Part #17033, Valve Lift 480/480, Duration 274/274, with matching component Kit sound? Would this be a good cam for my setup?

How much will I gain by having a ported and polished P90 head with a high performance camshaft with new rockers, pads, etc but with stock valves, compared to a stock P90 head? I am talking on a turbocharged engine, with, say 18-20 psi of boost, TEC3 engine management, T3/TO4B hybrid, large intercooler, 550cc injectors, 3" free flow exhaust etc. I know you can't give me any numbers, but an estimate perhaps? The question is if it is worth it, costs versus gain? What do you guys think? Or is this just a waste of money if I am not trying to get beyond 350-400hp?

How much does a complete P90 head with camshaft and everything weigh? Without the rocker cover though.

Hey ZXGTR. I am looking for a stock turbo as well, as I have one that has a ruined center section. So if yours only have a bad turbine housing, I could swap my turbine housing over on that one. How much do you want for it? E-mail me at: pjo046@student.uib.no

The best 0-60 time I managed to get with my G-force meter was 6.5 seconds. That's pretty good, considering the car was a 2+2, with no LSD, only 205 wide tyres and my crappy launches.

Oh, and by the way: If anyone finds it strange that I managed to get those numbers with such a high compression etc, that's partially because here in Norway we have access to 98 octane pump gas. That helps on keeping the detonation away!!! 8)

Hi! I just sold my 260Z on friday. Have had it for two years. That one had a stock NA L26 engine with a E88 head, and was converted to turbo. What was done to the engine to make it handle the turbocharging was only taking out some metal from the valve seats in the head to lower the compression some. The headgasket used was the stock one. Stock compression on this engine is 8.29:1, and with the modification to the head, I would guess the resulting compression was somewhere between 8.0:1 to 8.1:1. The engine worked very well with the turbo. I had a rajay turbo on it, 2.5" exhaust with custom downpipe and glasspack muffler, a Saab 900T IC and two additional injectors just before the TB(Controlled by a piggyback). This is a less than adequate way to do it, but it was already done by the PO when I bought the car. The engine produced 250hp, and was very fun to drive. Yes, I had boost in all gears, and I did not get less boost in the lower gears. The boost kicked inn just at 3000 rpm in every gear, and by 3500 I had reached 1bar(14.7 psi) which lasted till redline in every gear. So I would say it worked quite fine! And that wasn't even with a 280ZXT ECU, it was a ECU and intake(With injectors) from a 2.4 Maxima. But of course, much want more, and in the end I ended up selling it, to build my own L28ET in a 240Z, which is what I am using my spare time on now. I could of course have managed to get a higher output from the engine in the 260Z, by swapping the ECU and primary injectors for 280ZXT ones, changing to a hybrid turbo and get a better intercooler and 3" exhaust. But that would cost so much, that I decided it would be better to start from scratch, and make a really powerfull engine instead. 8)