Z32 Headwork

[MclarenF1]

Hey guys. How's everyone doing? I hope things are well here in Z land.

Just wanted some advice.

I'm helping my uncle rebuild his (very) ragged out 1991 300ZX Turbo. I've got his heads off, and I'm doing the basics for him. New valves, springs, valve guides, and even an oem cam. (He already had all of these parts.) He called me yesterday and wanted to know if I should send the head off for machining while we're at it.

Long story short, I'm going to have a place called White's Performance do a port and polish, and maybe a basic valve job. (I had them do a MKIII Supra head for me once and the results were AWESOME.) HOWEVER, I'm also considering having them shave the head.

Do you think I could have them shave the head and still run the car on 93 octane? I'm sure some of this would depend on exactly how much the head was shaved by, so some input on that issue would be appreciated as well.

I should probably mention that the only other mods my uncle will be running are a Jim Wolfe ECU, boost controller, and Borla exhaust. (No downpipes or anything, though.) The turbos are rebuilt stock units.

For the record, I know that raising compression on a turbo motor is normally a bad idea, but I just wanted to see if the VG might have some "wiggle" room left in those tolerances. I'm having trouble getting a straight answer elsewhere, and I'm just trying to get my uncle the most bang for his buck.

Thanks everyone.

[k3smostwanted]

Originally Posted by MclarenF1

Hey guys. How's everyone doing? I hope things are well here in Z land.

Just wanted some advice.

I'm helping my uncle rebuild his (very) ragged out 1991 300ZX Turbo. I've got his heads off, and I'm doing the basics for him. New valves, springs, valve guides, and even an oem cam. (He already had all of these parts.) He called me yesterday and wanted to know if I should send the head off for machining while we're at it.

Long story short, I'm going to have a place called White's Performance do a port and polish, and maybe a basic valve job. (I had them do a MKIII Supra head for me once and the results were AWESOME.) HOWEVER, I'm also considering having them shave the head.

Do you think I could have them shave the head and still run the car on 93 octane? I'm sure some of this would depend on exactly how much the head was shaved by, so some input on that issue would be appreciated as well.

I should probably mention that the only other mods my uncle will be running are a Jim Wolfe ECU, boost controller, and Borla exhaust. (No downpipes or anything, though.) The turbos are rebuilt stock units.

For the record, I know that raising compression on a turbo motor is normally a bad idea, but I just wanted to see if the VG might have some "wiggle" room left in those tolerances. I'm having trouble getting a straight answer elsewhere, and I'm just trying to get my uncle the most bang for his buck.

Thanks everyone.

i wouldnt worry about shaving the heads...i cant see it being that beneficial for the risk of a bad job being done. me and my grandfather used to chave the heads on american V8's when we were building stock cars. i have never heard of doing it on the VG, but that always doesnt mean anything but in most cases, dont try to re-invent the wheel.

for your uncle's motor, technically, it will not benefit that great even to do the port and polish BUT if you get a good deal, it definitely wont hurt if it is a quality shop. it will open up air flow and probably help spool the turbos even quicker as for a very noticeable gain, it wont happen as the exhaust manifolds will be he next choking point for the engine.

my opinion, if you can get a good deal, have a light port & polish and 3 or 5 angle valve job done and take the exhaust manifolds in to have them ported also. this will make the engine flow much better and boost lag will be virtually gone if he ever decided to add a set of downpipes and the heads will be ready if ever wants to add some performance cams. i say all this because on a motor that is getting air rammed in it, the better it can flow the air, the better it will perform and the easier it will be for it to perform.

this will be an awesome basis for a JWT sport 500 upgrade. it would make an AWESOME track car.

good luck man, any questions ask away. i have researched headwork for the VG to the fullest because of turbo upgrades i have considered. it can get very expensive very quick.

[MclarenF1]

Thank you!!!

I forgot about having them work over the exhaust manifolds. Sometimes I get so caught up in reworking the intake tract that I forget to take car of exhaust matters. The money that would have been spent shaving the head shaved could be used on the manifold work.

As far as the shop itself goes, they spend most of their time working over domestic engines, and they claimed that the Supra head that I gave them was actually the first import head they had ever done. Regardless, they did absolutely beautiful work. I still remember that when I picked it up the guy just walked out, handed it to me, and with a big smile said "it'll be a screamer!" And man, was he right.

Anyway, the point in the above story is just that I trust the shop, and feel certain they'll do a good job.

As far as the performance benefit of a shaved head goes, I guess we can leave that part alone and possibly turn up the boost even more.

Speaking of boost, what kind of cfms can the stock turbos flow and still remain efficient? Do you think they would have any problem efficiently running 15psi- 18psi on a regular basis without monster lag or superheating the air? If they can pull this off, do I need bigger injectors and/ or a fuel pump yet?

I should also mention that I left out a mod- my uncle has some aftermarket intercoolers that he got from Stillen. I'm not sure if Stillen actually made them, or if they were supplied by someone else. They look pretty much like the stock ic's, but are a little deeper, and might have a bit more surface area.

Sorry for all of the questions. I REALLY appreciate the help!

[Broke_as_****]

Originally Posted by MclarenF1

Speaking of boost, what kind of cfms can the stock turbos flow and still remain efficient? Do you think they would have any problem efficiently running 15psi- 18psi on a regular basis without monster lag or superheating the air? If they can pull this off, do I need bigger injectors and/ or a fuel pump yet?

15-16 psi is the end of the efficiency peak from most of the dyno's I've seen. A few members on TT.net push 18-19 psi on their stock turbos but thats usually only on the drag strip where the heat build up from prolonged boost at those levels isn't an issue. That and longevity comes up at that point. As for lag, shouldn't be any increase from what you are seeing now.

15 psi on stock turbos is a good place to stop. With 93 octane and the intercoolers you should not have any problems with detonation. The stock fuel injectors are probably around 90% duty cycle at this point and don't have much more head room. The stock TT fuel pump is still well within it's ability to supply fuel, most guys running even 500+rwhp still have their stock fuel pumps.

As for the actual cfm the stock turbo is good for... I really don't know, its not something brought up often. Most everything is described as psi of boost, rather a pain in the ass since it is such a lousy yard stick for exact measurement of turbo and engine capabilities. Given that ~475 cfm is tossed around in some posts about upgraded turbos and using the very rough approximation of 1.5:1 ratio cfm:flywheel horsepower, ~300-350 cfm is probably the limit of the stockers, per side.

As a side note, with the head work, you may see the same power at lower boost levels so don't automatically shoot for 15 psi. The important thing for this particular sitituation will probably be to watch the fuel injector duty cycle and make sure you are not going to run lean.

I should also mention that I left out a mod- my uncle has some aftermarket intercoolers that he got from Stillen. I'm not sure if Stillen actually made them, or if they were supplied by someone else. They look pretty much like the stock ic's, but are a little deeper, and might have a bit more surface area.

Odd, the Stillens that I've always seen pictures of have quite a bit more surface area and are just a bit thicker. Maybe they have been changed over the years or something.

[k3smostwanted]

Originally Posted by Broke_as_****

Odd, the Stillens that I've always seen pictures of have quite a bit more surface area and are just a bit thicker. Maybe they have been changed over the years or something.

agreed, if they were ordered from stillen, they should be stillen intercoolers as i dont think they carry any other name brands. with that being said, stillen intercoolers are significantly larger then stocks and the stillen intercoolers also have their own set of intercooler ducts because they are much bigger than stock.

anyways, good luck with your work man. your uncle like every other Z owner will get the need for more and he will be ready for a small turbo upgrade like sport 500's, 555cc Nismo injectors, and downpipes.

also, if you are using stock downpipes, atleast make sure you gut them. the USDM have a set of pre-cats in there that should be removed. it will not effect emissions unless there is something already wrong.

also a good time for some maitenance. VVT sensors, O2 sensors, detonation sensor, PCV valves, etc.

[sanzoneb]

what state do you live in i'm doing the heads on my 91 n/a right now. I cant find a place to get my heads ported and polished.
Thanks

[k3smostwanted]

Originally Posted by sanzoneb

what state do you live in i'm doing the heads on my 91 n/a right now. I cant find a place to get my heads ported and polished.
Thanks

question is...where do you live?

i live an area that there are more than a few performance shops but they wont touch my motor so anything i want done i have to travel quite a bit.

[sanzoneb]

I live in New jersey, one shop said they can do it but i would have to wait two months to get the heads in there.

[k3smostwanted]

Originally Posted by sanzoneb

I live in New jersey, one shop said they can do it but i would have to wait two months to get the heads in there.

check out http://www.AMZperformance.com

i know mitch, real good guy, i dont think he does in house machining but i am sure he has a shop that he goes through. there should be tons a shops in the tri-state area...

do some searching on TwinTurbo.net

there are alot of guys with some nice built Z32's in he tri-state area and i know they are getting them built somewhere...

[sanzoneb]

Yea my 300zx is kinda new to me i had a 3000gt before it but i had to get rid of that. I got it knowing that i was going to have to eventually rebuild the engine but the body is mint and the price was right. The engine went a little sooner then i was planning so i dont have the money for a TT conversion. But my dad offerd to pay for mild cams, head work, headers, thortle body intake and ecu from jim wolf i have to do more research on it do you know how much this ecu unit will improve tourque and horse power.

Thanks for the help.

[k3smostwanted]

Originally Posted by sanzoneb

Yea my 300zx is kinda new to me i had a 3000gt before it but i had to get rid of that. I got it knowing that i was going to have to eventually rebuild the engine but the body is mint and the price was right. The engine went a little sooner then i was planning so i dont have the money for a TT conversion. But my dad offerd to pay for mild cams, head work, headers, thortle body intake and ecu from jim wolf i have to do more research on it do you know how much this ecu unit will improve tourque and horse power.

Thanks for the help.

i would go with the Ash spec ECU. it will save you quite a bit of money...
http://www.ashspecz.com

JWT mild cams are gonna run you $1000. i suggest going with the reground stock cams from Z1. it will also save you $500.

whats a throttle body intake? the 300zx intake is called a pop-charger. it connects at the Y-pipe at the end of the intake hosing. just remove the stock air box and pop it on.

headers, if you dont already know...there are a few headers on the market now-a-days. Stillens will be a pretty penny while you can get ebay ones for about half the price or even less. also, AMZ sells a set.

just some advice whether you take it or not is up to you...

the N/A ECU upgrade should net you about 10rwhp and about the same torque.

[sanzoneb]

I ment throtle body and intake i forgot the comma. My dad is ordering the cams from JWT for like $600, i know the ones you are talking about they are really expensive. Thanks again for the advise.

[MclarenF1]

Well...

The heads are going out tomorrow morning. We've decided to have a five angle valve job and a basic port and polish done. I'm going to take the intake plenums with me and see what they would charge to work them over, too. I guess they would have to extrude hone them or something. I can't say I'm familiar with how that whole process works, or if the shop even does that sort of thing. If not, my uncle could get a set from Stillen later on if he is so inclined.

As for the intercoolers, they are definitely from Stillen. They were already on the car, and it has been a long while since I have gotten to look at a set of stock ICs. Sure enough, the Stillen units are quite a bit bigger- even more so than I thought. Funny thing, though. He had a dealer put them on a while back, along with the rubber/plastic shrouds that are supposed to channel air to them. Whoever put on the shrouds attached them upside down and backwards. You can tell they knew something wasn't right because they cut the shrouds up and and did all kinds of crazy stuff just to make them fit. All they had to do was flip them and switch sides. I really wonder about people sometimes...

Someone asked where the shop I'm using is at. I'm in TN, up in the Eastern part of the state. I've found that it's best to hunt down a good machine shop that has some experience with a little bit of everything. The shop works on heavy equipment, performance marine engines, and all kinds of automotive performance applications. We have a few shops that supposedly specialize in "import performance" but they usually suck. They spend most of their time installing fart pipes and slapping on stickers, and can't seem to do much else besides run their mouths.

Anyway, time to start taking apart the bottom end!

Thanks alot for everyone's input. I'll probably have some more questions in the near future.

[k3smostwanted]

Originally Posted by sanzoneb

I ment throtle body and intake i forgot the comma. My dad is ordering the cams from JWT for like $600, i know the ones you are talking about they are really expensive. Thanks again for the advise.

hey no problem...

the JWT that are reground is he 400 series i believe. they are just reground stock units, i forget the specs on them. they should help none the less...

[k3smostwanted]

Originally Posted by MclarenF1

Well...

The heads are going out tomorrow morning. We've decided to have a five angle valve job and a basic port and polish done. I'm going to take the intake plenums with me and see what they would charge to work them over, too. I guess they would have to extrude hone them or something. I can't say I'm familiar with how that whole process works, or if the shop even does that sort of thing. If not, my uncle could get a set from Stillen later on if he is so inclined.

As for the intercoolers, they are definitely from Stillen. They were already on the car, and it has been a long while since I have gotten to look at a set of stock ICs. Sure enough, the Stillen units are quite a bit bigger- even more so than I thought. Funny thing, though. He had a dealer put them on a while back, along with the rubber/plastic shrouds that are supposed to channel air to them. Whoever put on the shrouds attached them upside down and backwards. You can tell they knew something wasn't right because they cut the shrouds up and and did all kinds of crazy stuff just to make them fit. All they had to do was flip them and switch sides. I really wonder about people sometimes...

Someone asked where the shop I'm using is at. I'm in TN, up in the Eastern part of the state. I've found that it's best to hunt down a good machine shop that has some experience with a little bit of everything. The shop works on heavy equipment, performance marine engines, and all kinds of automotive performance applications. We have a few shops that supposedly specialize in "import performance" but they usually suck. They spend most of their time installing fart pipes and slapping on stickers, and can't seem to do much else besides run their mouths.

Anyway, time to start taking apart the bottom end!

Thanks alot for everyone's input. I'll probably have some more questions in the near future.

extrude hone tends to be expensive, i dont know the process either but everything that i have seen that has been extrude honed is very pricey. plus at the power level your at, the performance gain will not be noticed.

port and polish will benefit nicely on a Twin Turbo...i really wish you would upgrade the turbos now instead if pulling the motor to do it later. the benefit would be awesome. the stock turbos just arent gonna be worthy of all of these other upgrades. 5 angle valve job and no upgraded turbos...

Stillen Intercoolers are very nice...i am buying a set for my Z as they are supposedly one of the best offered. thats ignorance about those ducts, the ducts are like $250 from Stillen.

and i agree, the better performance shops are the ones that arent that deep into the import scene or whatever. like race shops...they may be pricey but the work is above par.

good luck man...whats going on with the bottom end? if you upgrade the bottom end i will be even more upset if you dont upgrade the turbos.