RIP TimmyD

iTrader: (1)

I have a 1992 sc300 with a turbonetics t66 setup running 8lbs right now. I want turn the boost up to 18lbs witch cometic head gasket do i need? A part number would be great. And what cc injectors do i need to switch to? Thanks for the help

That-Guy

iTrader: (1)

if you are only going to be running 18 pounds of boost, you should be fine with just the 2jzgte oem manifold, i think you can get em for like 100 bucks,, if not i'd go for the cometic 1.3 mm anything over that is gonna be getting into low compression and you're engine won't be as peppy so you'll have to make up for it with more turbo power. I don't know what kind of numbers you're pushing so i won't say anything in stone, but those are the 2 gaskets i'd look for. Along with the gasket i'd do the timing belt if you haven't and get some headstuds,

injectors depend on the power you're looking for. 525's from boostlogic or 550's from the fc rx7 turbo are both direct fits, if you want to stay in the 300-450ish range in hp, but you could run injectors alot bigger if you want.

SMP142

if you deal with suprastore be careful. alota guys on supraforums have had bad experiences with them. your better off going through PHR or MVP. dusty will hook you up.

get a thicker HG like a 3mm and turn up the boost. you will be able to add more fuel and you wont be disappointed.

Blk97SC300

iTrader: (4)

www.cometic.com

http://www.cometic.com/contactus.aspx

call them and order a 2.5mm head gasket for a 2jz-GE motor.. It's less than $200. That's what I have on my car.

hyjaxx

iTrader: (1)

Call Sean at Titan Motorsports- they will give you way below MSRP and the customer service is great. A 2 mil is probably your best choice. Then go to an injector website like RC Engineering and use their flow chart- you plug in the #'s and they tell you what you need.

1sxyrxy

think u would be ok with 550's maybe little more

madmax98

I don't think 525 or 550 injectors are good for 18 psi from a 66, i recommend getting the biggest you can, assuming you can control them of course. But 680's are safe for 80% duty cycle and some head room too....

bens sc

iTrader: (2)

First off, do NOT deal with the suprastore...they blow.
Second just get the supra tt stock head gasket and some arp head studs.
The stock tt headgasket has been proven in high rwhp cars (think 700rwhp).
As for injectors...its really up to you keep in mind that 1cc of fuel is roughly translated to 1rwhp. It is better to get a larger injector to be safe and so you will have room to grow. Keep in mind that you should also change your fuel pump to keep up with the larger injectors.

Make sure you have a way to control the new injectors (aem ems, haltec,etc)
you car will not run properly if you just drop them in.

TLDriver

iTrader: (4)

My question before suggesting anything... What are you using to control your fuel? What type of fuel are you planning to use? Anything else on there other then boost?

5sp_jzz30

iTrader: (2)

injector size? here:

http://www.rceng.com/technical.aspx?...0fTbkCuXVSlGjv

use that as a guide. dont exceed 85% duty cycle. the more duty cycle you run the hotter the injectors get. at a certain point they lock up, either closed or open, and that in itself can cause a blown motor.

head gasket?

do some research seriously!!!

find the stock CR, combustion chamber volume, gasket volume, piston disk volume(positive or negative) and based off of that figure out what thickness gasket you need. you have to have a goal for CR so you can find gasket thickness.

if you cant calculate any of that yourself you should just drop off your car at a shop and have them do all the work or google ways to calculate CR. btw google could have solved all your questions. there is nothing specific in your questions that pertains to the SC. its pretty much the same formula for any street going 4 stroke IC engine.

That-Guy

iTrader: (1)

took out that little bit bout supra store, i've never dealt with them, just saw the kit, and it looked aight, but i guess they aren't the ebst around, i was under the impression that the stock tt headgasket was 1.0 mm, but i have been recently informed that it is actually 1.6mm, can anyone verify this?

Gunnar

GTE headgasket and ARP headstuds here.

stevechumo

iTrader: (5)

There're some concerns that you'll need to prepare when going for Cometic head gaskets. Many people have run into the coolant leak problem with Cometic, including myself. First, you'll need to make sure the surfaces of the block and the head are really straight and have mirror-like finish. Second, a little more tq is required. Therefore, going with ARP studs is a must with Cometic so you can torque the head down more. The tq should be around 70-75 ft/lb for the ARP studs. If you have iron block, a little more tq than 75 ft/lb is to be sure you won't have to re-torqe the head. Missing either of the above preparations will cause the coolant leak because the Cometic gaskets are very hard and don't seal very well on rough surfaces. You can google and you'll see a lot builders (amateur and professional) complaining about Cometic gasket leak.

5sp_jzz30

iTrader: (2)

why is it that amateurs complain about cometic leaking? my boss has been using cometic forever, at least for 6 years that i have known him, and has never had any issues. the only variation was TRD gaskets for 4age motors.

the only cometic that i know of blowing was on a dyno fun using some exotic race fuel. it was left overs from the Renault F1 team that was here for the US Grand Prix in 2005 i think. it was highly oxygenated ELF race gas. the motor went lean and blew the gasket. no other damage. i have not seen any other gasket failures with cometic and this one wasnt even the gaskets fault. we didnt anticipate the gas to be so "exotic" compared to even C-16 and some other 110+ octane stuff we used.

your results will depend on your preparation. if you take a razor blade and clean the surfaces you will have a **** seal...period. if you prep it right you wont have issues.

btw you dont need to re-torque metal gaskets even after break-in period. that is only required for "organic" type gaskets. adding extra torque may help with the sealing but it has its drawbacks as well. the ARP studs as previously recommended are not torque to yield or "stretch bolts." they will stretch with use but not like stock bolts and can be reused. over torquing them leads to premature stretch wear. using stock bolts, even new is a waste of a gasket. stock bolt specifications are not completely known. they can be easily found but i have not seem any evidence. torquing bolts down and then furthermore torquing them via a degree method is not at all accurate. it is easier with a digital torque wrench that can actually beep when a preset degree mark is reached. it calculated the torsional twist in the tool and the bolt.

all xJZ series blocks are iron. over torquing can be an issue in aluminum blocks.

stevechumo

iTrader: (5)

You're right. There's nothing wrong about it. I guess your boss knew what he does, but what I stated is happened not uncommonly, including pro builders. Unless the builders have the experience with Cometic, otherwise, they may have the leak issue. The Cometic is a very strong gasket. I didn't know of any case it blew. I just knew it can cause coolant leak if not prepping the surfaces right the first time. However, graphite gaskets (weak) can seal a lot better even the surfaces aren't perfect. The Cometic can also be re-used according to Cometic, but who wants to try?

Over stretching the ARP studs is not common, because the ARP can take a lot of tq unless the builder intentionally wants to break something. With ARP studs, a wrenching degree when torquing isn't recommended. For example, a standard method for stock bolt & gasket is 29 ft/lb, then 90 degree, then another 90 degree again. That's only about 50 ft/lb as from what I measured and remembered. The Cometic will have a chance to leak at this tq. However, instead of 90 degree, break the tq down to 29 ft/lb, then 40 ft/lb, then 50 ft/lb, then 60 ft/lb, then 70 ft/lb or a little bit more will ensure the even strength and sealing. I'd rather take it slow in torquing than do it fast and have a leak.

There's a missing link between the ARP tq recommendations from ARP and Cometic recommendation. It is the ARP only lists the tq for the stud size, but not for the gasket materials. The Cometic lists the tq for their gasket (such as factory recommended) but not for what kind of stud is used and what application the engine is for, NA or FI. The FI takes a lot more beating so the NA method can't be used. The reason ARP studs are used not only because to make sure they stay, but also to enable more tq can be applied. This debate isn't common, but how it's used depends on the builder's preference and experience with certain products and technique.