Sunyi

Hi guys!

My name is Andras and I live in Sweden.

I´m hoping that you guys can help me out with my project.

I recently bought a 1987 C4 zf 6-speed corvette with an engine that has a blown head gasket. The old engine is going out and I´m going to order a custom made 421cui small block that will hold up for 15-20psi boost with a twin turbo setup.

The car is definitely not a daily driver as you can see, but I still want to be able to take it for a spinn trough town to show off some American muscle

I need your help to build an engine/drivetrain with parts that is compatible.

The guys at cnc-motorsports.com will put he engine together after my specs and ship it overseas in a crate as a long block.

Here´s my hardware list:

1987 Corvette C4 13” brakes, upgraded chassie.

Gearbox from a 1989, ZF 6-speed with black label, Dana 44 rear end 3,58 gears.

Customized twin turbo (2 x T3 turbo) setup with front mounted intercooler.
Bougt it here: http://cgi.ebay.com/ebaymotors/Chevy... 260271450729

421cui 8,5:1 compression (based on 75cc)

Eagle 4340 forged steel crankshaft
Eagle H-Beam connecting rods ( Bushed Fit Pins )
SRP Professional custom forged high performance aluminum pistons
High performance plasma moly piston rings
ACL/Clevite 77 Rod & Main Bearings
Dura Bond Cam Bearings
Dura Bond Finishing Kit
Victor Reinze Rear Main Seal
Internaly balanced
8" SFI balanser
Dart Little M sportsman block

Haven’t ordered it yet but I can choose from 1 or 2 pc seal.

AFR SBC 210cc Street Eliminator Heads, L98 angle plug w/heat riser, 75cc

Comp Cams NX276HR
Intake Duration @.050": 224 Exhaust Duration @.050" 236 Intake Lift .502Exhaust Lift .520 Lobe Separation 113°
Retrofit roller lifters

Holley stealth ram with lowered and welded plenum (stock hood)
68lbs injectors, large capacity fuel pump
Megasquirt engine management system
Small cab distributor
Broadband Lambda

Kevco 8 quart 7" deep oil pan, 6 gates, a diverter, full windage tray & scraper
Melling high volume oil pump

Now the clutch/Flywheel... I have not the faintest idea of what works or not.
Read a couple of threads about DM to SM swaps but haven´t got any wiser.

I know one ting, and that is that I want a combination that bolts right up on my setup and will hold up for 600-700rwhp. I really don´t want to go with parts that don´t fit when I´m bolting the tranny on to the engine.

Even emailed ramclutches.com and explained my situation but still no reply. I really hope that there is a ZF 6 guru on this forum that can take me under his wing and help me out. This is the only thing stopping me from completing my order on the engine above.

Regards from Sweden
/Andras

SurfnSun

Andras,

I have no personal experience with it but McLeod twin disk clutches are the one you want for the power you'll be making. I know of a few cars making 7-800rwhp with them.

tpi 421 vette

I have a Mcleod dual disc in my car, and it holds up fine. I'm sure if you got one, it would handle the power with no problems.And they are great, it feels like a stock clutch. The only downside is they aren't very forgiving on rear end parts. There is ZERO slippage, and they can break rear end parts. But if you don't put sticky tires on it and drag race it, your rear end parts will have a better chance of living.

Sunyi

Anyone that knows exactly what parts I should get that has the similar setup on his ZF black tag that is proven to work? Prefereble without the notorious "gear rattle".

Also, does anyone know if a 168 tooth flywheel will fit inside the ZF bellhousing?

As earlier stated, I don´t want to end up with parts that don´t fit.

What do you think of this kit:

http://store.summitracing.com/partde...5&autoview=sku

Curveit

I noticed that you had an 8" harmonic Balancer listed above... I think you need a 6 3/4" - 7" to clear the Crossmember. Good luck with the build....

Sunyi

The crossmember can be "massaged"

About that, do you think I could go with the 6 3/4" on my combo?

rklessdriver

You can put the 6 3/4 balancer on it as long as the balancer and crank are both internal balance (or both are external).

The 6 3/4 will be lighter.

Gear rattel in the ZF6 is a product of the gear desgin and there is not much you can do to quiet it down other than run a DM FW and a stock cam.

Also not knocking your engine plan but...
15-20PSI on a 421 is going to require better than SRP pistons. A 1.060 compression height on a 4032 allloy piston wouldn't be my first choice that kind of boost/heat/cyl pressure either.

Personally I would knock some stroke and rod lenght off it to get a taller compression height piston (better ring spacing). 3.75 stroke with a 5.7 rod will also give you plenty of piston speed on and off TDC/BDC to get the turbos spooled up quickly and the taller compression height will help the rings live much longer. Even thou it expands more, the 2618 alloy is far stronger than 4032 alloy. You'll never notice the little extra bore clearance once its warmed up.

If you just have to have a 421 inch motor, i'd suggest you use a 5.875 length rod and buy a custom set of 2618 alloy pistons from BRC, Ross or Wiesco.

No real reason to build a big motor thou with your HP goals. With (2) T3/T4's (strait T3 turbines are going to be way too small IMO), depending on what trim the compressors are 600-700 HP would be possible using a 350 inch motor.

Good luck
Will

TheCorvetteKid

Andras, it's too bad you're not closer to Umeå or I'd tell you to give me a call when you've got this turbo charged 421 in the car. I'd love to see (and hear) this thing when it's done!

Sunyi

The engine will be internaly balanced. Looks like I will go with the 6 3/4" balancer.

Talked to the guys at cnc-motorsports and they also noticed the issue with the pistons. They suggested to put in custom made pistons from JE. Will post some specs when I get them. Will pass the rod and stroke issue on as well.

The reason I´m going with the 421 is that I want to be able to upgrade the turbos to larger once I get this combo tested and running.
HP goals can change in the future and I want to have my bases covered.

I had a feeling that the turbos aren´t quite going to cope. Although they will spool up quickly What other turbines do you recomend for my 421 for future mods?

Do you have an oppinion on my cam specs. Any suggestions?

About the clutch, I found a complete DM/SM conversion kit:
http://www.ramclutches.com/Specialty...Conversion.htm
Anyone that have any experiance with RAM clutches?

Does anyone know if Mcleod has a similar conversion kit?

pr0zac

you might as well start off with twin t4's instead of t3's. with all that displacement pushing them it would be silly in my opinion to run such a small turbo. as for the flywheel. you can only use a 158 tooth flywheel with the zf6

88BlackZ-51

421 with turbo's. that's awesome!


did you buy the AFR's yet? if not, send tpi 421 vette a pm, and he can possible help you out!

James93LT1

L98/LT1 & LT5 CORVETTE KITS 1989-1996

http://www.mcleodind.com/application..._GM_Parts.html

bogor

I´m running a McLeod Street twin with steel FW in my -90. No gear rattle so far (still braking it in though). The clutch and rotating parts were balanced together (internally balanced) and I recall the machine shop made some weight adjustments of the supposedly 0-balanced flywheel.
I think I am closer to you than Umeå...Check your inbox

TheCorvetteKid

Yeah, Umeå is pretty much the edge of civilization

C-4 Now

Sounds like awesome build! Would think, but not sure that you need 1-piece rear main crankshaft for flywheel compatible with ZF-6? I've been collecting parts to upgrade Callaway TT to 409? bowtie block so would like to hear how this project goes

rklessdriver

Incorrect. SPEC makes a 2pc rear seal single mass FW desgined for running a ZF6 behind early style blocks, if he wants to go that route.

Sunyi -

IMO the Mcleod street twin is going to be your best bet for a clutch capable of holding this kind of power and offereing some similance of driveability.

My opinion of your cam... is that its small for a 400+inch motor. That could be a blessing thou, as it would be easy to tune and offer great driveability. Its going to peak at a rather low RPM. My Eingine Analyzer indicates it peaks at 5600RPM. I don't know how hard you plan to turn it.

As for turbo recommendations. I now they are older tech but I would start out with twin TO4B's or TO4E's. Either in a twin set up will go up to or slightly over over 1200HP. They are proven low boost (B's)/high boost (E's) compressors that would give you plenty or room to grow in the future while providing plenty of power to get started. At 15psi either would work but that is the high limit of (most) the availiable TO4B compressors. I would talk to Turbonetics tech line and let them decide the trim on the compressor wheels and buy what ever they recommended.

Will

C-4 Now

Will: I appreciate you input. I was not aware of Spec flywheel. Everyone with that type of horsepower recomends McLeod street twin!!

slickfx3

http://www.zfdoc.com/

bnio

You can run almost any type of flywheel setup you want. The important thing is to keep the hydraulics happy with setting the pivot fork height correct for the difference in flywheel depth and making a longer pushrod if you ditch the dual mass. Theres a ZR1 clutch fork pivot that is longer than the stock L98 so when you ditch the DM Fly you can use this to put your hydraulics back to the correct height with the longer pushrod. Thats What I did. The pivot ball for the ZR1 is longer than what you need, all you need to do is to turn down a spacer, then grind off the excess stud. Of course you need to measure the thickness from the crank face to the friction face of the DM, then the same for your new setup then adjust accordingly to the difference of installed height. The gear rattle isn't bad either but I understand why you don't want it also. By the way Ram has a single mass replacement setup with new throwout bearing that converts the hydraulics back to push instead of pull. If money is an issue use the ZR1 stud and single mass 153 tooth flywheel, it will be done cheap fast and reliable.

Good luck

bnio

I went back and reread your post and noticed you mention possible advice on engine setup. I saw you stated T3 turbos, those won't be nearly big enough by any means especially for a 420 cuin motor. Another member posted TO4B or T04E, forget the TO4B and look at the TO4E only. The 4B is outdated and the compressor efficiencies compared to the 4E aren't even close. The TO4E series will be far superior. You will want at least a 60 trim compressor if you are looking to make 15 to 20 psi on that 420. I imagine roughly you should be looking at displacing around 100 lb/min of airflow on that size engine and boost range easily and I am probably under estimating. Also 1 lb/min = 10 hp approximately. Now that I think about it you will be outpacing the TO4E compressors for airflow so you may have to turn to the newer GT series garrett or Borgwarner turbos. Borgwarners if money isn't an issue are really good on efficiencies.

That 20 pounds of boost on afr 210 head and a 420 cu in should be in the neighborhood of 1000 plus flywheel horsepower and those heads may even be too small for that engine displacement. If you want a street car it will be great but if you want all out power by all means increase head size, that 420 will out pace those 210's easily if you increase cam duration, it should be easily in excess of 550 hp on all motor no boost if compression ratio isn't to low. Also just so you know I have my own cnc equipment, flow bench and I do head porting as a hobby, so I have a good solid understanding of airflow and engine requirements. Those AFR heads just make a ton of power, they work extremely well out of the box. I think you have a very good all around set up, the only thing that scared me was that I saw you had T3 Garrett turbos listed on your description and those will be too small if that was indeed correct. You should do some calcs on engine VE to determine what airflow will be under boost then start sizing the compressors accordingly. The turbines I imagine would be in the P trim to Q trim range if you refer to the old TO4B designations which is still common for many turbos today.

Check this thread also if you haven't already found it about clutches.
http://forums.corvetteforum.com/c4-t...zf-clutch.html