I just completed installation of a TPI ZZ4 crate motor in my 1988 IROCZ Convertible. Previous to this motor I had the TPI 305, the only motor offered for the convertible in 1988. I have used this website to get advice during the installation and I thought I'd pass on my experiences and the present status after 70 miles.

The component list reads like this:

1. GM ZZ4 GM crate motor.
2. TPIS Big Mouth, adj. fuel reg., PROM.
3. Edelbrock Victor reverse rotation water pump.
4. Edlebrock street legal headers.
5. Random Technology Hi-Flow Cat and 3" Cat-back system.
6. 700R4 with custom shift kit.
7. B&M Megashifter.
8. B&M Holeshot 2400 torque converter.
9. GM 24#/hr injectors.
10. MSD 8.5mm resistor ignition wires.

I live in Ca. so I will have to negotiate the smog check in about one year. I left everything on, air conditioning, air pump, etc.

Problems I ran into were:

1. The need for a reverse rotation water pump.
2. EGR valve (welded fitting to the headers and ran an EGR tube similar to the vette).
3. Alternator and AC support brackets.
4. Coil and EGR solenoid mounting.
5. Dipstick - I have one on the motor but can't reach it.(Loktar) Hope to successfully deal with this in a few days.

The motor fired almost immediately, adjusted the timing with the proper jumpers at 6BTDC.
The Random Technology kit is very thorough but very loud.

I have a very bad exhaust leak. I will need to take it down to a muffler shop tomorrow to have the exhaust leak welded. The slip joint between the Edelbrock Y tube and the Random Catalytic converter doesn't quite fit right. The clamp provided makes the Cat tube oval around the header Y tube. I suspect that this could create problems with O2 sensor readings (I'm hoping that curing the leak makes the car run better).

This my first attempt at a performance car and I don't quite know what to expect. The car appears to be running fat/stumbling at low RPM but wants to jump at about 3000RPM. I believe the exhaust leak is really hurting performance but at this point I can't tell.

I'm not getting any check engine lights but I don't know if the PROM made by TPIS generates the same codes as stock. I am running a stock throttle body, MAF detector, and runners. I plan on upgrading these components down the road but I don't expect the stock items to be creating problems. Does anyone have experience with the 52 or 58mm throttle bodies? How about sources of large runners?

Something just isn't quite right. Any insight other members might provide would be greatly appreciated. I hope this has been informative to those that are thinking of this engine swap and I thank those that have provided me with solid advice.

I'm almost there! Rodding is great!

 

So far, thanks for the advice. My 305 is soon to be replaced with a 350. The ZZ4 base is probably what i am going to go with. Then slap on my own heads, and everything.. Lot of research to do. How much horsepower & Torque are you getting through the TPI system? I hope more people reply to this post so i can have more info on my future engine too!

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1990 Iroc-Z 305ci
*Flowmaster Exhaust (80 series)
*Hypertech Performance Chip & Airfoil
*Powerstop rotors
*8.8 mm Accel Wires
*Splitfire plugs
*MSD coil (48,000 volt)
*177.1 RWHP & 243.7RWTQ (keep in mind: 137,000 miles and only the above mods)

Future Mods:
350, TQ Conv., 3.42 gears, Headers, Ported plenum, Streetfigher 700R4 Trans., etc

AIM: Onfire4jesus324

My Car in Member Rides

 

I can't give you horsepower and torque because it isn't running good enough yet. It's missing on #4 and my troubleshooting has led me to believe that I have a bad injector. On seven cylinders I had more power than the 305TPI ever had. I can't wait to get it running on all eight.
Since I have to take the injection apart again I'm going to install large runners, a modified MAF sensor and probably a 52mm throttle body. I don't want to mess with the engine any more. The ZZ4 has great potential.

 

Oh yeah, the bigger throttle body will help smooth things out.. or should.. bad injector huh?.. all spark plugs and wires good? My goal is 320-330HP & 400 TQ

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1990 Iroc-Z 305ci
*Flowmaster Exhaust (80 series)
*Hypertech Performance Chip & Airfoil
*Powerstop rotors
*8.8 mm Accel Wires
*Splitfire plugs
*MSD coil (48,000 volt)
*177.1 RWHP & 243.7RWTQ (keep in mind: 137,000 miles and only the above mods)

Future Mods:
350, TQ Conv., 3.42 gears, Headers, Ported plenum, Streetfigher 700R4 Trans., etc

AIM: Onfire4jesus324

My Car in Member Rides

 

If you havent gotten it yet I think the 58mm t-body for the cost differenct is worth it. Also is you chip custom to your application? If not it would be worth it to get a new one or learn to burn your own.

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1991 Z28 ZZ4 with LPE superram base, SLP runners, LPE 58mm T-body,Random Technology ramair,TES headers,24#svo injectors,ZEX nitrous,Walbro 255lph f-pump,Accel AFPR,Random Technology catback,!cats,and mutch more.

 

I haven't got the throttle body yet. I was looking at Edelbrock or Holley - in a 52mm. The 58mm is tempting, I just don't know how it will effect throttle response and torque.
any comments on this?

With respect to the fuel injector, I had tested spark to the end of the wire and then put a new plug in the hole. No change. Electrical signal to the injector was good - I'm thinking it's an injector although they all were new 24#. My common sense tells me ignition but I can't find an ignition problem. I'm going to get all the injectors flowed and tested, reassemble and try it out.

 

Considering that the Ram Jet 502 uses an L98 throttle body, I seriously doubt you need a bigger one.

Fix the exhaust leak, and the TPIS prom is definitely not the best one for any setup either. Spend the money to program your own and you will be better off in the long run.

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1990 IROC 350
Mods: Too busy trying to make it run right to mod it.
Airfoil, Dynomax cat-back, MSD coil, 180 t-stat, Bald Eagle tires,
Hypertech fan switch, Accel 23# injectors, Holley module, ported plenum,
Ported Daytona Yellow stock base, Moroso valve covers, other stuff,
Streetdampr, Ruger P95DC, hot wife, new oil filter, !cats, !TBC, !AIR.
18.0 @ 85MPH since I'm one big-a$$ MF
"It's better to have and not need than to need and not have."

 

I understant the contraversy about TB size will never end but I can tell you through my experiance and that of others I have seen in this combo it works and is worth it. Given the giant amount of TQ the ZZ4 makes trading a very small amount for a good gain in high rpm HP it is a good idea.

 

keep talking guys. I am making a zz4 clone out of a 91 L98. I have the vette alum heads and an accel base. How did you do the EGR conversion. I have heard I have to do this but I know nothing about it. Keep us all informed It has been helpful sofar.

Jeremy

 

The EGR conversion is straightforward if you have the correct intake manifold. The corvette heads (if they are similar to the heads in a ZZ4) have no EGR passages. The way EGR is handled on a corvette is to use a special intake manifold that has a passage to the EGR valve and a port that is connected to the exhaust manifold through a small (1/2" diameter) tube. I have the "big mouth" manifold from TPIS which although pricey is not nearly the price of a corvette manifold (new at least). TPIS also sold me the tube (at 1/2 the dealer price) and the special fitting that I welded to the exhaust header. You may want to buy headers for your car because it will be difficult to weld to cast iron. Maybe your Accel manifold has the port. Anyway, thats how I did the EGR - other members of this board advised me.

 

I am activly planning on putting the ZZ4 into my 91 replacing the stock 350, i thought the specs for the ZZ4 were 355hp 405 TQ, what could i expect to get at the wheels after a tpis intake and runners, and a porting of my stock base plus a 56 or 58 TB ? And i thought i read that somone put up a website for help, what's the site address ?

 

The GM specs of 355HP and 405 ft-lbs were obtained with a different intake system, the configuration of which is unknown to me. Although I haven't seen TPI/ZZ4 HP/Torque specs. a similar setup was tested in a recent issue of Chevy High Performance. The car, an 87 or 88 Camaro did 12.3sec. for the quarter with a speed of over 100mph (I think it was 108). I haven't the foggiest what that translates to in HP/Torque but I'd be real happy if my street car could run high twelves or low 13's. All the stuff I've read would indicate that the high RPM HP will be restricted by the TPI system - lots of torque though. If you don't have to deal with emissions (I do in Ca.) I would look into a TPIS miniram, or better yet, their 450HP turnkey 350ci.