I am making a zz4 for my vert. I was wondering if the stock 350 injectors will be enough with them turned up, or should I get bigger. This has been a econ buildup, believe it or not, and cost is a concern.

Thanks
Jeremy

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WE WILL MISS YOU #3
92 Z conv
5-spd B&M shifter
home-made ram air, air foil, headers, no cat, TB bypass, kevlar pads, slotted rotors, BMR panhard, alston SFC, 3.42's, Edelbrock STB, 350 in the works

 

a stock 22# injector will be fine. if you are
more performance minded maybe a 24# would be
better for future upgrades (cams, heads, rpm)
but to keep budget.. 350 injectors will be
fine. you might want ot have them flowed and
cleaned. approx $15 each is fair..
airdeano

 

The GMPP people told me to forget about using the ZZ4 and TPI combo. They said the cam is not suited to injection and does not produce enough vacuum and will end up setting a code. Is this true?

NE1 using a ZZ4 engine or cam and TPI?

A CHP magazine article also said that the stock L98 cam makes better power than the ZZ4 cam at the sort of RPM that the TPI systems run at. WTF? Should you only use a heavily modded TPI with this engine/cam?

 

perthz28,
the zz4 is a fine idle cam, produces plenty
of idle vacuum. speed density systems have no
problems with the cam. we even have a zz4 in
a cross-fire with no chip change.
the TPI works fine with the ZZ4. the problems
most dont figure are the limitations of what
the cam was designed for. high rpm. the TPI
kills the notion over 4200rpm. the zz4 redline
on output is 5250rpm. so youll lose 1000rpm.
the better manifold is the miniram, or LT1 intake
converted like john millican has done.
the TPI is torque.. if your building for high
rpm horsepower build a miniram. if you have
a 5400+ lb vehicle you better build torque.
between 3000-4000lb you try and build equally
due to the trade off of daily driver and track
terror...
airdeano

 

Not true...years ago I ran my ZZ3 cam (same cam) with stock TPI, stock chip and gutted MAF with no codes, no problems. Idled just fine too. Even when I went to SLP runners there were no problems.


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1989 IROC-Z, ZZ3 shortblock with some bolt-ons.
13.20 @ 108.69, 2.2 60'

 

I and others run the LT4 HOT cam (218/228 on a 112 LSA) which is quite a bit bigger than the ZZ4 cam with little difficulties. The big caveat is that you'll need to be able to burn your own chips or have a friend that can burn them (as in multiple iterations, not just one chip) for you. I have my idle in Park (850 rpm) up to 15 1/2 inches of vacuum and running quite smooth. The key is increasing the timing at idle, not the base timing; this has to be done in the chip. I tried timing from 18 to 30 degrees of total timing and found it ran the best (most vacuum, least amount of airflow, runs smoothest) at 30 degrees.

To answer the original question, I agree that 22# injectors will be fine unless you're building the engine up further with better heads and a bigger cam, along with better runners. With these, you can wind a TPI engine out to 6000 rpm and still make power, with a friend having the dyno graphs (301 rwhp) and timeslips (12.18 @ 109.6 mph) to prove it.

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Greg Westphal
'87 IROC 355TPI/A4

 

The heads have been ported and worked a little and the plenum has been ported. I am going to attempt to make a 50 mm TB this winter. with the headers and no cat, I think I have the airflow down. I am kind of stuck with the stock runners, since I autocrosss and I can get this motor in under stock rules in the local events. They keep putting me in with the new Z's, and I am tired of being down 100 horse.

Jeremy

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WE WILL MISS YOU #3
92 Z conv
5-spd B&M shifter
home-made ram air, air foil, headers, no cat, TB bypass, kevlar pads, slotted rotors, BMR panhard, alston SFC, 3.42's, Edelbrock STB, 350 in the works

 

my 86 with 85 TPI setup and harness runs fine,and im still using stock 305 prom,and 19#svo injectors ant 53 psi.Have had it in the car for about 2 years ,no goofy codes or driveability probs.O2 voltage is .875-920 at WOT in 3rd gear pull.So the smaller SVO injectors are working fine for my combo,i believe they are real close to 22 lb at the GM rating pressure of 43.5.

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86 z28 zz4 ssm lift bars ,3.73 simesed runners and a traction deficient 13.707@101.02,on a 2.16 60 ft on 295/50/15 junk street rubber ,best MPH run 13.82@102.7,69 AMX,390 4 speed sticky tires and other stuff..12.94@102.3

 

will the stock 305 tpi chip work until I can tune one for myself? I am trying to learn but the pocket programmer will not recognize the chip is erased.

Jeremy

 

24# svo injectors are cheap and work well with this application.

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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.

 

It will run with the 305 chip but very badly. I would not do the project untill you can include the cost of the chip in your budjet.

 

opps,didnt see yours is a SD car,being Mass air,mine is a LOT more forgiving

 

I used a 305 5-speed chip in my 350 ZZ4 with mild ported heads, roller rockers, SLP 1 5/8" headers, ported stock TPI intake, and 52mm TB. It made 280 HP @ 4700 RPMs and 380 TQ @ 3400 RPMs to the rear wheels. The ZZ4 cam has a 208 degree intake duration, that is pretty mild. I also used stock 22lbs injectors. ZZ4 engines and TPI work very well together. The heads dont have EGR, so you will need a Corvette-style EGR setup if you have to pass emissions tests.


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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
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