Need Help: Fuel/Air management Question

[Jwalsh]

I have an 87 Gt, Have my ECM already out of a 93 gt going to buy new throttle body, EGR spacer, mass air meter, Injectors, and a new fuel pump.
in a few months will probably stroke my engine. was wondering what the best combo of sizes and injector size would be. I know I might as well get the 255lph fuel pump, Was thinking going 70mm all the way with the mass air assembly, spacer and throttle body, with 30 lbs injectors. Will this still keep good drivability on my stock motor before I can put the stroker in, and if so will it have a fuel/air starvation when I put a higher compression 347 in there?

All info would be much appreciated. Also will my stock fuel lines and regulator do the job?

 

[jrichker]

A Pro-M MAF is best at 73 MM or greater considering your future plans.

The 30# injectors and 70 MM TB are going to be way overkill for a stock motor, but will work fine for a 347 stroker. You may have some driveablity problems using them, The 70 MM TB will decrease your low end torque somewhat. You may need a custom chip burned to get the 30# injectors to work with the stock engine. Either that or experiment with turning down the fuel pressure. I would keep the stock 19# injectors until you do the stroker thing if the car is running good. You can send the Pro-M MAF back for recalibration (cost maybe $100 to get it done) when the time comes to switch to the 30# injectors.

 

[Jwalsh]

Thanks alot for the info. My car really breaks up on high rpm around 4000 but my heads are ported, along with intake, new roller rockers 1.7 and full exhaust/headers. If I just put the new fuel pump in will it pull hard all the way through?

 

[autoXr1]

"...My car really breaks up on high rpm around 4000 but my heads are ported, along with intake, new roller rockers 1.7 and full exhaust/headers. If I just put the new fuel pump in will it pull hard all the way through?..."

You are under the assumption that it is a lean condition creating this issue? What evidence supports this?

Are you still using the stock valve springs and/or lifters? If so, perhaps you are experiencing some valve float. What is the condition of your alternator and distributor? Perhaps you are experiencing a lack of voltage or missfiring. Along those lines, as RPM increases, voltage may drop to your fuel pump...just when you need it most. A voltage regulator such as a Kenny Bell "Boost-a-Pump" or Jacob's Electronics "Accuvolt" unit would solve the issue.

4000 is not high RPM, even for a stock engine. However, there may be several reasons for power loss as RPM increases.

Just trying to extract some more information so that we can help out.

 

[Jwalsh]

Its very slight most people can't even feel it, I think that is breaks up probably more than others since I havent driven the car since August, but my distributor is older, alternator is new, lifters are new, and valve springs are new. Also I am still on speed density, got all the hardware to do the conversion when my car returns from the iceburg its under hehe.

could it be the "surging" that I might experience from the ported heads/intake, on the speed density system?

 

[autoXr1]

It MAY be a distributor and/or TFI module problem that is common to the older 5-ohs. However, this typically occurs, at some extent, across the RPM band. The distributor bearings can get a little play in them and not want to maintain a steady ignition advance creating minor missfires or surges. The TFI module may also create little ignition gremlins, as well.

I had a similar problem with an intermittent miss at all RPMs...idle, cruise, etc...pulled my hair out trying to find it. Got a new MSD Billet distributor/TFI...cured the problem.

It MAY just be a tank full of old fuel. Sometimes just burning off the old stuff and filling it up with fresh 93 octane does wonders.

I don't think your speed density car cares about the ported heads/intake, as the majority of the computer's information is being retrieved before the intake.

 

[Jwalsh]

Thanks alot for the advice