95 Chevy 355 TBI Build

**dave w** · 04-01-2014

Originally Posted by 355chev

Dave do you remember if guys used a stock fuel pump for that particular application?

I don't remember. Sorry.

I would recommend upgrading the fuel pump for 18 PSI.

dave w

**355chev** · 04-01-2014

Thanks for the information EagleMark! So basically what I get from the information given its probably a good idea to get 454 injectors and have a minimum of 18 psi and a larger pump such as a EP381 or EP377?
BUT if I can get by with 350 injectors it would be nice mine only have 100k on them. Correct me if I'm wrong though!
Thanks
Max

**EagleMark** · 04-02-2014

The 5.7L Injectors are going to require a lot higher pressure then the 7.4L injectors. Raising pressure is to supply more fuel needed to meet the HP demands of the motor. HP = fuel, more HP? More fuel!

**Fast355** · 04-02-2014

Originally Posted by 355chev

Thanks for the information EagleMark! So basically what I get from the information given its probably a good idea to get 454 injectors and have a minimum of 18 psi and a larger pump such as a EP381 or EP377?
BUT if I can get by with 350 injectors it would be nice mine only have 100k on them. Correct me if I'm wrong though!
Thanks
Max

Max,

Even off the show room floor the old TBI injectors can vary as much as 8-10% from injector to injector in flow. I would looking into getting a pair of serviced/flow matched injectors. Even at only 100K it is amazing how unbalanced it can be. Having balanced injectors makes a HUGE difference.

**355chev** · 04-02-2014

Originally Posted by Fast355

Max,

Even off the show room floor the old TBI injectors can vary as much as 8-10% from injector to injector in flow. I would looking into getting a pair of serviced/flow matched injectors. Even at only 100K it is amazing how unbalanced it can be. Having balanced injectors makes a HUGE difference.

Wow I knew they weren't the best but 8-10%! Thanks for the info Fast355.

**EagleMark** · 04-02-2014

At 100k miles they are worse. Every set I've had serviced has shown differences in injectors from 2% to 13%. They all seem to be spot on after service. SO I think they are matched from factory, but each set can be 8-10% differant.

**355chev** · 04-02-2014

I looked on the site Im buying my throttle body at said has flow matched injectors. http://www.rvmorsemachine.com/product.htm Get those?

**EagleMark** · 04-02-2014

Cheaper to just have yours serviced. Click the banner ad for Mr Injector.

**355chev** · 04-03-2014

Got the tranny out today the easy way ha. I will be getting the block and heads back from the machine shop tomorrow. I still have to order some more goodies but its moving along!! Oh and thanks to all that help me out with questions and give advice!

**EagleMark** · 04-03-2014

Please tell me there's jackstands there I can't see?

**355chev** · 04-03-2014

Originally Posted by EagleMark

Please tell me there's jackstands there I can't see?

Yea Mark if you zoom in by the red creeper on the right there is a red 6ton jackestand both sides.

**dave w** · 04-03-2014

I've been thinking ... using Vortec heads opens up the option of upgrading to MPFI (one injector per cylinder). The factory 1996 ~ 2000 L31 Vortec intake system is one injector per cylinder. With some internal modifications to the 1995 PCM / Memcal, can be set up to run the L31 Vortec injectors. The 1995 PCM will operate the L31 Vortec injectors like the older TPI computers operated the TPI fuel injectors.

There are several parameters in the PROM chip that need to be reconfigured for the 1995 PCM to effectively operate MPFI. There might be a few mounting headaches using the 1995 serpentine belt drive system with the 1996 ~ 2000 L31 Vortec Intake system.

Something to think about? I firmly believe that 8 injectors is better than 2 injectors for the +300 HP SBC!

dave w

**Fast355** · 04-04-2014

Originally Posted by dave w

I've been thinking ... using Vortec heads opens up the option of upgrading to MPFI (one injector per cylinder). The factory 1996 ~ 2000 L31 Vortec intake system is one injector per cylinder. With some internal modifications to the 1995 PCM / Memcal, can be set up to run the L31 Vortec injectors. The 1995 PCM will operate the L31 Vortec injectors like the older TPI computers operated the TPI fuel injectors.

There are several parameters in the PROM chip that need to be reconfigured for the 1995 PCM to effectively operate MPFI. There might be a few mounting headaches using the 1995 serpentine belt drive system with the 1996 ~ 2000 L31 Vortec Intake system.

Something to think about? I firmly believe that 8 injectors is better than 2 injectors for the +300 HP SBC!

dave w

Shouldn't be any clearance issues, just have to find something to brace the back side of the alternator and compressor with since you will no longer have the intake to bolt to.

That being said I had one of those JUNK L31 intake manifolds. The factory spider crapped out at only 57K. Even with the upgrade MFI spider in it, it was still ran like junk. When the upper plastic plenum cracked at only 85K I picked up a marine intake and went to something that was 100X better. I am glad I did all the injector trash in the top of the intake, right in the flow path of the air really killed the power potential of my ~300 RWHP 350. 8 injectors maybe better than 2 as long as they are outside of the intake manifold. My brother recently picked up a 1996 S10 4.3. Its getting a marine intake within the next few weeks as well.

The 7427 will also control the factory linear egr valve on the vortec intake.

**EagleMark** · 04-04-2014

There's no doubt a marine MPFI intake is a better choice, but the cost is up there too!

As far as a stock Vortec intake yes they are on the cheap and limiting side. But it's still a big step up from TBI. Just depends on the engine build and budget.

Mine is a 1998 and has 124k on it and no issues. Had the factory intake gaskets replaced around 100k and the spider was also replaced I think do to the previous owners obsessions in maintenance! It's unbelievable how many parts of this truck were replaced, it was more done by the book then just waiting for something to fail...

**Fast355** · 04-04-2014

Originally Posted by EagleMark

There's no doubt a marine MPFI intake is a better choice, but the cost is up there too!

As far as a stock Vortec intake yes they are on the cheap and limiting side. But it's still a big step up from TBI. Just depends on the engine build and budget.

Mine is a 1998 and has 124k on it and no issues. Had the factory intake gaskets replaced around 100k and the spider was also replaced I think do to the previous owners obsessions in maintenance! It's unbelievable how many parts of this truck were replaced, it was more done by the book then just waiting for something to fail...

The factory intake gaskets on the Express crumbled at 57K and killed the stock engine by breaking the #2 connecting rod on startup.