TBI 400 Small Block

[93V8S10]

Sounds like you've get a plan, just need to get it all back together, so you can work on diagnosing the original problem. Don't worry about the stock 400 cam, it will be just fine, as evident by how well it ran with stock tune.

[EagleMark]

Sounds like you've get a plan, just need to get it all back together, so you can work on diagnosing the original problem. Don't worry about the stock 400 cam, it will be just fine, as evident by how well it ran with stock tune.

Agreed!

Your origanal issue, since you had spark but ran with ether was a fuel problem. So could be faulty relay, plugged fuel filter faulty ful pump?

You ran good on a stock 5.7L chip on a 400 engine is probably why you ran out of power at higher RPM.

Rough idle, surging and poor fuel milage could all be tied together to a vacuum leak.

If you put it all back together we can diagnose what went wrong, fix it, then move you on to tuning the chip for a differant motor.

I don't see any flaws in your plan. Just have to pay attention to detail like vacuum leaks when you do the intake change and TBI install. Rest is pretty simple plug and play.

[Xenon]

Great!!! I was thinking I'd have to go with the stock TBI cam... this, then, is not necesary?

What do you think about the ECM1 fuse blowing? I'm pretty excited about getting this this TBI'd again. Part of the reason I stopped driving it and got the '98 was the poor fuel economy with the carburetor... Also, it's a 4x4 and the '98 isn't, and being in ND the 4x4 is much needed in the winter. Except for this winter...

I'm almost done with the bodywork... fixed the rust and am going to paint it when the weather turns good.

Also just completing an axle swap from the 4.10s to 3.73s...

[gregs78cam]

When you get ready to put a 4L80E in, I have some ideas and tips for you, and if i can find the website, a guy talks about how he adapted the TH400->NP205 adapter plate to work on the 4L80E. But I concur.....get that beast back together, and let go from there.

[Xenon]

Great... It's all about MPGs for me right now, as the 400sbc is more than enough power for daily driving and occasional trailer towing without much extra help... So the 4L80E swap is high on my list once I get it figured out and gather all the parts...

[EagleMark]

Your cam ran good before so it's a good EFI cam. The tune for more cubic inch will help. I wouldn't change a cam for your reasoning...

Suburbans have plenty of room for bigger tires! Stay skinny and go taller and you'll have same overall ratio change instead of changing gears. Tires will be cheaper and WAY easier!

[Xenon]

Ok. I was just worried that the dead spot off idle and the fact that it didn't really open up till 3000 rpm was because of the cam...

Though I've read alot on SBCs since then and they do need to rev more to make power compared to a big block...

Mainly the big dead spot was my worry.

Another thing it used to do was under some conditions (uphill with a load, say) you could floor it and it just didn't have the guts. Then it would shift down and rev up, and then it would really rocket away. Thinking back, this was likely because it was not sending enough fuel for the 400...

Thoughts?

[EagleMark]

Big dead spot could have been a mechanical issue showing up that ended up failing? Could have been the tune was for differant engine? If the engine is sound and mechanical issues are in order it can be tuned!

If it's still running do a vacuum test. What is the reading? Is it steady? Also can do a compression check. You can't tune out a low cylinder compression reading or a bad valve...