350 help

[Binderman]

I have a choice of two Chevy 350 engines to use in a street rod project.  One is from a 1990 Impala cop car with TBI and a 7004r trans; it's seemingly in good condition, engine oil and trans fluid are both clean and clear.  The other is from a 1999 Tahoe, Vortec TPI, no trans, about 180M miles and what sounds like a rod knock.  Neither has the ECM or wiring harness.
A couple of questions come to mind:  which would be the higher performance engine?, Will the 1990 trans bolt right up to the 1999 engine?,  If I decided not to mess with hooking up the computer stuff, what needs to be done to eliminate all the computer stuff and just run as a carbureted engine?.  There's probably a lot more questions I should be asking, but just don't know enough to ask.
After reading this board for several months, there's obviously a lot of talented engine guys who know the questions to ask, but more importantly, have the answers.  I'd appreciate any help and advice you could offer.
Thanks, Binderman

[Dave]

I have a choice of two Chevy 350 engines to use in a street rod project.  One is from a 1990 Impala cop car with TBI and a 7004r trans; it's seemingly in good condition, engine oil and trans fluid are both clean and clear.  The other is from a 1999 Tahoe, Vortec TPI, no trans, about 180M miles and what sounds like a rod knock.  Neither has the ECM or wiring harness.
A couple of questions come to mind:  which would be the higher performance engine?, Will the 1990 trans bolt right up to the 1999 engine?,  If I decided not to mess with hooking up the computer stuff, what needs to be done to eliminate all the computer stuff and just run as a carbureted engine?.  There's probably a lot more questions I should be asking, but just don't know enough to ask.
After reading this board for several months, there's obviously a lot of talented engine guys who know the questions to ask, but more importantly, have the answers.  I'd appreciate any help and advice you could offer.
Thanks, Binderman

Im gonna make a wild guess and say the cop car engine has more hp.. The trans should bolt to either engine. I dont know what heads these have but i would think you should be able to just put  an aftermarket intake on em and a carb. Unless of course im wrong and they dont make an intake that will bolt up but i sure think they do. Do some searching on the net there are a lot of sites with good answers..
Dave

[UGLY OLDS]

The '90 engine should be roller cam & easily converted to run on a carburator...( Change the manifold & run HEI ignition..Might have to change the dist gear..not sure )..The '90 trans still has a TV cable...No electronics....Good simple basic combination..nothing "Hi-Tech" ...I think it all depends on what results you are looking for.....IMHO

[enjenjo]

You can switch either one to a carb, but do you want too? Let me explain.

With EFI, the compression ratio was raised back up from it's low in the 70s, early 80, because they could, and it made more power. This was done with a knock sensor that adjusted the timing with every revolution of the engine to give optimum timing under most conditions.

They also started grinding the cams with a different profile that took advantage of the fuel injection. Since the fuel mixture was normally right on with fuel injection, and the timing was adjusted constantly, the cams were ground to be much more aggressive. Also, there is no provision for a mechanical fuel pump, so you will have to go electric.

To change it over, you have to change the intake, add a carb, and change the ignition at a minimum. I've done this, and it works to a point. With the stock cam, they are very prone to detonate in high gear.You can use an ignition retard box to fix this, but it is a compromise. So really you should change the cam too.

Now, a manifold for the late engines is about $200, and a carb is$250 at best. A good ignition is $150, and a retard box adds another $100, or $200 for a cam. Add another $100 for a fuel pump, and you are at $800 to $900. A wiring harness to use the EFI is $300 to $350, and $100 for a pump. Even if you need all the sensors, thats only another $200.  $100 for a computer, and $100 more for a chip. So the price is about the same, and the EFI will make more HP, better mileage, and be more drivable.

Another thing top consider is todays fuel is formulated for EFI, and is much more prone to vapor lock that it was even three years ago. Cars that never had a problem, are now having problems with vapor lock. I've had problems with every carbureted car I own in the last couple years.

That's my take. I am converting the old 300 engine in my Buick to EFI, because I think that it's the answer. And you can do it without losing the look of a hot rod engine.

[Dave]

I got a retard box... I carry it on my shoulders.  
I gotta go..............

[Binderman]

So would one be any better than the other?
Thanks for the input, that's the kind of info I'm looking for.

Binderman

You can switch either one to a carb, but do you want too? Let me explain.

With EFI, the compression ratio was raised back up from it's low in the 70s, early 80, because they could, and it made more power. This was done with a knock sensor that adjusted the timing with every revolution of the engine to give optimum timing under most conditions.

They also started grinding the cams with a different profile that took advantage of the fuel injection. Since the fuel mixture was normally right on with fuel injection, and the timing was adjusted constantly, the cams were ground to be much more aggressive. Also, there is no provision for a mechanical fuel pump, so you will have to go electric.

To change it over, you have to change the intake, add a carb, and change the ignition at a minimum. I've done this, and it works to a point. With the stock cam, they are very prone to detonate in high gear.You can use an ignition retard box to fix this, but it is a compromise. So really you should change the cam too.

Now, a manifold for the late engines is about $200, and a carb is$250 at best. A good ignition is $150, and a retard box adds another $100, or $200 for a cam. Add another $100 for a fuel pump, and you are at $800 to $900. A wiring harness to use the EFI is $300 to $350, and $100 for a pump. Even if you need all the sensors, thats only another $200.  $100 for a computer, and $100 more for a chip. So the price is about the same, and the EFI will make more HP, better mileage, and be more drivable.

Another thing top consider is todays fuel is formulated for EFI, and is much more prone to vapor lock that it was even three years ago. Cars that never had a problem, are now having problems with vapor lock. I've had problems with every carbureted car I own in the last couple years.

That's my take. I am converting the old 300 engine in my Buick to EFI, because I think that it's the answer. And you can do it without losing the look of a hot rod engine.

[enjenjo]

The TPI ahould be able to make more hp. Eiring them is about the same.

[39deluxe]

If the 99 Tahoe engine has a TPI unit on it it's been changed. I had a new 99 Tahoe and it was TBI. The 99 engine is a L31 Vortec truck engine. It has heads that are far superior to the 90 cop engine. The fast burn combustion chambers came along a lot later. These chambers in either the aluminum fast burn heads or the iron L31 Vortecs will tolerate higher compression and more timing before you run into a pinging problem. That is why the Edelbrock heads switched to the fast burn chambers a few years ago. They are the same Vortec heads that you buy from GM Performance Parts or Summit ect. It's also a roller cam. You can get a carb intake for Votec heads from GM Performance or Edelbrock and switch ignitions but I  don't think that I would.

There are enough of these in the yards by now that you should be able to pick up the harness, ECM and anything else that you are missing for a low price. The TBI will give you better mpg and drivability. If you want to warm it up some Crane makes cams for these that are compatible with the computer system. There are also GM performance cams for this (made be Crane) and performance intakes for the TBI system. Remember that you can reuse roller lifters that are in good shape on a new cam. Since they don't slide on the lobe like a flat tappet there is no run in time involved. It sound like you are going to have to open the engine up to find the source of the noise anyway. With a little thought this engine could not only look cool but be a pleasure to start and drive.

Tom

[Binderman]

Thanks guys, all the information is helpful to an old novice like me.
Binderman