383

[Pat K]

I am trying to resist temptation. Please help me. I am contmplating replacing my 305 with a new unit. 95K miles, I would like to start over.

But then I got thinking, why 305? why not BIGGER?. I am guessing a 383 is about the nastiest small black that would fit without major modifations.

Anyone done this? Please tell me this is a really dumb idea. Please!

PK

RQB4143

[billy]

Hi PK, what is your reason for replacing the engine?

1 more HP

2 don't like the 305

3 have money to burn

4 increase the Avanti value

5 want fuel injection

6 just because

7 want to go 200 mph

8 other

I'm contemplating putting a GM TPI fuel injection on my 305 just because I like the looks of TPI.

bill

87 Avanti

[plwindish]

PK, I purchased an 89 convertible last December that had been resto-modded with the installation of a 383 stroker SBC, Computer adjustable 4L60 AOD trans and a Ford 9" rear end with 4.86 gears. Yes, it is nasty and more crazy fast than I drive, but like the way it gets to cruising speed in a hurry. I'm just driving the car locally as it loves to gulp gas. My other Avanti, the 76 has its original 400 motor in it that was taken apart and rebuilt over 3 1/2 years ago, turning out 365 hp and 460 pounds torque when put back into the car. I've put over 19k on it since the rebuild driving to Gettysburg, South Bend, Colorado Springs, St. Louis, and Dover to meets.

The 383 is not the typical route for engine replacement that I have seen, as the 350 crate motor would be more reasonable, quicker than the 305 and still be fairly economical. Personally if I was putting another engine in an Avanti, I'd go the LS route. I know there's a lot of extra work with the LS with putting in a high pressure electric fuel pump in the tank and the computer instal, but those motors are great running, have a lot of power and are reliable.

[Avanti83]

PK, I purchased an 89 convertible last December that had been resto-modded with the installation of a 383 stroker SBC, Computer adjustable 4L60 AOD trans and a Ford 9" rear end with 4.86 gears. Yes, it is nasty and more crazy fast than I drive, but like the way it gets to cruising speed in a hurry. I'm just driving the car locally as it loves to gulp gas. My other Avanti, the 76 has its original 400 motor in it that was taken apart and rebuilt over 3 1/2 years ago, turning out 365 hp and 460 pounds torque when put back into the car. I've put over 19k on it since the rebuild driving to Gettysburg, South Bend, Colorado Springs, St. Louis, and Dover to meets.

The 383 is not the typical route for engine replacement that I have seen, as the 350 crate motor would be more reasonable, quicker than the 305 and still be fairly economical. Personally if I was putting another engine in an Avanti, I'd go the LS route. I know there's a lot of extra work with the LS with putting in a high pressure electric fuel pump in the tank and the computer instal, but those motors are great running, have a lot of power and are reliable.

This is a good summary. My 74 has a 383 with a T56 that is not road legal yet but on my back road even with the 3.55 posi that does well off the line. When finished, I'll probably put a 4:10 or so in it but we will see. The 383 uses a 400 crank in a 350 block and that is the only SBC that needs to be externally balanced. If you stay with your 4-speed auto it will require you to change the flex plate and harmonic balancer. Both are known for their torgue as they have the longest stroke of any SBC. It's usually easier to find the 383 as they are based on the 350 block. 400's were used in a limited time frame and are not known to come with good breathing heads so if you wish to go big, plan on a change in heads or at least a major valve job and smoothing the passages. Most decent crate engines have all that done. If I had a 400 I would have started there but the 383 was cheap for a number of reasons so I bought it.

Let's get to what I would do with a clean slate. LS without a doubt.

The things that need to be changed are motor mounts and conversion mounts are available. Exhaust changes to find the correct headers/manifolds and the installation of the computer system. You will also need to have the computer reprogrammed to eliminate it's looking for VATS and some other input you won't have available. I talked with a guy that had done several LS3 conversions into older Chevrolets and he said that the reprogramming was about $85 in the Grand Rapids, Mi area.

But for the price of a 383 crate motor, I'll bet you can find a low mileage LS with tranny ready to drop in and get the benefits of the newer power/mileage that doesn't exist in the pre-computer era. www.car-parts.com (Look Here)

As far as adding TPI to an existing engine you are looking at minimally $1000 up to $3500. Not a problem if you have a great engine to start with but for the $2-3K for a commercial conversion you are well on your way to an LS conversion. The conversion will help driveability but I doubt one would see sufficient mileage improvement to warrant it. I have a Holley Avenger EFI on my 355 in my 83 and it solved a problem that I chased for a while so it was worth the cost to me but anymore, I'd just go LS.

Bob

Edited July 20, 2014 by Avanti83

[grobb284]

" I know there's a lot of extra work with the LS with putting in a high pressure electric fuel pump in the tank and the computer instal, but those motors are great running, have a lot of power and are reliable."

It is no longer necessary to put pump in the tank.

[Charlie Kile]

I located the pump on the right frame rail. Although it works well, the sound of it running in a little annoying.

Charlie

RQB3921

[Gunslinger]

I located the pump on the right frame rail. Although it works well, the sound of it running in a little annoying.

Charlie

RQB3921

Gotta agree. The electric fuel pump in my car is on the right frame rail. Some electric pumps might be better or worse as far as sound goes but it does work and works well.

[IndyJimW]

TPI like this:

[grobb284]

Gotta agree. The electric fuel pump in my car is on the right frame rail. Some electric pumps might be better or worse as far as sound goes but it does work and works well.

The pump with the LS1 has been placed on the left rear x-member, near the driver's seat. It has been mounted in rubber and urethane clamps, with flexible hose. No hard mounting. It can only be heard as it pressurizes the fuel rail prior to ignition. It can not be heard once the engine fires. However the exhaust is quieter than I anticipated.

As Gunslinger said, it works well.

Edited July 22, 2014 by grobb284