1980 Performance

[jccatwb]

I have a new -to-me 1980 Avanti with a 350cid sbc, TH400 trans, and type44 (3.07) differential. It does not perform as well as my old 63 R2 with power-shift and a 3:73 diff.  The exhaust system is a mess But is functional so it will wait. What have some of you all done to make these strangled engines perform a bit better?  (On a budget!)  (The meadow burner is thankfully gone as well as smog pump and all that crap. )  Best timing?   Thanks in advance!

[Gunslinger]

Put a full dual exhaust system on the car and remove the catalytic converter (if state laws allow by exempting cars over a certain age)...make the pipes 2.5" diameter and let that puppy breathe!  I know you said "on a budget"...but performance costs and there's no way around it...especially with a smogger engine.  

We can really get into the weeds with recommendations but you have to start with a plan...what do you want out of the car regarding performance?  A smooth boulevard cruiser...an all-around fun car or an all-out road burner?  Each will require it's own set of plans and specifications to achieve the desired end result.  You can go crazy with a carburetor...intake manifold change...headers...camshaft...pretty much everything mechanical.  

Before getting into the engine's internals (assuming it performing as designed with no issues)...look at installing a 200R4 or 700R4 transmission.  The 700R4 will smoke the tire in first gear as it's designed for a much heavier vehicle.  The 200R4 can be very stoutly built and has a better spread of gears for the average driver.  The 4-speed automatic should give a nice improvement in performance by itself.  

If you want to go crazy with improvements...doesn't sound like that's your desire...get EFI and ditch the carburetor.  

One thing can easily lead to another and suddenly you're financially very deep.  That's why you need a plan.

[Murder]

By far the one most noticeable bang for the buck change would be to swap out the 3.07 for a 3.73 or higher (numerically) ratio rear gear. 

[mfg]

9 hours ago, jccatwb said:

I have a new -to-me 1980 Avanti with a 350cid sbc, TH400 trans, and type44 (3.07) differential. It does not perform as well as my old 63 R2 with power-shift and a 3:73 diff.  The exhaust system is a mess But is functional so it will wait. What have some of you all done to make these strangled engines perform a bit better?  (On a budget!)  (The meadow burner is thankfully gone as well as smog pump and all that crap. )  Best timing?   Thanks in advance!

A lower rear end ratio would help.

(As ‘Murder’ said!)

Edited Thursday at 12:20 AM by mfg
Added text

[jccatwb]

What is the best timing for it? That can make a huge difference all by itself. New pipes and headers will have to wait a bit, but are anticipated. Camshaft is a huge item too but a lot bigger job than setting timing. And, besides, I'm not sure acceleration an elderly fellow should be allowed.  A 3:07 rear end isn't too bad especially out here where there is a lot of cruising and not a lot of stop and go. I think a 3:54 is a nice compromise.

[mfg]

6’ Advanced from TDC.

PS…. Go with true dual exhaust, but avoid the headers… too many negatives to make them worthwhile!

Edited 1 hour ago by mfg
Added PS