350 under 305 stuff

[olde man]

Hi Guys: I want to do something nice for my pride and joy which is a 1984 caprice 2dr. I also have a 1980 gmc 3/4 ton van that I have no use for,it has only 47k on the 350ci it has min. emission equip. egr,cat.runs real good.Do you guys think I could ease the 350 in without the 305 stuff knowing about it {comp,carb,dist.etc} and what do you think would happen if it found out.
All kidding aside this is my plan for my caprice.I know I'll be alright with the carb,I don't know about the advance curve programed into the computer or if it can take care of the timing thats going to be required by the 350,I also know that I can use the hei on the 350,but I would like to keep the computer control dist.pros&cons please

THANKS GUYS olde man

[silicon212]

Originally Posted by olde man

Hi Guys: I want to do something nice for my pride and joy which is a 1984 caprice 2dr. I also have a 1980 gmc 3/4 ton van that I have no use for,it has only 47k on the 350ci it has min. emission equip. egr,cat.runs real good.Do you guys think I could ease the 350 in without the 305 stuff knowing about it {comp,carb,dist.etc} and what do you think would happen if it found out.
All kidding aside this is my plan for my caprice.I know I'll be alright with the carb,I don't know about the advance curve programed into the computer or if it can take care of the timing thats going to be required by the 350,I also know that I can use the hei on the 350,but I would like to keep the computer control dist.pros&cons please

THANKS GUYS olde man

My car, as delivered, had a 305 in it. Actually, it was the 305/TH2004R combo. I had a 350 sitting in a car that was falling apart, so I put that in my Caprice in place of the 305. The TH2004R only lived about 15,000 miles behind that 350. That's another story, though. The only thing I did was readjust the air valve on the secondary of the carb. If your car has a knock sensor, you will have to replace that with one for a 350. The PROM in the ECM is still for that 305 and it runs just fine. Actually, it runs great - strong enough to break a 4L60 reaction sun shell... I believe the distributor advance curves are a little more aggressive for the 305 than those of the 350 PROM, so that could actually help. Blue Bowtie can clarify that for us.

Distributor is the same between engines.

Really the only big things are the air valve adjustment and the knock sensor (if equipped).

Your car should have a Th700R4 in it - given the model year you might want to get a 1987-up 4L60 (TH700R4 v3.0). They're stronger.

[Blue Bowtie]

As usual, Silicon is right on it. The 305 spark tables are actually more aggressive than the 350 tables (smaller bore, less bore/stroke ratio). As long as the ESC is working and the EGR functions, there shouldn't be too much trouble with detonation. Run the base timing about the same.

You will have to use a 350 knock sensor, but the 305 ESC should be fine with it. The carb should be fine with a little AV adjustment, and you'll have to run the procedure for M/C solenoid setting (and probably raise the rich stop a little). If the truck also had a 4MV you may want to save the secondary metering rods and hanger for the '84, since they are probably a little closer to what the 350 will need. You may even have to use the intake from the 305 to get all the necessary holes and fittings.

I think you'll actually like the 350, since the 305 TCC lockups were set rather low for the 305. The 350 will just torque right through those lower lockup RPMs without a complaint.