i have a 87' T/A 305 TPI and i was thinking of droping in a old style 350 and keeping the TPI. i know i'll have to swap the heads with the TPI ones, but will they work? the 350 is NOT roller cam. what kind of cam can i use? will my 305 computer accept it? i have a aftermarket prom allready. can this be done and whats involved in changing over? will it work with my 305 parts?

 

Everything will go smoothly as long as you change the heads with the TPI setup. The only thing that I would look into getting changed for the swap is your injectors. Get some 350 TPI injectors.

 

Don't forget about the old block's 2 piece main seal that's going to need a flex plate/flywheel to match. Just use a aftermarket low lift/duration hydro cam and lifters that will match well with the torquey TPI runners. You're going to have high compression(54cc 305 heads), so you'll have to run premium, and probably back the base timing off a couple of degs. Everything else bolts up just fine. It should be a pretty good little stump puller.

 

what should my lift and duration be for this engine? i want to get the most power but keep my drivability. can i just get a adjustable fuel press. regulator and up the fuel press. instead of buying new injectors? i just put those injectors in recently

 

I agree with Monk (except the heads are 58cc, not 54cc). Unless the 350 has dished pistons and you use fairly thick composite head gaskets, compression will be quite high. For the very little hassle that modifying the center two bolts on each side of the base will be, it makes more sense to just use 350 heads (64cc) and keep reasonable compression. Or, get '87-later 64cc heads.

Check into the Crane computer compatible cams. You won't be able to handle the one I've got because the TPI is rev limited, but the computer will stay happy with something like the 2030 (or perhaps the 2040 in a 350).

You can run your 19 lb injectors with higher regulated pressure. For some reason, that is supposed to make them wear out quicker (haven't figured that one out yet).

 

i thought i had to keep the TPI heads because the intake angle was different. so you mean any sb chevy heads will fit to the TPI intake? and what are you talking about modifying the center two bolts? i found the 2040 cam and i like the price! i'm gonna get it

 

The TPI heads are better than TBI heads, true. But, your main concern has to be 305 vs 350 because of the chamber size and the effect that has on compression going from 305 to 350. Dished pistons can make 305 heads on a 350 do-able, though.

The older 350 heads won't have the TBI problem. How good they really are is a good question, though. If you have more information about them, let us know. They may be 76cc heads, and if you do have dished pistons, compression will be really low.

Other than that, the bolt angle is the only '87-later vs. '86-earlier issue. On the center two bolts on each head, the older engines were all at the same angle. On the later heads, those are at a different angle (makes them easier to get at to torque them down). All you have to do to your base is elongate the bolt holes so the bolts will fit into the earlier heads (squaring the bolt face on the intake isn't a bad idea, but probably not necessary). Or, you could try to find a '86-earlier TPI base.

 

i have another TPI base but i don' t know if it's 86' and earlier how can i tell?

 

Or you can get a 85-91 TPI base from a Vette.

As for selecting a cam, just make sure that the LSA is proportional to the duration. In other words, when you get more duration on the cam, make sure the LSA is higher too. Most flat tappet cams that aren't designed for FI you'll see have pretty much a standard LSA of 110*. For FI compatible cams, they have LSA's of 112-114; of course being proportional to the duration. Some LT1 cams and the later L98 cam have a LSA of 117* even.

Check the TPI base by looking at the two centerbolt holes on either side. If they're at the same angle as the outside bolts, then it's 86 earlier (or 85-91 Vette).

 

All 350 engines from the beginning through 1992 have the same angle on the heads where the intake mounts. ONLY difference is late 1987-1992 the 2 center holes in heads are tapped so that the bolts are almost straight up and down. The TPI intake holes have to be slotted to match. All earlier heads, the bolt holes are perpendicular to the intake mounting surface. I installed a 91 speed density system in my Vette with original 350 LT1 engine. Only had to slot the center bolt hole in intake. Runs great!

 

What if the older 350 has no hole in the block for the knock sensor.
Won't this be a problem.


Jeff

 

I seem to recall removing a plug somewhere above the fuel pump.

 

It fits into the water jacket drain hole plug.

 

Keep in mind that the 85-91 TPI from the Vette is all the old style to match the L98 Aluminum heads. ONLY 87-92 F-bodies have the different style.

 

The reasoning behind the 19 lb injectors "wearing out" faster is because of the higher fuel pressure pushing against them trying to resist their opening. Also the computer may have to pulse them longer to get enough fuel to satisfy tho O2 sensor, which makes for an increased duty cycle on the windings in them.

If he just put new injectors in I doubt he will see any of them "wear out" for 5 years or more unless one or more were weak from the factory. The increased duty cycle would find an injector that was not up to par faster.