The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 1985 4x4 Crate Engine Swap old school 350 or Vortec 350

rich weyand · 01-04-2015, 03:36 PM

Do NOT go with the 350/290hp GM crate engine. All it is (for an extra $500) is the 350/260hp crate engine with the cam out of a 1967 Corvette 350/350hp high-compression engine. In particular, it has high overlap that reduces dynamic compression at low rpms, which, with a high-compression engine, you can afford to give up and it allows more advance because the low dynamic compression at low rpms will reduce the tendency to knock.

What a cam like that means on a low-compression engine is that you will have no bottom end at all. It will completely suck in a truck until you get 3000 rpms under it. It is also a very old cam design, without the high-speed ramps and computerized design of modern products. Also, the fuel mileage will completely suck. We're talking mid-single-digits here.

On the other hand, it will be a two-lane terror with a really nice 50-90 time with your foot in it.

I went this route myself, and ended up recamming the motor. Since the only difference between the 350/260hp and 350/290hp crate engines is the cam, I could have saved the extra $500 (and the expense of changing out the cam), and just gone with the 350/260hp crate engine and recammed it from the get go.

After all of this, my recommendation for a cheap performer is the #10067353 350/260hp crate engine, with a Comp Cams 12-235-2 cam. That's the cam Sean Murphy over at SMI recommended to me a couple years back, and several people have gone with it and liked it. With headers and a dual-plane manifold, you'll see 290hp @4000 and 415lbft @2500, which is a really nice torque number down low where you want it. You should upgrade the springs with this cam, but that's it. If you put it in a never-run 350 crate engine, you don't even need to change out the lifters.

I went with the Comp Cams 12-300-4 cam, which gives 275hp @4000 and 423 lbft @2500. No spring change required, but I did lower the shift points 500 rpm at WOT by changing out one weight on the transmission governor, which is a half-hour job.

But if you go with the 350/290hp crate engine, you will be disappointed. Been there, done that.

01-04-2015, 03:36 PM	#25
rich weyand Registered User Join Date: Apr 2014 Location: Bloomington Indiana Posts: 1,041	Re: 1985 4x4 Crate Engine Swap old school 350 or Vortec 350 Do NOT go with the 350/290hp GM crate engine. All it is (for an extra $500) is the 350/260hp crate engine with the cam out of a 1967 Corvette 350/350hp high-compression engine. In particular, it has high overlap that reduces dynamic compression at low rpms, which, with a high-compression engine, you can afford to give up and it allows more advance because the low dynamic compression at low rpms will reduce the tendency to knock. What a cam like that means on a low-compression engine is that you will have no bottom end at all. It will completely suck in a truck until you get 3000 rpms under it. It is also a very old cam design, without the high-speed ramps and computerized design of modern products. Also, the fuel mileage will completely suck. We're talking mid-single-digits here. On the other hand, it will be a two-lane terror with a really nice 50-90 time with your foot in it. I went this route myself, and ended up recamming the motor. Since the only difference between the 350/260hp and 350/290hp crate engines is the cam, I could have saved the extra $500 (and the expense of changing out the cam), and just gone with the 350/260hp crate engine and recammed it from the get go. After all of this, my recommendation for a cheap performer is the #10067353 350/260hp crate engine, with a Comp Cams 12-235-2 cam. That's the cam Sean Murphy over at SMI recommended to me a couple years back, and several people have gone with it and liked it. With headers and a dual-plane manifold, you'll see 290hp @4000 and 415lbft @2500, which is a really nice torque number down low where you want it. You should upgrade the springs with this cam, but that's it. If you put it in a never-run 350 crate engine, you don't even need to change out the lifters. I went with the Comp Cams 12-300-4 cam, which gives 275hp @4000 and 423 lbft @2500. No spring change required, but I did lower the shift points 500 rpm at WOT by changing out one weight on the transmission governor, which is a half-hour job. But if you go with the 350/290hp crate engine, you will be disappointed. Been there, done that. __________________ Rich Weyand 1978 K10 RCSB DD.