Need help picking the correct 350 crate engine
Thread Starter
Member
Joined: Nov 2017
Posts: 147
Likes: 8
From: California
Car: 1991 Camaro Z28 Convertible
Engine: 305 TPI
Transmission: 700r4
Need help picking the correct 350 crate engine
Im on the Chevrolet performance website and im confused as to which one would be the correct engine for my 305 tpi to 350 tpi in my 1991 camaro z28. Im inexperienced with all the numbers and would appreciate help. Thank you everyone
Re: Need help picking the correct 350 crate engine
There isn't an exact replacement. Really hasn't been since GM started using Vortec heads on everything.
As for what a 91 Z28 would have had originally, it'd be a 305 or 350, 1 piece rear main seal, roller camshaft, passenger's side dipstick, with a 9.3:1 compression ratio, and 64cc (58cc for 305) chamber, non-swirl port heads.
Breaking that last paragraph down, 1 piece rear main seal (RMS for short) refers to the oil seal around the back of the crankshaft. Before 1986 small block chevy engines used a 2pc rear main seal, ie it was cut in half and clamped around the crank by the main bearing cap. 1pc RMS came around because the 2pc seal leaks. As a side benefit, 1pc v 2pc use different flywheels. To avoid having to mess with tracking down a different flywheel, and potentially different starter, blah blah blah stick with a 1pc RMS engine.
Roller camshaft refers to the cam, and not so much the camshaft is on rollers as much as the lifters have rollers that roll across the cam instead of steel sliding on steel. Before 1986 GM didn't use roller camshafts. After 1987 you've got a mixture, some Chevys had the old flat tappet lifter cams, and others had roller lifters. Roller lifters don't require some of the chemicals in motor oil that the old flat tappet lifters required. Those chemicals cause polution, blah blah so if you want to run modern oils and want to have a camshaft that lasts virtually forever, stick with a roller cam engine.
Passenger's side dipstick... For whatever reason GM moved the dipstick somewhere around the late 70's/early 80's. Thirdgens have the dipstick on the passenger's side. If you get an engine with the dipstick on the driver's side, the stock exhaust manifolds won't fit. You can get around it with headers, but it's easier just to buy a later engine with the features mentioned above.
On to the heads... I mention the compression ratio and chamber volume, because MOST small block chevy engines have dished, low compression pistons, and sloppy smog friendly chambers. Which is fine for the smoking farm truck that never goes over 50mph, but sucks ***** for performance. You can do better than stock 1991 Z28 heads now, but 99% of the Double Hump, Camel back, fuellie 487X, whizz-bang cylinder heads in the scrap heap at your friendly 'dirt tracker' racer buddy's garage, are kind of crap. As long as you stay away from used garbage, and the entry level GM crate engines, you don't need to worry about this so much. Also, be aware that any crate engine advertised as a replacement for small blocks before the mid 80's is going to have heads that won't directly bolt up to a 1987 or newer intake manifold, unless a couple of the bolt holes are drilled/filed open.
Re - Swirl ports. TBI cars and trucks used what they call swirl port heads. For any kind of performance, you don't want swirl ports.
Ok, so then what? -
Option 1 - 87-95 L05 TBI truck engine
https://www.summitracing.com/parts/nal-12681430
Aside from the swirl port heads, and puny camshaft, it'll pretty much bolt in place of a 91 350, it'll just be down on power. Change the heads and cam and it wouldn't be so bad. Should have provisions to change to a roller cam but comes with a flat tappet.
Option 2 - 96-2000 L31 Vortec truck engine
https://www.summitracing.com/parts/nal-12530282
Roller cam and better heads than the TBI truck engine. Better heads than a 91 Z28, cam could use upgrading. Vortec heads require a third type of intake manifold, a stock tpi intake won't bolt up at all. http://sdparts.com/i-23896057-sdpc-s...baseplate.html
Also noteworthy, the L31-R Vortec truck engine adds 4-bolt mains, which is pretty much irrelevant, but whatevever https://www.summitracing.com/parts/nal-12530283
Option 3 - 330hp 350 HO base engine
https://www.summitracing.com/parts/nal-19210007
Kind of like option 1, with Vortec heads. Seems like a waste of money to me, but whatever.
Option 4 - ZZ? whatever they want to call it this week. Again Vortec style heads. Lots of whizbang trickery. Seems like a REAL waste of money to me, but again... Whatever.
Hope that helps.
As for what a 91 Z28 would have had originally, it'd be a 305 or 350, 1 piece rear main seal, roller camshaft, passenger's side dipstick, with a 9.3:1 compression ratio, and 64cc (58cc for 305) chamber, non-swirl port heads.
Breaking that last paragraph down, 1 piece rear main seal (RMS for short) refers to the oil seal around the back of the crankshaft. Before 1986 small block chevy engines used a 2pc rear main seal, ie it was cut in half and clamped around the crank by the main bearing cap. 1pc RMS came around because the 2pc seal leaks. As a side benefit, 1pc v 2pc use different flywheels. To avoid having to mess with tracking down a different flywheel, and potentially different starter, blah blah blah stick with a 1pc RMS engine.
Roller camshaft refers to the cam, and not so much the camshaft is on rollers as much as the lifters have rollers that roll across the cam instead of steel sliding on steel. Before 1986 GM didn't use roller camshafts. After 1987 you've got a mixture, some Chevys had the old flat tappet lifter cams, and others had roller lifters. Roller lifters don't require some of the chemicals in motor oil that the old flat tappet lifters required. Those chemicals cause polution, blah blah so if you want to run modern oils and want to have a camshaft that lasts virtually forever, stick with a roller cam engine.
Passenger's side dipstick... For whatever reason GM moved the dipstick somewhere around the late 70's/early 80's. Thirdgens have the dipstick on the passenger's side. If you get an engine with the dipstick on the driver's side, the stock exhaust manifolds won't fit. You can get around it with headers, but it's easier just to buy a later engine with the features mentioned above.
On to the heads... I mention the compression ratio and chamber volume, because MOST small block chevy engines have dished, low compression pistons, and sloppy smog friendly chambers. Which is fine for the smoking farm truck that never goes over 50mph, but sucks ***** for performance. You can do better than stock 1991 Z28 heads now, but 99% of the Double Hump, Camel back, fuellie 487X, whizz-bang cylinder heads in the scrap heap at your friendly 'dirt tracker' racer buddy's garage, are kind of crap. As long as you stay away from used garbage, and the entry level GM crate engines, you don't need to worry about this so much. Also, be aware that any crate engine advertised as a replacement for small blocks before the mid 80's is going to have heads that won't directly bolt up to a 1987 or newer intake manifold, unless a couple of the bolt holes are drilled/filed open.
Re - Swirl ports. TBI cars and trucks used what they call swirl port heads. For any kind of performance, you don't want swirl ports.
Ok, so then what? -
Option 1 - 87-95 L05 TBI truck engine
https://www.summitracing.com/parts/nal-12681430
Aside from the swirl port heads, and puny camshaft, it'll pretty much bolt in place of a 91 350, it'll just be down on power. Change the heads and cam and it wouldn't be so bad. Should have provisions to change to a roller cam but comes with a flat tappet.
Option 2 - 96-2000 L31 Vortec truck engine
https://www.summitracing.com/parts/nal-12530282
Roller cam and better heads than the TBI truck engine. Better heads than a 91 Z28, cam could use upgrading. Vortec heads require a third type of intake manifold, a stock tpi intake won't bolt up at all. http://sdparts.com/i-23896057-sdpc-s...baseplate.html
Also noteworthy, the L31-R Vortec truck engine adds 4-bolt mains, which is pretty much irrelevant, but whatevever https://www.summitracing.com/parts/nal-12530283
Option 3 - 330hp 350 HO base engine
https://www.summitracing.com/parts/nal-19210007
Kind of like option 1, with Vortec heads. Seems like a waste of money to me, but whatever.
Option 4 - ZZ? whatever they want to call it this week. Again Vortec style heads. Lots of whizbang trickery. Seems like a REAL waste of money to me, but again... Whatever.
Hope that helps.
Thread Starter
Member
Joined: Nov 2017
Posts: 147
Likes: 8
From: California
Car: 1991 Camaro Z28 Convertible
Engine: 305 TPI
Transmission: 700r4
Re: Need help picking the correct 350 crate engine
Oh wow thank you for the great lesson. I went and looked at videos for the different parts you mentioned (to get a visual) and i learned . i will definitely go with a 1 piece rms and rollers . ill have to see which of those I'd want to go with because I've never looked at them. Appreciate the detailed information 