Hey guys!
While the Tuned Port Injected engine in my truck does run now, the engine is far from optimum for making good power, esspecially with EFI.
Right now, I have the stock rotating assembly with a stock set of heads, an XE262-H comp cam, and the TPI intake slapped on top. It runs very rich at an idle due to the cam's overlap, and due to the low compression, it just doesn't run as good as it could.
So, I just tore the 355 from my 89 apart to see if the damage in it is major, or something easy to fix. I found 1 worn out conn rod bearing (down to the bronze), 1 cracked piston skirt, 3 gouged conn rod bearings, and 1 gouged main bearing.
The cylinder walls are glazed over, and need to be honed (same problem as my GMC, TBI was thrown off by cam overlap, and ran rich enough to wash the cylinder walls, glazing them, causing nasty blowby, and gas fouled oil), but will not need an overbore.
The gouged bearings were damaged due to dirt in them when the engine was first rebuilt, cause it was a deep gouge, and I can't think of any way I could possibly have gotten crap that big into the bearings. The knocking bearing would have been the worn out one, which was caused by running the engine low on oil due to a nasty rear main leak, and the other knock must have been the cracked piston.
The cam bearings look great
So, since the engine block doesn't need anything more than a hot tanking and a honing, I am going to build it up for my GMC with EFI in mind
So, here is my plan:
- 86-89 Corvette Aluminum L98 heads (58cc combustion chambers, 163cc intake runners, 1.94" intake and 1.50" exhaust valves. Possibly a mild port job)
- Cam with specs similar to 212 in. / 218 exh. Duration @ .050, .449 in. / .456 lift, and an LSA of 112 degrees
- Dished pistons to bring my compression ratio to approx 9.5 - 9.8:1 compression, highest I can go without requring higher than 87 octane fuel
- Clevite 77 bearings
- Felpro gaskets
- Stock crank and connecting rods
- LT1 intake converted for use on a SBC
I am aiming for strong torque, moreso than horsepower. The truck is used for daily driving, and towing on a regular basis (13 000 lb bobcat). The cam should give me a very strong vaccum signal for the MAP sensor, and have very little overlap, so the 02 sensor should not have any issues at an idle. The high compression should give me lots of engine braking with the standard transmission, and give me lots of snot off the line to show up a ricer if needed
The LT1 intake may not come until later, as it a bit pricy, and I'll be short on cash having built the engine in the first place. The LT1 intake uses all the same electronics to run as the TPI intake does, however, it flows way better, and will accomodate the engine through it's full powerband, while the TPI will be totally out of breath by 4800 RPM tops.
Anyone have any thoughts? Any predictions on horsepower / torque curves? What is the maximum compression I can run with the aluminum heads and not require better than 87 octane?
While the Tuned Port Injected engine in my truck does run now, the engine is far from optimum for making good power, esspecially with EFI.
Right now, I have the stock rotating assembly with a stock set of heads, an XE262-H comp cam, and the TPI intake slapped on top. It runs very rich at an idle due to the cam's overlap, and due to the low compression, it just doesn't run as good as it could.
So, I just tore the 355 from my 89 apart to see if the damage in it is major, or something easy to fix. I found 1 worn out conn rod bearing (down to the bronze), 1 cracked piston skirt, 3 gouged conn rod bearings, and 1 gouged main bearing.
The cylinder walls are glazed over, and need to be honed (same problem as my GMC, TBI was thrown off by cam overlap, and ran rich enough to wash the cylinder walls, glazing them, causing nasty blowby, and gas fouled oil), but will not need an overbore.
The gouged bearings were damaged due to dirt in them when the engine was first rebuilt, cause it was a deep gouge, and I can't think of any way I could possibly have gotten crap that big into the bearings. The knocking bearing would have been the worn out one, which was caused by running the engine low on oil due to a nasty rear main leak, and the other knock must have been the cracked piston.
The cam bearings look great
So, since the engine block doesn't need anything more than a hot tanking and a honing, I am going to build it up for my GMC with EFI in mind
So, here is my plan:
- 86-89 Corvette Aluminum L98 heads (58cc combustion chambers, 163cc intake runners, 1.94" intake and 1.50" exhaust valves. Possibly a mild port job)
- Cam with specs similar to 212 in. / 218 exh. Duration @ .050, .449 in. / .456 lift, and an LSA of 112 degrees
- Dished pistons to bring my compression ratio to approx 9.5 - 9.8:1 compression, highest I can go without requring higher than 87 octane fuel
- Clevite 77 bearings
- Felpro gaskets
- Stock crank and connecting rods
- LT1 intake converted for use on a SBC
I am aiming for strong torque, moreso than horsepower. The truck is used for daily driving, and towing on a regular basis (13 000 lb bobcat). The cam should give me a very strong vaccum signal for the MAP sensor, and have very little overlap, so the 02 sensor should not have any issues at an idle. The high compression should give me lots of engine braking with the standard transmission, and give me lots of snot off the line to show up a ricer if needed
The LT1 intake may not come until later, as it a bit pricy, and I'll be short on cash having built the engine in the first place. The LT1 intake uses all the same electronics to run as the TPI intake does, however, it flows way better, and will accomodate the engine through it's full powerband, while the TPI will be totally out of breath by 4800 RPM tops.
Anyone have any thoughts? Any predictions on horsepower / torque curves? What is the maximum compression I can run with the aluminum heads and not require better than 87 octane?
