Please help! This car is driving me crazy...and broke.
I have an 87 trans am GTA with the 5.7 tpi engine. The other night I was driving about 10miles and the second I got off the freeway I lost all oil pressure so I parked it in a lot. 5 hours later i try to drive it back home, it turns on and has decent pressure but once again the second I get off the freeway no oil pressure. Then the 3rd time this happened I had only driven a mile or two on city streets and it dropped to 2psi and started backfiring several times. The oil is not low and not leaking.

 

Looks like a bad cam bearing.... on a freshly rebuilt engine. Im ****ing over hp

 

How are you judging the OP?
Have you fitted a mech OP gauge ?

 

Its a true pressure reading no doubt about it.

 

Have you drained the oil for inspection? A failed bearing makes pretty metal flake oil.

 

It looks like metallic black spray paint. It even swirls the same. This is also the original oil since the rebuilt engine only has about 200 miles. It deffinetly is pointing towards a bearing though.

 

I think you found the problem - that is a SURE sign of a bearing going out - I wouldn't drive it until you pull the pan and check all the bearings - I wouldn't be suprised if you found rod bearings going out due to the rods not being re-sized properly during the rebuild or the crank journals ground wrong and clearances were wrong...

 

Thank you for that extra advice. I'm going to pull the engine and get a line bore done also. Since it was rebuilt 200miles ago because of a spun bearing. Makes me think something about this block is prone to cause bearing faliure.

 

Have the cam tunnel checked for straightness also.

 

Ahhh - rebuilt because of a spun bearing - (rod, main or cam?) what was done during that rebuild (or do you know exactly?) If it was a rod bearing and they didn't re-size the rods or grind and polish the crank properly then you may have the same problem.... I've seen guys drop in a "crank kit" with "matched bearings" into an engine that had spun a bearing only to be re-doing it shortly because the rod end is egg shaped as it got knocked out of round as the thing slapped on the crank... it "looks good" to the naked eye because the bearing shell took the beating but get out the mic or dial indicators to measure and you'll quickly find that they're out of round...

 

I did the build myself, it spun a rod bearing originally, and I purchased a new crank, rod, can, and bearing kit.

 

Did you take the rods to the machine shop to have them re-sized?

 

No 8( ahhh well it was my first rebuild and an expensive lession.... thanks so much for everyone's help. I bought "engine builders handbook" by HP books and I'm going to attempet this build again with more knowlage.

 

you might find some good info and diagrams in this link?
http://forums.chevyhiperformance.com...sure-question/

 

Thank you. Hey just wondering, If I decided to do a 383 stroker kit this time around would the stock ecu be able to run it or would I have to burn my own prom chip?

 

It'll be fine, A tune will help you but if you leave the stock heads, cam, intake and exhaust your not going to make much more than 30ftlbs of tq and maybe 20hp.
If you upgrade all the parts you'll get more than just doing a 383.
I didn't get into much detail here but you get the idea.

 

I have upgrade exhaust, intake, and heads. I was thinking a cam and stroker kit are next.

 

Since you have upgraded the heads, intake and exhaust (depending on what they are) then you'll definately notice a bump in power with a properly built 383 stroker. You will have to burn a new chip as the fueling requirements are going to be way outside the stock computer's parameters (and you'll likely need bigger injectors too requiring a change in the PROM) I'm suprised that you're still running the stock chip with upgraded intake, exhaust and heads - usually that many modifications really needs a tune to run at it's potential..

 

It has been running lean/hot with my heavily modified "stock" heads and other mods. The tpis chip was next on my list before all this happened. Now as far as compression goes for a car running on 98.. is it true that i shouldnt go with anything over 10.5:1 ....because if seen 383s with 64cc heads and flat top pistons that make around 12.5:1 and are street driven

 

I'm assuming 'pump gas' here and not race fuel or E85 - you can run a 14:1 engine on the street with race fuel but to me that's not practical...

So the answer - it is an "it depends" - running a low Dynamic Compression Ratio (DCR) does help a LOT to get it streetable on pump gas, high stall converters and low gears prevent lugging the engine causing pinging, good combustion chamber designs of a 'modern head' helps a lot, etc. A GOOD tune paying attention to the timing and fueling will help - running slightly rich will ward off detonation a bit as well as pulling timing (and using the knock sensor to pull timing if it hears knock)

As for the claims of compression - A LOT of it comes down to how the calculation was done (and if it was done properly as a lot of times the piston's advertised compression ends up being high and the 'real' compression is about a point or so lower than advertised due to the pistons being down in the hole, the headgasket being thicker and larger than the bore, and the heads not being 'right on' the volume.

That said - unless you're going to deck the block then I would assume you're going to end up with the pistons about .020-.025" in the hole. Use a compression ratio calculator that takes this into account as well as the headgasket bore size and thickness, the piston volume and the bore/stroke and get some real world static compression ratios - then find yourself a good DCR calculator that takes the timing information from the cam card and calculate the DCR and see where it falls - generally I target about 8:1 as good on 'any' premium pump gas and if someone asked I tell them to push it to 8.5:1 if they can get non-ethanol 91 or 92 octane easily.

 

The moral of this story is never build a motor without the services of a competent machinist. Prepping a block includes first checking for cracks so that you don't do all that work on a junk block, then truing the crank center line, cam centerline, and of course bores and deck. For a small additional fee, the machinist will also verify the trueness all of your clearances. Oil clearances for a hot street or race motor that will run straight 40 or 15-50 oil are .0025". A good tolerance for this oil clearance is .0001". Archie Somers charges me about $100 for clearancing as part of a complete block prep that runs around $650 total. That's cheap insurance.