Olds 403 engine troubles

[boysatt]

I am new to olds engines. I am a chevy guy but i got this 1979 trans Am last fall that had a 403 in it. The car needed some tinkering and the previous owner didn't have much time to fix it. but I got it running, it has a 403 with under 2k on the rebuild, pumched .20 over, high performance cam, edelbrock performer intake, mild porting on the heads and intake, had new rods and lifter installed, and the usualy new stuff, and I also have headers on it. I am runnning a remanufactured stock q-jet carb, bevlieve its like a 800-850 cfm carb.

Well I started working on the car this spring since I wanted to drive it and I can't get the engine to run right. It runs alright, but not smooth, engine shakes a little and enhaust sounds like a drag car. I checked the timing and its set I think at over 12 advanced, ( I think that is what it is, but the mark is showing before the gauge on the timing cover, and when I try to turn the distributor to get it to 0 the engine starts to run rougher and rougher until it will die at about 6. So I am not sure what is going on there.

I got the timing set the best I can to make the engine run as sooth as I can and judging from the timing gauge, its at like + 14 or 16, wich I think is way too far.

Now I know this engine should be making some power, but when I step on it, there isn't much there, its like its only running on 2 barrels on the carb, accelerates slow. Then the engine tops off at around 4K rpm, then is will start to sputter, won't rev past that.

Any ideas? I know this engine stock has some torque because I have had a stock 403 trans am a few years ago and it could burn the tires off all day long.

Mike

[Mines69Olds]

Do you know and trust the guy that built the engine. It doesn't sound like he really knows what he is doing. Your best bet might be to take the timeing cover off and see where he made his mistake. He probably didn't line the cam up right or maybe he ran it really hard when he put it together and it jumped time.

[MrPbody]

Sounds more like tuning issues. You NEED to know what cam it is. Often, when facing a choice about cams, when one should go "smaller", they go "bigger". It's a "young man" thing...

You're right, the correct carb for that car is an 800 CFM Q-Jet. With proper recalibration, an excellent choice for a street performer. Look for a new book in the very near future, from Cliff Ruggles, about the Q-Jet. He's one of the best Q-Jet guys on the entire planet, and is NOT a "Chevy boy" (He likes Pontiacs...). He has customers going mid-9s with a single Q-Jet and no power adders.

The timing mark on the harmonic balancer may have "slipped". Olds balancers are known to do that from time to time. You may not be getting accurate readings. You must do the "positive stop" thing in no. 1 cylinder to determine if the balancer is accurate or not. That procedure is outlined in many publications (finding "true" TDC).

Yes, it should have SOME power. 403s aren't exactly performance engines to start with. Don't expect it to beat up on anything near its' size, though. A Camaro with a 400SB or T/A with 400 Pontiac will tear it up.

The vast majority of 403s we see are either true restorations or "class" racers.

Jim

[86k10]

I don't see anything to wrong with your timing, after all the 403 in the Olds cars are timed at 20 so your 14 to 16 is still slow.

[APIA]

Is there any way to find out the cam specs? Sounds to me that the duration of the cam is probably around 300 degrees. I have a little experience here. The easiest way to determine how wild the cam is is to put a vacuum gage on the engine and see where you are at. The vacuum gage should be pulling around 10 to 12 inches if my memory is correct. Anything less, then the cam is likely BIG. Does the car have power brakes? This is a likely indicator as they do not work well with a wild cam. (About two applications of the pedal and the pedal gets hard) Also unless you have a 4 row radiator the engine will probably run warm, around 210 to 230 normally. You may have to play around with the timing till it is right, beware of getting it too far advanced as this will cause detonation and tear up the pistons. When it is too far the engine will usually tell you. Normally if this engine is cammed big the engine usually does not start "breathing" till around 2500 to 4000 RPM depending on cam duration, The only alternative then with an auto trans is a higher stall converter, then we have rear gears. Playing with camshafts can get expensive...

[BLUETA]

I have seen several posts about a vibration issue with the 403 Olds but I have not seen anyone come back with a resolution. Now I have a Vibration in my 79 Trans Am with an Olds 403. It vibrates like crazy when reving it up. Please Help

[maxwedge]

Welcome to AF, this can be a very difficult diagnosis. Is this in neutral? If so many things can cause this, did it always do this?