tbi timing how to?

[99xcss4]

I have heard read some people say set either 4 degrees advance or 4 degrees retarded where did that come from

 

[termite]

I ask because I made him watch this and he is still not buying it

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Show him the Factory Service Manual?

 

[Schurkey]

92 C-1500 extended cab short bed 350

guy ordered a crate engine I have a part 2 to this question the instructions say on first start up to hold rpm between 2100 and 2500 rpm for half a hour to break in the flat tappet cam should we do that first or base timing first

Paint a stripe lengthwise on the upper part of the pushrods, so you can easily see that they're spinning when the engine runs. I have been known to sacrifice some Treasure Yard valve covers to make viewing windows for this purpose. This can be part of the first ten-minute run time. (Pontiac covers shown.)

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Get the distributor static-timed so that the engine will start and run, and plug in the timing connector so the timing will advance along it's programmed curve. Assure the fuel pump primes, make sure the radiator and oil pan are full. Have a garden hose handy so you can mist the radiator if the temperature climbs beyond normal limits. A box-fan in front of the radiator can help.

I hate seeing flat-tappet cams any more. They're an unneeded risk. Yeah, you're going to have to run the engine at ~2K for that half-hour. I tend to do it in three, ten-minute spurts with some cool-down time in-between. (Minimize idle time.) Verify actual timing with the timing light--it'll be considerably more advanced than "0" at 2K rpm. (12--25 degrees advanced.) IF (big IF) the engine was assembled with thick, moly-based paste lube on the cam lobes, the moly can plug an oil filter in twenty minutes, and you'd have to change it...but I'm guessing that this crate engine doesn't have thick moly paste on the cam.

I have heard read some people say set either 4 degrees advance or 4 degrees retarded where did that come from

7.4L get timed officially at 4 degrees advanced. Small-blocks are officially timed at "0", but lotza folks add a degree or five of advance, and seem to have good results.

I'd have VERY little problem with adding a few degrees of advance during cam break-in; engines tend to run hot and lean at 2000 RPM/no load. Some extra advance can be nice.

 

[udidwht]

The 454s are timed at 4BTDC with the connector disconnected. Once connected they are generally setting at 15-16 degrees advanced at idle. If you have an OBD-1 live scan you can see what the timing is prior to pulling the distributor and use that timing as your base setting when reinstalling the distributor if you do not disconnect to connector.