Chevy 383 TBI timing questions (1 Viewer)

[Raven361]

Hey everybody, I have a FJ60 with a stroker 383 and a TBI injection setup. I am at a lost and have done multiple searches on the web and forums and cannot find the exact situation that I am experiencing. I have gone through all of the timing procedures (disconnect the ESC wire, set base timing, disconnect (-)battery cable etc...) to get this thing dialed in and have come up with some interesting questions that I'd like to figure out:

1) When setting the base timing, I have to advance the dizzy so that my timing mark on the crank no longer hit the degree marks on the timing cover - if I were to guess, this is in the neighborhood of 20+ degrees advance. The question here is, why does this thing run like it is supposed to performance wise than at the 0 degrees that the factory states for base timing?
2) When the timing is set to "best sound" of the engine, why am I running super rich?

Outside of pulling the engine apart to figure out what the cam profile is, or to see if someone degreed the cam when they built it, what do you think my options are? (I have a coolant temp sensor on order and have checked the resistance on all other sensors and have checked the idle air control).

Thanks in advance!

 

[gregnash]

Ok somewhat of a dumb question but what type of timing light/setup are you using? I know that there are those that will advance the timing for you so I am wondering if something is up with yours. I would start with trying a different gun and see what happens. @norsk is the only guy that I know of currently that has an SBC on here and is active, @orion just pulled his for a Vortec swap but I am pretty sure his was carbed and not TBI.

Also, are you getting any codes when you are running the truck? May be something is off in the computer. Just my wild guesses.

 

[Raven361]

Ok somewhat of a dumb question but what type of timing light/setup are you using? I know that there are those that will advance the timing for you so I am wondering if something is up with yours. I would start with trying a different gun and see what happens. @norsk is the only guy that I know of currently that has an SBC on here and is active, @orion just pulled his for a Vortec swap but I am pretty sure his was carbed and not TBI.

Also, are you getting any codes when you are running the truck? May be something is off in the computer. Just my wild guesses.

I'm using just a standard inductive timing light. Not getting any codes. I talked to tbichips.com and the guy suggested that I may have a hotter cam than what the chip is programmed for. Thanks for the reply!

 

[Elbert]

Assume you are running a GM HEI distributor and your base timing is set correctly. If you don't disconnect the wire on a TBI setup and then set based timing you'll introduce too much advance. TBI computer is "dumb" it has no way to interpet the mechanical settings. Base timing on TBI is disconnect the wire and set timing to zero degrees. Then you connect the wire and the computer takes over timing. Has to be on zero withe the TBI 5.7 I had or runs like crap (base timing wise).

It sournds like you are adjusting timing on top of the "base" timnig......which the computer has no way to manage...in reality you could bump that a little, but what happens when you set it stock like "GM says". TBI has limits, you can't tune it like a carb setup.

Assume you have no check engine codes and all your required sensors are functional

 

[Raven361]

Assume you are running a GM HEI distributor and your base timing is set correctly. If you don't disconnect the wire on a TBI setup and then set based timing you'll introduce too much advance. TBI computer is "dumb" it has no way to interpet the mechanical settings. Base timing on TBI is disconnect the wire and set timing to zero degrees. Then you connect the wire and the computer takes over timing. Has to be on zero withe the TBI 5.7 I had or runs like crap (base timing wise).

It sournds like you are adjusting timing on top of the "base" timnig......which the computer has no way to manage...in reality you could bump that a little, but what happens when you set it stock like "GM says". TBI has limits, you can't tune it like a carb setup.

Assume you have no check engine codes and all your required sensors are functional

I have disconnected the ESC before running my base timing. This is why I am stumped because it needs so much advance just to get a good idle (with the ESC disconnected). I appreciate the double check though and I wish that it were that easy and that I was being a dummy. I am replacing the CTS tomorrow, but that is only feeding the computer when the ESC is plugged in.

 

[Elbert]

If you are running the stock GM distributor and stock TBI fuel components and Stock ECM controls.... and there are no trouble codes, then I'm not sure unless potentially two things. (1) bad ECM or ECM needs need modificaitons to align with engine mods (2) potential distibutor issues. My stock tbi 5.7 I had a few years ago was extremely picky on timing and distributor orientation....of course it was stock. I don't know off hand but I'm guessing the stock TBI setup as far as range of timing is very narrow, it simply may not be able to deal with things outside the stock range its been setup to exepct.

 

[KWalkerM]

Ok somewhat of a dumb question but what type of timing light/setup are you using? I know that there are those that will advance the timing for you so I am wondering if something is up with yours. I would start with trying a different gun and see what happens. @norsk is the only guy that I know of currently that has an SBC on here and is active, @orion just pulled his for a Vortec swap but I am pretty sure his was carbed and not TBI.

Also, are you getting any codes when you are running the truck? May be something is off in the computer. Just my wild guesses.

Hey!!!! I still technically have a TBI 350!!!


There is a possibility your timing marks or target thing is inccorect. I have run into that once on a Ford? in the past where it turned out the timing marks were inccorect and giving us weird timing crap. I forget how we figured it out but it was similar circumstances. Its more likely your truck is set up for different timing from factory though.

 

[Raven361]

Hey!!!! I still technically have a TBI 350!!!


There is a possibility your timing marks or target thing is inccorect. I have run into that once on a Ford? in the past where it turned out the timing marks were inccorect and giving us weird timing crap. I forget how we figured it out but it was similar circumstances. Its more likely your truck is set up for different timing from factory though.

That's a super good point, I will look for some pictures of where these timing marks are supposed to be. Thanks!

 

[Raven361]

If you are running the stock GM distributor and stock TBI fuel components and Stock ECM controls.... and there are no trouble codes, then I'm not sure unless potentially two things. (1) bad ECM or ECM needs need modificaitons to align with engine mods (2) potential distibutor issues. My stock tbi 5.7 I had a few years ago was extremely picky on timing and distributor orientation....of course it was stock. I don't know off hand but I'm guessing the stock TBI setup as far as range of timing is very narrow, it simply may not be able to deal with things outside the stock range its been setup to exepct.

That very well may be the case. I have lots of experience with the TPI set ups and know that the ignition module is super sensitive. I have a spare one laying around - maybe it's time to throw it in. Hopefully it is either that or the timing marks being in the wrong spot like KWalkerM suggested.

Thanks all, and keep the punches coming!

 

[Raven361]

Found out the problem... Apparently there are two different harmonic balancers for the SBC. One has the timing mark etched in at a two o'clock position in reference to the key-way, the other is at the 12 o'clock position. With that said, there are two different style of timing marks that are on the timing chain cover, one is straight up and the other is at the two o'clock position. Mystery solved! Thank you all for the questions and input! Without it I surely wouldn't of investigated that...

 

[KWalkerM]

Found out the problem... Apparently there are two different harmonic balancers for the SBC. One has the timing mark etched in at a two o'clock position in reference to the key-way, the other is at the 12 o'clock position. With that said, there are two different style of timing marks that are on the timing chain cover, one is straight up and the other is at the two o'clock position. Mystery solved! Thank you all for the questions and input! Without it I surely wouldn't of investigated that...

That was going to be my next question haha glad you got it solved. I was thinking about that on the drive i took today.

 

[Elbert]

I was not aware of the two different balancers....of course the 5.7 family of engines covers a lot of ground and likely are interchangeable. I do know some of the timing tabs that are used to reference the balancer are different. Good find....

 

[Raven361]

That was going to be my next question haha glad you got it solved. I was thinking about that on the drive i took today.

Thanks for the thinking! I knew there was an easy solution, well, I hoped there was one. I really didn't want to dig in the block to figure out what cam it has in it (not yet anyhow).

 

[Raven361]

I was not aware of the two different balancers....of course the 5.7 family of engines covers a lot of ground and likely are interchangeable. I do know some of the timing tabs that are used to reference the balancer are different. Good find....

It was for certain a surprise. I thought that all gen 1 sbc's were the same. My TPI had the 2-o'clock timing marks and so does my other 350 that's laying around.

 

[Raven361]

Well got the timing done with a WAG as to where 0* is for the engine since there isn't a timing arrow/mark where it should be for that balancer, but it runs like a champ now! Also found a few vacuum leaks and installed a new coolant temp sensor. Small steps but I believe that this bad boy (Bane shall be his name) will be able to roast some tires!

Also, the person before me decided that it was a good idea to wire the fuel pump not only to the ARB locker solenoid and air compressor switch in the cab, but they used two strands of 27 gauge phone wire... so I found the fuel pump relay and fuse, made sure that there was power to it at key on, during cranking and while running - thus I solved the mystery of low and spastic fuel pressure! Now to fix the ARB wiring...