Engine Upgrade

77bigblock · November 10, 2009

hey guys, need a few answers. just put in a 350 in my 89 gmc 2500. removed blown up 350 tbi, installed 72 350 030 over flat tops, built heads. big cam, converted intake to fit old style heads. to keep f.i. problem is having troble with idle and timing, what do i need to do? tried moving timing up and down doesn`t help. any help would be greatly appreciated. thanks.

Nytemare · November 10, 2009

hey guys, need a few answers. just put in a 350 in my 89 gmc 2500. removed blown up 350 tbi, installed 72 350 030 over flat tops, built heads. big cam, converted intake to fit old style heads. to keep f.i. problem is having troble with idle and timing, what do i need to do? tried moving timing up and down doesn`t help. any help would be greatly appreciated. thanks.

Did you install a HEI distributor in the 72 engine? That's where it gets its timing from for the ECM. It doesn't matter if the timing is correct if the ECM cant read it.

Also did you touch the TPS during the rebuild process...If so you have to set it up again to have it work properly.

WilliamBos · November 10, 2009

hey guys, need a few answers. just put in a 350 in my 89 gmc 2500. removed blown up 350 tbi, installed 72 350 030 over flat tops, built heads. big cam, converted intake to fit old style heads. to keep f.i. problem is having troble with idle and timing, what do i need to do? tried moving timing up and down doesn`t help. any help would be greatly appreciated. thanks.

And , you remembered to unplug the wires on the passenger side firewall before you set the timing, right? (that is after you put the correct distributor in, right??)

77bigblock · November 10, 2009

hey guys, need a few answers. just put in a 350 in my 89 gmc 2500. removed blown up 350 tbi, installed 72 350 030 over flat tops, built heads. big cam, converted intake to fit old style heads. to keep f.i. problem is having troble with idle and timing, what do i need to do? tried moving timing up and down doesn`t help. any help would be greatly appreciated. thanks.

Did you install a HEI distributor in the 72 engine? That's where it gets its timing from for the ECM. It doesn't matter if the timing is correct if the ECM cant read it.

Also did you touch the TPS during the rebuild process...If so you have to set it up again to have it work properly.

yes i used factory dist, and i didn`t bother tps just drilled out center holes in intake.? one thing i didn`t do is the old style block doesn`t have hole in block for knock sensor so i never hooked it up. is it have any bearing on timing? thanks.

77bigblock · November 10, 2009

hey guys, need a few answers. just put in a 350 in my 89 gmc 2500. removed blown up 350 tbi, installed 72 350 030 over flat tops, built heads. big cam, converted intake to fit old style heads. to keep f.i. problem is having troble with idle and timing, what do i need to do? tried moving timing up and down doesn`t help. any help would be greatly appreciated. thanks.

And , you remembered to unplug the wires on the passenger side firewall before you set the timing, right? (that is after you put the correct distributor in, right??)

yes, i used the stock dist from 89. and i by-passed to set timing. but as i replied in the other message i never hooked up knock sensor , since no hole in block for it, didn`t think it would hurt anything but not sure. thanks.

Nytemare · November 10, 2009

Yeah that's your problem...99.9% sure anyway. Its reading nothing, so it thinks the knock sensor is gone....which i guess it is.

Try putting a 3.9Kohm resistor in the connector, bridging the two wires. That's the resistance of a stock 350 Knock sensor and is the zero reference, meaning no knock.

Just be damn sure on your timing and run mid grade or higher fuel as you will have no knock detection and no spark retard during shifting...when coming off WOT...etc.

77bigblock · November 10, 2009

Yeah that's your problem...99.9% sure anyway. Its reading nothing, so it thinks the knock sensor is gone....which i guess it is.

Try putting a 3.9Kohm resistor in the connector, bridging the two wires. That's the resistance of a stock 350 Knock sensor and is the zero reference, meaning no knock.

Just be damn sure on your timing and run mid grade or higher fuel as you will have no knock detection and no spark retard during shifting...when coming off WOT...etc.

oh ok, thats great, i`ll get one tomorrow and hook it up. thanks for the help. i`ll let you know if it pans out.

Nytemare · November 10, 2009

You should also retard the timing a couple degrees to compensate for shifts. I would set it up at 7* BTDC instead of the normal 10* with the advance hooked up. Or roughly 1-2* ATDC with the spark bypass unhooked...(Base Timing)

77bigblock · November 10, 2009

You should also retard the timing a couple degrees to compensate for shifts. I would set it up at 7* BTDC instead of the normal 10*

ok, will do thanks for all the help. i`ll get back with you. thanks again.

Nytemare · November 10, 2009

Just to make sure you got my last post after I edited it.....

7* BTDC with Bypass connected

1-2*ATDC base timing (Bypass Disconnected)

77bigblock · November 11, 2009

Just to make sure you got my last post after I edited it.....

7* BTDC with Bypass connected

1-2*ATDC base timing (Bypass Disconnected)

yes, i got the last post last night, picked up a resistor on way home from work today off tomorrow so if rain ever quits i`ll install tomorrow. thanks again for the help.

Nytemare · November 11, 2009

Keep us posted..I have another couple of things that I thought about if this doesn't solve the issue.

77bigblock · November 11, 2009

Keep us posted..I have another couple of things that I thought about if this doesn't solve the issue.

sure will would like to get this old boy back on the road.

77bigblock · November 11, 2009

Keep us posted..I have another couple of things that I thought about if this doesn't solve the issue.

just tried to hook up resistor, knock sensor only has one wire? not sure how to hook up.any ideas?

Nytemare · November 11, 2009

one end goes to ground and the other end to the sensor wire...I PM'ed you back..sorry i was out getting drunk with all the war vets' today is remembrance day in Canada...so all us service personnel go and get drunk with the old guys and listen to their stories.