starting my 66 stang

carboy · 01-30-2002, 05:11 PM

my engine starts and almost sounds like it's missing at low rpm, and also starts to backfire at low rpm. am i getting too much gas?
just rebuilt carb and engine and at med rpm it does sound good.
anyone have any suggestions?

Gearhead999 · 01-30-2002, 06:55 PM

Sounds like it is lean not rich. Is the firing order right?? Where is the timing??

carboy · 01-30-2002, 09:33 PM

would too lean make it backfire at low rpm when just trying to idle?
also timing is tdc and when i move the distibutor a little each way it doesn't make it get better.
any suggestion on adjusting this carb,,holley 4-barrel 4110, vacum secondaries.
also when trying to start, it backfired through the carb and blew both caps off my valvecovers.

PKRWUD · 01-31-2002, 02:02 AM

Sounds like the timing and the mixture are off. To adjust the mixture you need to:
1) Gently turn both mixture screws in until they bottom out.
2) Back them both out 1 1/2 turns.
3) Start and Warm up engine
4) Turn idle speed down as LOW as the engine will maintain.
5) Adjust the screws, in two round trips (adjust one side, then the other, then come back to the first side, then go back to the other side) to get the highest RPM.
6) Add an aditional 1/8 turn out for each screw.
7) Reset idle speed to desired level.
8) Shut off engine and check that both screws are the same. If they're not, set both to the average of the two.
9) Restart engine to check idle quality.

Take care,
-Chris

carboy · 02-01-2002, 12:49 AM

after i ran it for 20min , it sounds a bit better, i will try tomorrow on what you suggested.
thanks for the help.
David
Corpus Christi TX.

Gearhead999 · 02-01-2002, 06:47 PM

It blew the oil caps OFF??? Sounds like it is way off.

Are you sure the firing order is right??

302 and 351W are different. The cams will interchange and you have to set the firing order per which cam you have.

How about vacumn leak at intake manifold. Or a messed up carb. If it is backfiring through the intake and carb. the power valve is surely gone. When it goes the motor will run very rich and won't adjust [idle] at all. You have to get it to stop backfiring or the valve will just continue to go bad one right after the other.

If you cover the top of the carb with you hand while it is running and [sort of hand choking it] does it run better?? Be careful if it is barfing back.

You have something off here. What does the vacumn read at idle??

Who adjusted the valves?? Are they too tight??

Do you know if the balancer is correct??

01-30-2002, 05:11 PM	#1
carboy Registered Member Join Date: Jan 2000 Location: Corpus Christi, Texas Posts: 66	starting my 66 stang my engine starts and almost sounds like it's missing at low rpm, and also starts to backfire at low rpm. am i getting too much gas? just rebuilt carb and engine and at med rpm it does sound good. anyone have any suggestions? __________________ 66 coupe, 306 balanced bluprinted, performer intake,725 Road Demon, Crane Cam, Tri-Y Headers, factory Shelby glass packs 2 1/4 with exit in front of rear wheels, 3:50 rear, 8 inch rear, mustang plus suspension, 41/2 mideye leafs, 620 springs on front, kyb gas shocks. tony branda shelby hood, r-model valance, rear side scoops(functional),stainless steel slotted front brake system,,13.39 1/4 mile with no slicks and no posi.

01-30-2002, 06:55 PM	#2
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	Sounds like it is lean not rich. Is the firing order right?? Where is the timing?? __________________ "Support our Troops" Dave 1968 Cougar 2004 Thunderbird 2007 F150 Harley-Davidson, SuperCrew 1986 LTD 1997 Ranger 1992 Honda Civic

01-30-2002, 09:33 PM	#3
carboy Registered Member Join Date: Jan 2000 Location: Corpus Christi, Texas Posts: 66	would too lean make it backfire at low rpm when just trying to idle? also timing is tdc and when i move the distibutor a little each way it doesn't make it get better. any suggestion on adjusting this carb,,holley 4-barrel 4110, vacum secondaries. also when trying to start, it backfired through the carb and blew both caps off my valvecovers. __________________ 66 coupe, 306 balanced bluprinted, performer intake,725 Road Demon, Crane Cam, Tri-Y Headers, factory Shelby glass packs 2 1/4 with exit in front of rear wheels, 3:50 rear, 8 inch rear, mustang plus suspension, 41/2 mideye leafs, 620 springs on front, kyb gas shocks. tony branda shelby hood, r-model valance, rear side scoops(functional),stainless steel slotted front brake system,,13.39 1/4 mile with no slicks and no posi.

01-31-2002, 02:02 AM	#4
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Sounds like the timing and the mixture are off. To adjust the mixture you need to: 1) Gently turn both mixture screws in until they bottom out. 2) Back them both out 1 1/2 turns. 3) Start and Warm up engine 4) Turn idle speed down as LOW as the engine will maintain. 5) Adjust the screws, in two round trips (adjust one side, then the other, then come back to the first side, then go back to the other side) to get the highest RPM. 6) Add an aditional 1/8 turn out for each screw. 7) Reset idle speed to desired level. 8) Shut off engine and check that both screws are the same. If they're not, set both to the average of the two. 9) Restart engine to check idle quality. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

02-01-2002, 12:49 AM	#5
carboy Registered Member Join Date: Jan 2000 Location: Corpus Christi, Texas Posts: 66	after i ran it for 20min , it sounds a bit better, i will try tomorrow on what you suggested. thanks for the help. David Corpus Christi TX. __________________ 66 coupe, 306 balanced bluprinted, performer intake,725 Road Demon, Crane Cam, Tri-Y Headers, factory Shelby glass packs 2 1/4 with exit in front of rear wheels, 3:50 rear, 8 inch rear, mustang plus suspension, 41/2 mideye leafs, 620 springs on front, kyb gas shocks. tony branda shelby hood, r-model valance, rear side scoops(functional),stainless steel slotted front brake system,,13.39 1/4 mile with no slicks and no posi.

02-01-2002, 06:47 PM	#6
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	It blew the oil caps OFF??? Sounds like it is way off. Are you sure the firing order is right?? 302 and 351W are different. The cams will interchange and you have to set the firing order per which cam you have. How about vacumn leak at intake manifold. Or a messed up carb. If it is backfiring through the intake and carb. the power valve is surely gone. When it goes the motor will run very rich and won't adjust [idle] at all. You have to get it to stop backfiring or the valve will just continue to go bad one right after the other. If you cover the top of the carb with you hand while it is running and [sort of hand choking it] does it run better?? Be careful if it is barfing back. You have something off here. What does the vacumn read at idle?? Who adjusted the valves?? Are they too tight?? Do you know if the balancer is correct?? __________________ "Support our Troops" Dave 1968 Cougar 2004 Thunderbird 2007 F150 Harley-Davidson, SuperCrew 1986 LTD 1997 Ranger 1992 Honda Civic

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