Timing & Dwell ??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

71elect · 06-26-2003, 12:12 AM

As of yet I still don't have a shop manual for my 71 GMC W/ 307 V8. Does any one have the specs for Dwell and Timing. It would sure help out a lot to know where I should be running. It's a 307 V8, 2Barrel rochester, manual choke, non A/C, 3spd manual tranny. Thanks for any help you can give.
Josh

stelth2002 · 06-26-2003, 03:09 AM

i have all the 67 manuals and it says for a any v8 28-32* dwell and gap @ .019 with the timing inbetween 2-8. depending on the engine.... what town you live in?

GMC Jim · 06-26-2003, 04:44 AM

'71 Chev. Service manual has the following specs for 307 V-8 w/ manual trans.:---Centrifigal advance-- (degrees @ RPM) 0 @ 800; 2 @ 1200; 12 and 24 @ 4300. Vacuum advance:-- ) degress @ 8" vac and 20 degrees @ 17" vac. Dwell setting :--31 to 34 degrees. Timing @ idle 4 degrees before top dead center @ 600 RPM (vacuum advance hose disconnected and plugged).
Another GM service manual ( #SD-100 1971-80 Tune Up Specifications ) shows a dwell angle of 29-31 degrees.... The total advance ( cent. & vac.) should be 26 to 34 degrees @ 2000 RPM.

GMC Jim · 06-26-2003, 04:48 AM

Omissions from prev msg.....Vacumm advance is 0 degress @ 8 inches vac. and the cent advance is 12 @ 2200 RPM..... sorry about the ommisons ( was referring to manual and didn't check my typing!)

tom hand · 06-26-2003, 08:49 AM

GM manuals always have low timing specs for manual trans. That just robs gas milage. Run between 8 - 12 degrees timing (what ever the motor will tolerate without "pinging") and 30 degrees dwell.

71elect · 06-26-2003, 07:54 PM

Thanks guys! Was able to set the dwell to 30 degrees, and the timing to 8. Much better.
stelth2002, I'm over here in Twin Falls.

06-26-2003, 12:12 AM	#1
71elect Registered User Join Date: Nov 2002 Location: Southern Idaho Posts: 59	Timing & Dwell ??? As of yet I still don't have a shop manual for my 71 GMC W/ 307 V8. Does any one have the specs for Dwell and Timing. It would sure help out a lot to know where I should be running. It's a 307 V8, 2Barrel rochester, manual choke, non A/C, 3spd manual tranny. Thanks for any help you can give. Josh __________________ 72Chevy swb 4x4 71GMC swb 2x4

06-26-2003, 03:09 AM	#2
stelth2002 Young Gun wth Fast Inline Join Date: Jan 2002 Location: Idaho Posts: 1,475	i have all the 67 manuals and it says for a any v8 28-32* dwell and gap @ .019 with the timing inbetween 2-8. depending on the engine.... what town you live in? __________________ 1967 Chevrolet LWB with built 292! 415 ft. lbs of torque, 4 speed :O with 27% overdrive too, 3.73 Posi. Frame and body done... getting painted!!!

06-26-2003, 04:44 AM	#3
GMC Jim Senior Member Join Date: Dec 2002 Location: Portland, Oregon Posts: 901	'71 Chev. Service manual has the following specs for 307 V-8 w/ manual trans.:---Centrifigal advance-- (degrees @ RPM) 0 @ 800; 2 @ 1200; 12 and 24 @ 4300. Vacuum advance:-- ) degress @ 8" vac and 20 degrees @ 17" vac. Dwell setting :--31 to 34 degrees. Timing @ idle 4 degrees before top dead center @ 600 RPM (vacuum advance hose disconnected and plugged). Another GM service manual ( #SD-100 1971-80 Tune Up Specifications ) shows a dwell angle of 29-31 degrees.... The total advance ( cent. & vac.) should be 26 to 34 degrees @ 2000 RPM. __________________ '71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal).

06-26-2003, 04:48 AM	#4
GMC Jim Senior Member Join Date: Dec 2002 Location: Portland, Oregon Posts: 901	Omissions from prev msg.....Vacumm advance is 0 degress @ 8 inches vac. and the cent advance is 12 @ 2200 RPM..... sorry about the ommisons ( was referring to manual and didn't check my typing!) __________________ '71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal).

06-26-2003, 08:49 AM	#5
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	GM manuals always have low timing specs for manual trans. That just robs gas milage. Run between 8 - 12 degrees timing (what ever the motor will tolerate without "pinging") and 30 degrees dwell. __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

06-26-2003, 07:54 PM	#6
71elect Registered User Join Date: Nov 2002 Location: Southern Idaho Posts: 59	Thanks guys! Was able to set the dwell to 30 degrees, and the timing to 8. Much better. stelth2002, I'm over here in Twin Falls. __________________ 72Chevy swb 4x4 71GMC swb 2x4



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