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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old March 19th, 2015, 02:09 AM
Scoutmann Scoutmann is offline
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Default Timing and Tuning

Hey Guys,

I have a 1964 Vintage 305 V6 in an old school Hyster H150E forklift at work. I installed a new distributor, coil, plugs and plug wires. I've set the point gap at .016 and I used a dwell meter to confirm the dwell was at 32 degrees. I cannot for the life of me find the timing mark. I am unfamiliar with these engines. I know that there are three marks on the balancer. I'm assuming 7.5 degrees advance, TDC and 7.5 Retard. I cannot find the mark on the block to time it to. Any help appreciated!

PS any literature, shop manuals, etc. on this motor is greatly appreciated!
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  #2  
Old March 19th, 2015, 03:15 AM
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TJ's GMC TJ's GMC is offline
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Default Re: Timing and Tuning

On my 64's 305E the the block has a pointer...course my engine is a later engine as well. The pointer is a needle and its on the opposite side of the alternator. I'd take a scrub brush to the balancer if you can and see if some marks show up.
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Old March 19th, 2015, 09:25 AM
OLDTRUCKHAULER OLDTRUCKHAULER is offline
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Default Re: Timing and Tuning

Good Morning

Ebay is one resource for manuals, Amazon another.
I talk to the shop mechanics at the rental and repair
shops that I haul small equipment for. You can maybe
find the oldtimers may have the books, or have the info
in their heads for that unit.

Mike OTH

1965 1502 series ramptruck
1965 Cheby short step
1964 GMC 1000 parts truck
1985 GMC hybrid 3/4t dually
1962 willys p/u on 37's
1988 INT 5t Rollback
1967 GMC/Cheby? 1/2t longbed fleet 4 sale
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Old March 19th, 2015, 04:58 PM
Scoutmann Scoutmann is offline
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Default Re: Timing and Tuning

I have the marks on the balancer. I am having trouble locating the pointer. This project has been nothing but headaches!
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Old March 19th, 2015, 08:03 PM
bigblockv6 bigblockv6 is offline
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Default Re: Timing and Tuning

Here is a pic of the timing cover, if you look just a little bit to the right just above the center of the crankshaft opening there is a pointer
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Old March 20th, 2015, 02:09 AM
Scoutmann Scoutmann is offline
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Default Re: Timing and Tuning

Thanks So much!
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  #7  
Old March 20th, 2015, 06:09 PM
Scoutmann Scoutmann is offline
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Default Re: Timing and Tuning

The vacuum advance also does not seem to be functioning. Do any of you know what the vacuum PSI is supposed to be?
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Old March 21st, 2015, 12:43 AM
Clarke Clarke is offline
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Default Re: Timing and Tuning

Quote:
Originally Posted by Scoutmann View Post
The vacuum advance also does not seem to be functioning. Do any of you know what the vacuum PSI is supposed to be?
I'm not sure mine is working either... Everytime I have disconnected the steel line between the carb and the distributor (to set the timing), I don't notice any change in RPM like I have with other vehicles. And, when I put finger over the tube end I don't feel any change in pressure or vacuum.

It seems to run pretty good, so I don't worry about it. Maybe I should though. I'm interested in what others say.
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Old March 21st, 2015, 02:59 AM
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Default Re: Timing and Tuning

My '64 GMC (has a '66 305 V6 w/ Holley carb) was professionally tuned a year and half ago and here is what the guy gave me:

Idle: 600 rpm
Base Timing: 12* @ 600 rpm
Total Timing:38* @ 2500 rpm
Idle AFR set for best idle vacuum
Dwell is 30*
No vacuum advance - do not connect
Uses 89 octane fuel, with additive

Truck runs great.
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Last edited by Andice; March 21st, 2015 at 03:27 AM.
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  #10  
Old March 21st, 2015, 03:20 AM
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GMCDAC GMCDAC is offline
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Default Re: Timing and Tuning

Quote:
Originally Posted by Clarke View Post
I'm not sure mine is working either... Everytime I have disconnected the steel line between the carb and the distributor (to set the timing), I don't notice any change in RPM like I have with other vehicles. And, when I put finger over the tube end I don't feel any change in pressure or vacuum.

It seems to run pretty good, so I don't worry about it. Maybe I should though. I'm interested in what others say.
Hi David, and Scoutmann, I am going to stick my neck out here and guess that the carb you are using is "ported vacuum" which means there is none at idle. "Direct vacuum' usually comes from the intake manifold or the carb base. On the rochesters and holleys I have I just use direct vacuum. Then you will notice the difference when the line is disconnected.

If you have one of those vacuum type brake bleeders the vacuum advance can be tested with that.

DAC
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Last edited by GMCDAC; March 21st, 2015 at 06:32 PM.
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