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Old 05-02-2011, 08:17 AM
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Timing a 364 Nailhead w/671 blower - need advise

I have a 364 nailhead with a 671 blower. It is a mild street motor. It has a YCM Mallory Distributor , MSD 6AL box w/in the car dial timing control. I managed to get two mile passes last year and the car pulled good the entire way. The PO said timing was locked and I did not pay much attention to that. I pulled the blower due to blower gasket leaking. I noticed that the distributor did not have any vacuum advance so I pulled it to check further. I found it has no mechanical advance. Guess that is what PO owner meant by locked. I installed the distributor exactly as it was pulled and then marked the custom steel hub for TDC. The engine fired on the first revolution, idled and ran fine. I checked the timing and it is 10 degrees advanced. With the blower and firewall it is impossible to reach in to loosen and twist the distributor for more timing and the dial in the car gives a max of 20 degrees.

My question what effect is the lack of mechanical advance going have? I am leery about trying to make a full throttle pass with it now. Some have told me to run 33 degrees advance but I think this will make it difficult to start.

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Old 05-02-2011, 09:07 AM
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Quote:
Originally Posted by heyjude076
I have a 364 nailhead with a 671 blower. It is a mild street motor. It has a YCM Mallory Distributor , MSD 6AL box w/in the car dial timing control. I managed to get two mile passes last year and the car pulled good the entire way. The PO said timing was locked and I did not pay much attention to that. I pulled the blower due to blower gasket leaking. I noticed that the distributor did not have any vacuum advance so I pulled it to check further. I found it has no mechanical advance. Guess that is what PO owner meant by locked. I installed the distributor exactly as it was pulled and then marked the custom steel hub for TDC. The engine fired on the first revolution, idled and ran fine. I checked the timing and it is 10 degrees advanced. With the blower and firewall it is impossible to reach in to loosen and twist the distributor for more timing and the dial in the car gives a max of 20 degrees. My question what effect is the lack of mechanical advance going have? I am leery about trying to make a full throttle pass with it now. Some have told me to run 33 degrees advance but I think this will make it difficult to start.
I would give it 22-24 BTDC to begin with and work up from there- but I would caution against using anything more than 30-32 max until you can verify there is absolutely NO detonation taking place. This means reading the plugs very carefully, as there can be detonation that goes unheard- especially when at the track w/loud exhaust from you and/or the car beside you- plus you're concentrating on other things anyway.

ANY "peppery"-looking deposits on the insulator is an indication you're in the danger zone, that's aluminum you're seeing. Use the best available pump fuel for the street (if you can get E85, I would modify the fuel system for it ASAP), and consider using race fuel at the track for safety sake.

If you find it becomes difficult to start w/the timing locked in, you can use an ignition interrupter like you've seen NASCAR cars use. You trigger the starter w/o ignition, once the engine is turning over, trigger the ignition to start and release the temporary "ON" switch for the starter. There are other schemes for doing this, search here for more.

Another option is to use a distributor w/vacuum and mechanical advance and set it up to run w/an advance curve. If it was me, this is the approach I would take- especially if the boost isn't that high to begin with. BTW, what IS your boost or pulley ratio?

This all assumes the cooling system is doing its job and the engine isn't running hot to begin with- a hot running engine is much more detonation-prone and will limit the tune you can use.
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Old 05-02-2011, 09:32 AM
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Thanks. This is my first blower motor so been reading as much as I can on them. Appreciate the tips. Should have put this info in my original post. Car runs very cool 170 - 180 with no fans and air flowing through the radiator. At a red light it gets to 200+ but cools down as soon as you are moving. I avoid stop and go routes to the local cruises. Blower pulley is 6.5 and crank pulley is 5 so I calculate a 1.3 under drive. Boost last year was 7 but did not check the gauge after replacing gaskets. Checking belt runouts, timing, oil pressure, etc just plain forgot. Will check that this evening.
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Old 05-02-2011, 09:54 AM
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Sounds good. What is the engine in?
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Old 05-02-2011, 10:04 AM
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Old 05-02-2011, 10:21 AM
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A better measure of your blower drive ratio is the number of teeth on each pulley, are they modern 8 mm pulleys or half inch?
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Old 05-02-2011, 10:40 AM
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Ha! A Henry J, don't see that everyday. I'll guess '52, but they all looked similar along through there...

Quote:
are they modern 8 mm pulleys or half inch?
Looks to be 1/2" pitch.
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Old 05-02-2011, 10:41 AM
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Quote:
Originally Posted by 68NovaSS
A better measure of your blower drive ratio is the number of teeth on each pulley, are they modern 8 mm pulleys or half inch?
Will check this evening.
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Old 05-02-2011, 11:24 AM
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Quote:
Originally Posted by cobalt327
Ha! A Henry J, don't see that everyday. I'll guess '52, but they all looked similar along through there...

Looks to be 1/2" pitch.
51 Henry J

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Old 05-02-2011, 01:16 PM
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If you are not going to use the boost timing retard box , set the timing at 28deg.

If you will be using the boost retard box, set the timing at 36deg, then set the boost retard box to take out 2deg per # of boost, as the boost comes in.

You can ply a bit with the rate of boost retard. (degrees of retard per # of boost)

But max timing under boost will want to be 26 to 30deg reguardless, on 92+octane pump gas.

Use a timing light and a mechanics vacuum/boost hand pump to verify the timing and action of the boost retard box.
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Old 05-02-2011, 04:33 PM
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HEY...HEYJUDE, that is a sweet looking car, love Henry J's and nailhead Buicks....throw in a 6-71 and a Hilborn scoop, VERY NICE !!!
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Old 05-03-2011, 05:13 AM
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Thanks everyone for the info and compliments. This thread has been a real education for me. I have to do some thinking of the direction to go. That MSD w/boost retard sure looks like the answer but $$$.
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