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Discussion Starter #1
Hello, long time viewer, first time posting.

I have a '70 Nova factory SS. Came from LA, low miles. Originally a 396 car, now has a 72 454 4 bolt main and 396/427 cast heads. Add ons include; air gap intake, edelbrock 750 carb, ceramic long tube headers, flowmaster exhaust, march ser pulleys, edelbrock victor water pump, aluminum radiator w/ dual pushers and one puller fan, trans cooler. Drivetrain is the 454, th400 TCI street fighter, 12-bolt 3.73 w/posi, multileaf. Vac gauge in dash pulls 17/18 psi at idle(very steady), idles @ 850-900. stock style fuel pump running @ 7psi constant.

I have an MSD street fire carb, taylor 10.4 wires, delco plugs, and running on manifold vacuum. I have switched mechanical springs around (running one light and one heavy silver springs)

Problem is that @ 4* inital, 5 turns out on the vac. canistor, total advance is @ 47*. The car has a slight skip @ 3500-up. The motor feels like it is losing power above that. The cam is very mild (unkown specs) Shouldn't I be looking to get from 34-38* or so total timing? I can only gain this if im at 0* initial (im guessing, havent tried it) The car gets to 210-215-220 after 25 mins or so. (160* therm, straight water w/additive & smaller pulley) I have read the advance 101 and numerous timing posts. IF I screw the vac. advance to close, it doesnt chage anything. What am I doing wrong? Please help, it seems like I've tried everything!

Thank you in advance
Rob
 

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When you set total timing you should do it without the vacuum advance hooked up. Reqason is under full throttle you will not see any vacuum advance so you want to similate that. I would shoot for 34 or so to start and be safe. If you get any pinging under lighter loads you would want to limit the amount of vacuum advance with your adjustment.

As far as the overheating, I noticed the march pulleys. Often they are underdriven setups. Make sure your pulleys are turning the pump at least at a 1:1 ratio. the crank pulley should be at least the same diameter of the water pump. If not, could be your problem. Check all that, see what you have and report back...

And welcome to the site!!!
 

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47* seems like alot of timing. I'm guessing you should be around 36-38 total.
 

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Discussion Starter #4
Thanks guys

yes 47 seems way to much for me. I have march setup and read the posts concerning the pulley sizes. I bought a smaller option water pump pulley to get close to the same size as the crank. When doing this i went to the new aluminum water pump, big improvment, anyways...

When I remove the vacu. advance line, what should I look for for timing then, 34-38? I read a ton of posts from guys saying there initial was like 8-12 and i knew somthing was up. Thanks
 

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When I remove the vacu. advance line, what should I look for for timing then, 34-38? I read a ton of posts from guys saying there initial was like 8-12 and i knew somthing was up. Thanks
I'd start with 34-35 total without the vacuum advance.
 

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Discussion Starter #7
Timing....

Hey guys, thanks for all your help. Im going to work on this tomorrow after work, and I will hopefully figure this out. I will reply back....thank you!
 

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Get the mechanical advance set first before anything else and then connect the vacuum advance and take it from there. Chances are it will run great. Don't be afraid to go to 38 degrees total mechanical advance (vacuum advance disconnected and carb port plugged) as an experiment before you settle on 34. Every engine is different.
 
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