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Timing questions Engine Guru's needed.

K10 KRAWLER

K10 KRAWLER

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Carstairs, Alberta, Canada
Hello all, after some parts trading I just ended up with a Brand new MSD distributor that was re-curved. To be honest, I have no clue what a re-curve is (please don't flame me for getting it). I am just wondering what is involved in a re-curve and would it be a bad idea to use on my truck? The engine I would like to put it on is a freshly rebuilt 454 with a mild RV cam and 9.5:1 Compression. Its a pretty mild build, that I will be using a 770 Holley street avenger on. The paper I have on it says:


20 Degree Crank curve 2400 RPM
Advance Curve starts at 1000 RPM
10 Degrees total vacuum Advance

then there is a hand written note on it that says to set timing at 12-16 degrees

So how should I time my 454 when I put it in? is the 12 to 16 degrees right? or should I just dump this distributor? the engine built for low end rpm and is going into my dually which is only used for towing heavy loads.

any help would be appreciated
 
Set it at 12-16 basically the recurve means it will either advance slower or faster or just different depending in what it is curved too.
 
Basically what the info means is this.... there is 20 degrees of mechanical advance, 10 degrees total of vacuum advance. If you set the base timing at 12 degrees then you would have a TOTAL of 42 degrees advance....12 base timing + 20 mechanical advance + 10 vacuum advance. Most of the time you want between 32-36 TOTAL for best performance. The vacuum advance should be an adjustable type and the mechanical advance is able to be locked out as well. It will require a timing light with an advance feature for you to "dial in" what YOUR engine likes.
 
Thanks for the replies, I am actually ordering an advance timing light from MAC with my student 50% deal. I'm still an apprentice trying to learn all this stuff. I'm happy to know that this distributor will work for me. So basically when the time comes to time it, ill start off by setting my base timing normally to 12 degrees. then plug in the vacuum advance, set the light to 32, rev the engine to about 2500 rpm and it should be showing the timing at around zero degrees?
 
Not exactly how i do it but you've got the idea. I also don't suggest starting at 12 degrees base timing either. Unless the engine has a pretty large cam 12 degress initial is a bit much for base timing. I like to start about 4-6 degrees and bump it up slowly if needed. I also don't take what someone says as golden, I would get a vacuum pump and check the total amount of vacuum advance that the vacuum cannister will give. Basically the vacuum advance is for fuel mileage.

Here is what I would do. I would set base timing at 4 degrees, then i would check the amount of mechanical advance (do this with an advance type timing light hooked up and run the engine up to around 2500rpm while you move the advance feature of the light until you read ZERO on the timing pointer, now remove from this number your base timing which was 4 degrees and the number you have is how much mechanical advance is in the distributor). Now if you've already tested how much the vacuum advance will give (lets assume the vacuum advance does give 10 degrees) you would add the base timing (4 degrees) to the mechanical advance (lets say for argument sake 20 degrees as was stated earlier by you) and then add the vacuum advance and you have come up with the TOTAL advance. Now keep in mind that you can play with how fast the vacuum and mechanical advance come in. This will be a trial and error that you will have to play with since altitude plays a huge roll in what you can get away with.

Basically for fuel mileage you want the most advance you can get WITHOUT the engine detonating (I still like to keep between 32-36 total leaning more towards the 36).
 
ooooohh, ok i'm starting to get this now. I don't understand when you say you would get a vacuum pump. I am guessing the vacuum pump is a tool that you use to create an artificial vacuum, aside from the engine, use the timing light advance and read the max advance from the canister on the distributor? Why would you recurve a distributor in the first place? does the factory setup not offer enough for performance?
 
K10 KRAWLER said:
ooooohh, ok i'm starting to get this now. I don't understand when you say you would get a vacuum pump. I am guessing the vacuum pump is a tool that you use to create an artificial vacuum, aside from the engine, use the timing light advance and read the max advance from the canister on the distributor? Why would you recurve a distributor in the first place? does the factory setup not offer enough for performance?
Click to expand...

Yes a vacuum pump simulates the engine so you can just have the engine idling then pump the cannister and see how much advance it gives.

Factory distributors usually have ALOT of advance, along the lines of 50-60 degrees total from what i've seen in my past experiences.
 
OK i see why then. I guess when I get the engine in and start the timing ill let you know if I have any issues, thanks a lot! your help is greatly appreciated.

I actually Have one more question. How do you know if your vacuum or mechanical advance is advancing to fast or slow? I'm not to sure on how to adjust it as well. I'm assuming it will be tough for you to explain the how to part of that one, haha.
 
Usually if you have all of the advance in by about 2500rpm that is good. Like i said, you'll have to play with it and see what your engine likes for the altitude you're at. Make it come in sooner and see what it does, if it gets worse then make it come in later or vice versa.
 
K10 KRAWLER said:
Will do, and that will all be adjusted inside the distributor, right?
Click to expand...

The vacuum advance IF adjustable (pretty sure it is) is adjusted with an allen wrench through the vacuum port. The mechanical advance is another story, I can't remember if the distributor has to come out or not but I don't think so although a portion has to come apart to move the lock outs.

Forgot to add the the way you adjust how slow or fast the mechanical advance comes in is with the advance springs.
 
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