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Discussion Starter · #1 ·
Guys I need your help.

I finished my 454 rebuild and got it running ok - but I know the timing is not "dialed in" if you know what I mean.

It's a basic 454 street motor, bored .060 over (468), big hydraulic flat cam (2500-5500), dual plane intake, Holley 750, GM oval ported heads (reconditioned and ported) closed chamber style (about 10:1 compression) speedPro pistons, roller rockers, MSD ignition & distributor, 2" headers, etc.

Let's start from scratch. let's say you found this motor in your frontyard one day with a note on it saying "just built 454 - needs timing adjustment" where would you start with this? I have the vacuum advance type MSD distributor with adjustable bushings and springs also, and was told to use the vacuum advance since it's a street car.

where do I begin with this?

thanks.

Lee
 

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start with 12, but watch the total. if the total is low bump a few more degrees. if setting it at 12 results in some high total, like 40 or something you'll need to adjust the distributor to limit the mechanical advance. Ideally, you'd like to have 16 initial plus 18 or 20 total if the engine will stand it with out pinging.
 

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DITTO on what Tom said.

Scott
 

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Discussion Starter · #5 ·
cam specs??
torque convertor size and approx flash speed??
It's a Hughes GM 30, 3000 stall torque converter - new

The cam is a comp cams 11-250-3 Extreme Energy Hydraulic Flat Tappet
284/296 adv duration, 110 deg lobe seperation, .574 & .578 valve lift (1.7 ratio) It's beefy for the street I guess........

thanks.

Lee
 

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I'm guessing that is an 11" convertor.
install the black bushing in your MSD distributor & medium duty curve springs.
20° initial timing and your total should wind up around 36° or so.
Be Careful of Detonation.
If it doesn't want to idle in gear pm me.
 

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Discussion Starter · #7 ·
I'm guessing that is an 11" convertor.
install the black bushing in your MSD distributor & medium duty curve springs.
20° initial timing and your total should wind up around 36° or so.
Be Careful of Detonation.
If it doesn't want to idle in gear pm me.
yea, up till now I've just been tweaking it in by ear in parking lots then test driving it again and so on. I make an adjustment, get it on the street, light em up and see how she runs. I did not have vacuum advance hooked up, but I just reinstalled the vacuum canister on the distributor and will test drive it again soon. My method of just trial and error testing has been ok I guess but I know it's got to be off a couple degrees one way or another and without a dyno it's really hard to tell if it's "dialed in" right?

It's also frustrating with several centrifugal advance spring combinations and maximum advance "bushings" to choose which is best for me. to an expert engine tuner it may be easy but for me the combinations seem endless and I don't know which to choose. I currently have the silver bushing and 1 "light" spring and 1 "heavy" spring for the advance.

also with that 20 deg initial timing - you're right I think. the last time I checked at idle it was pretty high like 20 deg, yet most guys are telling me like 12-14 deg? . When I go down to 12-14 it won't idle.

Lee
 

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With your cam & motor setup 14 deg initial is too retarded becasue of the additional cam duration which is why it wont idle well at 14 deg initial.

You cam needs approx 18-20 deg initial along with 18-20 deg mech adv in the dist for a 36-38 deg total with your setup.

Scott
 

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Discussion Starter · #9 ·
With your cam & motor setup 14 deg initial is too retarded becasue of the additional cam duration which is why it wont idle well at 14 deg initial.

You cam needs approx 18-20 deg initial along with 18-20 deg mech adv in the dist for a 36-38 deg total with your setup.

Scott
hey scott - thanks again. Those numbers sound close to what it's set at now - thanks - I feel better. Everyone was telling me that 18-20 initial is too much - but again, it wouldnt idle at any less than that.

My timing mark on the balancer only goes to like 18-20 deg BTDC I believe. My timing light is a cheap one that does not have the adjustable advance feature. I need a new timing light with that feature right? Otherwise how do I check timing if it's off the mark?

Lee
 

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I make an adjustment, get it on the street, light em up and see how she runs.
Hey, you think we can get a video of that???

After you get the timing worked out, you may also want to look into your carb tuning. When I worked for a hot rod shop back a couple years back both would get tuned and the difference between before and after the tune was incredible.

I learned a trick that involves welding the distributor to keep your total timing around 36*. Has anyone even heard of doing this? I don't want to suggest you doing it until I know if it is something that is actually practiced or if its some back woods mechanic tricks.

DG
 

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Discussion Starter · #11 ·
Sorry no videos at this time.

I agree about the carb tuning - that will need to be done too - specifically the primary (and secondary) jet sizes. I don't even remember what's in there now - I'd have to pull the float bowls, and metering blocks to check the jet sizes. I'll get the timing set first - then attack the carb jets after that.
 

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Hook up your timing light and watch your balancer marks.
Have a friend put the car in drive with his or her foot on the brake.
Does the timing mark wander at all?
What is your idle rpm and when you put the car in drive what is the rpm drop?
Leave the vacuum advance disconnected until your mech advance is proper.
 

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Discussion Starter · #13 ·
Hook up your timing light and watch your balancer marks.
Have a friend put the car in drive with his or her foot on the brake.
Does the timing mark wander at all?
What is your idle rpm and when you put the car in drive what is the rpm drop?
Leave the vacuum advance disconnected until your mech advance is proper.
ok - I'll check that - but not for a little while yet, I started on something else (as usual) and the weather stinks. The idle definitely drops around 200 rpm when put in gear with the brakes on, I know that for sure. Don't know about the wandering timing yet.
 
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