Thread: Maiden Voyage - Fan Belt Trouble - Little Help?

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Well, took the new motor for it's first passes down the 1/4 mile tonight. Could have been better. First pass half track to check plugs for timing. Threw the fan belt... Great 60' for what I'm accustomed to at 1.71s. Checked plugs but not very experienced at reading them... ground strap was clean to about 1/16th" to the base and insulator was white with a couple specs at 32*. Dialed down to 30* second pass and went the whole 1/4 mile... threw the (new/spare) fan belt again! Now for plugs, ground strap clean and baked a little white all the way down to the base and insulator white everywhere with no specs/marks...

Belt setup: Single V-belt crank to water pump (no mechanical fan) to alternator installed tight. From the eyeball all looks to be in the same plane. Never threw a belt before but also never went above 6000rpm. I'm thinking maybe larger alternator pulley might help(?) Any other suggestions?

As for the motor: 439 BBC (427++) 10.6:1 SCR, 8.6:1 DCR with solid roller .630/.630 245/255@.050 aluminum heads at high altitude on 91 octane pump gas.

I was thinking I would be able to run full timing (at least 34-36*) on 91 pump gas but unless I'm reading the plugs wrong, I can't go over 32*?

Anyway. any insights or suggestions are much appreciated...

By the way, ran 12.44 @ 110 in the 1/4 very conservatively... I think it will drop into 11's easily enough (I've got well over 1000rpm to work with) but I might have to resort to 100 octane(?)

Thanks,

Chris

Thanks, Denny...

Is the timing dialed in at 32* or at 30*?

I'm thinking going bigger on alternator pulley only. I don't have a tension gauge but it's quite taught while stationary and very difficult to get over that last pulley with alternator cocked all the way over to valve cover.

I read elsewhere the smooth belts (like Gates or Dayco?) are better at staying put than the Goodyear "Gatorback" notched belts which is also new to the setup... (I was running a plain old smooth belt last season)... Have you heard this?

Thanks,

Chris

When I shopped around on my alternator,alot that I saw recomend not to turn them over 6000 rpm with stock ratio pullies in frequent 6000rpm+ applications for best longevity.
I messed up and got a alt with a chrome pully on it,it squeeks upon rapid accel and decell.I also went for the ribbed v-belt and noticed it seemed to jump around alot after 2000 rpm ........almost like it was loose.Stoped the engine and it was plenty tight,possibly a little too tight from what Denny posted.

Thanks for the insights... I'll shop around for a smooth belt today. I'll see if I can find an underdrive pulley locally, if not I'll just try the belt first...

left the car at the track overnight to run again this evening...

You might also look for a narrower belt that sits deeper in the pulleys

Pat

And you are convinced pulleys are in align? At high RPM, doesn't have to be much off to throw the belt. For short run, I certainly would run belt as loose as possible.

Jack

Make yourself a belt guard from 1/8" thick aluminum.
Easy to do.
Lay it out as centered as possible and make round in a lathe or use a drill press, mandrel and file to round off the outer edges.

The one shown is on a Pinto alternator.
There's usually enough threads on the shaft to bolt the guard directly to the pulley.

Never lost a belt with one of these - not up to 6200 rpm anyway....

I meant to add, make yourself a belt alignment tool from the correct length - whatever's right for your car - 1/4" x 1" aluminum strap.

I have several different lengths of 1/4" x 1" aluminum for straight edge use.
Cheap and works well.

You should be able to get 4 points of the pulleys flush against the belt.
IE: upper and lower point of the alternator pulley, upper and lower point of the crank pulley etc.
They should all touch indicating the pulleys are spaced out correctly as well as being in line.

Originally Posted by DennyW

Nice guard C9x.

Also, make sure the battery is fully charged. You don't want the alternator to be working hard while running it down the track.

DennyW's got a good point here.

A fully charged battery allows your killer ignition system to work as it was designed.

Most cars that have run an ignition system on battery only find they turn faster times with an alternator keeping the battery up.

So much for the old wives tales about HP loss due to the drag of an alternator....

you do not need to under drive the pulleys. just get i deep V alt pulley they work the best and check your pulley a lin ment . my gto would kick the belt off at 6500 but some fine tuning it has stayed on well past 7500. all alt brackets need to be rock solid to you need to look at pulley run out to i have had to face the hub of the water pump in the mill to get the run out in line

I'm an air cooled VW drag racer and we have been through the thrown belt thing many times. Basically as said above, you have to make absolutely sure that the belt alignment is spot on. By using a long piece of aluminum angle against the pulley you can measure how far the belt is away from the gauge at near the alternater and it has to be exactly the same at the other end in both directions. A little shimming, or bending might be in order to align everything correctly to keep it on at high RPM.

By trial and error we have settled on smooth faced DAYCO "TOP COG" belts on our race car and have never had a problem at 8000 RPM. They do not streach. We currently run just a mini alternator off the crank pulley but have also used this brand with our old air cooled fan without any problems at 7500 RPM. We buy our belts from FAT Performance in Orange, CA.

Thank you all for the great suggestions. C9x: that belt guard you fabbed is top notch.

I ended up picking up a 4" pulley and mounted to a Napa/reman GM alternator. Since the car was at the track while I'm picking up all this I picked up a selection of Dayco belts in 1/2" increments guesstimating what the difference in length would be from 2.5" to 4" pulley... I guessed ~2" and was wrong so the smallest belt I had was too long and I ended up with another notched style belt of the appropriate length.

I didn't notice so much with the old alt but the new alt installed and tightened down was cockeyed making the belt not straight. I think there is too much play between the bottom hole in the alt and the bolt through it and apparently the lower bracket is not so true... I'm told GM originally had a sleeve around the bottom bolt that took up this space(?)

Anyhow, I did end up throwing the belt again both trips down the strip but it stayed within the engine compartment both times. First time actually turned inside out and stayed on all the pulleys.


I ran 3 sizes bigger on the jets and half a tank of 110 hi test this time and got down to 12.0-12.1s with 36* advance.

Discovered why plugs looked so lean before, I backfired through the carb and blew off a large vacuum plug So my 12.44 run with 30* and 91 pump gas was with a HUGE vacuum leak... no wonder I had a hard time keeping it running at idle!

Back to the belt, while calling around looking for parts yesterday, I heard from multiple sources the belt was the main problem and they all suggested Dayco! Now that I know the right size, I'll pick up a couple so I always have a spare... I'm still left with the problem of the alt being cockeyed (I'll see if I can post a picture tonight) tilted inward toward the engine. I can straighten it out with the bolts loose, but as I tighten the bottom bolt it pulls the whole thing out of whack as much as I resist it...

Thanks again everyone,

Chris

Went back to the original alternator with the new 4" pulley. The new alternator rear face of lower mounting hole was far from square causing my crooked alternator problem. Also got the right size smooth v-belt (Dayco) and had no more trouble with losing belts.

Still learning the new motor and adjusting my launch technique. Burnout seems more difficult to keep the car in place I think from weight distribution more on the rear than before.

I got eliminated 2nd round in two classes but car was running well consistent 12.0-12.1... cracked off an 11.97 after I turned on the red light my last run.

Still quite a bit detuned but I'm going to sneak up on it slowly...

Anyone use MSD's timing controller? I'm thinking of getting one so I can more easily adjust the timing to fuel, weather, etc.

Thanks for all your help guys,

Chris