Breaking Blower Belts

Having a new problem of breaking 8mm GT blower belts around 1000ft. The motor is set up very rich and safe. A 526 with BAE 6’s, Littlefield K-11 blower, MSD 44. First pass about 1/8 mile the belt broke. Another belt and this time it broke about 1000 ft. Was told belt was not tight enough. So on the next outing tighten as per there instructions. Again 1000 ft broke. Then went to a 13.9 belt and pulleys, but could not get the adjuster install correctly. We were way rich and leaned the high speed by 10 (60 to a 70). Belt stayed on for he full run. In changing to the 13.9 pulleys the over drive went from 42 to 46% over. Found #1 had gone to 1204º and the ground strap had burnt off to the radius. Installed another set of pulleys to enable the adjuster to be installed correctly, now 50% over and richen the #1 port nozzle by 2. Third pass made it to the finish line before the belt let go, and boy does a 13.9 belt tear up the front of the motor as compared to the 8mm. On this run the #1 was 1137 and the plug ground strap was intact.
Suggestions to look?

 

Many belt failures have nothing to do with the belt. I have seen belts break when the fuel pump is falling off and I have seen them break when there are ignition problems. Is there a data recorder on the car? How much timing is in it? Too much advance or a lean spot can cause detonation which can break the belt. Unless my belts run off the end of the pulley I don't even consider them when they fail- I look at other factors first. It's easy to blame the belt but it is just a sign that something else is wrong. Dave Germain

 

belts

I like to ask the dumb questions first:
Pulley alighment, you would be surprised on how many people overlook this, with a fresh belt on and engine running does the belt climb forward or rearward on idler?
Is there a small chip or dent on the teeth on top or bottom pulleys?
Is there a stone or forien material caught in teeth.

I also like to run a barrel faced idler has this helps keep the belt in the middle.
P

 

Lean.....with # 1 that hot..dave
www.myspace.com/daveloweswr

 

Also make sure your idler is supported so it stays straight and true. Use either an RCD support or make your own so the idler pulley doesn't get pulled off square by the tension.

 

what about being to rich lugin the motor and it just happens to have a lean hole (he said it was rich with a safe tune up but it has a lean hole )

 

First off – thank you all for your response. Now for a few answers:

Dave – Yes I have a data recorder. I can watch all cyl temps, Fuel Pressure, blower pressure, Eng RPM, Drive shaft RPM and G’s side, forward/Aft.
28º Timing.
I agree with you it’s not the belts braking, it’s another problem. I trying to find out what’s breaking them.
Bob69 – Checked pulley alignment, O.K. Belt does not run forward or aft when warming up the engine. Top Pulley new, bottom pulley off a running combination. No dents, chips. I run a barrel faced idler.
Mike – Did not add fuel when we changed pulleys, EGTs on the other 7 cyl was 10XX, where XX is 34 to 86. I was told to keep it between 1050 to 1100 and not go over 1100. Even at 50% over the other 7 cyls were within that range and #1 had come down with the 2 size bigger port nozzle.
secondwindracing – Lean with the other cyls as stated above? I am definitely thinking the motor is lean, but the other 7 cyls look ok. No Mike, I did not read the plugs. If my life depended on reading plugs, I’d been dead a long time ago. I’ll have to get them to somebody who can read them.
Ken Sitko – I have the RCD support. Not the new pistol support, the round one. And yes it was tight.
jim phillips – waiting for somebody to answer you.

Also as stated in the “KB eating pistons” thread, could I have an air leak in #1? This cylinder goes lean and bang a broken blower belt?

Thanks again,

Mack

 

had same problem burred intake valve guide

 

http://www.dragstuff.com/techarticles/reading-alcohol-spark-plugs.html

Canter wrote a really good article on reading plugs.

 

I'd add 10 to the main then try turning the high speed around and make a pass and see if the belt stays on .
Then that will tell you if going lean is pitching the belt.
Just a sugestion...

 

I broke a belt once with a safe tune up. My intake valve springs were getting weak and I didn't know it.
So the valve must have been bouncing enough to light the A/F in the intake

 

Belts & Wires

I have a multi engine modified pulling tractor, a couple years ago I changed blower & ignition to some used Pro Mag 20's. I started breaking belts. I would break them at various places on the track. After going through 20 belts total on different motors, I decided to replace all the spark plug wires. I have not broken a belt in 3 years since replacing them.

 

What hat are you running? A few years ago, we broke a belt on every run for about 4 races before we realized the hat (short psi hat on a kobleco blower) wasn't letting in enough air. Changed to a buzzard, and it didn't happen again.

 

Will is 100% correct about the egts possibly being wrong!
Before I started to pinch any cylinders on my car I verified that each cylinder
on the data logger was reading the correct hole , and ITS A GOOD THING THAT I DID! because 1357 were reading as 2468 and 2468 were reading is1357 .
another thing that you might want to check is that your coil wire is good and not shorting out.

 

Braking Blower Belts

O.K. Gentlemen lets put this on hold until next year. While taking the motor apart I found the #1 cylinder had torched thru to the valley way. Both head and block damaged, also the push rod. Preliminary investigation disclosed I have O-rings in the BAE VI heads .050” wide and the receiver groves in the block are .040” wide. I’ll send the block to KB and the heads to BAE. After I get the motor back together I’ll try it again with some of your suggestion.
Will Hanna
“Is this blown alky or gas? How much boost/compression. Are your egt's on top or bottom of headers?”
Blown Alky; 25 – 30 lbs gage/11.2 compression; Egt’s on top. 3/16” protruding about ½ way into tube. 2” down from flange. And yes I checked that #1 is #1.
blown 375
New plug/coil wires this year. 2 runs on them before the problem started. Coil wire clear and good shape.

Thanks again for all the help.


Mack