popping the bust plate and breaking belts?

I have an issue with my car currently. I keep breaking belts and popping the bust plate it usually happens right around the 1/8 mile. I am having problems figuring out why it does that.

The car is a Top Doorslammer style car with a blown TFX hemi.

I checked all the intake valves and none are leaking. The valve springs are also all in descent shape. between 310 and 340.

I tried to take less fuel out with the high speed i also raised the rev limiter to make sure it wasn't hitting the limiter but neither helped.

More engine data:

500 cui TFX hemi
Stage 1 AJPE fuel heads
SSI standard helix 14/71 fuel blower (36 OD)
Fuel cam
cr 9:1

What gives, it is getting old really fast changing belt and bustplates.

 

i don't have a datalogger on the car.

here is a picture of a plug: https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-prn2/969375_10151634382904138_981715005_n.jpg

ignition system is a 44 promag with a powergrid. rev limiter was set at 8000 and then changed to 9000 with no change

Crank trigger is the one from good vibrations with a ground cable, both heads and ignition and crank trigger is ground to the same spot. no extension on the crank trigger.

timing was set to 34 degrees.

 

Sounds like a lot of timing , back it out to 25 degrees.

 

the plug in the pic does indeed have 2 runs on it, it is a NGK b10es

plug wires are old.

regarding timing i know of other engines similar to mine that run 39 degrees. Yes it is NOT fatheads, just old fuel heads

 

Put on new MSD plug wires, gap plugs at .015", give it a bunch of fuel, and see what happens.

 

Burst Panels and Belt problem

X2 but check for clogged nozzles, restricted or collapsed fuel lines to the nozzles and/or a stuck open high speed bypass. Sounds like a fuel issue to me. I have broken belts on a lean backfire. Also, oil soaking into your plug wires may very well be causing a crossfire. Even if you wipe off the wires, the oil may still in the insulation underneath. Change the plug wires AND the coil wire.

 

The b10's have the small ground strap and are prone to glow plugging. Do you have the mag mag phased close enough to the crank trigger? Are you running any kind of fuel management? The reason I ask is I had a buddy who took one of the jets out at the shop, got side tracked and never put one back in it. It ran real well until the panels come out of it. Are you changing the timing at all with the power grid? Have you double checked it with the timing light to very it is acting as it should?

 

regarding the powergird. the timing is the same during the whole run, timing was checked prior to every run. we also checked the phasing before the first run.

I agree with you mike to me the plugs reads as if it has plenty of fuel in it. and no where near on the edge. That is also my understanding from the tuneup we have in it. It should be plenty rich.

regarding nozzel lines and jets. Didn't think think about that. I will check those.

plug wires, getting a new set.

Thank you for all the input guys.

 

At what rpm's does this happen, at the shift?

 

Probably lean..... I once had an open -6 check with no pill in it at all ( I screwed up ) and the car ran like a raped ape during the day, air was not great, and the plugs looked fine......but as the night came in and the air got better it kicked the burst panel. Turns out the only thing that saved me was that it was soo lean it could not get hot enough to melt down. If I had added any more fuel (a little at the time) it would have burned to the ground. So if you richen it, give it plenty of fuel to make sure it's fat and then back it down from there. Sometimes a motor that is way fat will show hot on the egt,s due to the fuel burning in the pipes so read the plugs like Mike says.Worry about the egt's when you get the a/f ratio closer. They almost never blow the panel and break belt from being rich.

 

@ ta455

It happens in high gear. Some time after i shift gears. as i dont have a datalogger on the car i can't tell you the exact rpm. But it must be around 7000 - 8000 rpm.

 

That's when mine went pop also. I think you are lean. It gets worse the farther you go down the track. Always around the 1000 ft mark for me. If you are running high speeds turn them around and shut off any fuel management you have. Let it be rich and try a run. A lot of racers only race with one high speed and run pretty well like that. It's only when you want to run better than 4.00's in the 1/8 that you need to start looking at fancy fuel management . A friend of mine went 3.95 all day with nothing but one high speed on a pressure poppet with a big block Chevy with conventional heads.

 

This is an "after everything else" scenario....very obscure problem that John Dunn had on his NFC a few years ago...probably would not be as intense with an alcohol engine but here goes:

John blew the body off of his car several times....popped a burst panel or lifted the blower on just about every pass at 500' mark....

He rebuilt or replaced everything....fuel system....ignition...blower....changed about every part on the car except for the chassis and block...same problem persisted...

After several seasons of frustration he was talking with a road racing guy that had one of the super expensive data recorders on his car...they turned their little engines outrageous RPM (not even gonna guess) and the computer could detect the camshaft was deflecting at the end of the straightaway....actually "twisted" the cam core and changed timing on the rear cylinders enough to cause backfires....they replaced their cams every few events due to the very small cam cores wearing out...they got kinda "springy" and would "wind up" on the straigtaways...

So John swapped the camshaft that he had run for many years and no more issues! He had the small diameter cam before the block manufacturers went to the 2.125" or 60MM size journals on hemi blocks...

If you have a really old block with a stock hemi camshaft core....might be something to look at...it's very unlikely in this case but something for future reference....

I hope this helps someone out there...

 

A few years back we had a similar issue with our TAFC around the 200' mark. Found it after 3 belts and a bunch of fibreglass work. Fuel shutoff was vibrating closed. There's a variety of ways to fix this, but since then we have run a strip of duct tape around the shutoff at the pump once the car is started. Thin enough so when you go to shut it off it will still break the tape. Also we snugged up the bolt holding the lever in the car.

Just something simple to check.

 

others have spoken about lines sucking shut. we had an issue a few years back where the small rubber nozzle lines were breaking down inside and the motor went lean. if the rubber lines are old, i would think about replacing them. just something else to think about
Darren