Clunking Sound

[Mixalis 266]

Hello all,

 

A strange sound has developed after the last trip to the drags. Basically a heavy clunking sound on idle, both in gear and in neutral, disappears when driving however after backing off big revs WOT the sound returned (a lot higher frequency as revs were high) then back to normal clunking on idle. Left the car for a bit thinking the pipes may have somehow slipped off a hanger but seems like nothing is fouling. Sound seems to be coming from the gearbox.

 

Gearbox is the BW35 slush box behind a mild crossflow, i know they're not meant to last long behind this so has it cried enough? Here is a video of the sound when cranking:

 

 

Gearbox has had about 12 passes behind the new combo (has hi stall written on the converter so previous owner had it restalled, seems to be about 2000rpm, also dynoed very soft tune 166rwhp thru this box) and most passes have been loaded up on the converter with LSD diff and plenty of grip. So gearbox would have had a bit of stress through it. I think you can tell that part of me wants it to be the box so i can get a single rail in hahaha but just making sure.

 

Engine is definitely fine!

 

Any hep would be appreciated

Cheers!

Michael

 

[winton 399]

From the description I'd say the flexplate bolts have come loose.

[Mixalis 266]

Was thinking this too, started taking off the inspection plate and ran out of time yesterday, thanks for the response tho

[PRO250 1,506]

Id look at the flexplate 2

Ive had 3 cortys do that. Ive never looked at what caused it andys we upgraded to a c4 mine went a loader and beacon smashed 2 in a few months so we fitted a manual

166hp might not seem that much but a borgy35 even a new one will not take it long andys was a full built box and bumped up stall and it lasted less then a year

Time for a C4 brother and a snif of NOS  

[Mixalis 266]

Well that's 3 that have said that so looks like I got to get up and finish taking off that plate and fix it. Cheers Dave legend mate!

 

Hahaha mate in a dilemma it's either c4 and go fast at the track or single rail for some good cruising

 

Got to sort out ignition as well, got a couple of dads old msd's, on digital 7 that needs a coil that's unusable on the street... Then there's the non programmable 7al2 but apparently that ones not recommended either so thinking of selling both and getting 6al2 programmable, will be working it out closer to the day

 

 

Anyway ended up going 15.0 with this combo it can't launch for shit tho 60 footers still about 2.35 which is what it was doing when it was running 17.3's...

 

Dave come up with a nos kit so we an grenade this box hahaha

 

 

Sent from my iPhone using Tapatalk

[bear351c 10,270]

Nothing to do with your clunk, but you could try checking your stall speed by left foot braking at standstill, slowly depress accelerator and look at rev counter.

 

BW35 at the drags..!!   Not sure the Datsun 200B gearbox was meant for that. Let us know how ya get on.

[slydog 7,873]

Well that's 3 that have said that so looks like I got to get up and finish taking off that plate and fix it. Cheers Dave legend mate!

 

Hahaha mate in a dilemma it's either c4 and go fast at the track or single rail for some good cruising

 

Got to sort out ignition as well, got a couple of dads old msd's, on digital 7 that needs a coil that's unusable on the street... Then there's the non programmable 7al2 but apparently that ones not recommended either so thinking of selling both and getting 6al2 programmable, will be working it out closer to the day

 

 

Anyway ended up going 15.0 with this combo it can't launch for shit tho 60 footers still about 2.35 which is what it was doing when it was running 17.3's...

 

Dave come up with a nos kit so we an grenade this box hahaha

 

 

Sent from my iPhone using Tapatalk

 

I think if your dad has 1 let alone 2 7AL's and you use something else I'd suggest getting checked for a pulse.Either 7AL and a HVC coil will give you basically a plasma cutter which clearly is better than ANY 6AL could ever dream of.In fact I have a 6AL2 programmable unit here I'd happily swap for the Digital 7

 

A decent hyd cammed xflow in a corty should run 13's all day long let alone a solid cammed tuff 1 or 1 full of dope.Not hard to do bro just remember it's not all in the engine it's the WHOLE car so it doe's infact cost money to do it right.

[PRO250 1,506]

Its a super mega drag engine rob its never going to go 13s without a bottle 

you need at least 200hp to bump 13s in a corty with a stock suspension cause they will not move off the line without slicks
 

[Mixalis 266]

Hahaha rob mate they're from some older combos, the 7al2 was from his XY from memory back in the early 90's, all the msd were from old drag setups that he's held onto. You would be surprised tho they are not worth much second hand and I would happily sort one out on the corty if it was street able but apparently the 7al's need good circulation and proper choice in coil or else you start killing things

 

The digitals are unusable tho apparently because it required the use of one type of coil that is not intended for extended use ie street driving.

 

But yeh that's how old school this 7al2 is from way back then, chip rev limiters etc

 

Even brand new if you compared the 6al2 to the 7al2 I don't think there is a huge difference in price tho especially if you buy from usa

 

The way it is now if the 60's could be sorted with a proper gearbox, c4 with around 2500 cobverter, I think it should have mid high 14's in it

 

But yeh still stock suspension got a bit to sort out over the holidays

 

 

Sent from my iPhone using Tapatalk

 

Edit: said stumper instead of rob

[Mixalis 266]

Looking at it from this perspective it's primarily a street car and I reckon a 6 series would be better suited/reliable for long drives and the such, but I'll do a bit more research with the 7al2 if it can be set up for street reliably then I can definitely save a bit of money there

 

 

Sent from my iPhone using Tapatalk

[Mixalis 266]

Well, quickly got the car up with a mate and tightened the bolts, as suspected car was back to normal. Dropped him off home, gave some RPM, rattled loose again.... So going to put some loctite on for round 2, any suggestions as to what would be the best for this application?

 

cheers boys

[bear351c 10,270]

The red threadlock should do the trick. Can't recall the number (272 or something.) Bolts must be clean, and oil free, same with threaded holes.

Do 'em up to correct tension in stages with a good torque wrench.

[Mixalis 266]

Cheers mate that sounds like a plan then, will get on to it next weekend i reckon. Weird this problem just comes up now after all these years, bloody datto gearbox!

[slydog 7,873]

A engine balance and a really good ATI or custom Powerbond balancer is the ONLY thing that will fix it...Just saying

[PRO250 1,506]

Im with rob

As I was saying on the other forum inspect your balancer most of the cheaper engines ive had do it again and again cause the balancer is broken fit a nice steel one and see if it over comes your issue but if it does not like rob said pull it down and balance it again

 

[Mixalis 266]

Well definitely didn't want to hear that... Pretty irritating since the engine was balanced and i doubt its even got 2000km on it since the rebuild. Dave had a read of your whole post on the other forum as well. Seems pretty clear what the process of elimination should be from here and yeh to answer your qtn the revs were not exactly big relative to what you made in the post, just on the upper end of where this cam stops making power (hard to tell as tacho goes a bit happy 4500+). Thanks for taking the time to respond though

 

Thinking of grabbing some new ARP 7/16" flex plate to converter bolts (these are the ones right?), cleaning the thread out and grabbing some loctite. My manual says torque to 41nm, what do you guys do? Thinking of getting this done first just incase the problem lies on the simple end or incase i haven't done the bolts up tight enough. 

 

If that doesn't work, then move on to a good balancer, and if its not that, then engine is out. 

 

Sensing there will be some disagreement though going through the process...  

 

Will accept defeat if its the bottom end out of balance but just a tough pill to swallow at the moment since the engine was just balanced and has felt very smooth. But have noted down everything you blokes have said so far, please add in any more thoughts/opinions

[PRO250 1,506]

Have been here a few times I do feel your pain

Fit bolts and good balancer now as a first time thing, it may have done little damage you keep letting it happen you will damage the crank. The balancer is cheap enough that you can do it straight up

If this engine is doing this at say 5500 I do think you will be pulling it down for a rebalance ive been here a few times and unless the balance job is real good they just keep shaking the drivepate off and theres nothing you will do to stop its a shame this info was not around when I was having this issue

And people say to me why don't I run my big engine this is why LOL a stock clevo will turn 7000 all day and none of these issues that and I got sheepish when I lost a flywheel out of one missing a gear man that killed everything and if it went the other way id be missing s leg or 2

Tighten bolts to ARP spec but that's about on the money don't over tighten the bolts all ive found that happens is the bolts snap off

Just stick a stock engine in it and boost the fooker no revs needed then, funny a bloke at rocket told me that in like 2002   


  

[Mixalis 266]

Thanks for that Dave yeh you're right mate will be doing exactly that then. A good balancer and new bolts are an essential either way so yep car is off the road then until I grab those parts, at the very least, and if it needs to come out (which by the sounds of it) for another balance then so be it, better than more damage...

 

The funny (or not so much) part of it is that I specifically remember the guy saying "I was surprised how balanced it was, didn't need to do much at all"

 

On a side not while we are here, have done abit of research just want another opinion, going to a manual will definitely need the flywheel to be balanced with the rest of the motor wouldn't it? Slapping on a manual as it is, the flywheel will knock it out of balance correct??

 

 

Sent from my iPhone using Tapatalk

[gerg 10,871]

Depends if the crank was balanced with flex plate and converter or without. If done without, then a flywheel and clutch balanced together will suffice, and as you're not really going much past 5000, it shouldn't matter a great deal.

 

The harmonics on these Ford 6s are bad not just from a crank point of view, but as the revs get up there, you're starting to get major cylinder imbalance due to poor inlet manifold design. Just ask Ando or Stumpers about differences in flow between inlet runners. I think the long, whippy, non-counterweighted crank and the cylinder imbalance work together to create the harshness that you're experiencing.

 

Maybe you could try loctiting some studs into the converter and using serrated or wave washers under the nuts to stop vibration from loosening them.

 

Maybe you could even try chamfering the flex plate holes to take tapered spring washers like those on a land cruiser axle-to-hub (some call them taper-locks) No fucking chance of that coming apart!