Severe wheel hop issue

[Joe Dozzo]

I know this is the GT Forum but I also know there is a vast wealth of knowledge here and I'm hoping to tap into that...

I am close to completing a year plus long project, a 69 Mustang with a Boss 429 (actually 544 CID), port fuel injection, wide ratio Tremec 6-Speed, sub-frame connectors and independent front and "high horsepower" rear suspensions. I've not had the car (or engine) on a dyno but based on similar builds I've seen online, I estimate ~850hp and ~800ft-lbs torque.

Under most conditions, car runs and rides great! Problem is part throttle acceleration - say 2nd gear at !25 to 30 mph and mash the throttle. Wheel hop is massive!

I've contacted the vendor (nameless here because I have NOTHING nice to say about them, despite their reputation) and their suggestions have included upgrade to Delrin bushings (done), heavier rear springs (350 lb to 500 lb done) increase rear toe-out to 1/16th (done) and rear adjustable shocks set to softest setting (done).

 

[digman1]

Sorry you are having this problem.

Takes me back to the old leaf spring mustangs, and the shackles people would put on them. Different times.

 

[texas mongrel]

Not seeing any diff struts. I put IRS in my Vette-engined Mk2 Jaguar, based on an XKE unit. These are notorious for wheel hop, so I ran tubular adjustable struts either side of the front of the differential that run up to an anchor point on the frame.

 

[DakotaGT]

Sorry to hear about the wheel hop/tramp issue. I'm not much of a suspension guy, but do you have any sort of pinion snubber above the rear diff? Love the car!

 

[DakotaGT]

Not seeing any diff struts. I put IRS in my Vette-engined Mk2 Jaguar, based on an XKE unit. These are notorious for wheel hop, so I ran tubular adjustable struts either side of the front of the differential that run up to an anchor point on the frame.

looks like we were thinking along the same lines, at the same time

 

[GT@50]

If it's wheel hop you're probably going to need a leading arm from the upper control arm to the frame. That kind of power is going to twist a lot! This one I did didn't have that much power, just a Chevy.
1st 3rd member from them had used components in it and about .010 backlash variance. They sent another one.
Think of toe in as a triangle pointed to the front of the car. It sounds like you've toed in already. When you get on it it will toe in more. Toe out, triangle pointed to rear of car, 1/32 per side.

 

[GT@50]

Remember this?

 

[Joe Dozzo]

Thanks all! Some good thoughts - I knew I could count on you!

They may be difficult to see in the pictures (or maybe I took them early in the build), but there are diff struts, both sides. Both ends have Delrin bushings and I'll be changing those to spherical rod ends. OR maybe I've mis-understood... In my case, there are struts that go from the front side of the lower control arms forward. Are you recommending additional rods to the differential housing?

HA! GT@50, I know those folks too well.

 

[GT@50]

I'm thinking something off the top like a 40 to control wheel hop. If it's a driveline angle vibe then play with the diff mounts. Fix the toe to start.

 

[Joe Dozzo]

Sorry to be a dunce, GT@50, but a "40" what?

 

[GT@50]

Sorry to be a dunce, GT@50, but a "40" what?

GT40 like the last pic. Seems like you'd need slicks to get the knuckle to move but if you're hooking good maybe it is. If it's a driveline vibe, not actual wheel hop, you'll have to play with angles.

 

[Joe Dozzo]

Thanks, got it now... Not sure how to do it without MAJOR surgery, but I at least understand the comment!

 

[nota4re]

In pics it seems like the lock nuts for the adjustable control arms are all loose. While there's no danger of these actually changing length, the lock nuts are there to make each arm a solid piece. More importantly, if these are loose, what else is loose? Finally, I don't think this would be your wheel hop problem.

 

[twobjshelbys]

tires and inflation too

 

[AJB]

Joe,
Pinion nose angle (the angle between the pinion nose and the driveshaft) is important.
You do not want them to both line up at 180 degrees. The small amount of angle “off of 180 “ is relevant . if I recall angles of
3 degrees to 8 degrees is all that is needed .

If your vehicle still had the hotchkiss rear suspension (leaf springs) you would find that either:
A. The camber of the main leaf of the leaf spring is formed during quenching to set the pinion angle or
B. A small cast iron wedge is inserted between the spring seat on the axle and the main leaf of the spring itself .
…Either way it sets the pinion angle.

At Ford motor company, we would release various cast wedges that could be used in the field to correct shudder, wheel hop and axle noise (whine).

Although you now have a link/ arm type suspension and not leaf spring/ hotchkiss,
This could be your issue.
AJB (Andy)

 

[2112]

When you get a chance, I would like to see pictures of the B9 mill. Kaase heads I presume?

Also what are your wheel and tire sizes?

 

[Joe Dozzo]

The suspension pictures were all taken during assembly so some of the jam nuts aren't tight and in one the coil unit look askew. Those were all addressed in final assembly before hitting the road.

Engine and Drivetrain Details:
•Kasse Boss 429 Heads and Single Plane Intake
•Ford MotorSport 460 Block
•Bored and Stroked to 544 CID
•Port Fuel Injection (Note - used 1050cfm carb on test stand for run-in)
•10.5:1 Compression
•Est 850 HP, 800 ft-lbs
•Tremec T-56 6 speed
•3.25 positrac

•American Racing Wheels,
255x45 on 9x17 Front
285x40 on 11x17 Rear

 

[2112]

Very Nice! FPA headers? Is that an aluminum bell housing?

Who built your engine and tuned the EFI?

Did you shave the shock towers or do the OEM B9 tower mods?

Very cool build.

 

[AJB]

Joe,
Wheel hop corrected. ?
Andy (ajb)

 

[Joe Dozzo]

2112 - Thanks! Yes, the headers are FPA. Bellhousing is steel. I bought the engine from a builder / drag racer in CA but I am doing the EFI tuning.

With the Independent front suspension kit I have, shock towers are completely removed. Steel plates replace them. We added some braces (you can see them in the installed engine pic) but I suspect they a more decorative than functional.

Hello Andy, I WISH!!! New GoPro arrives tomorrow so I can capture some video and - hopefully - gain a better understanding of the cause(s) before I throw more money at this! At this point, I'm guessing the solution will include some or all of:

new dual / triple adjustable shocks (QA1 or Vi-King). may go back to 350lb springs.
solid rod ends for the forward supports
solid mount for engine (a plate I can bolt to the driver side head and to some tabs I'll weld to the frame)