TD Ben's Twin GTP Engine nascar making many 8 second passes

[Rent Free]

God I hate flexplate issues, this reminds me I need to order a billet one!

 

[Turbocharged400sbc]

You using the "short" 5/16ths arp bolts with the 3/8" 6 or 12 point hex head? Or the longer ford pressure plate bolts (large hex and with a unthreaded shank)?

 

[twinv6gtp]

Arp short 6 point

 

[Turbocharged400sbc]

ive never had any problems with em, but with the low amount of UHL for stretch and them not being TTY like the OEMS its a smaller window for the TQ, i shoot for 26-28ftlbs and never use loctite, just arp lube... the TR held together just fine with the small arp's and stock flexplate for quite some time and including the 608whp dyno

i do hate how if you dont have a nice quality 12pt socket they love to strip off...yay

with the counterbore and longer shank/larger head dia i figure clamping is much better as well as shear strength since the shoulder is at the flexplate opening. i always hold the flex at counter clockwise while tightening the first few fasteners to keep the flexplate up against the shanks.

anyways this post and the one below it have the info/link

http://www.thechicagogarage.com/forum/midwest3800s/146403-assploded-2nd-flex-plate.html#post3132826

 

[twinv6gtp]

Well the repair is done. But it vibrates a lot... tried a pass knowing it could break shit...

A power connector for the ignition switch backout at 100 mph. That switch was the main for most accessories... my shift controller was one of them. That means at 100 mph both trans went to 1st gear. The front engine shut off but the rear has a seperated ignition switch. Rpm went above 7100rpm with a strong vibration from a possibly warped flex plate. Rear engine has a knocking sound. The high power plus vibration did it in...

 

[Turbocharged400sbc]

ah fuck man

 

[twinv6gtp]

ive never had any problems with em, but with the low amount of UHL for stretch and them not being TTY like the OEMS its a smaller window for the TQ, i shoot for 26-28ftlbs and never use loctite, just arp lube... the TR held together just fine with the small arp's and stock flexplate for quite some time and including the 608whp dyno

i do hate how if you dont have a nice quality 12pt socket they love to strip off...yay

with the counterbore and longer shank/larger head dia i figure clamping is much better as well as shear strength since the shoulder is at the flexplate opening. i always hold the flex at counter clockwise while tightening the first few fasteners to keep the flexplate up against the shanks.

anyways this post and the one below it have the info/link

http://www.thechicagogarage.com/forum/midwest3800s/146403-assploded-2nd-flex-plate.html#post3132826

It has held for the equivalent of 200 passes plus with tuning passes.
Front still is perfect with the same method and hardware. I have meziere flexplate btw..

I believe the larger torque converter and high rotating mass puts additional stress in the flexplate to engine bolts.

Longer thread and a non threaded shoulder would help not having this happen. stretch bolts would be better for not backing off. These arp bolts are very hard dry and will loosen over time imo.

 

[Turbocharged400sbc]

did you have the billet rebalanced to match the L67 bottom end?

the mez is a 20 oz/in offset. ive measured a few and the sc seem to end up at 21-22

loctite isnt a good lubricant for the tq of those bolts... but whatd ya tq em too?

ive done oem lots over the years, and breakaway tightening always seems to be around 28ftlbs. i like the ford bolts with a larger head/washer (it does clear the billet converter cover we have fyi)

 

[twinv6gtp]

did you have the billet rebalanced to match the L67 bottom end?

the mez is a 20 oz/in offset. ive measured a few and the sc seem to end up at 21-22

loctite isnt a good lubricant for the tq of those bolts... but whatd ya tq em too?

ive done oem lots over the years, and breakaway tightening always seems to be around 28ftlbs. i like the ford bolts with a larger head/washer (it does clear the billet converter cover we have fyi)

No didn't rebalance it. Bought off ZZP. Figured it was "bolt" on...

I torqued a little more than factory. by 5 ft-lbs. Forgot what the number we settled on but I think it was like 35 ft-lbs.

Front engine has zero rattle... I'll inspect before next season. But I bet their tight...

The massive torque converter and higher mass in the 4t80e and the high revs (7000rpm) probably helped loosen it over time.

 

[Rent Free]

Let me ask a few questions so Im on the same page.

The issues your having is with the billet flex and bolts?

The front has oem flex and what bolts?

I know the OEM flex does have to be "clocked" or it will rattle and vibrate, found out the hard way once.

Also the Assploded flexplate was a thread I started. I hope between you and James I can have a decent solution, Right now after 2nd assploded flex im back to Stock flex and stock TTY bolts.

I'd like to pick up a billet flex for this car, and engine is coming out again when I get home so would be a good time to unfuck these flex plate issues as Im a little leary that the stock flex and TTY bolts will hold up.

I cant lie and will say I do tend to beat on my shit so far the only thing I've really broke are these god damn flex plates.

Other than not having time to sort out why the rear valve cover was blowing the gasket out the valve cover before I left. That's why the engines coming out again. I don't know if I can save that engine. Ill have to start with a compression test and for some reason I think Im pressurizing the crank case. 2.8 is almost 20#s of boost according to Aeroforce. I will also be switching to at least 1 valve cover breather maybe both front and back.

Can anyone show me a pic of what the best possible option is for bolts? Ill tap the crank threads deeper if need be.

I'll be pretty pissed if I end up destroying a 3rd flex.

Last one was 130 MPH interstate brawl against a G8 LOL..... FUCK! speedos climbing I was like 2 cars ahead then my foots to the floor and speedos going backwards....... GOD DAMN IT 2nd plate and bolts went bye bye.

Edit IIRC there are NO ARP GM 3800 Flex plate bolts the ones being sold by ZZP and Intense are Ford botls correct?