7/16 Converter Bolt Length

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Wvbuzzmaster

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So I bought a brand new FTI torque converter and a TCI SFI flexplate because of the need for 7/16-20 converter bolt holes. The TCI flexplate is .107” thick and the converter holes are threaded .700” deep. ARP converter bolts are .500” below the head... and are to be torqued to 60 or 70 foot pounds. The max engagement into the converter is only going to be .392” and at that much engagement and that much torque... it seems like not enough engagement. I was always told bolt engagement depth needs to be bolt diameter times 1.5 meaning on a 7/16 bolt it would be .656”, which the converter will support. However, the aftermarket bolts will not... what is everyone else using?
 
1 times the diameter is all you need. What you have is close enough. You could look for some 5/8 long bolts but I wouldn’t bother.
 
Same length thread as the flexplate to crank bolts. For years I would mill the heads on extra crank bolts to the same thickness as the original flexplate to torque converter bolt heads. Now I just buy ARP. If you buy bolts from a bolt store the heads will also be to thick.
 
Wvbuzzmaster said:
So I bought a brand new FTI torque converter and a TCI SFI flexplate because of the need for 7/16-20 converter bolt holes. The TCI flexplate is .107” thick and the converter holes are threaded .700” deep. ARP converter bolts are .500” below the head... and are to be torqued to 60 or 70 foot pounds. The max engagement into the converter is only going to be .392” and at that much engagement and that much torque... it seems like not enough engagement. I was always told bolt engagement depth needs to be bolt diameter times 1.5 meaning on a 7/16 bolt it would be .656”, which the converter will support. However, the aftermarket bolts will not... what is everyone else using?
Click to expand...
I just went through this with installing my FTI 4000 hard hit (9.5”) converter. I’m using a B&M flexplate which is approximately .125” thick AND I had to run .120” washers between the converter and flexplate for proper converter pull-out from the pump. That takes away about .245” or so of bolt thread engagement using the standard ARP 7/16 bolts (for Chrysler)
which leaves only about .265” or so of bolt thread engagement.
I used ARP 230-7302 bolts. 7/16-20 x .725” threads. Come in a pack of three so I had to order 2. And i used ARP 200-8530 .120” washers to get my converter pull-out correct (approximately.125”)
Pictures show how much thread would be engaged with both sized bolts with .125” flexplate and .120” washer
D34E9AD7-40BB-4042-A8DD-686A2D7BDEAB.jpeg


The FTI I have has deeper threaded bosses so I had no worries of bottoming the bolts on the converter
 
I never had to shim the converter bolts. The longer bolts you have pictured are the same as mopar flywheel for standard shift. We run a 5500 loose 8 inch . . How does your thrust bearing hold out with a trans brake. With the converter back that far before under pressure I would imagine that you must be installing a spacer in the registry hole of the crank. Otherwise it would just pressurize out to the crank where it would ride originally while under a pressurized load.

We had a similar problem with a install of a Common rail installed on a 47re. We just milled the trans adapter.
 
The picture is just for reference (the two washers represent the flexplate and a washer and how much thread shows) Only using one washer between the converter and flexplate. With the converter fully inserted into the pump on my 727, the lugs of the converter are about .253” from the face of the flexplate. The ideal pull out is no more than 1/8” (.125”) from all I’ve read as well as what many converter companies recommend. Doing that I still have about an 1/8 to fill, thus the one washer. The converter pilot is registered in the crank adequately.
I know there are some who disagree with using washers at all. TA, FTI and some other companies mention using washers to get converter pullout in range. The FTI has a billet front cover, the mounting bosses are approx .700” deep. With bolt threads at .725”, a flexplate of.125” thickness and the washer being .120” thick, that combined leaves .480” of bolt thread remaining. Hope that makes things clearer
 
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