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PostPosted: Fri Sep 27, 2019 12:18 pm 
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Joined: Mon Nov 05, 2012 3:54 pm
Posts: 80
johncroft wrote:
So here is what I found with block rigidity. This is a post from years ago(2010???) on the old forum. The engine plates definitely fixed it.



Lets start with the specs.1981 Capri 393 Scat stroker bracket racer.Crane solid roller cam(smallest on the spec sheet) and 218cc 3V CHI heads.The engine had no problems with the stock stroke but would take out the back side of the thrust when the stroker was in the same block.First thought was torque converter.Transmission is a trans brake powerglide.Replaced torque convereter,front pump,gear set,flex plate,checked centering of JW bell,checked persuures in cooling system of trans and changed everything all trans guys could think of and still would take the trust out.It moved so bad that it broke #2 main web in the first block.The engine has the external oil line,full groove mains with chamfering on the thurst to direct more oil to the back of the trust,oil restrictors on all cam bearings including#1,lifter bore bushings on right side of block with .040" restrictor hole,high volume oil pump,100psi relieve spring in oil pump,4 bolt main conversion(Milodon),main cap girdle,Canton oil pan.Engine is filled with Hard Block to about 1.25" of the deck.Assembly was balanced and the last crank was a forged Scat unit.It had already ruined 2 cast Scat cranks.You could run this car with the stock stroke and everything would live.Put the stroker in and it could move the crank .007" in 3 passes.Mark Mckeown's words were"you have done everything to make this work,lets talk about the chassis".The car had solid motor mounts with straps from the heads to the frame rails,Southside Machine cross member with removible center section and solid trans mount with solid mounted crossmember.Mark said I think the chassis is twisting enough to pinch the trust bearing(remember the motor mount bolts are on either side of the thrust bearing).He said it is time for a front plate and a mid plate.He also wanted more pull out on the torque converter but I don't think this had an effect on the problem(I had more pull out then he suggested in the past).16 passes at the last race and the crank never moved.The extra power of the stroker was enough to flex that block.Mark you are a genious!!! Thank you,thank you!


I think an equally big issue from what I read in your post was the solid trans mount. I learned the hard way that one should never run solid motor mounts AND a solid trans mount regardless of whether it's a OEM framed car (weld-ins or not) or even a fully chassied car. The twisting motion helped break a number of tranny cases (iron cased 4-speed) in our BBC '69 Camaro until a wise head asked me about the mounts.

P.s. on the Glidden comment, I want to clarify that his engines looked to be on a ground-hugging flat cart with wheels and no traditional engine stand rotating head installed. Guess they had to pick it up by hand or use a shop crane to flip it over.


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