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New SFI flexplate and looks like it's got alittle wobble.
Just pulled my stock 5.3 flexplate which I had enlarged the holes for my 2004R and it worked fine. I just installed a PRW gold series 29.1 SFI rated flexplate and used ARP bolts. It wasn't as tight as the stock flexplate over the crank when installing. I tried my best to line it up but I bolted it up and put the engine in the car. I just when to torque down the converter bolts and the flexplate kisses the inside of the trans bellhousing at one point on the flexplate. It only did it a few rotations but it wasn't like it locked up, just like it barely scraped. Now it seems to move freely. But when I looked through the starter area u can see the flexplate moves alittle as it's rotated again at like one short area. Looking straight on at the teeth the flexplate is dead even and doesn't have any noticable run out. The flexplate just seems to not be centered on the flexplate perfectly or the flexplate isn't perfectly round. The motor and trans converter move freely and the converter is centered in the pilot with slip fit Hughes adapter.
Is this going to be a problem like vibration or starter grinding?
Reason i I upgraded is my 5.3 got a custom cam and ported heads so hp output at 12psi will be 650ish hp. Figured it was a good time to upgrade the stock thin flexplate.
pulling the motor/trans is not going to make me happy but I want it to work properly.
It needs to be centered. Are you using the dowel hole at all to help center it?
i tried to use it but there is no dowel in the hole. Just empty. The OE one was really tight around the crank so there was no adjustment but the SFI one had clearance around it so had play. I tried to eye ball it and Tq'd it down. I originally tried to stick a old flexplate bolt in the hole to help align it but that didn't work.
How Does one align it with the dowel hole if there is no
dowel?
Last edited by customblackbird; Feb 25, 2017 at 09:13 AM.
I really did try to line it up and it seems like the offset is probably a slight out of round of the flexplate only because I took a pic of the installed flexplate and I got it lined up pretty good. The issue was the SFI flexplate had a ton of room around where it slips over the crank and it seems to spin on center except for 1 small section. U can see it's alignment here.
but on a side note. How does the dowel align the flexplate of the center section has play in it. Seems like the crank opening is what would have to center it more than the dowel. The actual flexplate bolts only allow so much movement of the plate. And since the dowel is not centered the gap around the crank will still cause it to be off.
I measured the flexplate with a dial indicator to see how far it was actually off and it's hard to get a clear reading due to it bouncing off the flexplate teeth alittle but I would Say it's something around .010 to .030" max. It also only really contacted in 2 small spots of about 4 teeth each and only on the back edge on the converter side.
Is something this small even worth worrying about? Will that even affect the balance or anything since the converter should be centered via the crank pilot anyways?
I just had a similar conversation with Jakes performance. I ordered a dished SFI flexplate from them (PRW sourced) along with a Jakes converter. Everything bolted up well for me but the ring gear on the flexplate was too large. The starter would slam into the plate and grind away. Ultimately (after lots of research) I shimmed the starter (almost 3/16) to get it to work. I have driven the car minimally but have not noticed any vibrations. However it still concerns me.
Yes you're correct, I guess I would use that as a piece of the puzzle to see where the issue is. But yes you're right it should be a pretty snug fit.
A peice of the puzzle in the worse spot! Lol. I'm going to measure the stock flexplate crank opening and the other PRW flexplate I have. They sent 2 by mistake. My guess is that they are both 2 large in that area.
I just had a similar conversation with Jakes performance. I ordered a dished SFI flexplate from them (PRW sourced) along with a Jakes converter. Everything bolted up well for me but the ring gear on the flexplate was too large. The starter would slam into the plate and grind away. Ultimately (after lots of research) I shimmed the starter (almost 3/16) to get it to work. I have driven the car minimally but have not noticed any vibrations. However it still concerns me.
Maybe PRW had a bad run of flexplates?
thanks liquid, when u said the ring gear was too large did u mean the whole thing like the DIA? Or was it just out of round and certain areas where larger in DIA?
Reason I ask is that when I spin the crank the flexplate will basically look lopsided slightly. It might not even be that it's off center but it could just be from welding. All I know is that I can see it move when it's rotated but how much being off actually affects the performance and will cause a vibration? There has got to be tolerances built in as nothing is perfect.
My worry wih shimming the starter is what about the rest of the flexplate that isn't at the farthest part or the lopsided mess? Does it just not contact the ring gear teeth as much and therefore more prone to stripping.
Mine was too large in the overall diameter. I rotated it and checked it in 90 degree intervals to confirm. If its out of round its just barely and would require finer measuring than with a naked eye referenced against the starter teeth. My biggest concern was very few people have shimmed an LS starter and it was almost unanimous that its not needed (generally). So i hated the idea that i was the exception because that implies i screwed something up.
I drove mine a bit more this past sunday. No issues were noticed. The car drove well under full power, on freeway, no vibrations (Solid motor mounts), no starter issues, etc. My suspicion is the flex plate starter ring/teeth are just out of spec (too large) which required the 3/16 shimming with the starter. I have probably started the car 30-40 times now without any issues. I plan on pulling the inspection cover off soon to re-check everything.
This is on a gen 4 6.0, S475, full manual 4L80e and ford 9" at 10lbs of boost.
Good to know liquid! I'm going to progress putting the motor and other stuff together at this point. Once I get finished I'll start it and verify any noise or other issues. If I have to pull the flexplate the I will but it's coming out the tranny side.
Yours was just larger in DIA right? Was it a tight fit over the crank?
I did not notice any wobble or other out of round issues when i mounted it. It went on clean and all the bolts went in smoothly without play.
i used chevy sb starter shims, drilled holes and cut to length.
I will continue to update if any issues arise or are relayed to me (for future search/reference). It am still very nervous about having to use the shims.
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New SFI flexplate and looks like it's got alittle wobble. 
