Question about flexplate

[TigerVette]

Is the 168-tooth flexplate stock for 1985? I seem to get different finds on my own search.

It needs to be externally balanced for my 383 [for 1985 Corvette auto trans - new short block w/ 400 crank]

Appreciate the help

 

[grumpyvette]

the stock flex-plate is a 153 tooth internally balanced design, the 168 tooth flex plate WILL clear the stock bell housing and work but you'll need a different starter and in most cases headers and other clearance issues will restrict your choices to the high torque mini starters, most 400 sbc require a externally balanced flex plate and matching externally balance damper or balancer, in many cases it a larger diam,. and that can cause clearance issues with the front K-frame in some cases

viewtopic.php?f=70&t=458&p=2911&hilit=+mini+starter#p2911

viewtopic.php?f=70&t=458&p=1545&hilit=starters#p1545

http://www.atiracing.com/products/flexp ... xplate.htm

http://www.carcraft.com/techarticles/cc ... ewall.html

http://www.gmpartsdirect.com/performanc ... D=913.html

keep in mind theres 3 and 6 bolt torque converters and several bolt pattern diameters
the spline counts and shaft diameters differ in various applications so do the required research
EXAMPLE
10.750 in.
11.500 in.

OEM flex plates are far thinner and more flexible than the SFI certified flex-plates , so they are far more likely to crack and split over time

.the raised side of the indentations go TOWARD the converter , in the picture above the crank flange mating side faces away from you
Instructions

1

Determine which side of the flexplate goes against the crankshaft. Looking at the center of the flexplate, where the bolts go, one side is recessed. This side faces away from the crankshaft.
2

Clean the mounting flange on the crankshaft and the mounting area of the flexplate with parts cleaner and a shop rag.

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3

Mount the flexplate on the crankshaft with the recessed part facing away from the crankshaft. Line up the mounting holes. You will be able to see that the flexplate is flush against the crankshaft by looking at the mounting holes.
4

Install the bolts by hand until finger tight. You must use the special flexplate bolts. These bolts have a special shoulder and a thin head. If you try to use regular bolts, the torque converter will not fit properly; the flexplate will not be held against the crankshaft properly. Damage will ensue.
5

Stick a large flat-head screwdriver through one of the slots toward the outside of the flexplate. The end of the screwdriver should rest against the engine block. This position will keep it from moving when you torque the bolts.
6

Use a torque wrench and socket to torque the bolts to the factory specification for your specific engine and transmission. Torque the bolts in a crisscross pattern, similar to how you would tighten lug nuts.

 

[TigerVette]

the stock flex-plate is a 153 tooth internally balanced design, the 168 tooth flex plate WILL clear the stock bell housing and work but you'll need a different starter and in most cases headers and other clearance issues will restrict your choices to the high torque mini starters

Thanks Grumpy! Yes, I've got a new mini starter and headers - so I'm set there.

any issue with torque converter on the different 400 flexplate?

 

[grumpyvette]

the stock flex-plate is a 153 tooth internally balanced design, the 168 tooth flex plate WILL clear the stock bell housing and work but you'll need a different starter and in most cases headers and other clearance issues will restrict your choices to the high torque mini starters

Thanks Grumpy! Yes, I've got a new mini starter and headers - so I'm set there.

any issue with torque converter on the different 400 flexplate?

http://www.atiracing.com/products/flexplate/flexplate.htm

http://garage.grumpysperformance.com/index.php?thr...
remember to use ARP grade 8 bolts with loc-tite in the threads RED SUGGESTED 271

https://www.summitracing.com/parts/arp-230-7305
http://garage.grumpysperformance.com/index.php?thr...
remember to use ARP grade 8 bolts with loc-tite in the threads RED SUGGESTED 271

https://www.summitracing.com/parts/arp-230-7305
read thru these
http://www.jegs.com/i/JEGS-Performance- ... Id=1359671

in almost all cases, it bolts up and runs fine, but in a few odd cases you'll have clearance issues, due to converter diam. or the converter bolt pattern on the flex plate will be a problem, so ask if your converter bolts to the flex plate you order before you order one, and be sure the correct side faces the crank flange(usually its marked)

viewtopic.php?f=71&t=2400&p=6331#p6331


DZAUTO POSTED THIS UINFO
The SB400, and all engines that are built with a 400 crank, such as a 383, require BOTH a harmonic balancer and a flywheel/flexplate which have additional weight added to one side. Thus, they are referred to as EXternal balance. The reason is because SB blocks do not have enough internal room in the crankcase for bigger crank counter weights to clear. Therefore, the added weight for balancing a 400 crank is added to each end of the crank on the balancer and flywheel.
Below is a comparrison of a regular 350 and a 400 balancer. As can be seen, the 400 balancer has a BIG notch about half way around the outer ring.

the 85-earlier and 86-later cranks have a completely different bolt pattern on the rear of the crank, which requires different flywheels. The hole in the center of the two flywheels is also a different size. So you MUST match the year model flywheel to the crank you're using.
Below are pictures of a regular (neutral balance) flywheel and a flywheel for a 400 with the added weight on one side.

IF YOUR GOING TO PUT THE TIME AND EFFORT INT A DECENT ENGINE BUY AN SFI CERTIFIED FLEX-PLATE< STOCK ONES ARE SO THIN THEY CRACK CONSTANTLY IF SUBJECTED TO HIGHER STRESS

the next question that comes up,
("can I re-use my 350 damper and flexplate or flywheel ?")

OEM flex plates are far thinner and more flexible than the SFI certified flex-plates , so they are far more likely to crack and split over time, sometimes a small crack can make a constant banging noise thats hard to isolate , other times it rapidly causes a failure that fairly easy to locate :mrgreen: :roll: