flexplate - The 1947 - Present Chevrolet & GMC Truck Message Board Network

crosby · 07-23-2005, 05:11 PM

I have an 87 K20 pickup (on a mid 70's frame), and a 350 I pulled out of an 87 Jimmy (FI). The pickup is an auto, the Jimmy was a standard. I bought a flexplate for the engine, and it turns out that the hole in the middle and the bolt circle is too big for the crank. Is there a different crank for standard shift engines? Also, when installing an engine, do you bolt the flexplate to the torque converter AFTER you install the engine? Thanks very much for your help guys!!

edman87 · 07-23-2005, 07:59 PM

There is a difference in the bolt circle on 1 piece rear main cranks and 2 piece rear main cranks. I have an extra for a 1 piece seal crank, but it is still installed. Andyes, bolt the torq converter to the flexplate after installing trans, otherwise it probably wont seat the torq converter right.

crosby · 07-24-2005, 03:29 AM

Hi Ed, thanks for the message. I am installing the engine only, the trans is already there with the torque converter. Do you mean bolt the flexplate to the converter AFTER I install the engine? The engine is an 87, as is the truck, but the tranny and xfer, etc. are mid 70's vintage (TH400, NP203). Thanks very much for your help!

edman87 · 07-25-2005, 12:08 AM

yup, torq up the flexplate to the crank and drop in the motor, then bolt the flexplate and tconverter together, it will take a while!

crosby · 07-25-2005, 08:23 AM

Thanks again Ed. I guess I should figure out if it's one piece rear main seal or two, it is an 87 (engine). I think that's the year that was different, one year only that they had a certain combination of characteristics. How can I tell the difference between one piece and two (assembled)? I won't be taking it apart to rebuild until I have the new frame ready. It will be a while

Thanks very much for your help!

edman87 · 07-25-2005, 06:34 PM

Not really sure how to tell the difference when motor and trans are in truck. I know there is a diff looking up from bottom, but it has been a while since looking at a 2 piece. With the flexplate removed, it is easy to tell. If engine is 87 smallblock, it is a 1 piece seal. 86 was the year that was different, it had the 1 piece seal, but had non tbi heads. 87-94? were all the same. I can't think of the measurements for the bolt patterns to tll the diff in flexplates when they are laying out. I think it was posted here before, but not sure. Good luck with everything. I would measure the 2 flywheels that I have laying out if I was at home, but have been at hospital for 6 days now with an early baby, but everything is fine. I will be home in 3 days, so if you still need some info, i could get pics and measurements if you need them.

crosby · 07-26-2005, 08:40 AM

thanks Ed. That's not necessary. Hope everything is going well with your new baby. They don't sell parts for those

I have a new flexplate on order, the parts store said the wrong one was ordered the first time. Hope I can make it work because we're tight on money right now, and vacation and the new school year are right around the corner. No money for truck parts

Oh well, I have most of the pieces I need to make it go, so I am happy about that.

Thanks again for everything, best of luck with your new baby! Congratulations!

Slonaker · 07-26-2005, 09:57 AM

'86 and up engines have the one piece rear seal, and use a different flexplate than '85 and earlier.

Slonaker

edman87 · 07-28-2005, 01:08 AM

thanks man, best of luck to you too, my truck fund just took a back seat

07-23-2005, 05:11 PM	#1
crosby Registered User Join Date: Aug 2004 Location: New Hampshire Posts: 437	flexplate I have an 87 K20 pickup (on a mid 70's frame), and a 350 I pulled out of an 87 Jimmy (FI). The pickup is an auto, the Jimmy was a standard. I bought a flexplate for the engine, and it turns out that the hole in the middle and the bolt circle is too big for the crank. Is there a different crank for standard shift engines? Also, when installing an engine, do you bolt the flexplate to the torque converter AFTER you install the engine? Thanks very much for your help guys!! __________________ Crosby 1978 Chevrolet K10 stepside NH

07-23-2005, 07:59 PM	#2
edman87 junk collector Join Date: Dec 2004 Location: above Baton Rouge, LA Posts: 693	There is a difference in the bolt circle on 1 piece rear main cranks and 2 piece rear main cranks. I have an extra for a 1 piece seal crank, but it is still installed. Andyes, bolt the torq converter to the flexplate after installing trans, otherwise it probably wont seat the torq converter right. __________________ '87/89/76 K5 in progress '99 K2500 short crew '91 camaro rs '98 jeep tj '52 willys cj3a

07-24-2005, 03:29 AM	#3
crosby Registered User Join Date: Aug 2004 Location: New Hampshire Posts: 437	Hi Ed, thanks for the message. I am installing the engine only, the trans is already there with the torque converter. Do you mean bolt the flexplate to the converter AFTER I install the engine? The engine is an 87, as is the truck, but the tranny and xfer, etc. are mid 70's vintage (TH400, NP203). Thanks very much for your help! __________________ Crosby 1978 Chevrolet K10 stepside NH

07-25-2005, 12:08 AM	#4
edman87 junk collector Join Date: Dec 2004 Location: above Baton Rouge, LA Posts: 693	yup, torq up the flexplate to the crank and drop in the motor, then bolt the flexplate and tconverter together, it will take a while! __________________ '87/89/76 K5 in progress '99 K2500 short crew '91 camaro rs '98 jeep tj '52 willys cj3a

07-25-2005, 08:23 AM	#5
crosby Registered User Join Date: Aug 2004 Location: New Hampshire Posts: 437	Thanks again Ed. I guess I should figure out if it's one piece rear main seal or two, it is an 87 (engine). I think that's the year that was different, one year only that they had a certain combination of characteristics. How can I tell the difference between one piece and two (assembled)? I won't be taking it apart to rebuild until I have the new frame ready. It will be a while Thanks very much for your help! __________________ Crosby 1978 Chevrolet K10 stepside NH

07-25-2005, 06:34 PM	#6
edman87 junk collector Join Date: Dec 2004 Location: above Baton Rouge, LA Posts: 693	Not really sure how to tell the difference when motor and trans are in truck. I know there is a diff looking up from bottom, but it has been a while since looking at a 2 piece. With the flexplate removed, it is easy to tell. If engine is 87 smallblock, it is a 1 piece seal. 86 was the year that was different, it had the 1 piece seal, but had non tbi heads. 87-94? were all the same. I can't think of the measurements for the bolt patterns to tll the diff in flexplates when they are laying out. I think it was posted here before, but not sure. Good luck with everything. I would measure the 2 flywheels that I have laying out if I was at home, but have been at hospital for 6 days now with an early baby, but everything is fine. I will be home in 3 days, so if you still need some info, i could get pics and measurements if you need them. __________________ '87/89/76 K5 in progress '99 K2500 short crew '91 camaro rs '98 jeep tj '52 willys cj3a

07-26-2005, 08:40 AM	#7
crosby Registered User Join Date: Aug 2004 Location: New Hampshire Posts: 437	thanks Ed. That's not necessary. Hope everything is going well with your new baby. They don't sell parts for those I have a new flexplate on order, the parts store said the wrong one was ordered the first time. Hope I can make it work because we're tight on money right now, and vacation and the new school year are right around the corner. No money for truck parts Oh well, I have most of the pieces I need to make it go, so I am happy about that. Thanks again for everything, best of luck with your new baby! Congratulations! __________________ Crosby 1978 Chevrolet K10 stepside NH

07-26-2005, 09:57 AM	#8
Slonaker Insert Witty Text Here Join Date: Oct 2002 Location: San Antonio, TX Posts: 3,415	'86 and up engines have the one piece rear seal, and use a different flexplate than '85 and earlier. Slonaker __________________ '86 Chevy C10 (Sold 04/19/13 ) Stock '01 Silverado

07-28-2005, 01:08 AM	#9
edman87 junk collector Join Date: Dec 2004 Location: above Baton Rouge, LA Posts: 693	thanks man, best of luck to you too, my truck fund just took a back seat __________________ '87/89/76 K5 in progress '99 K2500 short crew '91 camaro rs '98 jeep tj '52 willys cj3a

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