69 vs.70 340 relative to damper TDC position

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jawbone

jawbone

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Trying to understand the physical difference in place between the 1969 and 1970+ 340 engine. I know the timing chain cover is different but what else. Are the cranks keyed differently which would mean different part numbers. Cannot find part number for the 70 year crankshaft. My parts book does not have an engine section. The 69 is 2843868. May be cam keyed differently. If anyone has time to respond please do.
 
The different year dampers and timing covers can be used together, but you will need to find true TDC on #1 and re-mark your balancer to match your timing tab or install a timing tape (you should do this regardless when using a factory balancer to confirm that the outer ring has not slipped- if the ring has slipped, the balancer is junk). '69 and earlier balancers, and '70 and later balancers are marked differently by ~90*.
Beware of differently weighted balancers between any of the neutral balanced engines, and the externally weighted balancers of the LA360, late '72&'73 340s, and the 5.9 Magnum engines- none of which are interchangeable.
 
oldkimmer said:
Their keyed the same. U have to use the matching damper and cover together. 69/69 70/70 kim
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Oh so the damper is different. Went down the damper path with my parts house but they were no help. Makes the most sense but could not get confirmation. ATI does not differentiate between years. Would not know who else to check. Summit does not do a good job either. Thanks for the response.
 
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Professor Fate said:
The different year dampers and timing covers can be used together, but you will need to find true TDC on #1 and re-mark your balancer to match your timing tab or install a timing tape (you should do this regardless when using a factory balancer to confirm that the outer ring has not slipped- if the ring has slipped, the balancer is junk). '69 and earlier balancers, and '70 and later balancers are marked differently by ~90*.
Beware of differently weighted balancers between any of the neutral balanced engines, and the externally weighted balancers of the LA360, late '72&'73 340s, and the 5.9 Magnum engines- none of which are interchangeable.
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This is all making perfect sense but was not sure. Built my 70 340 as a 1970 partially due to my lack of understanding. No regrets. Everything worked out. The 90* difference rings a bell from previous reading. Thanks for responding.
 

It's really not an early a body question. I was going to move this to small blocks, but since you received good information.
I will leave it here. No harm. Good luck on your project.
 
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AAR 64Valiant said:
It's really not an early a body question. I was going to move this to small blocks, but since you received good information.
I will leave it here. No harm. Good luck on your project.
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Thanks. I had noticed that after it was posted and your right, got my question answered successfully.
 
I picked up a 68 damper for use on my later 340 if i dont find the correct damper Ill use it with a timing tape I plan on degreeing the cam so inding tdc is in the plan.
 
Dartswinger70 said:
I picked up a 68 damper for use on my later 340 if i dont find the correct damper Ill use it with a timing tape I plan on degreeing the cam so inding tdc is in the plan.
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That will work. Make sure the outer ring has not slipped. That damper is getting older as I type.
 
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