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post #1 of (permalink) Old 11-30-2002, 01:56 PM Thread Starter
 
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Swapping 305 and 350... Any tips?

I am taking the 350 out of my 77 w/ sm465 and installing it in a 85 w/ th350. The 85s got a 305 that I am putting in my 77 to mess around with. I know the flywheel and flexplate will need swapped. He wants to keep his AC so that will be swapped, what brackets need swapped with it? I know that there are 6 bellhousing bolts, 3-4 torque converter bolts (the 85 only), starter bolts and the two motor mount bolts that need to be removed. Does anything (other than hoses and fuel lines and some wires) need to be removed to make the swap any easier or is that it? The clutch fans will be removed to clear the rad easier too. While the engines are pulled, how much harder would it be to do the main seals on the crank? Stupid question: how do I identify main seals? Thanks in advance...
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post #2 of (permalink) Old 12-01-2002, 12:40 AM
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Re: Swapping 305 and 350... Any tips?

kevin,
only one thing.... pull the radiators!!!!! much easier than buying new ones when your long time buddy pushes instead of pulling
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post #3 of (permalink) Old 12-01-2002, 02:50 PM
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Re: Swapping 305 and 350... Any tips?

gottagofast took it right out of my mouth!! [img]images/graemlins/grin.gif[/img]
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post #4 of (permalink) Old 12-02-2002, 06:26 AM
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Re: Swapping 305 and 350... Any tips?

You've missed a number of things. The flywheel on the 77 is a larger bolt pattern and center hole than the flex plate on the 85. They won't swap. When GM went to the 1-piece rear main, they changed the bolt pattern on the back of the crank. You'll also need to put a pilot bushing in the back of the crank of the 305. Passengers side exhaust manifold of the 85 uses the "7th" hole in the block (furthest back towards firewall). The 77 block probably doesn't have this tapped. So, a new manifold will be required. Drain and take out the radiator. yes, pull the starter. There are 3 bolts on torque converter. That's all I can think of right now.
post #5 of (permalink) Old 12-02-2002, 05:46 PM Thread Starter
 
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Re: Swapping 305 and 350... Any tips?

Thanks ILNDR for those great tips, they will be put to good use. for the exhaust, could I use the 77 manifold on the 85 with no worries? If I can't get the 305 back into my 1/2 ton without a bunch of problems, thats no big deal, I just want the 350 to work in the 85
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post #6 of (permalink) Old 12-03-2002, 05:52 AM
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Re: Swapping 305 and 350... Any tips?

The passengers manifolds are different. The 305 uses the 7th bolt hole, and the exhaust exits in front of the last exhaust port. The 350 manifolds use the 6th bolt hole, and exits behind the last exhaust port. Thus, making the "Y" pipes different. If you had converted to Headders, or dual exhaust using manifolds, you won't have a problem. If you change the "Y" pipes with them, you shouldn't have much trouble either. I went through a similar swap, (350 in an '86 in place of the 305) one Thanksgiving weekend a few years ago. Needed the truck back on the road Monday morning. These exhaust problems are what held me up. I ended up bringing a set of cheap headders and some pipe Monday night, and threw them in. It was a lot easier than screwing with the manifold/Y problem.

Good luck to you.
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