Engine swap question
06-30-2009, 06:23 PM
#3
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Join Date: Jun 2001
Location: TX
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There are some things to look out for. 1st is the motor mounts. Just use the existing ones if they are in good shape (305 and 350 blocks are identical externally), but if one is bad ( common to find the driver's side fubar during a swap) be aware that Chevy used different mounts even among small blocks.
The differences mean the motor mount (part with the rubber) must match the mount tower (metal part). Saddle width is the problem. Can't install a narrow mount over a wide tower, can put a wide mount over a narrow tower, but it'll be loose on there. The 305 never came stock in a 67 so you can't just go to the parts store and ask for a 67 mount for a 305 if you need a replacement.
Just take the existing motor mount to a cooperative parts store and find a SBC mount with a matching saddle width. If they only carry one width for a 67, look at what they have for a 69 or 71. 72 up mounts have a much different mounting system, so don't look at anything for a 72 up.
Also, depending on the year of the 305/350s used, you might have problems with the exhaust manifold and dipstick. Some newer 305s used manifolds with the passenger rear bolt in a position father to the rear than older SBCs. Heads had an extra bolt hole at the ends for it, older heads are missing this bolt hole. If who ever did the 305 swap used that type manifold, and the replacement 350 doesn't have the end holes, you can run the manifolds with the last bolt missing, but you risk a leak.
Also that style manifold can block the dipstick hole depending on the year of the 350. Older SBCs had dipstick on the driver's side, newer on the passenger side. Headers will cure both the bolt hole and the dipstick issues.
Last, early engines had a 2 piece crank main seal, later have a one piece. Flywheel bolt patterns are different, one piece uses a smaller bolt circle. If replacement engine already had it's own flywheel/flexplate and matching starter, no problem. But if it doesn't, you have to make sure flywheel will bolt on.
There are 2 sizes of flywheels, 153 teeth & 168 teeth. 305s typically used the small wheel, 350s the bigger one. Either is ok as long as it bolts on, has converter bolt pattern needed, and starter used matches the flywheel. The starter for the small wheel uses straight bolt pattern, one for the big wheel uses an offset pattern. Blocks should have bolt holes for both patterns (rare blocks are missing one bolt hole for the offset starter). Starter bolts are special in that they are knurled and shanks (part without thread) extend slightly thru the starter nose so that they index into the block to positively align the starter. If you need replacements, parts stores have them in the HELP section. The 2 types of starters use different length bolts.
Welcome to the world of engine swaps, and to the board.
The differences mean the motor mount (part with the rubber) must match the mount tower (metal part). Saddle width is the problem. Can't install a narrow mount over a wide tower, can put a wide mount over a narrow tower, but it'll be loose on there. The 305 never came stock in a 67 so you can't just go to the parts store and ask for a 67 mount for a 305 if you need a replacement.
Just take the existing motor mount to a cooperative parts store and find a SBC mount with a matching saddle width. If they only carry one width for a 67, look at what they have for a 69 or 71. 72 up mounts have a much different mounting system, so don't look at anything for a 72 up.
Also, depending on the year of the 305/350s used, you might have problems with the exhaust manifold and dipstick. Some newer 305s used manifolds with the passenger rear bolt in a position father to the rear than older SBCs. Heads had an extra bolt hole at the ends for it, older heads are missing this bolt hole. If who ever did the 305 swap used that type manifold, and the replacement 350 doesn't have the end holes, you can run the manifolds with the last bolt missing, but you risk a leak.
Also that style manifold can block the dipstick hole depending on the year of the 350. Older SBCs had dipstick on the driver's side, newer on the passenger side. Headers will cure both the bolt hole and the dipstick issues.
Last, early engines had a 2 piece crank main seal, later have a one piece. Flywheel bolt patterns are different, one piece uses a smaller bolt circle. If replacement engine already had it's own flywheel/flexplate and matching starter, no problem. But if it doesn't, you have to make sure flywheel will bolt on.
There are 2 sizes of flywheels, 153 teeth & 168 teeth. 305s typically used the small wheel, 350s the bigger one. Either is ok as long as it bolts on, has converter bolt pattern needed, and starter used matches the flywheel. The starter for the small wheel uses straight bolt pattern, one for the big wheel uses an offset pattern. Blocks should have bolt holes for both patterns (rare blocks are missing one bolt hole for the offset starter). Starter bolts are special in that they are knurled and shanks (part without thread) extend slightly thru the starter nose so that they index into the block to positively align the starter. If you need replacements, parts stores have them in the HELP section. The 2 types of starters use different length bolts.
Welcome to the world of engine swaps, and to the board.
Last edited by angel71rs; 06-30-2009 at 06:28 PM.
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