68 Impala two issues

I have a 68 Impala with a SBC with a tremic 5spd. I'm putting a BBC in and want to know if the engine mount towers are the same for a BBC. Will the engine and trans sit back any further in the engine bay or cause any problems with trans crossmember not bolting up in the same location.

I also would like to know if I use a long water pump instead of the short one, will I have any clearance issues with the fan hitting the radiator. I'm planning on using a serpentine belt and pulley system. I know the 68 came stock with the short, but I would like to use the long if there's enough room.

68's came with BB's. If your changing from SBC to BBC you will need to change your frame mounts to BBC.
As far as useing a long pump. Yes you can but you will loose or have to modify your fan schroud and radiator spacer.

The dimmensions are close to the same between the BBC and the SBC the mounts. The BBC was an interlocking design before the recall of 1968 mandated a change, and because the mount was thicker the frame stands are shorter to compensate.

If you use a regular non-interlocking SBC motor mount from 1958-'68 then the BBC will fit just fine if you can find the correct 1958-'68 SBC motor mount to use (most autoparts stores sell only the wrong size 1969-'72 variant that they think is what you need) on your existing SBC frame stands.

big Dave

The main problem you will encounter is that the oil pan will not clear steering or may hit the front crossmember.

I've done this big block swap about 8 mos. ago and engine and frame mount"s worked fine and no hood clearance issue's either. Also to remember if you have power steering like I do watch those hoses around manifolds. I am using the sm. block hoses now but I"ll be wrapping them in header wrap soon just for insurance.

Quick question then, since you have done this conversion. I have a 454 that I am going to drop. It had a 327 in there with the 400. The transmission shouldnt move at all, just the engine push further forward. Did you use the same towers? and then just mount the 454 mounts to that? The 68 came with a 454, so I can't imagine that there should be too much to put one in. Where did you find the new motor mounts?

For me I used the small block engine mounts for now, but I have a set of mounts for a BBC Corvette. The only differance that the Corvette mount have a perfect through hole for the mounting bolt and they are the interlocking style, and they are also the short type so you will not have hood clearance issues. If you go this route you may have to elongate the holes for it to line up on the stands, like I'll have to...I test fit mine before I put them in but did'nt have the time to modify them. And yes you will need a BBC oil pan or an aftermarket one that works with rear steering components. ( 454's were not available in 68' but I think they were in 70'/71' after the 402's--which is what I have installed-- died off.)
I can't remember if I had to move the trans mount because I allready had both factory bracket positions on the frame of my convert.
BTW. tower's are the same.

In 1968 theonly big block Chevy engine installed was either a 396 or a 427, both of which share the same block dimensions as the 454 which was not introduced until after 1969 (you could convert a 427 engine into a 454 starting in 1969 by buying the LS-7 crank and pistons over the service counter beginning in 1969). The reason you will have oil pan fitment issues is after 1973, the Big Block Chevy (BBC) was only available in light duty pick-up trucks and medium duty sized trucks and busses. A pan off a truck is too deep to clear your front cross member in a car.

In 1968 GM experienced a factory recall about their motor mounts. In 1969 all engines used the same motor mount interlocking style as were previously used with only the BBC or a hot SBC (they also changed the width of the motor mount stand in 1969 to keep you from using the previously recalled "unsafe at any speed" motor mounts that were used in all Chevrolets from 1958 to 1968).

If you retain your factory SBC stands for an under 300 horsepower hydraulic tappet equipped engine (which includes all of the small block Chevys factory installed in an Impala) Then you may buy an aftermarket polyurethane interlocking motor mount to fit that will keep your BBC exactly where it should be sitting. There are factory made BBC that were shorter to accommodate a factory rubber interlocking motor mount that was thicker than the vulcanized non-interlocking motor mount that failed in service prompting the factory recall. The problem is that they are not reproduced in the aftermarket and they are out of production now with Chevrolet so you can not buy them as a service part.

You are also correct in your assumption that the front face of the bell housing is identically located in the same place with every Chevy motor made regardless of size. So any motor will bolt in front of any transmission without that parting line between the rear of the motor and the front of the bell housing moving at all. You shouldn’t have to move the transmission back or forward as it will align with the factory holes if you use Impala (B-body) frame stands and not the Corvette frame stands (which are out of a Y-body with a different frame than the Impala).

Big Dave

I may not have been clear in typing although was right in my head :) I was meaning the engine mounts for a Corvette on Impala stands......oooops! :)

Big Dave,
Thank you for the great breakdown. So, would I be correct in my assumption that a 396 mount would work for my application? As far as I am aware, the BBC has the same motor mounts externally throughout the years. So a aftermarket block should have the same external mounts as a stock 68' 396? As for my specific issue, a 67' 396 mount would work perfectly for me then. I should be able to mount the big block to my stands by using a reproduction mount for a 67' BBC 396 or 427 through Classic or Sinclairs. As for the Oil Pan, I bought a pan that was designed for a 68' 427. This should eliminate any clearance issues... I hope!

Yes if you can find a BBC motor mount for a 1965-'68 396 or 427 from a reproduction house it will fit like a glove.

An example of a frame stand that bolts to the frame with either three or four bolts depending upon model and year and it looks similar to this:

http://i45.photobucket.com/albums/f63/3454545/BBCFramestand70-72CamaroKW324-1.jpg

The motor mount always bolts to the block and looks like this before 1973:

http://i45.photobucket.com/albums/f63/3454545/MotorMountSideView.jpg

http://i45.photobucket.com/albums/f63/3454545/MotorMountTopView.jpg

The difference between a truck oil pan on the left and a car oil pan on the right.

http://i45.photobucket.com/albums/f63/3454545/15panchange.jpg

Big Dave

I am going to reuse the stands that held the 327 in place. I found a set of mounts on-line for a 67' 427 that looks exactly like the ones you posted. They should fit like a glove, I hope! Thank you. Next will be getting everything to fit right in there. A after market radiator and GM Type II Power Steering Pump. Do it right the first time.