68 Impala two issues - Impala Tech
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post #1 of 24 (permalink) Old 02-18-2010, 09:18 PM Thread Starter
 
 
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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.
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post #2 of 24 (permalink) Old 02-19-2010, 07:12 AM
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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.

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post #3 of 24 (permalink) Old 02-19-2010, 05:52 PM
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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.

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post #4 of 24 (permalink) Old 02-19-2010, 06:07 PM
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The main problem you will encounter is that the oil pan will not clear steering or may hit the front crossmember.

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post #5 of 24 (permalink) Old 05-08-2010, 10:08 PM
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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.
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post #6 of 24 (permalink) Old 08-05-2010, 05:46 AM
 
 
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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?
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post #7 of 24 (permalink) Old 08-05-2010, 10:52 AM
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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.

Last edited by 68imp; 08-05-2010 at 02:10 PM.
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post #8 of 24 (permalink) Old 08-05-2010, 03:54 PM
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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).

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post #9 of 24 (permalink) Old 08-05-2010, 06:26 PM
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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!
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post #10 of 24 (permalink) Old 08-06-2010, 06:56 AM
 
 
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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!
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post #11 of 24 (permalink) Old 08-06-2010, 11:26 AM
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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:



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





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



Big Dave
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post #12 of 24 (permalink) Old 08-07-2010, 09:03 AM
 
 
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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.
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post #13 of 24 (permalink) Old 10-29-2010, 07:44 PM
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umm....

Great info guys, just wanted to point out that BBC were still offered in full size chevy passenger cars (Impala/Caprice) Big Mike. My buddy has a 75 Caprice Convertible with a factory 454 BBC and I've also seen a 76 Impala 4dr with the factory 454 . Im just sayin....

Last edited by Heartofthacity; 10-29-2010 at 08:03 PM.
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post #14 of 24 (permalink) Old 10-30-2010, 06:35 PM
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As I recently did this swap in my 68', the frame mount's and the Corvette engine mount's will work without any clearance issues. The power steering pump I used was for the small block I had in there but you will have to tweak the hi pressure line to clear the #1 cylinder exhaust part of the stock manifolds, proof is in the pics. if you want to see.
As for the oil pan, I just returned from the Good Guys Rod and Custom here in NC and I passed on up for $20. I was debating but I have one already BUT someone usually needs one eventually....oh well.
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post #15 of 24 (permalink) Old 10-31-2010, 06:40 PM
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Here are some pics. of my set up. I'm using the small block p-steering pump and hose's and small block frame stands.

Last edited by 68imp; 09-18-2011 at 10:51 AM.
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post #16 of 24 (permalink) Old 12-17-2010, 05:22 PM
 
 
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John,

Thanks for the info! The pics are worth a thousand words. Can you take a couple of the towers and the mounts? Just curious to see how you did it.

Alex
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post #17 of 24 (permalink) Old 12-17-2010, 08:07 PM
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The towers and mounts are small block and bolted up as you would a small block. I just changed mounts to the interlocking type (corvette style); that all I did.
Sorry but it is a little cold out there to get on the ground! .
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post #18 of 24 (permalink) Old 12-18-2010, 09:47 AM
 
 
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No worries! Thank you though. I am ordering the mounts today and will be dropping in the motor next week. I am ordering the mounts that will fit a 1968 Impala 396, as they look like the same mounts that the Vette used. I just wanted to make sure that the towers would accept them.

Next comes the fuel tank! Thanks again
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post #19 of 24 (permalink) Old 12-18-2010, 10:38 AM
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If I remember things right, there were to different width mounts. I had the mounts break on my '69 327, and I tried to put on some interlocking mounts I got from a guy. He said they were big block mounts. They would not fit my frame mounts. I did go to the parts store though, and they had both size interlocking mounts in stock. I don't remember the exact details about what was different, it was quite a while ago.
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post #20 of 24 (permalink) Old 12-18-2010, 12:26 PM
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Quote:
Originally Posted by AK99 View Post
If I remember things right, there were to different width mounts. I had the mounts break on my '69 327, and I tried to put on some interlocking mounts I got from a guy. He said they were big block mounts. They would not fit my frame mounts. I did go to the parts store though, and they had both size interlocking mounts in stock. I don't remember the exact details about what was different, it was quite a while ago.
As I said above GM was involved in the first Federally mandated product safety recall of all time. It occured in 1968 and was the result of Ralph Nader and his friends suing GM because the old oil soaked vulcanized rubber motor mounts used on low performance motors were seperating.

GM switched to the interlocking high performance motor mount for all motors made after 1968 but changed the dimensions on the motor mount to keep the old stock on the shelves at parts stores from fitting the new cars. So 1969 to 1972 have different sized motor mounts than 1958 to 1968 cars.

Big Dave
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post #21 of 24 (permalink) Old 12-18-2010, 01:01 PM
 
 
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Thanks Ralph Nader. The more I tear into this car, the more I realize that 1968 was a bastard year for the big boys. Parts seem to be available for 1965-1967 or 1969-1972 without any issues, but 1968 is a killer. The hard part being that Chevy reproduction companies focus more on the 64' to 67' year group than anything else, so finding parts for the 68' is just murder at times.

Thanks for your help though. With a little luck Big Blue will be on the road this summer. I do have a question Big Dave, since you seem to know more about the B body's than anyone I know... Did the 68's come stock with seatbelts? And if so, were the 3 point with the roof mounted belts standard? It is a bench seat (My car is an oddity... I have the original build sheet, and it started out as a 396 SS, with the T-400 tranny and a 12bolt, but at the last minute he ordered the 327 HO).
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post #22 of 24 (permalink) Old 12-18-2010, 01:09 PM
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My '69 had the original non-interlocking mounts. The recall on my car did not involve different mounts (well it did, but only because it broke and needed replaced. It was replaced with the original type non-interlocking). The dealer installed the safety cables, so if the mounts broke again, the cables would limit engine movement. This all happened when the second owner had the car, around '73 or '74 is what he told me. By the time I got the car, one mount was broken again. It went unnoticed for a while because of the cables, that's when I installed interlocking type mounts.
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post #23 of 24 (permalink) Old 12-18-2010, 05:52 PM
 
 
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I purchased the mounts today and they are the interlocking kind. When placed on the towers they are kinda snug, mostly because I had the towers powder coated when I was rebuilding the beast. It looks like I just have to spread the mount a little and then she will fit right on there.

Well, hopefully when I place the engine on there all will align and sit on straight.
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post #24 of 24 (permalink) Old 12-18-2010, 11:52 PM
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The newer 1969-'72 motor mounts are not only tight going over the unpowder coated frame stands but the bolt holes will not line up; so it is nearly imposible to get the bolt through the hole without damaging the threads (I have beaten quite a few in before I figgured out what the problem was).

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