My '68 with an '81 engine/tranny swap

[jpusmc1341]

Just thought I would post how my swap is coming along and maybe help others or possibly someone can point out something I may have overlooked. I got a deal on a good running 305/700r4 combo which I am currently installing. I used the thread by roj2323 for installing the '81 motor towers with clamshell mounts and it went well, only I had to drill a hole for the rear top bolt on the frame. The distributor sits a few inches from the firewall, the 700r4 sits good. I bought an aftermarket tranny crossmember that fit in the stock mounting holes in the frame. The driveshaft was shortened about an inch and a half. So far that's as far as I have gotten. I have a lokar shift linkage on order and a new column indicator. I am currently wiring up the engine. Once those are done/installed I can install rad and shroud to see how the fan fits. I'll try to keep updating if I can remember to do so.

[jpusmc1341]

Here is the 700r4 clearance with the crossmember. How the driveshaft yoke sits and the carrier bearing sits. I installed the driveshaft and measured from the center of the carrier bearing holes to the end of the tailshaft housing, plus I marked the yoke where it sat in the seal to take to the driveshaft shop. I think it worked out to be an 1-1/2 shorter. So far the only problem I think I will run into is my headers are about dead on center to my crossmember. That may make for routing issues

[mechanicalman]

From your picture, it appears the transmission is at an angle like going down-hill in relation to the cross-member. First, make sure what the cross member is for, 67-72 or 73-87? How does the new cross-member stack up height wise (mount pad) compared to the original?

I have read other members state that when you use the later model towers with the clam-shell mounts that the engine will sit too high.

I urge caution on this as I believe you may be creating improper driveshaft angles and possibly some driveline vibrations/instability.

The only reasonable way to correct this, IMO, is to lower the front of the engine. You could put your old towers/mounts back in; if you have already shortened your driveshaft, just re-drill the mounting holes on the frame for your old towers and the long water pump on your new engine should get your fan close. OR get some 1972 big-block towers that use the clamshells.

Otherwise, raise the trans tail-shaft, raise the carrier bearing, and adjust the pinion angle to the new carrier bearing location (angle shims to the trailing arms) or if it's a GMC angle shims to the leaf springs. But you might run into clearance problems with the floor of the cab.

If the engine/trans is tilted too far, your fluid dipstick readings may not read correct, and the fan shroud could get complicated. Electric fans?

[jpusmc1341]

Mechanicalman, I do wonder if the engine is too high, myself. I am still not 100% convinced it will all work. When I saved this truck from going to the crusher, it was missing all the v8 mounts such as motor mount towers and crossmember, which is why I used the newer style. I tried finding orginal motor mount towers but could not. The crossmember is specifically for a 68 c10 700r4 install. So if the engine does sit to high I will have to continue my search. If you know anyone that has a set, I'd be interested also a solid drag link would be nice to get rid of the ram assist set up. Thanks for the reply

[mechanicalman]

Strongly advise you to take another shot at finding the early style engine mount towers. Clearly the best route to go to take care of your problem, and even if the driveshaft is already shortened you can re-drill holes like I said and your long water pump fan setup will maybe come close to being right with your shroud. Surely someone has a set, lots of parts available near you.

https://stjoseph.craigslist.org/sear...ry=67-72+chevy

Also, a 68 should not have the ram assist power steering. There appears to be a number on the frame just ahead of the driver's side mount tower, part of it is in one of your pictures. If you give me all those numbers I may be able to identify what year the frame is.

I suspect it might be an earlier model. Are you sure your truck is 68? Does it have side marker lights, big or small back window? Makes a difference when you try to put a power steering gear on the frame.

BTW, when you start driving it with the 700r4, make sure you have the torque converter clutch (TCC) working otherwise you will burn up the overdrive clutches and contaminate the entire trans. You can drive it without the TCC, but you must drive it in "drive" not "overdrive" (3rd gear, not 4th).

[mechanicalman]

BTW, I used to live in St. Joe. Grew up in Stewartsville.

[jpusmc1341]

I have decided I don't like the pitch of the engine. If I don't come across a set of oem then I'll just go to the aftermarket tubular type. I wonder if I6 mounts would work, my buddy has a set of them. The truck has a large back window, it has dummy marker lights on fenders, they are lenses but the hole for a bulb doesn't exist. The number on the frame says 8J140240. I had removed the assist set up at first and installed an integral gearbox but I couldn't find a drag link so I went back with the assist.

[mechanicalman]

Originally Posted by jpusmc1341

I have decided I don't like the pitch of the engine. If I don't come across a set of oem then I'll just go to the aftermarket tubular type. I wonder if I6 mounts would work, my buddy has a set of them. The truck has a large back window, it has dummy marker lights on fenders, they are lenses but the hole for a bulb doesn't exist. The number on the frame says 8J140240. I had removed the assist set up at first and installed an integral gearbox but I couldn't find a drag link so I went back with the assist.

It's a 68 for sure by the partial VIN, the power ram steering assist maybe an early production left-over, not sure, many others on this forum know all the little ins and outs. If you have had a power assist gear on it, and it bolted flush to the frame, you are good to go on that.

I6 mount towers will work, they are designed to go in the rear-ward set of holes on the frame. I say get them and make them work you have already shown you have what it takes to do that. Just buy the standard V/8 mounts for the 68-72 small block.

If you put the I6 towers in the factory rear holes, then the linkage bracket on the frame has a 50/50 chance of being in the right holes. There is a rearward set of holes and a forward set of holes in the frame for the towers and also a rearward and a forward set of holes for the linkage bracket on the frame so you may have to move that back. If the Lokar is an aftermarket shifter, you wouldn't have to worry about this unless you need the linkage to run the indicator.

Now did you already shorten the driveshaft? Looks like you have about an inch and a quarter driveshaft yoke sticking out. When you install the I6 towers, notice the holes are slotted on the top rail not sure about the bottom hole but you could slot it to match. "Cheat" the towers forward as far as you can and polish the driveshaft yoke for the seal to ride on and you might get away with it. Again, if non-column shifter, you could just re-drill and mount it where it lays with the yoke where you want it about an inch out, but you might need the linkage for your column indicator. You can get away with less yoke to trans clearance because it's a 2 pc driveshaft, but you don't what it bumping.

It can get complicated. Tell me more about the trans linkage/column indicator you are going to use.

[jpusmc1341]

I will grab those I6 towers and try them. I did have the driveshaft shortened about an inch and a half, so I should have some play in that area. Im using the orginal column shifter. I have brackets for both a th350 and a 700r4. The linkage my buddy is using in his 71 is the lokar linkage, and has not had any problems so far.

[mechanicalman]

Originally Posted by jpusmc1341

I will grab those I6 towers and try them. I did have the driveshaft shortened about an inch and a half, so I should have some play in that area. Im using the orginal column shifter. I have brackets for both a th350 and a 700r4. The linkage my buddy is using in his 71 is the lokar linkage, and has not had any problems so far.

Oh hey that's a nice linkage set-up, and appears to be just what you need. So, you can put the I6 towers in whatever position you need to get the driveshaft clearance between the yoke and the trans housing correct and not have to worry about the shifter bracket as you don't need it with the Lokar. I think you about got this whipped.

I like it.

Now, it would seem to me you have it down to the fan. Hopefully the blade diameter will match your shroud, and you can play with spacers maybe to get the blade sunk into the shroud just right. Optimal airflow has the fan about halfway sunken into the shroud, and maybe a little deeper is a little safer. You don't want it hanging out, and you don't want it sunken in too far. Install the trans mount without shims and check the angle of the fan in relation to the shroud. You can raise the tail to square it to the shroud, but you would have trouble lowering it. Just a little shim can make a lot of angle, and if the angle is off because of the aftermarket cross-member, to correct it to the shroud would also most likely move it to a better drive-line angle.

Hedman makes nice collector pipes with S-curves that might get you under the cross-member or maybe over it if it sits low.

http://blog.hemmings.com/index.php/2...eader-hookups/

[mechanicalman]

Originally Posted by jpusmc1341

Just thought I would post how my swap is coming along and maybe help others or possibly someone can point out something I may have overlooked. I got a deal on a good running 305/700r4 combo which I am currently installing. I used the thread by roj2323 for installing the '81 motor towers with clamshell mounts and it went well, only I had to drill a hole for the rear top bolt on the frame. The distributor sits a few inches from the firewall, the 700r4 sits good. I bought an aftermarket tranny crossmember that fit in the stock mounting holes in the frame. The driveshaft was shortened about an inch and a half. So far that's as far as I have gotten. I have a lokar shift linkage on order and a new column indicator. I am currently wiring up the engine. Once those are done/installed I can install rad and shroud to see how the fan fits. I'll try to keep updating if I can remember to do so.

BTW, take that small wire you have going to the HEI and run it as an activation wire through a HD relay using power directly from the battery to run the HEI using a heavier wire. Summit has a trick connector that plugs into the HEI with power lead and tach lead. You should probably go ahead and make a junction block between the battery and the starter for add-ons starting with this and the choke, etc. The stock ignition switch will not handle the HEI. Others may say they have ran it, and it will run but it won't put out strong spark and will be weak when hot cranking.

http://www.summitracing.com/parts/acc-170072

http://www.summitracing.com/parts/ms...MVvhoCJxLw_wcB

[jpusmc1341]

Ok, thanks for the links, those s-curve collectors are just what I need. I do plan to run HEI similar to what you stated. Thanks for the help, you have saved me some headaches. I'll update this as I go along. It may take a bit as I'm a traveling mechanic so I don't always have time to work on this beast. Thanks for the help thus far. I'll pm if I have more questions.

[mechanicalman]

Originally Posted by jpusmc1341

Ok, thanks for the links, those s-curve collectors are just what I need. I do plan to run HEI similar to what you stated. Thanks for the help, you have saved me some headaches. I'll update this as I go along. It may take a bit as I'm a traveling mechanic so I don't always have time to work on this beast. Thanks for the help thus far. I'll pm if I have more questions.

Don't hesitate. I daily drove my 72 for 23 years and still drive it as a back-up. I'm restoring a 68 SWB now as well. This forum has been a gold mine of information for me.

[jpusmc1341]

Update on the old 68. I ended up using the 6 cyl mounts but moved them forward a bit, drilled my own holes. It sits great. The body had more rust and bondo than I thought so I quit putting cosmetic money into it and am now just getting it road worthy and it's close. To recap, I installed a 82 model 305 with 700r4, shortened driveshaft, headers, redid all brake components (manual drum) and a ton of other stuff. I have about 6 months and 3k into a daily driver, thats probably worth about 1500, but it is coming along. I will try to get some pics up. Really all I'm lacking now are new shocks, power booster for brakes and upgrade the ram assist steering to solid draglink with integral steering.