86" Sierra K2500 motor mounts not lining up

[fang508]

So I have this 86 sierra k2500 that used to be a diesel. When I bought it there was a tired 350 in it with a lot of small but costly issues so I decided to put a sbc 350 crate motor in it. Before putting the engine in I ordered these mounts through Classic Industries that turned out to be the wrong set http://www.classicindustries.com/pro...ts/t83099.html . Instead I should have bought these http://www.classicindustries.com/pro...ts/t83132.html . The difference between these that the mounting holes do not line up 100% on the first set of new mounts while the 2nd set does. From what I understand that the 2nd set of mounts were designed for diesel/454 k2500s. The sbc clamshells that bolt to the engine meshing with the crossmember mounts has a 1/2" diameter hole. However, the center bolt on my diesel mounts is 7/16" diameter. The P/O had 7/16" bolts going through the 7/16" diesel mounts but since he had the a sbc the clamshells holes were 1/2" which explains why the engine vibrated and bounced around 1/4"~1/2" when idling. So my question is.. would it be a good idea to drill the 7/16 center hole on my mounts to ame them 1/2? I would only be taking off 1/32" of material off on all sides and there would still be a rubber liner in the mount. Perhaps if I didn't have an original diesel truck this probably wouldn't be an issue. Thanks, and sorry for the wall of text.

[D13]

If I understand, you have an ex-6.2l diesel truck which now has a SBC in it.

The diesel and 454 use one set of clamshell mounts, the SBC uses a different one. You have that sorted out and have the SBC mounts.

Your problem is that the other side of the mount has a smaller bolt hole? And you would like to drill it out?
If everything lines up, and it's 1/16", and it's a mild motor, it shouldn't be a problem. On the other hand GM made a ton of SBC powered trucks, so the mount shouldn't be rare.

Do you have the trans braces? IIRC those bolt to the mounts and that mount might be slightly different.

[JIMs70GMC]

Search "recoverteam" on you tube. This guy had the same issue going from diesel to SBC in a 88 V30. The towers are different and he just swapped the towers from a SBC truck to the K30 and kept on getting up with his energy suspension mounts.

[fang508]

Originally Posted by JIMs70GMC

Search "recoverteam" on you tube. This guy had the same issue going from diesel to SBC in a 88 V30. The towers are different and he just swapped the towers from a SBC truck to the K30 and kept on getting up with his energy suspension mounts.

That is the exact problem I had thank you very much for finding this. I think I may have fixed my issue with fitting my mounts. I did some reading on poly inserts for mounts that require you to drill the holding rivets out of the mount shells. So I did that on both sets of mounts and used the rubbers with 1/2" hole (sbc) and put them in the the mount shells that had the 7/16" hole (diesel). Now I can use my 1/2" bolts, washers, and block clamshells. The only difference between the rubbers of both sets of mounts is inside hole diameter. So, I think for the angle and height of the towers I should be ok especially since the crate engine and old engine are the same gen. I am hoping it just slides in..

So what am I to do if I can only get one pin to go in on the mounts? I have read many stories of people getting one side to line up perfectly but not the other.