Is an 86 shortblock the same as an 87 and up shortblock? I know the heads are different. I got a good one for free and I'm going to use it because mine is starting to burn oil. I just wanted to make sure I wouldn't have any problems switching all my stuff that I have now over. Thanks.
No they are not the same. The pistons do not have the larger valve reliefs that the 87's and up do. If you are planning on running this with the combo in your sig. then you will most likley have P/V clearence issues.
shouldnt have any problem with the stock cam the 86 pistons dont have any valve reliefs at all so ull probally get a slight increase in compression too
The bottom end of the motor is still the same, just the pistons are differant. They are still forged, but like sleeper said they have no valve reliefs. They are a true Flat top. the TW heads have a differant valve placement and clear on the 86 block. Search on the Corral. there have been quite a few guys run the 86 motor and the TW heads with decent cams. The stocker will clear, but i donno about the TFS cam.
Also, if it is an 86 non H.O motor, it will have the same style pistons as a 87-93 car, except they are hypers like the 92-93's. Only the 86 H.O. cars had these pistons.
I wouldn't think there would be a clearence issue with a stock cam but just to be safe I would check with some clay and make sure before you put all those other expensive parts back on.
Maybe someone has already tried the combo of TW's with an 86 block and will chime in for you.