Intake bolt angle and angle of spacer needed for SBC intake swap

I know I've seen this info covered in one form or another but I figured I'd post it here for visual aid.
As you can see in the picture below, the angle the intake bolts are drilled and tapped on the lt1 heads are 72° when measured from the intake deck (not sure of its technical name) and the intake to head bolts. When paired with an SBC intake that is drilled at 90°, you would need to spot face the intake 17° or have some 17° shims made (107°-90°).


If this is contradictory to anything someone else has found, please feel free to call me on it. I arrived at these numbers by measuring many different ways. For some reason I recall hearing an 18° shim is what's needed but every way I've ran it, its came out to 17°.
http://img.tapatalk.com/d/14/06/07/apure2a8.jpg

http://img.tapatalk.com/d/14/06/07/aje3y3uh.jpgGood visual man. I had a local machine shop make my spacers at 17*. And I mean really, if its 1* off, its prob not really gonna make a dif... haha

Making you silky smooth...

Probably not. But I'm glad they were made 17°. That tells me my numbers must be close!

Good info here for anyone wanting to convert to a SBC intake. Isn't there a difference in bolt pattern as well?

There definitely is. There are bolts in the center that are way off (and most just omit because they don't seal anything on the lt1 heads). The 4 very outer bolts are in the correct location and the next inward bolts from them need moved. @ZOHAN (or anyone else) if you know what that distance is, feel free to chime in. I'll be posting up in a few days the reasons for what I'm drawing up. ;)

Yup, I redrilled my center holes but couldn't get the bolts to fit in past the intake runners (right frickin next to them) so I didnt use the centers. The 4 outer bolts are in the correct location but at least with my intake, redrilling them put the hole right at the outside of the metal. So I used the washer to support as well, can kinda see in the pic above how the intake curves in way before the outside of the washer. The second set of holes front and rear, are about 3/8-7/16 further apart on the LT head. Or if you are having any head work done, you could always have the heads redrilled for the gen1 bolt pattern. I already had my heads mounted when I decided on the single plane

Making you silky smooth...

Or for a nominal fee id build one for someone. Haha

Making you silky smooth...

Quote:

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Originally Posted by firebird_1995

I know I've seen this info covered in one form or another but I figured I'd post it here for visual aid.
As you can see in the picture below, the angle the intake bolts are drilled and tapped on the lt1 heads are 72° when measured from the intake deck (not sure of its technical name) and the intake to head bolts. When paired with an SBC intake that is drilled at 90°, you would need to spot face the intake 17° or have some 17° shims made (107°-90°).


If this is contradictory to anything someone else has found, please feel free to call me on it. I arrived at these numbers by measuring many different ways. For some reason I recall hearing an 18° shim is what's needed but every way I've ran it, its came out to 17°.
http://img.tapatalk.com/d/14/06/07/apure2a8.jpg

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I wanted to thank you for posting this, your info will be usefull for my single plane swap. http://www.forum.uni-hannover.de/ima...lies2/beer.gif

nice it doesnt sound like much of a difference till you see the spacers... damn

great info.
:claps:

I got a super vic jr that I spot faced the bolts to work without the spacers. Sold the motor but still have the intake.