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

**JCzNova** · 10-21-2014, 07:24 PM

Originally Posted by firebird_1995

I'll be posting up in a few days the reasons for what I'm drawing up.

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**BIG CAT** · 10-21-2014, 08:00 PM

To add some information. You can drill and tap the heads to use the std sbc pattern with the exception of the outer 4 bolt holes. At that point you can use unmodified fp1206 gaskets.

**jakesz28** · 11-11-2014, 10:41 AM

Another good reason from drilling the heads to use sbc intake pattern is you can buy gaskets in many different port sizes and gasket thicknesses. Different thickness gaskets can help align ports if needed.

**Ryan Stout** · 11-11-2014, 12:29 PM

I know of another guy running washers like in post 2. If anybody makes a set, sign me up.

**96LT1355Z28** · 05-24-2016, 10:10 PM

Just got my heads back from being converted to SBC intake bolt pattern and I figured I's share some pics to help show difference for future searches. The difference is not only the spacing but also the bolt angle. The LT1 enters the head at an angle compared to the SBC that enters at 90* to the gasket surface.
100_0604.JPG 100_0606.JPG 100_0605.JPG

The bolt spacing is also different, the outside (4) line up (but are at the wrong angle). The center 4 need to be drilled/tapped. It's the ones just outside the runners that are tricky because the holes overlap. Here's and SBC gasket over an LT1 gasket:
100_0608.JPG

LT1 gasket laying over SBC, notice the holes overlapping outside the outer ports:
100_0609.JPG

There's a few ways to make it work, my local shop wanted to use epoxy and king serts to correct the angle and line up the outer (4) holes. This way I can use any SBC intake without any modification needed. As posted previously angled spacers can be made, and people have widened the holes outside the runners to retain use the LT1 hole and then omitted inner bolts. I'm sure all methods work, but here's the way I decided to go. King serts installed in outer four with epoxy sealing the LT1 holes and new holes drilled/tapped in the center.

100_0607.JPG

Hope this helps explain the difference for those looking into converting to SBC intake in the future!

**Tinbender59** · 06-09-2016, 09:51 PM

I plugged the 4 middle bolt holes with brass all thread, filled smooth, then used a jig to get the correct 90 degree angle. drilled standard SBC bolt pattern and drove on. I'll try to get pictures.

my first attempt I drilled the manifold used bushings washers bla bla bla , looked like Jethro

had built it

**zooguy** · 06-10-2016, 04:36 PM

took my heads to a wheel repair shop and had all center 8 holes welded up then with a jig i made i used a drill press and redrilled and tapped the holes for SBC bolt pattern.

http://ltxtech.com/forums/showthread...TERBIRD/page46

post #457

cost me $40 at the rim shop and about 3 hours to drill and tap the heads going very slow