Hi guys this is Tracy G up in Reno Nevada. I was just under the hood of my '85 Subaru GL wagon, 1.8L 4cyl ohc w/ a 2 bbl feedback carb. I have no pics yet and have not pulled the carb, BUT, it looks like the throttle body section is thin, possibly too thin to fit a groove under the primary butterfly. Also the throttle body is made of iron. I was imagining having a spacer plate made (aluminum?) to extend the throttle bores enough to fit a groove-maybe epoxy the throttle body and the spacer together put bolts/nuts thru the stud holes bolt together till epoxy sets well. There is a thin (maybe 1/8 inch) black plastic heat isolater spacer under the carb now (factory stock). Not having the carb off yet I guess that much material may allow room for a groove. Also I'm concerned about grooving in iron, I wonder that a bit may get used up or dulled badly working in iron. If I did get a spacer made or even tried grooving w/the iron and plastic together there would be a difference in material hardness going on, and again I wonder if that would be weird to work on. I found a donor car at Pick-n-pull w/ same carb so I could get that and do grooving on it then switch throttle bodies. Has anyone tried this idea on a carb w/ a thin throttle body (i.e. Quadrajet, Thermoquad, foreign. etc.?) The only other idea I can think of is to switch to a Weber carb and groove it-- but car is computer control feedback carb equipped and we do smog tests here; I would talk to the State Emissions control lab folks first, as the computer and LOTS of things would go Deep Six that route, and getting an OK for that might be like getting a permit to have a Watch Crocodile chained up in an unfenced yard a block from an Elementary School!! If you have suffered this far reading this you have realized I have not done my first Groove yet. Anyway sorry for the long twisted post here, but that is what I think is going on w/ my Subie!! Thanks for reading, TracyG

Hi Tracy,

I don't think I would be comfortable cutting into iron either but if you attempt it you will want to run the dremel at a much lower speed and plenty of lubrication.

If I remember correctly Ron had mentioned at some point about Quadrajets not being a good candidate for the groove, mostly for the reason you mentioned. If you can get a replacement that has more meat under the throttle plates that would be better.

Keep in mind when you do the groove on a cabled TB/carb, the idle should be adjusted so the plates are in a fully closed position.

Afterwards, you'll adjust the idle and your idle air screws accordingly.

Also, on a fly by wire unit, you would want to set the throttle plate at the idle position to groove this type of TB.

If you haven't read through the posts on the different vehicles that have been grooved, there is a lot of information that can be gleened from them.

Welcome to the Team

Karl Fortner
Tacoma, Wa.
Gadgetman Tacoma

Hey Karl thanx for that. Ive been reading around the site. Today I got a used carb from a Subie just like mine at Pick n Pull. Throttle body is thick enough to groove w/o spacer. But as attached pics show, there is an area under the Primary butterfly where the bore is notched alongside the big screw clamping throttle body to main body. And throttle body is cast iron. Hopefully you and others can see this in the pics. I believe its risky regarding bit life to groove in iron, so I would use 3 in 1 oil, PB Blaster or other to lube bit also run at slow speed. The material between the screw notch and the butterfly is about1/8 inch wide. There is also a tiny vacuum port that the groove would probably pass over but I think I could ensure its still open even if in the Groove. What does anyone think about a "compound" groove, that is using a larger bit for most of the Groove and switching to smaller size under this notch...? I could maybe grind down the big screw head to reduce diameter a bit and then try JB Quick to fill in this notch--BUT I'm also concerned that there may not be much native material for JB to bond with w/ attendant risk of JB falling into the intake..? OR using a partial Groove that ends without trying to squeeze into this thin area under the notch..? My plan is to groove this iron throttle body then swap w/ one already on my car to minimize downtime. BTW my last daily driver an '81 Mazda626 also had an iron throttle body...but I think we Gadgetmen/Gals wont see many cars like this as most are gone today. Thanks to all who read this long post, TracyG

Hi Tracy,

Is that the fully closed position or the 'idle' position?

Also, when you do attempt the groove, I would carefully touch the bit off the material with plenty of lubrication and then check to see the results. If it doesn't displace any material then all you are going to do is ruin the bit, which you do not want to do.

Iron has a tendancy to hold in heat so it will require lots of cooling as well as lubrication.

Good luck

Karl Fortner
Tacoma, Wa.
Gadgetman Tacoma

Hi Tracy,
The bits were made to cut aluminum. You will definitely be sacrificing the bit(s) and I will be surprised if you get much cutting done. Just so you know what you are getting into. The bits are not carbide cutters.
Nick Gadgetman of the Fingerlakes

hi Karl, yeah that's the fully closed position, idle speed screw backed all the way out.