If i buy a new or rebuilt 4 barrel carb, and a nice new intake for my 289 2V engine. And lets say it has some other mild upgrades, headers and a mild cam. What do the following cost, how much bang do i get for the buck, and which ones can i do myself with a dremel or a drill:

basic intake and head porting (gasket matching)

intake and head full port and polishing job

above plus 3 angle valve job.

Alex has suggested before that new heads is cheaper than porting. but I was wondering if i could match the ports on the new intake to the heads with a simple gasket match, and do it myself? How much horsepower might I gain by doing these things?

Polishing sounds like a lot of effort for little gain? One guy even told me that polishing can hurt combustion and you should leave the intake ports dull.

Any opinions and experiences are always welcomed.

http://www.sa-motorsports.com/diyport.htm

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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA/MCA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl

On the exhaust side, try to remove as much of the exhaust guide in order to eliminate the flat spot in the port roof that the guide area makes. If you have the thermactor hump, remove it to the level of the port roof. These exhaust ports like to have the roof raised but the floor makes little difference. If you try raising the roof be sure not to exceed your header or manifold size. You can "D" shape the roof slightly, this shape flows best with these heads.

I used to do a lot of work on these heads trying to make a competitive modified small block. Now I would just buy a better head. These heads will work very well for a hot street car if you are willing to do your own grinding. If you are going to pay somebody, buy aftermarket heads.

Like Alex said, skip the polishing. It is only useful in the combustion chamber. A polished surface reflects more heat back into the combustion chamber but you wont see the difference on a street motor.

I'm currently doing port matching and a little bowl cleanup on my vintage '66 289 heads. Is the "thermactor hump" you mentioned the bump in the upper left corner of each exhaust port?

Thanks,

Yet another question (excellent, to-the-point-no-bull post, by the way. Thanks).

When you say to try to "remove as much of the exhaust guide to eliminate the flat spot in the port roof", are you telling me (us) to make the exhaust guide area look like that of the intake--kinda scooped out?

does a '68 289 have thermactor humps?
(save me from having to look myself!)

Keeping the constant radius in mind, that is what you are trying to accomplish at the exhaust guide also. Remove the guide support on the headder side as much as possible. You are trying to minimize any projection into the constant radius.

There is a ridge where the factory machining meets the cast port floor. Just like I described on the intake. Take this ridge away also.

Indyphil - You probably have the hump, I think all the heads after mid 67 had the hump cast into them.

Just to expand on the larger valve idea. I don't remember which valves interchange but I know you can use stock replacement valves with a larger diameter such as Chevy valves. Just make sure the stem length is close to the same as stock. I don't know what machine shops charge to put in larger valves but as long as the size change isn't too dramatic it is fairly easy to do and shouldn't cost too much. These heads really like a slightly larger valve.

In case you are wondering, Yes I did all this work and tested it on a flow bench.

Just to make sure I don't screw anything up... I can grind off the entire thermactor hump, both on the left side of the port and up to the current port roof?

John

I'm all ready to do the intake port matching but I'm having a helluva time placing the intake gasket. It seems it could go up or down an 1/8" or more and still function. Give me a hint as to where to place the gasket vertically. Horizontal doesn't seem to be a problem.

Thanks,

OK. I've removed the thermactor hump--even with the roof and even with the side of a standard exhaust gasket. I can feel the depression you spoke of left behind the thermactor hump, but what should I do about the ramp-like depression remaining on the same side coming up from the floor where the casting halves meet?

deadhead