Porting hemi heads?

I have my 241 Dodge down at the moment. I have always wanted to relieve the bumps around the intake guides. What would be the tool of choice to cut both the iron head and the sides of the valve guides? I have one carbide cutter I used on the flathead intake ports but was not impressed with the material removal rate. Would abrasive rolls be a better choice? I have an electric die grinder 30k rpm, an air grinder, and electric drills. I know hemi blocks are harder than hell so am intimidated with the thought of removing metal from the heads. Thanks for any recommendations! I could experiment but would like to order the best stuff so I can reassemble for the HAMB drags.

 

Carbides should have a faster removal rate than abrasive rolls. Is your carbide sharp? Abrasive rolls should work well to smooth out after the carbides do the work. From what I have heard about Hemi heads, I would not do a lot of porting though, just smooth them out a little. Hope you get them smoothed out.

 

The 241 heads have a huge bump around the valve guides. The valve guide is also huge and has a taper so the base is really wide. I just want to cut the bump down so it is like what the 325 heads were like.
HH sells some bronze guides that have smaller stems. Does anybody have an opinion on them?

 

Any Hemi breathes better stock than most other engines. If you dont have an air powered die grinder, you wont make the HAMB drags. Screw it together now and race what you have. A slow day at the HAMB drags may be the best day of your life so far.

 

Cast cuts well with a carbide cutter,I use a flame and a egg mostly.
Lately I have been using stones,they are cheep and plentiful.
Shape them into any shape with a lapping stone to get into hard spots.
Finish in a 60 or 40 grit stone,lots of advice on surface texture on the web.
Either electric with a speed control or air this is a preference thing.
If you do not have access to a flow bench,take carfull measurements with a divider and try to stay consistent from port to port. Less is more in most cases.
1inch before and after the valve will be your biggest improvements.
A good valve job using a 70 degree throat and some back cuts on the valves will
Show big improvements up to 300 lift.
Good luck and have fun.
Gary

 

When I port heads especially Vintage Mopar I remove the bump completely and bore and install a new guide. (I prefer SBI iron knurled ) I take the guide as supplied , taper the end I want to use for in the port. and then measure the legth i need and make up all the guides I lube them with Sunnen lube or lucas oil treatment after cooling them in the freezer for a while and drive them in (FROM THE SPRING SIDE to the proper height. Your instincts are right on the money. That bump is a huge pbstacle to airflow andeven more important to non turbulent air flow. If you go to my thread on porting the slant six head you will find more on this andsome pics as well. And as you have aleady surmised the bump has no function.
Don

 

Here is a pic of the finished deal. New guide just sticking thru although same almost exact length and support as stock as was with the big ugly boss /bump around it. Now the boss is gone and air can flow SMOOTHLY (as in non turbulent) which is the WHOLE ball game on getting a port to flow. Huge improvement. Hope this helps. You thinking is sound BTW
Don

 

If you are going to use valves with smaller diameter stems, I would keep the stock guides and use bronze liners. You can taper or knife edge the boss around the guide, but do not eliminate it. The guide needs support too.

 

I have both the Craftsman electric and the Makita electric die grinders and both are hooked up to my Dremel table top speed dial.. As for the carbide cutters, I use the "double cut" cutters for cast iron and the "single cut" cutters for aluminium.....

 

There are some single cut that are not as aggressive you can use for both.
A diamond cut tends to give a smoother finish removing less material.
I have tried a lot of different makes and types,again it's what works for you.
Stones on cast iron seems like old technology but it removes material quickly and leaves a finish closer to what I found to be optimum.
Shape it with a lapping stone and its limitless. I have to stress safety is a must for eyes as well as respetory. Use the best you can.
I had spent a week at mondellos when he was in paso Robles.
What I got most after a week was how to get a good shape and finish through technique. In a timely manner.
The rest is trial and error through testing. I have a flow bench and its a tool that's a must if you want to take it seriously.
It can be very humbling at times,just like the drag strip as I too have learned.
A great read if you wish to take it up a notch is engine airflow by Harold Betts from super flow fame.
I gained a lot after I read this one.

 

I've thought about building my own flow bench... Making all the fixtures is the easy part.. It's all the other equipment that can cost some serious $$$..

 

A couple of random thoughts. Why do you feel the need for the port work? Are you planning some high rpm operation? Have the heads been flow checked and found to be 'needing'?
Unless the rest of the engine is in some sort of 'race' trim, IMHO, you are wasting your time.

As to the guides, rely on your machinist to offer replacement suggestions as there are several ways to go; liners (cast or bronze), 'false' guides (thicker than liners), or, complete removal/replacement (not often needed).

.

 

No bronze for me, guides are fine by themselves. Liners are for lazy folks who dont want or dont know how to set up an head in a seat guide machine. They are certain death on some engines in an exhaust application at recomended clearances while cast iron NEVER gives trouble. Usually Bronze is ok for intakes but why bother when cast iron works so well. Bronze is excellant in aluminum heads where heat transfer is high but can be a problem in an iron head. Usually shows up as mysteriously bent pushrods (or valves if you are really unlucky) after engine has run a few runs and sat hot a bit. Exhaust guide snags the valve sometimes pulling the guide down a bit. The machinist who did the heads has a thousand reasons why it is not his fault and not related to the work or the guide but eventually you learn if you dont quit that cast iron ex guides dont have this trouble. Have helped more then one fellow machinist and machineshop out of this mess. What may be fine for Granny's car will sometimes bite you in a race or hi perf application. I also learned it the hard way. Often an engine fails and the reason is never found . Many are traceable right to this exact problem. We have a tendancy all of us to think bronze is better because it is exotic. I bet right now someone is reading this thinking I WONDER IF THAT IS WHAT WAS WRONG WITH MINE. Some will get this some will get upset. Doesnt change the facts.
Don

 

Dolmetch, Thanks for the insight. I had always been leary of the bronze guides. Way back, I was to assemble an exotic housing. It had bronze bushings to be installed. I had to heat the housing and cool the bushings for installation. Only one end could be done at a time. After I installed the other bushing, the heat had expanded and failed the first bushing and it fell out. Great design. I have always thought it could happen in an engine. I am just going to cut the sides of the guides and the bump to remove some of the bottleneck. I want to wake the engine up. It does not pull as well as my flathead. I have 315, 325 heads so I can see what the factory did. I want to make my 241 heads to flow as well.

 

No disrespect don,I have read plenty of your posts and found them very informative.
I'll throw my hat in here and say I have not had any of these symptoms thin wall or .502 replacement bronze magnese guides.
My question to you or anyone with these problems is ,how was the guide finished,reemed or honed.some are ball broached and considerd good to go.
Lots of choices here.
Clearence checked how? Assume that the size reamer is what it finishes too ,deflection is a sneaky one commonly overlooked.
Valve stem finish,if you have a surf to check them you will be surprised.not to mention,how straight are they. Off shore stuff is horrible.
They can act like a rat tail file if you don't check or polish them.
What works for me,ream to .0010 under final size then hone to final size. Using a split ball bore guage to measure.
On 11/32, .0018 on intakes and .0022 on the exhaust,No more than .0001 taper when finished.
Cast is more forgiving granted but to condem all bronze guides,nah.
Bronze holds up better in higher load conditions period. Most of the failures you listed can be linked to oversight to the machinist experiencing the issue.
Don I think you will agree,there is no substitute for good machine work.

 

Actually, it takes more guide machine knowledge to install bronze liners than it does to install new guides in an early hemi. Here is the factory tool for removing and installing early hemi guides.

On the early hemi, it makes more sense to use a liner in the existing guide. ( to either get back to factory 3/8 specs or to downsize to 11/32 stem)

 

I have done several sets of Desoto hemi heads. I use a carbide cutter that looks like a pine tree. Spray a little WD-40 in the port from time to time to help with cooling. The boss around the intake guide is the biggest blockage in the port. Streamline the boss till it comes to a point in the shape of a tear drop with the point of the drop streaming toward the valve. A round object has about 10 times the air resistance of a streamlined shape of the same thickness, so just streamlining the boss will add gobbs of flow. Good luck.