head porting

[dodgepu360]

I have a set of '79 360 heads (dont rember the casting number) that are cracked in between the seats and from the seat to the spark plug hole.
1. I also have a welding machine, can I weld the cracks and use the heads?
2. I want to port the heads and would like to hear any advice on what to do and what not to do cause I am a porting virgin

I figure if I screw up the heads by get into a water jacket Im not really screwing up a good set of heads, unless I can weld the cracks

[moeflo]

Consider starting with with a later casting. The ones with a raised floor in the exh-port.(sorry, I don't recall the casting numbers, but many, here can help), It's such a better piece to begin with. And cast-iron repair can be difficult.

The safe things you can do:
Blend the factory machine-cuts into the bowl. Don't get into enlarging the bowl, much, as great differences in wall thicknesses can bite you here. But get rid of the sharp edges.

Narrow the valve guide bosses. just a good smooth shape, remove any sharp edges. You can probably remove around .100" per side.

Especially on a SBM, at the push-rod choke, "carefully" open the p-r "intrusion" about .050". These walls can vary by .100" in thickness, in the same head. This operation is easy to get to, easy to do, looks good, so resist the temptation to go "just a little more" (if you're weak, I can help with good expoxy repair, also)

For the following, and the push-rod operation, here's a handy tip. Do some looking, at your friendly neighborhood carbide store. With some calipers, find a ball end-mill, that measures close to .100" larger than the shank immediatly behind it. This can be used as a depth-guage. If you sight the cut, at at a right-angle, and notch the head, untill the shank is about to come in contact with the port wall, you're in the .050" ballpark.

Last. The divider, or straight-wall.(opposite the push-rod)

With your handy new ball-end mill, cut the .050" depth notches, from floor to roof, down the port. Then take a larger carbide and move the rest of this wall back, untill you've blended all the notches away. This has moved the wall .050" Take this to the short-side and blend into the bowl. Much more than this and you'll need to skip down to "how to sleeve a head-bolt"

You'll need to get yourself a good valve job. On the intake leave the edges created by the valve-job. A vertical cut(parallel to the stem) of .85-.88 the valve-diameter on the intake, about .200 deep would be good, if it's not already this big(again blend away the sharp edge in the bowl). On the exh, (careful, again) radius the edges into the bowl.

This will give you a good pocket-ported head, and after you finish these, you'll never bitch about head-porting prices again.

Good luck

[Tarrbabe]

Welding cast iron is a job for professionals ONLY. It is expensive and therefore forget your heads and get solid heads to start with. Look for some #308 off the 89-91 year models. Because of the cost and possible dangers of heads cracking again, welding cast heads should only be considered on heads that have already had a lot of money spent on them. Cast iron must be heated in an oven and brought up to a high temp welded by someone that knows what they are doing and then cooled in very specific increments to keep them from cracking again. Takes about 24 hrs to do it right.
This is probably not what you want to hear, but it's better to be fore-warned.

[dodgepu360]

well I was afraid that welding the cast iron would be a pain in the a$$

I dont have a job so I cant buy another set of heads now (they will have to wait untill I am done with school) so I think I'll just practice with the junk heads so that I'll be more confident when I start grinding on good heads

moeflo, thanks for all that good info I am sure I'll have more questions when I start working on the heads

what kind of cutters will I need to get the job done

the semester will be over in two weeks then I'll have 4 weeks to play with a grinder, chase women, and drink beer

[451Mopar]

I have never tried welding heads, but I did fix a chip in the block.
You need to use nickle welding rod, grind open the crack so you can weld fill it, and I think you should pre-heat the heads before welding them?

[deadhorse66]

Originally posted by 451Mopar
I have never tried welding heads, but I did fix a chip in the block.
You need to use nickle welding rod, grind open the crack so you can weld fill it, and I think you should pre-heat the heads before welding them?

Pre heat, absolutely. Also, the Iron has to cool at a very slow rate, or it will crack again right around the weld when it cools because the weld will contract a little faster than the iron does, and it will "pull" the iron apart. The iron must be kept hot after welding to allow it to reshape around the weld as it cools. As stated before, I would not try it, just thought you might like to know.

[451Mopar]

Since the heads are already cracked, it's not a big loss to try welding them. I'm not sure I would invest alot of money on them, but for expermenting with, what the heck

[dodgepu360]

451mopar, your right its no big loss if the heads crack more so I think I will try welding them just for the hell of it

and if I do a good job porting them and I dont screw them more when welding them I can test them on my "seat o pants" dyno

[Fast One]

I have welded several heads now & can say it's not easy, having a good welder is a bonus too, I use an ARC welder with the Nickel rods.

Yes you have to grind the crack right out & fill with weld.

Pre heat the head with a direct gas flame, I use one of them long gas barbecue burners.

The head has to be slowly brought up to temperature then full heat, welding has to be done with the gas heat still going, yes it's hot work mate!, when you've finished the gas heat has to be slowly turned down, then after that I wrap the head in an old woollen blanket ( tightly), it will stay hot to warm for about 6 hours plus, don't unwrap it until the head is completely cool

Good luck !

[71SATELITE]

Hey guys just a quicky, what do you use to polish your heads after you port and what grit. I have a project I am working on this weekend so step by step instuctions if you would. I have a broken chebby in the driveway (again) not mine by any means just a favor. This guys head craked like the grand canyon. Worst I have every seen. I have done a lot of stock rebuild/overhauls but never any proformance massaging. This way if I screw up on his new heads no great loss, just a chebby. One more thing, alligment porting, how to do this and what grits, once again. Thanks.

[451Mopar]

I do the most porting with a carbide cutter and sometimes don't even polish the ports.
I think the polishing I have done was with 80-grit? tootsie roll sanding rolls. I tried some finer grit, but it din't seem to work better, just took longer. The sanding rolls work good for polishing the combustion chamber too.

[deadhorse66]

I don't use anything finer than 40 grit rolls. This is not considered polishing, rather deburring. You don't want the intake runners polished because you need a little turbulance inside the runner to keep the fuel atomized. Polished runners have a tendancy to allow fuel to "puddle" on the floor of the runner and enter the chamber as "clods" of fuel rather than as a vapor. This can lead to fouled plugs, erroneous performance, poor idle quality, etc. You can polish the exhaust, but all that really does is prevent carbon from collecting as rapidly. Use a good selection of carbide burrs and some 40 grit rolls and that should be good enough.

[deadhorse66]

Originally posted by 451Mopar
Since the heads are already cracked, it's not a big loss to try welding them. I'm not sure I would invest alot of money on them, but for expermenting with, what the heck

Absolutely.

[451Mopar]

You may be right on the grit, I know it is fairly corse and like you mentioned, the intake can use a slightly rough surface to keep the fuel mixed into the air.

[71SATELITE]

Thanks for the quick response. What about align porting? I have idea's but need to consult the experts. Do I just shave off the excess metal on the outside of the gaskets? Thats what it looks like if so no problem. What is the proper procedure for intake to head?

[sidehackbob]

plant the head on the block with no gasket and scribe the shape of the cylinder. DO NOT USE THE HEAD GASKET FOR A TEMPLATE!!
Carefully open up the area between the valve and cylinder to unshroud the valve. Remember now the head has to go back on the bank it was marked on. Blend in the sides of the chamber but resist the temptation to open up the combustion chamber in any other areas.