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Discussion Starter · #1 ·
I came across aluminum heads ported excessively. 4-5 intake port walls broke through to the other side. The holes are about the size of a thin tooth pick. If I used these heads, I'd be running e85, so epoxy is too risky. Normally issues are like this are easy. I could put a temporary aluminum backing plate behind the hole, then make a couple passes with the welder from the opposite side.

The issue is the holes are deep inside (about 2.5"). I could get smoothing/grinding tools in there, but I wouldn't get a welding tip that far down. Outside the hole is inaccessible because push rod guides, etc. I could get a backing plate on either side of the hole, but a welding tip would not fit on either side.

Question:
Can I put a backing plate inside the runner up against the hole, and pour a little molten aluminum on the opposite side? Then tilt the head so the aluminum goes where it should.
 

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Put your money else where the head’s are junk.

Epoxy and aluminum have very different rates of thermal expansion, the epoxy will always fail it’s a question of when not if. For a racer where the engine is just an expensive consumable on the way to the winners circle it’s OK as long as you are aware of this, on the street simply assume that it will fail at a point furthest from home on a holiday weekend.

Nice thing about aluminum is it can be welded, in your case the downside is not knowing if there are other thin spots that will crack later. You’d need to do a sonic test to find out. By the time the welding is done you’ll no longer be able to trust the valve seats so their replacement gets in order which drives a valve job. In the end you’ll put nearly as much into fixing these as the cost of new heads so my recommendation is cut your losses and move on.

Bogie
 

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if it's a race engine it may not matter---i worked on a engine that had heads which were ported into the head bolt hole between the runners---the original builder said not to worry about it and it had been running that way for awhile, just make sure to seal the head bolt upon installation
 

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Question:
Can I put a backing plate inside the runner up against the hole, and pour a little molten aluminum on the opposite side? Then tilt the head so the aluminum goes where it should.
Nope. The moltemn metal you pour in will not stick to the existing metal. In order for it to stick and join with the base metal of the head, you have to melt the interface point.....which is how welding works.

Pouring the molten aluminum onto unmelted base metal is no different that laying down a weld bead without enough heat....it doesn't stick and hold.

Is the point you need to fix open to water jacket....or is it like Imsport posted and just into a head bolt through hole??
 

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The process that works the best on a hole into the pushrod passage is thin wall hard brass tube with a light body fit in the hole sealed with Locktite or super glue. Frankly I’m not to thrilled with porters that chop this out, ala Headbytes, but it’s common. The 23 degree SBC’s biggest flow problem is the short side turn into the pocket, not counting the merge to the seat and the port side guide glob. Really good head’s flow well beyond .5 inch lift but nearly all OEM or aftermarket lose ground pretty fast beyond this point. The Vortec being the singular OEM exception. What this info is telling you is the flow on the short side turn is breaking off the port floor and skating across the backside of the valve. At this point one or two things are happening:
One, is the separated flow is acting like a valve and is shutting down the main flow off the upper region of the port.
Two, is the sum of the short side flow and roof flow is more than the curtain area can support. In this case, however, I’d expect the total flow to level off but most often you see it fall which speaks to either extreme turbulence or a throttling effect of a cross flow.

In either of these cases a larger valve might help, especially in case two. GM’s approach on the L31 Vortec was to widen the floor leading into the short side (floor) turn. What this does to the local flow is that increased area slows the flow, it gains pressure so it is better able to make the short side turn and not skate over the backside of the valve. The other thing it will do is cause low pressure (higher speed flow) along the roof to want to pull the higher pressure flow up which may do a lot to help it ease the turn. Here we’re talking about playing games with pressure gradients within the port which really takes a lot of flow bench time on model ports, but when doing your own porting this is something to model rather than just hogging the port out everywhere. If I learned anything in decades of porting and playing with airplanes is you cannot leave the flow to find its own way, that generates lots of turbulence which can make a port flow a lot less than expected.

Sometimes theory’s fall down the LS cathedral port case in point. The theory says this should flow better especially around turns than a more squarish port of the same area and volume, but it didn’t. That was a big surprise to me.

Bogie
 

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Discussion Starter · #8 ·
Nope. The moltemn metal you pour in will not stick to the existing metal. In order for it to stick and join with the base metal of the head, you have to melt the interface point....
Is the point you need to fix open to water jacket....or is it like Imsport posted and just into a head bolt through hole??
That's a good point...so only the pour-in metal would be ready to mingle. No water jacket close by. Boring but inaccessible spot.
 

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That's a good point...so only the pour-in metal would be ready to mingle. No water jacket close by. Boring but inaccessible spot.
Is it the head bolt hole that is between the two intake ports??

If so you can either leave it, as it has been proven to mot matter as far as flow is concerned, all you have to do is make sure you get a water tight seal at the bolt threads and then oil tight seal under the bolt head or washer.

Some guys will opt to just sleeve it, not hard to do with 1/2" dia x .015" wall thickness brass hobby tubing, a drill press, and a .499" dia chucking reamer.

Sbc head bolt sleeve | Yellow Bullet Forums
 

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Discussion Starter · #11 ·
It's to the outside. In this photo, this example has a slit right about where it starts to curve. Push rod guides are on the other side. Owner did not run unusual fuel so he just used epoxy. He's also using the tube trick.

616752
 
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