Tips on filling Exhaust Crossover

[ss3011]

I want to fill the exhaust crossover in a set of stocker heads I have. Most heads I have seen are done with aluminum. What is the best way of filling them ? Any pitfalls and lessons learned on how to do this ? How close to the bowl can you go legally, and what would you do to fix it , if it got into the port ? Thanks for any wisdom !

[Mike Taylor 3601]

I buy zinc alloy from Mc Master-Carr industrial supply, about $40.00 will do 2-3 sets of heads, melt it with a acetylene torch into a steel container with handle on it, I made one by welding piece of tubing to flat bar, bolt a plate over intake side of heat riser passage and pour from exhaust side I use a small metal funnel and extend with tube if need reach deeper to heat crossover.
I fill crossover up within 1/8-1/4" of exhaust port,if you overfill can tilt head and pour some out or if sets up on you before you can pour out can turn head over and melt some back out or clean up excess with torch.
zinc alloy will stay for years and years.
Mike Taylor 3601

[rallye bob]

http://classracer.com/classforum/showthread.php?t=45505

[ss3011]

Thanks for the information . That early post has lots of good info. It looks like depending on how the exhaust flows, and how much heat transfer you get in the port, will determine what material you can fill the crossover with. Zinc alloy melts at around 750 degsF, and aluminum melts at around 1220 degsF. I think I will try melting down some old pistons, and see how that pours into the crossover. Thanks again !

[R. Thorne]

I ended up using the cotronics 940ht high temperature (3000 degrees). I don't have access to a torch and on the performance years web site a number of people had good results with it. It was a little pricey (about $100 for the quart size), but I have done 2 sets of Pontiac heads and could easily do another set or two. After two years of running, the adhesive has held up fine. Ron.

[Rich Biebel]

Originally Posted by ss3011

Thanks for the information . That early post has lots of good info. It looks like depending on how the exhaust flows, and how much heat transfer you get in the port, will determine what material you can fill the crossover with. Zinc alloy melts at around 750 degsF, and aluminum melts at around 1220 degsF. I think I will try melting down some old pistons, and see how that pours into the crossover. Thanks again !

That is how we did it in the shop I worked at. Melted old pistons down.... Used a big plumbers ladel for melting lead with a torch. It had a long handle....Melt pistons.....remove slag while it's liquid as it will form on the top.....

Pour in with intake flange facing down and a plate bolted on it to keep the aluminum flush. Aluminum will get solid very quickly. You can warm the head up some before pouring the molten aluminum in.

It's tricky.....and there is zero working time there....

If you pour too much in you will have to use a die grinder to grind it back....

I have seen some furnace type cement used that held up very well but never knew what product that was or where to get it....

[Ed Wright]

Originally Posted by Rich Biebel

That is how we did it in the shop I worked at. Melted old pistons down.... Used a big plumbers ladel for melting lead with a torch. It had a long handle....Melt pistons.....remove slag while it's liquid as it will form on the top.....

Pour in with intake flange facing down and a plate bolted on it to keep the aluminum flush. Aluminum will get solid very quickly. You can warm the head up some before pouring the molten aluminum in.

It's tricky.....and there is zero working time there....

If you pour too much in you will have to use a die grinder to grind it back....

I have seen some furnace type cement used that held up very well but never knew what product that was or where to get it....

This the only way I ever did it. Old Pistons.

[Dwight Southerland]

I have used pure plaster of paris (not the kind with silicon in it) with success. Just be sure there are no bubbles in it. The heat from the engine exhaust fires it like in a kiln. Harder than heck to get out after its been run a while.

[Ed Wright]

Originally Posted by Dwight Southerland

I have used pure plaster of paris (not the kind with silicon in it) with success. Just be sure there are no bubbles in it. The heat from the engine exhaust fires it like in a kiln. Harder than heck to get out after its been run a while.

Hmm, first I heard about that.

[Mark Yacavone]

I still use aluminum and a torch, but I don't fill it from the port side anymore..Too much room for error and extra work.
Instead I make little tin or aluminum tabs that are the shape of the passage, with a little tail on them ,which I prop up against a bolt stuck down in the valve guide.
I melt more than enough aluminum, skim, and pour it down in with the intake side horizontal, leaving it a little high. I then smack it with a hammer a few times while it's still warm. Grind it flush with a 40 grit soft disc and some cutting grease.
Pull the tabs and you're done.

I've been told by one of the best in the business that leaving the fill recessed back just a little, doesn't hurt the flow at all.