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General Category => General Discussion => Topic started by: Hymes Inc. on October 23, 2020, 01:06:29 AM
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I've been tasked with working on some garden pulling tractor blocks. I have a stock kohler block that they want to move/enlarge the intake port. Because this is a stock block there isn't a whole lot of meat in the casting of the intake port, there is actually a through gap between the port channel casting and the cylinder cooling fins directly behind it. Normally someone would try to braze up the backside of the channel in that gap but it is very tideous and can be hit or miss.
My question is, what do you think of blocking off the back end of the gap and pouring smelted brass/bronze in to completely fill the gap? If it would hold this would be infinitely stronger and easier. Cooling is not a factor as these engines only run for 300 feet.
My plan is to bring the block up to as high a temperature i can comfortably maintain, smelt some scrap brass i have, pour it in the gap, and gradually reduce the temperature of the block over a day.
Thoughts?
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I assume that the engine in question is a flathead engine? And cast iron cylinder block? I guess it would be possible to pour molten brass/bronze inbetween the cooling fins if you block it off carefully. The block have to be spotlessly clean and very well degreased. Perhaps sandblasted in the spot you need to pour.
Are the crank bearings roller bearings or white metal bearings? If white metal bearings maybe you have to be careful about heating the block too much, if it is roller/ball bearings they will probably just fall out when heated.
Also make sure that there is absolutely no moisture in the engine block what so ever. but that should be taken care of by the heating.
Good luck and let us know how it goes :)
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Your desired end result isnt clear. Are you trying to move the port in a way that would only thin the wall excessively, actually move the port wall into the open area, ??
I would either use epoxy, which is the common approach for facilitating intake port modifications without welding. block fill. https://www.summitracing.com/parts/hnh-860228?seid=srese1&gclid=EAIaIQobChMIu9ih-dXK7AIVGW6GCh02bQazEAQYASABEgLTm_D_BwE (https://www.summitracing.com/parts/hnh-860228?seid=srese1&gclid=EAIaIQobChMIu9ih-dXK7AIVGW6GCh02bQazEAQYASABEgLTm_D_BwE) is another option that is specifically designed for such use usually in water jackets, not within interal/combustion or lubricated areas.
Molten brass against a cast iron or alloy block...? different metals (or even the same metals) will not structurally marry simply by melting one and pouring it against the other that is well below molten temp. That's why brazing operations require proper cleaning and flux so the joint/union actually works.
Before doing much work- The air gap outside/adjacent/surrounding the intake port is an insulator to help keep intake port/charge temps lower. Eliminating that air gap will likely raise temps, which may negate any flow benefit gained by moving the port. jmho
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I will try to get some pictures up. Hate typing on a phone. Cast iron flat head correct. Runs on alcohol. They triple the size of the intake port and move it closer to the piston were the casting gap is. They already use epoxy but I'm told over time it flakes off. Want a more permanent solution.
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Im assuming here that you are talking the tired and true Kohler K single cyl? How much are you looking to move, and enlarge the port? Ive heard lot of smoothing and reshaping the intakes, and exhausts, but it normally doesn't make much improvement because of the issues of flow inherent in the chamber. I would think that if you are turning the RPM to need much more, you are probably at the point that using one of the custom bullet blocks might be the best bet.. That being said, I would think think epoxy would be best. Its been used in automotive heads for years. Not sure what brand/type they use though.
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Molten brass against a cast iron or alloy block...? different metals (or even the same metals) will not structurally marry simply by melting one and pouring it against the other that is well below molten temp. That's why brazing operations require proper cleaning and flux so the joint/union actually works.
I was going to say this.. <shrug>
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JB Weld, Liquid Steel, etc., etc, ??
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His big brother builds these engines, and they turn 9200 RPM! Factory stock was 36-3800. There is almost nothing these guys won't take a stab at.
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Stock block
(https://i.ibb.co/FYjKjw9/20201023-111841.jpg)
Race block
(https://i.ibb.co/QpZsRdT/20201023-111808.jpg)
This is the side view of the intake port I'm going to try to fill with brass
(https://i.ibb.co/X5cqgns/20201023-111827.jpg)
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What is the preferred machine for pulling? Hydro or gear transmission? I have a friend that uses the older Cub Cadets for pulling.
Larry
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Gear
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Update for anyone interested.
Cleaned the engine block with muriatic acid then sand balsted. Made a plaster/silica sand paste for the form. A buddy of mine gave me a bucket of bullet brass to smelt down. All was going pretty well. Had the block set in a propane oven i made and sitting at 700 degrees Fahrenheit. Smelted the brass in my coal forge in a 2kg crucible. Got one full pour done which i was hoping would be enough, it wasn't, going to take 2. Learned a valuable lesson about smelting bullet brass. Rim fire casings have residual primer propellant in them and explode. Figured this out right away and was being careful to pick them out. Guess i missed one stuck inside a larger casing and ended up blowing the side out of my crucible :violent1. Poured what little brass there was left in it and came up a bit short. Letting it cool in the oven now and will snap some pics when it's cooled off. Time to order a new crucible. Can't wait to get a closer look at this block when it cools. Been a fun project.
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(https://i.ibb.co/3mhct9L/IMG-20201107-112045-01.jpg)
(https://i.ibb.co/DMpyHfs/IMG-20201107-112026-01.jpg)
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Fun stuff! Exploding melts are quite the rush..BTDT!!!
-AJ
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Any more progress?
-AJ
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He's waiting on a new crucible.
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Yes, still waiting on the new crucible. Might have some issue with multiple pours as brass smelting gives off zinc oxide. Comes out looking like spider webs but turns to dust when you touch it. There is a bit of it on the casting. I'll know when I get off work today how easy I can get rid of it.
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Multiple pours are not a good thing..
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Finally got back to this experiment. First thing I did was pre-cook the gun brass.
(https://i.ibb.co/BnV1G1T/20201127-112019.jpg)
Worked great, got about 10 cook-offs. Melted it down and poured it in. I did heat the existing brass to melting right before pouring.
(https://i.ibb.co/Gvw294S/20201127-140339.jpg)
We'll now just have to see if it holds up. Long time out for that. Good lessons learned and next time will be done in one pour.
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While it's a very low tech method, you can clean the joint area around the intersection of metals and wet it well with water to see how long the joint stays wet compared to the surrounding metal. Any void (crack isn't the right word right now, but may also be relevant) should be obvious as an area consistently that stays wet much longer than everywhere else. Where possible, heating the same areas can also cause moisture in liquid or vapor form and avaialbe loose debris to be expressed along the same wetted area. This can help you get an idea of what is secure and what is not, which would be helpful to know before moving forward.