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What is the top cylinder max temp on a 321 as measured on a mycron 5? Probably 421 degF is a bit much.....which is what we saw in testing today before calling it quits....This engine has already cooked the top cylinder once....it was running 1" deep and with 1/4 inch setback off the transom following the first cook. It is still running way too hot. Help!
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Someone can solve this problem. How about it. -
Is your 321 on a hydro or runabout?Chris Fabbro 2-F CSR / Carson Fabbro 95-F 25ssr, CSR, CSH, 300SSH / Greg Fabbro 63-F CSR, 25SSR
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Hydro....CSH/20ssh/300ssh
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I also have been working on this on and off this season. What we have found so far is that the powerhead is not the culprit, it's the additional baffle in the tower. I know the 300SSH committee will be meeting again soon, and I know a few other racers are testing as well, so once we have this fixed, information will get out faster. I can confirm it's in the tower, as I ran my 302 powerhead on the 321 tower and had the heating issue. It's not a cooling issue, it's a heating issue. I didn't have the opportunity to change over towers this weekend in Kittaning, but will be doing that in Grass Lake next month to test in race conditions.
When it comes to boat racing and the wife, it's easier to ask for forgiveness than it is permission, and of course I spent a number of nights sleeping on the couch!Comment
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This is a significant issue as some of the CSH guys are having to run deep, etc
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To answer your question - 450 on the top cylinder with good oil, you'll be ok. You'll need to replace the manifold gasket and probably deck it too. Just don't completely let off the throttle once you get that hot - no throttle means no fuel, means no oil, means its stuck. I've seen 500 + and been ok.
In respect to the 321, my initial comment made in February that there is nothing different between the 321 and 302 cooling-wise, was completely wrong. I suspect I came to this conclusion because when we test in the winter, the water is much cooler. Even knowing this, I didn't think the cooling would be THAT bad/different.
I have to run at 7/8 to 15/16 deep to finish a flat-water heat. 1" when the water is rough with the 321. I know much of it is my boat design, but I can run at 3/4 flat-water and pump with a 302.
The tower seems to be the culprit for a variety of reasons (smarter people than me can comment why they think it is so) but one thing I did try, is swap the brass plug in the 321 tower to the plug that comes on the 302. I think it did help the cooling slightly, but not dramatically and had only two heats to test it.
Moral of the story, in my perspective, is: will a newbie buying a 321 have as good a chance to go fast at 3/4" in CSH as someone who has their hands on a 302/102. Answer right now is no, absolutely not. CSH is a stock class, so is 20ssh and 300; do we really want water pumping issues to be a concern in a stock class? We already control the speed by the depth of the LU and every other stock class has an impeller.
What's an easy solution that does no alter the motor whatsoever?
As for me, my 321 has been relegated to my CSR/25ssr exclusively.Comment
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Not a stock guy, but has anyone looked at the water exit size? I had an issue with too large of an opening exiting the head of a pro 125. Very little back pressure through the head made the water inefficient at cooling. Would run 2-3 laps and then start to overheat. Reduced the exit to about 0.080" and the overheating went away. Made it real consistent on temp.
Dan
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The pathway for the exhaust on the 321 is about 2 ft longer for most of the exhaust. This has to have three significant effects; the temperature in the tower must stay higher, the pressure in the tower must be higher, and the engine must be quieter. The cooling water tube runs up the tower in this hotter exhaust so it must be preheated a bit more than a 302. One possible solution is to permit a hole be cut in the baffle that diverts the exhaust into the longer pathway. You can see the baffle that blocks the normal 302 exhaust flow in yellow in the 321 cutaway photo. Cutting this away should make the exhaust path the same as the 302. There still remains the generic cooling issue with all Yamatos that the Stock Commission should also address in order to lower the cost of racing the Yamato engine.
John Adams
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Wouldn't changing the exhaust flow distance alter performance characteristics?Dane Lance
700-P
CSH/500ModComment
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Why don't we change the Yamato height to 0" from the bottom. The motor rebuilders
could come to the races and rebuild and over bore everyones engines and get ready
for the next race!
I have never understood why we run these heights, Yamatos were not designed to run at
3/4" or 1/2". Runabouts and 300s generally do not overheat. Everyone would suffer equally
if the height was 1" or 1 3/8". We would save a lot of frustration and money. A lot of testing
is done just to try to prevent overheating, what sense does that make? Everyone is looking
for a solution to overheating that does not change height. Google Occam's razor for the
obvious solution.Comment
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There has been tremendous investment in propellers that run at 3/4 of a inch. The cost to change the baffle would be very little compared to changing thousands of propellers.Comment
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Confusing, this is suppose to be a stock engine not to be altered. How come in Japan, they don't have this problem? Thought all engine are suppose to be run as received. If anything is changed, it is modified.Comment
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Bob, take a look at a CSH foot and compare it to a Stock 300ss foot. There are significant modifications allowed. In Japan they run much deeper and slower.Last edited by GrandpaRacer; 08-25-2016, 06:55 AM.
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Is it legal to run a 321 head on a 302 tower for CSH and 20ssh?
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