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-   -   BBC Crossover Temperatures (https://www.offshoreonly.com/forums/general-q/353818-bbc-crossover-temperatures.html)

distantthunder 05-09-2018 07:33 PM


Originally Posted by convincor (Post 4625695)
Besides ditcting the bypass, did you change anything else? Mod t-stat? Running a pressure relief?
And where are your temps running?

I added the holes to the Tstat, going to put the single hole high flow version back in the port engine and test this weekend. Only added the intakes, carbs, and crossovers this season. Also added the dump lines from the rear intake water crossover ports to the exhaust manifold after the first stuck valve.

I am determined to make this work. This system had no issues on my previous boat, not sure why crossovers have such a varied outcome from engine to engine. For now, she is parked next to the house and covered while I regain my motivation to tear it back down. It was great having it on Friday for those two hours after this extended winter that Maryland has experienced. Nothing like hitting the water with good people and enjoying the noise, speed, and beers.

distantthunder 05-09-2018 07:37 PM


Originally Posted by Full Force (Post 4625701)

no stats, no bypass, tempsmight see 110 on a good day, people say it’s not good but been that way for years with no issues, current boatbset up from Hawk has no bypass, no stats been that way for 31 years ... clearances must be right more then anything else

My first Formula with a clone blue engine was set up this way. Ran 110 in the dead of summer. No issues with water or condensation.

Mbam 05-09-2018 07:47 PM

It is just not possible to properly maintain temp with a crossover setup. You always have cold water at one end and hot water at the other. The only way to gain temp is by having less water flow through the block. There is no way to have even temps.

The circ system is always moving water (and a lot of it) at basically the same temp through the block/heads. As the T stat opens hot water is let out allowing cold water to enter the loop. So the loop is pretty much a constant temp.

By some combination of restrictors & holes you might manage to get something that looks normal on the temp gauge but that does not tell you what is really going on in the block, center and rear of the heads. Try putting a temp sender in the hole next to the exhaust in the middle of the head. To be honest I don't know if that hole is even there any more on the newer stuff. On aluminium heads we used to drill & tap it ourselves. It is common to see 140-160 in the intake manifold and peg the gauge on the middle sender (which is next to an exhaust port) meaning there was a steam pocket there.

Full Force 05-09-2018 08:09 PM


Originally Posted by Mbam (Post 4625707)
It is just not possible to properly maintain temp with a crossover setup. You always have cold water at one end and hot water at the other. The only way to gain temp is by having less water flow through the block. There is no way to have even temps.

The circ system is always moving water (and a lot of it) at basically the same temp through the block/heads. As the T stat opens hot water is let out allowing cold water to enter the loop. So the loop is pretty much a constant temp.

By some combination of restrictors & holes you might manage to get something that looks normal on the temp gauge but that does not tell you what is really going on in the block, center and rear of the heads. Try putting a temp sender in the hole next to the exhaust in the middle of the head. To be honest I don't know if that hole is even there any more on the newer stuff. On aluminium heads we used to drill & tap it ourselves. It is common to see 140-160 in the intake manifold and peg the gauge on the middle sender (which is next to an exhaust port) meaning there was a steam pocket there.

I agree with that, just seems to be fine for my setups over the years as long as clearancing is good, The Hawk Gun I am leaving as it has been for 31 years, the Mistress I played with all kinds of options and ended up same, no bypass, no stat, 110 ish temps, oil temps always been more important to me to get right.

Rhythm and Blues 05-17-2018 11:23 PM


Originally Posted by Full Force (Post 4625712)
I agree with that, just seems to be fine for my setups over the years as long as clearancing is good, The Hawk Gun I am leaving as it has been for 31 years, the Mistress I played with all kinds of options and ended up same, no bypass, no stat, 110 ish temps, oil temps always been more important to me to get right.

Agreed Tim, I f’ing futzed around with several drilled tstats, and restrictors to no avail, dialing in the temp/psi was just bs.. In the end I went with no Tstat, no bypass and we’re using Mr.Cool thermostatically actuated oil coolers to get the oil temps up. I’m condident after all that wasted time that this will be the answer..


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