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View Full Version : WOT Cooling Question...



Rootsy
08-06-2002, 07:43 PM
Ok all of you knowledgable Donzi folks, i have one for ya that hopefully won't be too difficult to help me solve if you'd all be so kind.

Engine is finished and back together and i've been doing tuning an dtesting... ran it sunday night, hit 180 warning buzzer... stop and it cooled down ran it again no issues...

Tonight... hit it hard.. 5000 rpm for a good half of a mile and it hits 180 and the buzzer goes off.. dropped to 1000 rpm cools down buzzer still screaming at me. shut her off and fiddled with all of the warning sensor wires. started it up no buzzer anymore...

MadPoodle,

The other post with my motor photos you question the lack of hoses on my risers. Do you have experience with the merc IMCO risers? They flow through the flange so no external hoses are required, BUT will they allow enough coolant through or are they restrictive and need external hose. In which case i'll have to mill off the front little IMCO stamping to get the plug out of the manifold.

I ran it hard a couple of more times after my initial stint... WOT it rises from 150 to 180 and holds solid.. AS SOON as i get off the gas instantly dropped back to 150, get back into it hard and after 20 seconds or so up she goes to 180 and so on and so forth...

So i am not sure if i have the risers restricting my flow, if i sucked a bunch of crap into my motor (sand, etc), if my impeller is getting a bit weak or if i am still lean, i jetted up 3 on the primaries and 2 on the secondaries last night... my 600 vac sec holley is now jetted at 71 primary, 76 secondary which should be PLENTY of fuel... YES i do need to do a plug check yet. but somehow i feel it is a lack of water flow for whatever reason.

This is a brand new problem, before cylinder heads and risers I NEVER had a cooling issue and i get a lot of water out of the exhaust pipes and it runs 150 - 160 all day long until i wind it out and trim it up. but i have seen what appears to be plenty of water at idle turn into not enough at speed...

i just dont't want to fight this and tear things apart and waste a lotta time if someone has already run into this... every impeller i've ever seen weak won't stop at a certain temp when runnign WOT, it just keeps on rising..

so if any of you oh wise ones would toss me some good info and feedback i'd really appreciate it... but hey, I BROKE 66 mph in a 16 classic w/ a full load of fuel and it was pretty much under control... wasn't hard to hold onto at all, maybe i needed more trim wink

http://www.donzi.net/photos/jaroot037.jpg

BigGrizzly
08-06-2002, 08:55 PM
u have a estriction. easy way to check is divert water from the ex- manifold overboard- after the engine of course that will let uou know befor replumming that unit
.
Randy

MOP
08-06-2002, 09:41 PM
You can make up a nice little tester using a cheap pressure/vacuum gauge. make up a tee that will fit your hosing, this way you can insert it inline before and and after the pump to see what pressure your pump is suppying and what vacuum draw you have on your intake. Also check one risers pressure against the other to see if one or the other is restricted. Idealy you should check your stuff when new to establish reference readings. Intake vacuum should be quite low, pressure readings can vary alot between pump types. When checking inlet suction the gauge should be right at the pump, I have picked up on alot of colapsing hoses that way. That is one place I would start the lining of some of the hoses will suck in and restrick flow at speeds and not show up at cruise. Use a long hose from your adapter to the gauge so you can watch it while running.