6.5 and 6.2 GM owners I have a interesting discovery.

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6.5 and 6.2 GM owners I have a interesting discovery.

Postby Radrick » Wed Apr 09, 2008 10:22 am

I am a member of a GM Diesel forum and in doing some searching on the topic of heater hoses I made a interesting discovery. On the 6.5 engines there is a quick disconnect fitting with an aluminum tube heater hose unit that has problems as it ages. As it turns out there is a 5/16" restrictor in this fitting and when converting this to a barbed fitting and hose some people have experienced problems and have had to replace damaged heater cores. I'm a little surprised that this could cause heater core damage but it defiantly tells me that there is plenty of flow and gives me a way to regulate it. They are using the 6.2 barbed fitting from GM because it has the correct restriction in it. I am planning on running a open barbed fitting to replace the quick disconnect and putting a 5/6" restricter in the heater core branch of the wvo tee. This should ensure that I have plenty of flow to both my wvo system and my heater core. So if you are running a 6.2 or 6.5 you can easily reconfigurer your heater hose supply and increase your available btu's for you wvo system without affecting your cab heat. Just an fyi for the fellow gm owners.
1995 Chevy K1500 6.5 TD not on WVO yet but soon.
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Postby SunWizard » Wed Apr 09, 2008 10:48 am

Thats good info to know. Here is an idea thats even better than a restrictor, put a ball valve on there. Then you can adjust the flow to the heater core versus the VO side. This is how I did my truck. And it allows me for most of the year to completely shut off any flow to the heater core.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Postby Radrick » Wed Apr 09, 2008 10:57 am

SunWizard wrote:Thats good info to know. Here is an idea thats even better than a restrictor, put a ball valve on there. Then you can adjust the flow to the heater core versus the VO side. This is how I did my truck. And it allows me for most of the year to completely shut off any flow to the heater core.


What about those foggy damp summer mornings :cry: ? Oh thats right your in CO not MN. :) . I is a good idea once I get going on the plumbing on mine I will probably be installing quite a few valves. I like to tinker with stuff and it will be interesting playing with the balance. I think it is good to know that there is a fool proof way it can be done also.
1995 Chevy K1500 6.5 TD not on WVO yet but soon.
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Joined: Tue Mar 11, 2008 12:10 pm
Location: Rochester, MN

Postby VegMeister » Sun Apr 20, 2008 10:59 pm

foggy damp summer mornings: pop the hood, crack the ball valve just a tad!

Interesting situation I had yesterday: almost 80F in indiana, had the heater core shut off, hit Chicago and the fog reduced visibility to 50ft and lowered temp to c.a. 50F. No easy solution to that one without getting off the highway, so I rolled up the windows and slipped a shirt on. By the time I got out of Chicago traffic it was a hot enough night to not need to bother turning the heater core on.

My 6.5 only needs the SLIGHTEST bit of flow to the heater core, even on the coldest of days.

Here's a random thought: throttle the flow to the FPHE/heated lines/fuel pickup, but leave the ball valve on the return side (yeah, that's right, I have ball valves all over the place) wide open. That way you have lower pressure on that whole system. As long as your flow is good enough to keep your veg oil temps up, the lower pressure will avoid all kinds of problems in that system.
centralvalleybiodiesel CF
1993 GMC Sierra K2500 6.5L + homebuilt veg kit, OEM glowplug failure (update: rebuilt with a 6.2 block, working fine)
1988 Ford 6.9L OEM dual tank, 90+% veg oil blend.
1989 Ford 7.3L, 80+% veg oil blend.
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Postby Radrick » Wed Apr 30, 2008 2:59 pm

I have found some additional infomation that will help ensure that there is plenty of coolant flow. It seams that in all 1996 and older 6.2 and 6.5 GM diesels they used a 87 GPM water pump but in 1997 they redesigned the water pump and increased it output to 130 GPM. These water pumps will fit at least some of the earlier models. I am installing one on my 1995 this weekend. It not only will increase flow for the wvo system but helps to eliminate the overheating problems these engines can have when towing in hot climate conditions. I had the parts store pull out the replacement pump for mine and a 1998 pump and just did a comparison right there on the parts counter. everything matchs exept the size of the impeller.
1995 Chevy K1500 6.5 TD not on WVO yet but soon.
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