Blows like old faithful after 20 minutes of driving

mynauticaldog · Post by **mynauticaldog** » Thu Jul 28, 2005 8:11 pm

I have finally gotten my 67.5 1600 back on the road after sitting for 18 years(keiths carbs,GB EI,Rally brake kit,all new hydraulics,more and more,don't tell my wife what that stuff costs). And now a new set of problems. Car starts and idles perfectly, backfires under load around 2800 rpm when cold, holds temp at about 190 for 20 minutes of driving, then goes through thy roof and boils over. I caught it in time and tried 2 different rad cleaners and put in a new thermastat(this was absent up till now) but its still doing the same thing. Any and all thoughts will be greatly aprieciated. Thanks, Chris

SLOroadster · Post by **SLOroadster** » Thu Jul 28, 2005 8:22 pm

Check your headgasket. Retorque the head first, if that doesnt do it pull the head and check it for straightness, then replace the gasket. Does it backfire through the carbs, or out the back. If its through the carbs, you are way lean. How does your radiator cap seal look? How much advance do you have at the dizzy? I think you want 16 degrees on an R16.

Hope that helps,
Will

mynauticaldog · Post by **mynauticaldog** » Thu Jul 28, 2005 8:44 pm

I was hoping that it wasn't the head, it doesn't smoke much at all. Backfires out of the carbs, had a real good su guy ajust them and the timing. Double checked the timming and looked to be dead on 16, retarded it a couple points and backfire got a bit better. Rad cap seals well but i have seen a bid of seeping around the bolt that hold that housing on when its really hot. thanks, chris

DELETED · Post by **DELETED** » Thu Jul 28, 2005 10:44 pm

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JoeK · Post by **JoeK** » Thu Jul 28, 2005 11:05 pm

Call me a simpleton, but have you checked the thermostat. Could it be closing when it heats up?

Post by **itsa68** » Fri Jul 29, 2005 8:21 am

I had the same problem of backfire and overheating.
The main problem was I was running way too lean on the carbs.
To correct the problem, I re-torqued the head, re-adjusted the valves, made sure I had new gas in the tank, dialed in the timing, and re-tuned and balanced the carbs.
Have the reservoir tank cap tested at the local rad shop to see if its releasing at the the proper pressure, which I think was about 15 psi.

Ray B.

mynauticaldog · Post by **mynauticaldog** » Thu Sep 08, 2005 6:49 pm

I've got to thank you roadsterhaulic, I finaly got some time to work on the car and got myself a torquewrench, and T'd the head to 45-48 #. I let the car idle for about 1/2 an hour then drove it for about 20 more minutes and it never went over 170. I guess that means I have to tell my wife I'm not selling it anymore. Before when In was annoyed with it she said that was a good thing because she was scared to ride in it and had almost talked me into getting a Miata! Thanks again, Chris

SLOroadster · Post by **SLOroadster** » Fri Sep 09, 2005 11:49 pm

I'm not positive, but I think the R16 head should be torqued to 65 ft lbs like the U20. You might want to double check that.

Will

DELETED · Post by **DELETED** » Mon Sep 12, 2005 8:56 pm

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mynauticaldog · Post by **mynauticaldog** » Tue Sep 13, 2005 5:37 am

Geez, you don't have to rub it in, Mark. Oh well, I've done pretty well on ebay lately, so she let me buy a '65 Mustang instead!
Chris