what position is the heat riser supposed to be in cold.. mine the spring is holding the flapper so exhaust is diverted to warm intake in the cold position. this does not seem correct to me. my carbs have been boiling over so wonder if it is the heat riser.
The flapper is designed to be closed when the engine is cold and is supposed to open when the engine warms up. It might be that the heat riser needs to be "adjusted". The shop manual has a write-up on how to properly tune the spring. Another thing that might be causing your carby issues is the routing of the fuel line. If it is too close to a major source of heat, i.e. the exhaust manifold, it could cause the fuel in the line to prematurely vaporize causing headaches.
So that's what causes headaches!! I need to re-route my wife's fuel line so she'll quit answering "Not tonight, I have a headache." Or maybe it's the premature vaporization?
I always figured it was open when cold to quickly warm the intake on cold starts, then close when temp is reached.......kinda makes sense.
Here's a write-up and diagrams on the heat riser from the '54 shop manual. http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0604.html Hope this clears it up.
ok thanks.. checking my spring i broke it.. was in preatty bad shape. so have a new one on order.. sounds like it was hooked up correctly before i broke it.. anyway.. i think i will do the following.. Install new carb isolator at base (although i dont see how the old one could fail) lower my carb float level..(currently set to factory specs) wire my heat riser to full open (no heat) and see if that corrects the boil over problem.. I have a couple rochestor b's, a w1, and a yf.. all are rebuilt you would think one would work with out trouble..my understand via this forum is the yf is the better of the carbs. I am in panic mode now. my son just told be he wants the truck in his wedding in a couple weeks.. so i have to get fixed.. wowser so i will take any advise i can get to get this truck dependably running with out carb trouble..
K.i.s.s. I assume you've recently checked and aDJUSTED THE VALVE GAPS , POINTS GAP/DWELL AND IGNITION TIMINH , IN THAT ORDER... oops , sorry . There's no chance a mouse filled the muffler with dog food etc. ? the resulting back pressure will make it run hot . Coolant is clean and _translucent_ ? .
Nate, good to here from you, yep all tuned and adjusted, valves gapped.. all done to the letter of some of your earlier post. new muffler no mice that i know of. lol engine temp per gage is normal. truck runs,and idles great.. I can let it idle in drive with hood open for ever no carb problems.. but once i take it down the road... runs great at speed etc.. but after 5-15 minutes of driving the carb will boiler over at the first stop sign.. or as i pull in drive.. then die.. if i let it sit cool down she will fire up agian run rough till gas burned out.. then run fine again and the cycle starts over.. had this truck for going on 18 yrs now.. never had any trouble till a couple years ago.. been fighting with it since.. thought it was the rochector b's as they are know for leaking etc.. have tryed a few of them. all had different but simialr problems.. then last weekend tryed the first YF.. and it boiled over so got me wondering if it was the carbby at all.. but a cant figure out any other cause.
Heat Risor O.K. , to properly set it up , unhook the coiled bi-metallic spring and _gently_ rotate the weight , it should twist the shaft and lift up then smartly drop back down as soon as you release it ~ if not , go get some good pentetrant and soak the shaft where it goes through the exhaust manifold (note : never , EVER force it !) , then work it until it flops back and forth loosely , allow to dry and them puff some graphite powder or Heat Risor Solvent into it as you twist it , please to note you MUST NOT use chemical lubricants here as they'll gum up as soon a you start the engine and it gets hot ~ *very* important to lube it with graphite . Now it's all loosey-goosey , installing the spring is dead simple : coil it up so the weight is lifted when the engine is cold ~ if you cannot do this , remove the spring and flip it over , it was installed wrong last time . The valve should just _barely_ hold closed when the engine is cold , the idea is to open it up quickly as the engine warms . I hope this helped .
