I've got this 65 Valiant running pretty good considering it has an intake manifold gasket leak. I put a new gasket on 2 years ago when I got the car but never have driven it on the road but started it a few times. It's leaking now. It's hard to start up. I'm guessing that has something to do with the intake gasket leaking. It idles pretty good, timing is dead on, and idle mixture, and speed is correct. It hesitates at full throttle and pops through the carb. I checked it with a vacuum economy gauge and it's right dead on the line between fair and good vacuum. So is there anything I need to use in order to assure a good seal on the intake gasket? Someone told me to use Copper Spray.
Changing intake gasket on a 170, any tips?
- Thread starter wh23g3g
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nm9stheham
Well-Known Member
If you have a vaccum leak, it will show up mostly at idle and not effect full throttle operation. So I doubt that you have a serious vacuum problem. Yes, there is a sealer call CopperKoat in a spray can. But, I would use a thin film of blue RTV silicon sealer gasket sealer.
When you say it hesitates at full throttle, do you mean it hesitates when you go from idle or a partly open throttle and then open the throttle quickly? Or, does it do this with the throttle full open for all of the time that you hold the htrottle full open?
When you say it hesitates at full throttle, do you mean it hesitates when you go from idle or a partly open throttle and then open the throttle quickly? Or, does it do this with the throttle full open for all of the time that you hold the htrottle full open?
I remember when I had an intake leak on my 73 Charger with a 400 and it was causing all kinds of problems starting and idling. I was working on the Valiant last weekend and I reset the timing to 2.5 degrees BTC and did the mixture adjustment for smoothest idle just as the Plymouth service manual says. I got the idle at around 550-600 and it's smooth. It takes a few turns and pumps to get the engine to light up. Before I did all that you could be in park and rev the engine up full throttle and it would pop through the carb or drive it around and full throttle it and it would pop. Now it doesn't do it as much and it didn't seem to die when I did it, it took off with a lot of power. I was amazed at the power increase after I did the mixture adjustment and reset the timing to specs. I knew how much trouble an intake leak caused on my Charger so I checked this little 170 and sure enough it was leaking at the manifold to head enough to raise the idle up. I am shocked to see how much power this little 170 has with just a little 1bbl.
bigus1949
Well-Known Member
if it's backfiring thru the carb and or exhaust its most likely in the timing
cuda65vpt
cuda65vpt
A bad intake valve would cause backfire, not sure about a vacuum leak.
nm9stheham
Well-Known Member
A vaccum leak will typicaly cause bad/rough idle and stumbling off idle and light cruse. Ususally with open-throttle, it will be smoother. It would help if you tell us more what you mean by open throttle.
It certainly won't hurt to reseal the intake with some RTV; don't use the CopperKoat. It is just not the direction I would go. Let us know how that does.
I would be looking for something causing a lean condition at full throttle, like a fuel restriction, plugged fule filter, ported vaccum line leak, partly plugged carb, low float level, etc., or a distributor advance issue. Kind of a wide array of possible issues!
Does this distributor have the orignal points in it?
It certainly won't hurt to reseal the intake with some RTV; don't use the CopperKoat. It is just not the direction I would go. Let us know how that does.
I would be looking for something causing a lean condition at full throttle, like a fuel restriction, plugged fule filter, ported vaccum line leak, partly plugged carb, low float level, etc., or a distributor advance issue. Kind of a wide array of possible issues!
Does this distributor have the orignal points in it?
demoman3955
Well-Known Member
a leaking exhaust pipe will cause backfire on deceleration, a timing problem will pop through the carb, a bad accellerator pump will cause a pop in the carb and stumble on acceleration. so many possable problems.
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