Thread: inline six woes
View Single Post
  #7  
Old July 25th, 2014, 04:58 AM
GMCDAC's Avatar
GMCDAC GMCDAC is offline
Senior Member
 
Join Date: Jan 2013
Location: Green Valley, east of Rapid City,SD
Truck: I have 4 GMCs, none with a V-6 - YET! Have had 2 in the family.
Age: 67
Posts: 553
Rep Power: 210
GMCDAC is on a distinguished road
Default Re: inline six woes

Hi Pops, you said the vibration was occurring while stopped at a light? That couldn't be a U-joint as they would vibrate while moving. If I misunderstood, I apologize. A constant "poofing" out the tailpipe can be caused by a weak exhaust valve or seat. I am working on my '72 GMC and it had decent compression on #6 cylinder--125 psi(V-8) but was oil fouling plugs. I pulled a valve cover and ran it up to TDC on #6 to do a leak down and that valve was sitting an 1/8th inch higher than the intake. Valve seat was gone, but the valve was tuff enuff to kinda pound it's own seat into the head casting.

What Rochester one barrel do you have and what engine for that matter? There can be an issue with the power valve needle retainer spring if it is installed on the wrong side of the power piston arm with the Model M "MonoJet" carb. Drawings in the kits can be unclear and assume it was correctly built when they say to reassemble in reverse of dissassembly. I put the spring in the same position as it was installed on mine and it was running rich rough and smelly. Found out that a previous rebuild had put the spring on the bottom of the arm and I just assembled it as it came apart. Put the spring on top and it ran great.

I put a Pertronix in my 230 I-6 in 2011 and have not had any regrets.

DAC
__________________
Doug Crawford
Rapid City, SD

1970 GMC K5 Jimmy Mom drove 30 years
1972 GMC C2500 owned since 1979
1955 GMC 100 driver-project
2006 GMC Yukon Denali---wife's truck

Hope to have a '60 GMC Suburban again someday
Reply With Quote