If the spray I am using starts reducing the idle, wouldn't the vacuum go down if there isa leak or not? The confusing thing to me about this problem is if I spray starter fluid directly into the carb the idle dies rather than increasing. To me this is strange as I would think it would increase RPM. However the fact remains that I can get the same results of the engine decreasing RPM when spraying the intake manifold in a specific target area. Does this not tell me that I have a leak?
In a nutshell...no. If you spray carb cleaner at a vacuum leak, as Larry said, your temporarily plugging the leak with the fluid. That would make the engine idle increase as well as the vacuum reading. I honestly don't hear any difference in idle speed in your video
BTW the plugs on the car are clean and would reflect a lean condition, which I am told would reflect a vacuum leak. At the end of the day changing the manifold gasket would be a wise investment to rule it out. The garage is telling me they feel it is cam related and I am wasting time and money. If I go the intake manifold gasket and manifold inspection route I will keep the motor in the car. If I need to rebuild the cam/valve train/top end of the motor, I may just pull the motor. (which I do not want to do) It just kills me because all my senses tell me this motor runs great when driving down the road and is tight and quite. It just will not tune to specification or idle in drive/reverse. I feel like I am missing something simple. I am still thinking vaccum leak, bt not traditional. I am going to plug the PCV valve and all carb ports as Larry suggested and see if his test reveals anything.
The plugs would just indicate a lean mixture. Not a vacuum leak necessarily. Looks like your convinced about the intake gasket. Do it and rule it out. It's likely not going to fix the issue. "Test, don't guess"
I watched it on my phone and couldn’t hear a difference, but went to my home computer with a subwoofer and it’s clear the idle drops significantly
Watch the video until the last spray. You can hear the RPM drop clearly. It took a while to get to the exact spot of idle change. Afterwards we were able to repeat at each spray at the target spot. We also blocked the carb with cardboard to make sure it was not overspray.
Good thought, I always had to torque to 55 ft-lbs even though I've seen some people state that only 35 ft-lbs are necessary. -Bob C.
Starter fluid or even carburetor cleaner will richen the mixture a lot, so the idle will drop. If you spray it directly into the carburetor of a idling engine, the same thing will happen. Try something less combustible, like WD-40. Watch the vacuum gauge. If there is a leak between the intake flange and head, and you temporarily seal it, the vacuum and idle should go UP.
Like I said - when I've used less than 55 ft-lbs, including with aluminum intakes, I've had vacuum leaks with symptoms exactly like is being described here. -Bob C.
I've never had that happen. My SP1 is torqued to 40 ft. lbs with aluminum heads. TA Performance recommends 45 ft. lbs for aluminum intake/iron heads. http://taperformance.com/PDF/Torque_Specification.pdf
Find a new shop to work with.. They don't have a hard grasp on the theory, and/or the hard experience in real life, if they think that you can't perform that test with a hydraulic lifter. If they said that to me, my response would be "how much money do you have in your pocket right now"... their answer would be the basis for a wager that I could in fact do it. Any properly functioning hydraulic lifter will hold the oil in it, and not collapse. I have done this on the dyno, with hydraulic lifters, in engines just like yours.. every time we get a motor in for repair, and the issue is performance, that is the first thing we look for.. Heck, I have even done in on an engine stand.. as long as the motor has good lifters in it, that don't bleed down excessively. We are so conditioned to hydraulic lifters being of poor quality, that every time I walk by the engine for one of my race cars, which has been sitting in the shop with the valve covers off for over a year now, and number 1 exhaust valve is fully open still.. I have to chuckle.. It has hydraulic lifters in it. Any good motor man knows this trick.. find one. BTW.. it appears to me that your spraying right at the center of the manifold, to get the engine to react.. if that is the case, what your doing is introducing fuel to the engine via the exhaust crossover. If you get enough liquid there, reversion will eventually introduce enough into the cylinder to slow the motor down. You have one of two things going on here. A bad intake manifold leak, that is effecting only one cylinder.. which is why the "global fixes" (hand over carb) don't work. Someone has already fattened up the mixture to try and solve the problem, any more fuel kills the good cylinders. But a cam timing issue is still the most likely cause here. JW
My 70-455 was hesitating when I took off replaced carburator, Hei , I pulled the engine and rebuit it and foung a flat lobe on the cam replaced ,and runs great
Ok, More information on this issue plaguing me. I decided to change the PCV grommet when I saw a crack in it. (of course it was hard as a rock and a big piece fell in) Put a new grommet and PCV valve and no change. While I was changing the grommet I Had to heat up the manifold to get the PCV valve into the grommet without pushing another grommet into the intake. LOl While I was warming up the motor I accidentally let the vacuum line disconnected and it idled better than normal. I then hooked my vacuum gage and noticed it was the same 14lbs with the hose off hissing like mad. Put my thumb over the line and idle slows, but vacuum only increased slightly. Maybe 1 lbs. I always remembered that when I pulled a manifold vacuum line off while running the engine would die not start idling better and higher. Another thing I remembered is when I got the car it had a ticking exhaust manifold leak on the drivers side that I had fixed. 2 days after I fixed it I heard the tick again on a cold start one day. It warmed up and went away and has never come back. (thought that was weird) The other note is that the temp light has always been stuck on while running since I got the car. I discounted the issue because there is a separate aftermarket temp gage that stays in spec.(about 180 degrees) So I measured the temperature at the spot where the paint is gone from he exhaust crossover on the intake while idling. It was 319 degrees. I measured exactly where the temp sensor is and its at + 220 degrees. Obviously this is why the temp light stays on in the dash. Should the intake get this hot and would this be consistent with a vacuum Vally leak. Or is something else going on with the intake manifold. Tomorrow I am going to do the paper over the valve cover test, that I think Larry suggested. I should have done it while I had the PCV grommet out, but I forgot. I was to excited to see the cracked Grommet and that it might help.
You may have a short to ground on the Temp light circuit, either the wiring or the temp sender stuck in the "closed" position. Pull the ground wire when the car is cold and check the temp sender terminal to ground for continuity. It should read open in cold, and closed when (too) hot. The crossover temp is about right for fully warmed engine and heat soaked intake from exhaust though the crossover. Is your temp sender located on the front passenger side near the thermostat housing? Take a reading at the thermostat housing, and also on the end tanks of the radiator near the inlet and outlet of the radiator and post them. You state the other gauge reads 180F, where is that sender located. (Pics would help) You have a helmet fire going on and that has you grasping at any and everything. Work on one thing at a time. Eliminate the things that can cause damage first, and then work on correcting the issue that result in poor performance.
Are you saying the engine would idle with an open PCV 3/8" hose? Or was the PCV valve plugged into the hose, and just hissing because it was out of the intake?
To answer Larry70GS question, Yes the 3/8" hose was just wide open from the carb sucking air with a loud hiss. I hooked up my vacuum gauge and it was at about 13lbs mercury. When I put my thumb over the hose the idle slowed down, but the Vacuum only increased by 1 lbs. I would have thought a huge leak like that would react diferently. The PCV hole in the manifold was plugged off at this time with a socket extension in order to soften the grommet for easier install of the PCV valve. So the manifold was plugged, but the carb hose to the PCV was wide open sucking air.
