I think I might have a spare grommet in my parts stash, I remember I replaced the PCV valve but for whatever reason I didn't change the grommet. I'll check the torque on the manifold and see if there's an improvement. Also the intake gasket is metal correct? If necessary can they be reused with some sealer or is replacement recommended?
The PCV grommet will not cause a vacuum leak no how hard it is. The intake manifold may not be sealing because of a bad fit.
Disagree. If it has become brittle and shrinks with cracks the intake is exposed to unmetered air. That is the definition of a vacuum leak. This has happened to me before. edit: If you drilled a hole through the intake into the valley area would that not cause a vacuum leak? The carb is sucking full manifold vacuum through the valve, so any leaks are just ways for air to get sucked in by the pcv port of the carb
If there was a hole in the valley area that's tapping into the crankcase instead of the sealed manifold area right? Then if there was a hole that instead would act as a breather? Perhaps if the grommet does not give a good seal then air is getting past the seal and is drawn in that way?
Yes the stock gasket is aluminum. Sealant is typically used around all the ports, though some guys don't use any since the gasket is designed to be crushed when the bolts are torqued. I use grey rtv and haven't ever had a leak. I would get a new one if you remove the manifold, but re-torqueing the bolts to spec might solve the problem without removing anything. Correct but when the pcv hose is connected the carb is sucking full manifold vacuum from where the valve is. Maybe it's irrelevant clean air vs crankcase vapors but considering my rpm would change when spraying the pcv valve, that meant whatever I was spraying was getting sucked up by the carb. /shrug FWIW when I took the old grommet out it was so brittle that it broke into many pieces. Not a problem since my manifold was off anyway but if those fell into the valley area I wouldn't be very happy
Well I'm sure I have the grommet, and it's not something that's difficult to get to. When I get a chance later in the week I'll replace it and check the torque on the manifold, I'll look up the sequence in the manual.
No, that is the crank case, not the internal intake port. The hose to the PCV valve has manifold vacuum. The end of the PCV does not. The PCV valve is actually a controlled vacuum leak. The carburetor is calibrated to run with that controlled leak. If you pulled the PCV valve out of the intake and let it suck air outside the crankcase, manifold vacuum would not change one bit. The pressure inside the crankcase would go up some, but that's about it. If you pulled the hose off the PCV valve, you would create a massive vacuum leak which would probably stall the engine. You are confusing the crankcase with the internal intake tract/ports. If you drilled a hole through the intake manifold into an intake port, that would create a vacuum leak.
The grommet R+R was tough for me. I lost 2 into engine before my last attempt. I had an original pvc that had a smaller tube on it and that worked for me.If someone can show easier way .
Intake has been torqued and grommet has been replaced. Car "feels" better but I still get some pinging under WOT going uphill. WOT on level ground doesn't provoke pinging, next I think I'll try adding octane like Larry said. For the record I've been using 93 with a lead substitute.
Shouldn't be pinging with 93. If you're sure there are no vacuum leaks now the only thing I can think of is timing or overheating/hot spots. Maybe afr too lean to being with? Might seem silly, but do you have a thermac air cleaner on your carb? Sometimes the valve can rattle quite loudly. Would be funny if that was the culprit this whole time.
I do still have the thermac air cleaner actually, if that's what I've been hearing this whole time that would be hilarious. If the mixture is the culprit does Holley have tuning parts for the spreadbore carbs? I believe there's a metering plate but I'm still a carb newbie
Of course they do. Jets, power valves and most other parts are the same as used in the square bore 4150 carburetors. You really should get an air fuel gauge if you want to tune your carburetor. What Holley carburetor part number do you have?
I was adding a bottle of lead additive to my tank every time I filled up - This was on my way to the nats in bowling green years ago. Well don't you know no problems - until I come to the first intersection upon entering BG. Car cut off in left turning lane. I only way I was able to start was holding pedal to floor while cranking limped off to the side. Barely to pull into hotel.When I pulled a plug it was color of additive. Had a tooth brush so I cleaned a couple + it improved. My plugs not my teef Since it was raining next day anyway I walked around till I found new plugs.Then when I inquired about stop club/ next day at oil change the locals didn't think it was a good idea for me to go to it. ? ?
I think the Spreadbore Holleys' are double pumpers if not mistaken. My 650 was If you have numbers on top of the airhorn I can tell you what jets and such belong I have a Holley book with the list numbers in it. I would get an adjustable vacuum canister for the distributor. This always seems to be the problem with part throttle pinging. If you have followed Larry's tuning tips for getting the best out of your distributor then you just don't have it set right. There used to be an old trick of squirting water down the carb while keeping the revs up but you can't drown it. just use a squirter and slowly squirt it in with engine at 1500 rpm and this will get some junk out of the combustion chamber. ever seen a head after a blown head gasket that is leaking water? well it gets pretty clean in that cylinder. lol. You could try jetting up one number in the carb to stop the pinging or making sure the floats are up to proper level. You might just try a gallon of race gas with your next tankfull and that might be enough to keep it at a minimum. A NGK plug may work better in the engine and you may try one size colder if they are not sooted up and burning white. Those extended tip plugs can cause some of this too. There is something else on the video when you step on it and it rattles do you have the heat control valve on the passenger side of the car at the very end of the exhaust manifold? There is a valve there that closes when engine is cold and opens when the engine warms up. Well those things can rattle like mad when on the gas.
Wide open throttle going uphill is pretty much the biggest load. To some extent this is a common time to hear pinging, especially when you are working the edge of maximum timing advance. Remind me are you using the vacuum advance at this point? I would try backing off the timing by a couple of degrees and repeating.
Thanks everyone, I'm going to try and answer everyone's questions: Thermac air cleaner? Yes, I am using a thermac air cleaner however as a test I swapped it out with a spare aftermarket air cleaner that I had and the rattle seems to have subsided however I can still hear some slight pinging at WOT. Vacuum advance? - Currently the vacuum advance is disconnected from the distributor and plugged to prevent a vacuum leak. Holley Airhorn # - 80555-1 0113 (I've also attached a picture) Water down carburetor - I have heard of this trick, I have performed it on this car recently. Distributor setup: I have read through Larry's setup guide and he's been very helpful with me. However like you said I could have the distributor not set up correctly. I have purchased a dial back timing light and my current adjustment is 10* initial and 25* total. I can reconfirm this as well. Retarding the timing a few degrees to hopefully isolate the detonation is a good idea. It was also mentioned that the engine running hot could be a factor of detonation. The thermostat in the car I believe is a 195*, when according to the manual it should be a 190*. Can the extra 5* play a factor in this situation?
Unless you are having issues cooling, no. Problems arise in newer cars with the wrong temperature thermostat when they have an ECM expecting certain temps. If you aren't running hot then 5* shouldn't make a difference. Are you running hot? Another silly thing to check is if your car has EFE valve that can also rattle. It's vacuum operated valve that allows exhaust to flow through the intake manifold when the engine is cold. Also known to be a noisemaker
Okay, the car is pretty good at regulating temp so I shouldn't be worried about the thermostat then. The EFE valve you mentioned, is it under the exhaust manifold stove or is it in another location?
It's called a heat riser. If the engine uses one, it should be between the exhaust manifold, and down pipe. I don't think they did.
