Has anyone had an intake manifold leak on inside ? I HAVE BEEN CHASING ROUGH RUNNING MOTOR DOUBLE CHECKED VALVES, AIR FUEL MIXTURE,TIMEING,,PLUGS,WIRES,DISTRIBUTOR, NEW HOLLEY 600 ON QUADRAJET INTAKE WITH ADAPTER BLOCK I finally got infared thermometer passenger side 550,600,575,620. Drivers side 345,400,375,410. While taking temps I noticed pass side header blue color drivers side is still shiney stainless. IT seems pass side running LEAN only thing I can think of is intake leaking inside already check outside ,any ideas Mike
Sounds like you're not sure what the problem is. I would let it idle and pull the plug wires one at a time and see of the idle changes or not. That way you'll find any dead cylinders. If all are firing I would put a vaccum gauge on it and diagnose any symptoms seen on the gauge, this will help diagnose a vaccum leak of there is one. Plenty of articles and videos about that so I wont repeat it here. Good luck! Sent from my SM-A105G using Tapatalk
I'd say you're thinking the right direction. If it were a carburetor or jetting issue I'd think the center two cylinders on one side, and the front and rear cylinders on the other side would be similar in temp. That's assuming a dual plane manifold. You could check the top side for vacuum leaks by squirting some WD-40 or carb cleaner along the top of the head/intake joint, but I don't know any way to check the underside. Did it just start acting up, or has it always seemed a bit wonky? Lynn
Milled heads? Decked block? Cut enough off both or either and milling the intake manifold becomes necessary for proper sealing... This isn't an issue on flatheads but needs to be checked on OHV motors.
Did you check the float level? I had a poor running 350 and I popped the sightplug out gave the car a slight shake and nothing dribbled out of the sight plug the floats were a little low. Seemed to run a lot better after a small adjustment.
What year Q-Jet intake?? The pre '68 versions have a exhaust crossover track that runs under the gasket at the front of the carb pad....some of your adapter plates don't cover this well and they leak at the corners of that passage.
There's any number of things that can cause cylinders to run richer or leaner than other cylinders. It can easily be carburetion, but could be valves, timing, or even the headers themselves if they aren't true equal length tubes.
I've had something similar happen (although not an SBC). The intake manifold was just slightly warped so it had the tiniest of leaks on one of the intake ports. The result was that at idle it would run ok...maybe a little hickup here and there, but at 3/4-WOT, it would start pinging. I tore the motor down a few times, rechecked everything, and couldn't get it to go away. Ended up swapping the intake and it went away. If one side is running way hotter you could have leak on that side. I am assuming that you've checked your carb already.
If you have valvecover's with breather's in them, spray some carb cleaner in the breather hole and see if the idle changes. If it does, it has a vacuum leak, either a gasket or the manifold itself.
I did a R&R on the intake manifold one time and it ran good for a while. Then one day I noticed there was a little puddle of antifreeze under the car. It started running rough and fouled #7 plug and I thought it was leaking at the head gasket. I couldn't figure it out and one night laying in bed, I wondered if the bolts were still tight. I went out and checked and all the intake bolts had worked loose. DUH! I re-torqued them and off it went! It was sucking antifreeze in the intake port and running down the end of the head and off the end of the head gasket.
I used felpro permatorque intake gaskets on a 327 many years ago and they leaked under the manifold because they don't compress. The engine sucked oil and folded plugs. Now I only use Mr Gasket or Edelbrock paper type gaskets because they do compress and haven't had a problem since.
Woah! The temps might not be different!! You said headers on one side were shiny, IR thermometers read different temps on shiny versus matt. I would start with the basics amd see where you get. Propane torch cracked open and not lit waved around the carb and manifold can help you find a vaccum leak. Alternatively take a big draw on a cigar and blow the smoke into a vaccum line, you'll see the smoke come out of any leaks. Sent from my SM-A105G using Tapatalk
I don't know if anyone is still looking at this post , but wanted to try some of suggestions also talked to holley representative and he felt it was intake leaking passenger side, I replaced gasket didn't change a thing , to refresh post, not bad at idle, rev up 1500/1800 rpms runs ruff pass side excaust 500/600 hundred degrees driver side 350/400 degrees. Checked plug wires, plugs, manufacturer rebuild holley 600cfm on quadrajet manifold, carb adjusted properly, timing 12 tdc, what could make temps so far off holley rep said jets should not cause 1 side to lean out Iknow it has to be small fix any help please
Its hard to say without hearing it run. If its ok and starts running bad when you rev it up I would check the distributor drive gear and the distributor clamp to make sure timing wasnt changing. If you have a vacuum advance I would also check that. Vacuum guage is your best friend for this type of thing, the amount of vacuum and the behaviour of the needle will disgnose most fuel system problems. Sent from my SM-A105G using Tapatalk
I am having trouble grasping the black/ gray needle reference also my RA is causing typing problems sorry, Mike
I made a simple cheap smoke machine to find vacuum leaks. It works amazingly well to find leaks you might not otherwise be able to track down by sending visible smoke signals from even the most hidden leaks. I'm sure you can find some YouTube vids on how to make one. I made several and gave them out as gifts to gearhead friends. Baby oil has a low temperature smoke point, fiberglass wadding or strands keep the soldering iron wet, and the hoses will flood the entire vac hose and vac passage system with smoke, even at the remote areas of the system. Plug one hose into your car, and blow in the other hose. I even found one in a hidden spot under an intake manifold by looking at the smoke signals. It doesnt matter where you plug into the vac system, you can still flood the whole hose system and hoses with smoke. Sometimes I hook to a vac port, sometimes a brake booster hose, sometimes I even blow in thru an air cleaner hose after taping it down to a small opening. It all heads to the leaking spot anyway. Soldering iron, a dab of epoxy to hold it in the jar lid, baby oil, a wad of something to keep the iron wet with oil, two hoses to blow the jar of harmless smoke into your passages. Watch for smoke signals. less than 10$ usually. Great cheap gift for gearhead buddies who will then think you are a genius after they use it one time. WHY BE ORDINARY ?
OR....................take a spray bottle with water and squirt it on each exhaust manifold port. The one(s) that don't sizzle and spew are NOT firing and making heat. Beats shocking the fool outta your self or burning your fangerz!? Just another way to complete the same job........ 6sally6
Check for intake manifold gasket leaks and verify flatness of the manifold searing face. Aluminum manifolds are suspect and used manifolds may have been improperly machined, or machined to fit a block and / or head that had been decked.
Think a doubled gasket may have sometimes attempt, to seal. Not to advise this. I always center-punched the end seal surfaces mid-width, along a centerline, 6X, block & manifold. In case the ears didn't align the seal.
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