Torqueing bolts down to the 20/30 ft. lb.s specs, still using what I believe to be the original manifold clamps, I can only get around 150 miles before the rear clamp backs off enough that the clamp slips off completely. Motor is stock. I have zero previous experience with these motors and any help would be greatly appreciated.
It's 8 minutes after Midnight here so I'll have to wait until tomorrow to go out and crawl though the mess in the garage to see the side of my currently stock 68 292 to see what holds the manifold on. As far as I know that engine has never been apart it just leaked oil every place one can possibly leak when it was given to me. I can also take a look at the 250 in my truck that I know has never been apart and see what holds the manifold on it. Now all I have to do is remember to do that.
‘re lock nuts.......good suggestion, but not ‘ny-lock’......they melt......use the crimped type or aircraft style ....... Ray
Do you have a shop manual for that specific vehicle and engine? I'm not completely familiar with the manifolds on these engines, but I suspect that there's a particular procedure for attaching the intake and exhaust to the head, due to the fact that the manifolds are also bolted together independently from the head. Mopar slant sixes have a similar process for attaching the manifolds for the same reason with a very specific order of assembly and torque specifications. In any event, I don't think you'll want to assemble and torque down the intake and exhaust manifolds first and then bolt down and torque the whole thing to the head as an assembly. There may also be some requirements for re-torqueing after the engine has been thru a couple heat/cool cycles.
Are you using a truck header or car? And also I’d check the clearance of the header and firewall Sent from my iPhone using The H.A.M.B. mobile app
My 250 has been apart a lot for varies reasons, but the manifolds have never come loose without me taking them off. Add lock washers, and recheck after it's hot. Mine are really tight, way more then 30 foot pounds. Could also be the gasket you are using is it thick? Try a stock replacement if you haven't.
Most exhaust manifolds "grow" when they are hot and "shrink" when they cool. Depending on construction, some are hard on gaskets and packings due to this. Are you using a gasket ? Is the gasket compressing ? Also.....do the hangers allow for reasonable movement of the entire exhaust system when it expands, contracts, bounces etc. ? The correct bolts, washers etc. are probably the answer, but doesn't hurt to check out everything else.
The exhaust has the correct, stock, clamps. exhaust isn't rigid, as in, enough movement to allow for temperature change, are far as my non PHD opinion is concerned. I've heard these manifold can warp, I'm wondering if it's warped enough to be applying enough pressure to "overpower" the 20 ft.lbs the manual says to torque the bolt to.
stock gasket, manual says factory spec is only 20 ft. lbs. for the first and last clamp bolt. How tight are you torqueing yours to, even ball park, so I might get an idea of where you're running at?
To be clear, the manifold doesn't have studs. The intake/exhaust clamps are held in place with bolts. So lock washers or any such remedy will not work for this current set-up. However, I might just have to go with studs instead then utilize the Stover nut idea. Thank you all for the input.
If I remember correctly those bolts are 3/8, using a 9/16 wrench or socket to tighten. If so....20 lbs Torque seems a little light. More like 35 lbs seems right to me fir 3/8 bolts. Just my opinion. Bones
Back in the 60's when I was a helper, I was taught to tighten the manifold bolts on the 194-292 engines every time I did a tune-up on one. They all seemed to need snugging up but the end two bolts were always the loosest.
The end bolts on my 250, are bolts, al the others are studs. I use lock washers and really tighten them. No torque wrench, just longest 9/16" and really pull on it. Joe
You need studs get a stud that coarse thread to go in the block and fine thread brass nuts with lock washers to hold the manifold to the head.
are you the same guy that also joined yesterday under the name 66C10 and was putting a 454 in a 66 truck?
I like safety wire , After some experience working on aircraft , it is the most reliable method I have found to secure a recurring problem with fasteners.
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