Fuel push rod question ( noise )

[Bruce in southern OH]

My question is an aluminum intake on a 36 V8 21 stud motor to have a 7 3/4" push rod?? If so what is method to cut the rod 1". I heard the noise in engine and took motor apart to find noise. First thing I found was the 3/4" round tube that is pushed in to the fuel stand had came loose and was free flowing in 5" baffle. Put the round tube in stand and still has a loud noise from fuel pump. Found a fuel pump rod marked cast iron that is same length. This truck has not been started in 8 years and was like this, Now what is best method to cut to length. ( is 7 3/4" or 1" short correct for aluminum intake ? )

[Don]

Sent you some info Bruce,FP rod should have .020 travel,if you have 1/2,,way to much,check FP stand also

[JWL]

If the push rod is 1" longer than necessary there is no way in hell the fuel pump can be installed. If the new found pushrod is the same length as the original it should work but what is wrong with the original? The 2 rod lengths are 8 7/8" and 7 7/8". The travel is .200, not .020.

[scooder]

I agree with what John said.
Another thing, is your pushrod definitely 7 3/4"? If so it's 1/8" short.
Martin.

[Terry,OH]

I agree with scooder and JWL. Also what is the condition of the spring on the fuel pump arm ? When you reassemble the fuel pump to the adaptor pack some grease on the arm, spring, pivot point, cup, rod. Also make sure the arm does not wobble on the shaft, or have lateral movement. Lateral movement can be taken up by adding thin washers, wobble indicates a worn arm or arm bushing.

[Bruce in southern OH]

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I just measured my aluminum intake on flat table 2 3/8" from table to top of fuel tower opening. Placed a cast iron intake on flat table the same measurement, 2 3/8". What is up with that??? Push rod only travels about 1/4" or so, I have to use the long push rod, the short one does not come up in the tower very far at all. Yes, all my long rods measure 8.87" and the one I cut off now measures 7.87" as per book. Trying to locate the noise in motor, I changed the fuel pump to a later one with glass bowl to see if it made a difference. Still have a noise almost like a knock but more of air compressor air noise. Last thing I did was to remove pump, pump rod and installed a blank over pump opening in fuel tower. Installed 5" baffle, tower and ran with a gravity gas feed can, still have the noise. Thanks for the replies, ideas/thoughts appreciated, Bruce

[Ken/Alabama]

Hook up a small gas can and gravity feed the carb. crank it up with the fuel pump and rod removed to see if the noise goes away.

[Bruce in southern OH]

Last sentence of post, I tried that Ken. Going to ask Don P. to come up and maybe one other person to listen to engine. I might even take fan belt off and make sure of fan noise, water pump and generator. thanks Bruce

[Kube]

Tips of the push rods are hardened. Cut it off and so goes the hardness. Just buy the correct rod.

[koates]

Kube x 2. Those push rods are case hardened and once cut or ground you are then running a soft rod end on the camshaft, NOT THE DONE THING !! You need the correct push rod 7.87" long for the aluminium 36 intake. New rods are available from Macs and others. Regards, Kevin.

[Bruce in southern OH]

Koates, first as I was told, you would not cut the cam in the first place ( umbrella would not work ) , second I put the 8.87" rod back in. If you read my post the two intakes, cast or aluminum ( I have ) measure the same from flat surface to top of location opening for fuel pump tower. If I do find a use of 7.87 rod I will remember Kubes advice to have it hardened. Would rather make something than pay for China Junk, thank you for the info, Bruce
( just came from a car meeting and several of the seventy year plus men in attendance placed shims and pieces of leather in the pump end back in the day )

[BILL WZOREK]

Originally Posted by Bruce in southern OH

Koates, first as I was told, you would not cut the cam in the first place ( umbrella would not work ) , second I put the 8.87" rod back in. If you read my post the two intakes, cast or aluminum ( I have ) measure the same from flat surface to top of location opening for fuel pump tower. If I do find a use of 7.87 rod I will remember Kubes advice to have it hardened. Would rather make something than pay for China Junk, thank you for the info, Bruce
( just came from a car meeting and several of the seventy year plus men in attendance placed shims and pieces of leather in the pump end back in the day )

Bruce those suggestion's / Shims / pieces of leather would take up any looseness and help with fuel pressure
But you were asking about noise , you removed pump & push rod and said noise was still there / I think you thoughts to remove fan belt and run is a good idea / Noise travels in funny ways >>>

[JWL]

Sooooo, there are 2 things going on here. First the fuelpump and second the noise that IS NOT the fuelpump.

[Bruce in southern OH]

JWL, you are so right, just holding out for HOPE! Noise is from this end of motor, here I go again, if I have to I will pull motor and transmission together, leaky transmission also, if you fill trans oil on floor. Just another old Truck I drug in.
.
1936 Ford truck ( I have told story before, this time I got a call and told to come and get if still interested, THAT WAS EIGHT YEARS AGO I looked at truck!!! )
.

[Bruce in southern OH]

I went to garage this evening, put fuel pump rod back in engine, gasket, baffle, fuel tower and installed pump. Started engine with an Old Model 48 carb I have, it runs the best on this carb. Don P. suggested that I run a vacuum check on engine, started engine and I have 20 in. Hg.

Home > Articles/Videos > Technical Bulletins > Fiat/Lancia > Tips on Reading Gauges > Tips on Reading Gauges: Vacuum Gauges







Tips on Reading Gauges: Vacuum Gauges

Vacuum Gauge
Though little understood, the vacuum gauge is probably the best single indicator of your engine's health you can get.

A Little Background
When your car is idling-whether it's fuel injected or carbureted-the throttle plate or plates are restricting the amount of air the engine can breathe in. The pistons are attempting to "suck" the mixture past the throttle. (Of course, in reality, it is atmospheric pressure that is attempting to "push" air into the engine as the pistons travel downward on their intake strokes.) When throttle is closed, vacuum is high in the intake manifold, from the throttle plate(s) to the combustion chambers. By contrast, at wide open throttle there is relatively little restriction to outside air entering the intake manifold, so vacuum in the manifold is very low.

A vacuum gauge reads pressure differences from atmospheric pressure, so the reading is zero in our "normal" sea of air. By convention, vacuum gauges in the US read "inches of Mercury."

Reading the Gauge
Unlike a fuel gauge, the vacuum gauge will keep you entertained with its instantaneous, wide-ranging movements.

When you floor the accelerator pedal, you can watch manifold pressure (another word for vacuum) swing from strongly negative to nearly zero (atmospheric pressure). When your engine is "on the overrun," like using engine braking down a steep hill at high RPM, you'll see really high vacuum readings. Naturally, turbocharged and supercharged will show very different results, with readings swinging into the positive at high speed. IAP's vacuum gauge is not designed for turbo or supercharged vehicles. Your vacuum gauge is also a sort of "poor man's" fuel mileage indicator; when vacuum is low, you are burning more fuel.

Absolute readings are not as useful as changes over time. That is, if you establish baseline readings under a variety of circumstances, you will know what to look for if your engine begins to deviate. Everything else aside, a high vacuum reading tends to indicate a healthy engine.

Having said this, we can make generalities about the readings you can expect. Note that engines with performance camshafts tend to read lower vacuum. Readings are also lower at higher altitudes; the rule of thumb is approximately 1 inch of mercury for every 1,000 feet of altitude gain.

The following readings will not apply to turbocharged engines, or cars with a separate venturi for each cylinder (like Weber DCOE or Dellorto carbs). All readings are inches of mercury (in. Hg.).

ENGINE STATE VACUUM GAUGE READING INDICATION
Steady idle (800-1200rpm) Gauge steady, 17-22 Normal & healthy
Steady idle (800-1200 rpm) Intermittently drops several needle divisions Sticking valve or broken valve spring
Steady idle (800-1200 rpm) Steady, low reading, 8-14 Small vacuum leak or valve timing off; could have low compression/worn rings (verify with a compression or leakdown test).
Steady idle (800-1200 rpm) Steady, low reading, under 8 Vacuum leak (check brake booster, vacuum lines, etc.)
Idle (800-1200 rpm) Needle drops sharply on a regular rhythm Burnt valve, or a valve with clearance too tight
Idle (800-1200 rpm) Needle drifts up & down, along with rpm drift Mixture off or small vacuum leak
Idle (800-1200rpm) Vacuum gradually drops Excessive exhaust back pressure (plugged muffler or catalytic converter)
Idle (800-1200rpm) Intermittent fluctuation Ignition miss; sticking valve
Idle (800-1200rpm) Steady, above 22 Ignition timing may be too advanced
Open & close throttle quickly Drops to about 2, jumps to about 25 Healthy engine
Open & close throttle quickly Drops to 0, jumps to about 20 May confirm worn rings (especially if idle shows only about 15-20) Verify with a compression or leakdown test.
- Mark Lee

[Bruce in southern OH]

Compression check today 90 lbs. per cylinder. Checked old Autolite plugs on plug tester with compressed air. Old plugs very weak and would go out with air pressure up. Tested an old H11 Champion plug and it was bright blue. Traveled to O'Reilly's Auto parts for 8 plugs, wanted to get NGJ plugs but the plug bases were all 14 mm. Needed 18mm like old plugs. The heat range of a Champion H10 in book is 6, had to get same Autolite # as before. New plugs really helped the engine. Took truck for a test drive with Don P to listen to and he also could not place were the noise was made. We drove a couple miles away from garage and truck kept getting worse. Made it back to garage and turned off, truck would not start. Had to replace old coil, ran good/better on next trip but found out gas gauge is not correct, WE/I ran out of gas!!!!!! Neighbor gave us gas to get home. Runs good/better on new gas, newer coil, new plugs, condenser that measures 38mf. Will have to order a model 97 carb rebuild kit. Next week, thank you Bruce