superfragl
Active Member
You will have to cover the carb opening. This method will give you a better result. I was able to see the leaks at throttle shafts, etc.
Low low vacuum at idle
- Thread starter josehf34
- Start date
I'll do it in a moment!
Hey guys I have a question. Does the wet test can be done with automatic tranny fluid? or engine oil is a must? I did it using dexron III fluid but a friend told me that kind of liquid can give me a fake measurement
I repeat the dry test and now after the timing chain change and camshaft advance I have between 100 and 105 maximum 110 PSI on all cylinders, it still looks a bit low but If I'm right the compression ratio of this engine is 8.55:1 which sould be around 126 PSI at sea level (14.7*8.55)/1 but I don't live at sea level, I live at 5100 ft which should give me something like 105 PSI ((12.2*8.55)/1)
What you guys think? I've never trusted on this calculations but looks like my current compression test results are similar to those calculations, I hope the next week I'll get the leak down tester
superfragl
Active Member
Not sure on the pressure, but if you see improvement after messing with cam - your problem could be in the valve train. Still, leak down test will tell you a lot.
mr. fix it
Old Man with a Hat
disconnecting any vacuum sources and having any significant changes on vacuum would help detect or eliminate the source of the low vacuum.
PCV blocked off an noting a jump in vacuum may indicate a bad PCV hose, or a bad PCV valve that is allowing too much air to pass into the carb base
I had one where the hose had split underneath so a top view it passed visual inspection.
Blocking off the PB booster if you have PB's will indicate that your booster has a tear in the main bladder of the booster if you see a big jump in vacuum.
Other vacuum dependant items will cause this in varying degrees depending on how much vacuum they use at idle.
PCV blocked off an noting a jump in vacuum may indicate a bad PCV hose, or a bad PCV valve that is allowing too much air to pass into the carb base
I had one where the hose had split underneath so a top view it passed visual inspection.
Blocking off the PB booster if you have PB's will indicate that your booster has a tear in the main bladder of the booster if you see a big jump in vacuum.
Other vacuum dependant items will cause this in varying degrees depending on how much vacuum they use at idle.
mr. fix it
Old Man with a Hat
if they were would they not interfere with the pistons or possibly have very low compression as well?
superfragl
Active Member
I agree - that is a good way to troubleshoot. However, still don`t get how PCV can allow too much air? I thought it is accounted for...
mr. fix it
Old Man with a Hat
it may be defective...or the wrong one installed
I have some news
Checked for leaks using a cigar and didn't find anything, the smoke only comes out through the carb air horn
Also disconnected brake booster and pcv system but nothing changed
BUT! Checked again how tighten the rocker shafts were, both were A LOT tightened so i removed them and then installed again without applying too much torque and what a difference!!! The car now idles a LOT smoother and have between 14 and 15" of vacuum even sometimes tries to reach 17", the unique problem is that now i have a lot of valve train noise. What can be this into? Maybe i need to repeat the cam break in procedure? I checked how much play the shafts has and didn't notice Any with excessive play to produce all that noise
Checked for leaks using a cigar and didn't find anything, the smoke only comes out through the carb air horn
Also disconnected brake booster and pcv system but nothing changed
BUT! Checked again how tighten the rocker shafts were, both were A LOT tightened so i removed them and then installed again without applying too much torque and what a difference!!! The car now idles a LOT smoother and have between 14 and 15" of vacuum even sometimes tries to reach 17", the unique problem is that now i have a lot of valve train noise. What can be this into? Maybe i need to repeat the cam break in procedure? I checked how much play the shafts has and didn't notice Any with excessive play to produce all that noise
rexus31
Senior Member
Do you have the FSM? Refer to the torque settings in the back.
Nop i don't have it but if I'm right the torque spec is 15ftlb
rexus31
Senior Member
Looks like 17ftlbs.
Small Block Crysler 273 318 340 360A_Mopar V8 Engine Specs | Torque Specs - Cylinder Numbering - Firing Order - Distributor Rotation
You'd be wise to get the FSM for your car.
There's something strange on this, just once i start trying to apply some torque on the rocker shaft bolts the engine starts dying
Can be possible that the valve train noise is just the lifters and will go away after using the car for some time?
rexus31
Senior Member
It shouldn't be noisy. Are you certain the pushrods are the correct length?
Bring the number 1 cylinder to top dead center on compression stroke. Both valves should be closed at this point. With rocker assembly tightened to spec, little to no pressure on those two valve rockers. You may need to shim the rocker assembly if deck and heads were milled. Just a thought . I'm no expert.
Seems you are on the right track.
65sporty
Old Man with a Hat
Sounds like the pushrods may be too long, pull the intake so you can see the lifter as you tighten the shaft. On a lifter that has the valve closed look at how far the pushrod is pushing then center down. It should never be more than half the plunger travel.
When you loosen the rocker shaft is there play between the shaft and it's saddles? When everything is tight and you check a valve that is shut you can wiggle the rocker some, compare it to a valve that is open those the rocker wont wiggle because of the load on it. Check it out and report back to us.
superfragl
Active Member
You should be able to turn both push rods by fingers when cyl. 1 is at TDC on compression stroke. When a valve is open - you will not be able to turn it.
The lifters can be noisy only when motor is fired up first time after rebuild or after is has been sitting for a while (until lifters get pumped up with oil).
By the way - what is your oil pressure?
The lifters can be noisy only when motor is fired up first time after rebuild or after is has been sitting for a while (until lifters get pumped up with oil).
By the way - what is your oil pressure?
I'm a bit concerned about oil pressure, before dealing with the rocker shafts the pressure at idle < 1000 RPM was 25 PSI and now is about 13 PSI, at > 2000 RPM the pressure was 60 PSI and now is 45 PSI
What is the stock pushrod length on a 360 LA ? I'm disassembling the intake right now to take a look what's going on
65sporty
Old Man with a Hat
If the rocker shaft is not seated in the saddles because you loosened the bolts you will be bleeding off oil pressure, the rockers get oil through the shaft and one of the saddles should supply it. If I am wrong someone will chime in.
Already measured pushrod length and all of them are 7,519" long.
I went further with this inspect and removed both heads, did a sealing test but both heads failed
so looks like what I have here is a valve sealing problem, I'll call the machine shop tomorrow to get them inspected, maybe can be a valve seats problem or just maybe the heads need a valve seating job
I went further with this inspect and removed both heads, did a sealing test but both heads failed
so looks like what I have here is a valve sealing problem, I'll call the machine shop tomorrow to get them inspected, maybe can be a valve seats problem or just maybe the heads need a valve seating jobThe last week I have my heads back from shop, exhaust valve guides were replaced, valve steam seals were replaced and valves seats were rectified, they vacuum tested both heads before sending them to me but once I got them performed again a seal test and the results where great
Today finally have the engine running and everything in place but I'm even more concerned about the low vacuum idle. Before doing the heads I can get up to 15" vacuum with 25 degrees BTDC initial advance but now the most I can get is 12" and in gear it goes down to 5 - 8" BTDC, but the car performance is a lot better, WOT performance is amazing and idle is a lot smoother.
I checked for vacuum leaks using a cigar but didn't find anything, even removed both valve covers looking for smoke coming from down the intake but didn't find anything so I think I don't have leaks
I'm starting to suspect that maybe I can have an electrical problem, sometimes I feel that car performance with headlights on is not as good and today checking for spark I noticed that the spark coming from the wire is weaker than spark in my other car and both cars are using brand new pertronix flamethrower 65000 V coils. With car idling in gear I have between 12V - 12.2V at battery but I'm running an Delco CS130 alternator and according to manufacturer specs I should be getting something between 13.8 and 14.5V idling at 650 RPM or more . This alternator came with a serpentine belt pulley and I changed it for a V-Belt style which has a bigger diameter than the serpenting, can this cause any charging problem?
Today finally have the engine running and everything in place but I'm even more concerned about the low vacuum idle. Before doing the heads I can get up to 15" vacuum with 25 degrees BTDC initial advance but now the most I can get is 12" and in gear it goes down to 5 - 8" BTDC, but the car performance is a lot better, WOT performance is amazing and idle is a lot smoother.
I checked for vacuum leaks using a cigar but didn't find anything, even removed both valve covers looking for smoke coming from down the intake but didn't find anything so I think I don't have leaks
I'm starting to suspect that maybe I can have an electrical problem, sometimes I feel that car performance with headlights on is not as good and today checking for spark I noticed that the spark coming from the wire is weaker than spark in my other car and both cars are using brand new pertronix flamethrower 65000 V coils. With car idling in gear I have between 12V - 12.2V at battery but I'm running an Delco CS130 alternator and according to manufacturer specs I should be getting something between 13.8 and 14.5V idling at 650 RPM or more . This alternator came with a serpentine belt pulley and I changed it for a V-Belt style which has a bigger diameter than the serpenting, can this cause any charging problem?
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