03-21-2019, 06:52 PM | #1 |
Senior Member
Join Date: Jan 2019
Location: Florida Panhandle
Posts: 585
|
Valve Lash
It seems the typical exhaust sound of a Model A is a precise and distinct staccato repetition similar to the sustained report of a .50 caliber M2. My Model A exhaust sounds like a low muffled monotone with an irregular but noticeable wispy puff sound. Sounds like “putt, putt, pfst, putt,pfst, pfst, putt, putt, pfst”, etc. It has an electronic ignition and I just installed Champion W16Y plugs. The PO had the engine remaned by a reputable builder but sadly passed on after the engine was just broken in. I suspect the valve lash was never readjusted after break in. I cannot hear any tappet clacking and am thinking insufficient valve clearance may be a possibility. The engine does not miss but seems to be a little low on power and has a slightly rough idle. I will pull the manifolds and valve cover to check the valve clearance but just curious if anybody can describe the indications of too tight or too loose valve lash.
|
03-21-2019, 08:01 PM | #2 |
Senior Member
Join Date: Jun 2010
Location: Temecula, CA
Posts: 4,084
|
Re: Valve Lash
First thing to do is check the compression, and maybe even a leak-down test. Also look at the old plugs for color, indicating a rich or lean condition.
|
Sponsored Links (Register now to hide all advertisements) |
|
03-22-2019, 06:45 AM | #3 |
Senior Member
Join Date: May 2010
Location: Largo Florida
Posts: 7,225
|
Re: Valve Lash
I agree with starting at the beginning with a compression check.
The normal Model A sound usually comes from a low idle speed and with the timing retarded until the desired sound is heard. I'm thinking your ignition timing is not adjustable except for base setting. There is not too much to say about valve lash and exhaust note. The valve clearance is not too hard to check and the manifolds don't really have to be removed. |
03-22-2019, 09:52 AM | #4 | |
Senior Member
Join Date: Jun 2015
Location: Red Deer, Alberta
Posts: 5,042
|
Re: Valve Lash
Quote:
__________________
If you don't hear a rumor by 10 AM, start one!. Got my education out behind the barn! |
|
03-22-2019, 11:36 AM | #5 |
Senior Member
Join Date: May 2010
Location: Alabama
Posts: 8,099
|
Re: Valve Lash
Initial timing .
|
03-22-2019, 04:04 PM | #6 |
Senior Member
Join Date: Dec 2011
Location: SW Idaho
Posts: 970
|
Re: Valve Lash
Sponsored Links (Register now to hide all advertisements)
|
03-22-2019, 05:42 PM | #7 |
Senior Member
Join Date: May 2010
Location: Lynden, Wa
Posts: 3,550
|
Re: Valve Lash
You can always try the WD40 I think around the manifold to make sure you don't have a leak.
Mike
__________________
1930 TownSedan (Briggs) 1957 Country Sedan |
03-29-2019, 02:29 PM | #8 |
Senior Member
Join Date: Jan 2019
Location: Florida Panhandle
Posts: 585
|
Re: Valve Lash
OK, did some additional testing. Manifold vacuum is a steady 23 inches - seems a little high. Compression for cylinders 1 through 4 read 65, 65, 75, 70. Does this data tell us anything ? Still have a rough idle and inconsistent exhaust cadence. Thinking about going through the carb next. Engine has just over 1000 miles after high dollar rebuild. Just seems like it should run better.
|
03-30-2019, 09:19 AM | #9 |
Senior Member
Join Date: Jan 2016
Posts: 2,093
|
Re: Valve Lash
Do you hook the vac gauge up to the intake?
|
03-30-2019, 10:06 AM | #10 |
Senior Member
Join Date: May 2010
Posts: 2,592
|
Re: Valve Lash
PM sent
Last edited by Benson; 03-30-2019 at 07:37 PM. |
03-30-2019, 10:11 AM | #11 |
Senior Member
Join Date: Jun 2015
Location: Red Deer, Alberta
Posts: 5,042
|
Re: Valve Lash
What kind of camshaft is in that engine? Original, untouched? Reground? New w/a performance grind?
__________________
If you don't hear a rumor by 10 AM, start one!. Got my education out behind the barn! |
03-30-2019, 03:20 PM | #12 |
Senior Member
Join Date: Jan 2019
Location: Florida Panhandle
Posts: 585
|
Re: Valve Lash
Connected the vacuum gauge to the wiper vacuum tap at the manifold. Not sure about the cam but suspect it is a regrind. Did the flex tube routine on the carb and determined the fuel level is at 3/4 verses 5/8 inch below the parting line. Should mean the carb is running lean but not obvious considering high speed performance is good and the engine never pings. I will reset the float when I clean the carb. Noticed the plugs were especially clean when I pulled them to do the compression check. Just does not seem to have the classic A idle. The saga continues.
|
03-30-2019, 03:32 PM | #13 | |
Senior Member
Join Date: May 2010
Location: now Kuna, Idaho
Posts: 3,778
|
Re: Valve Lash
Quote:
The higher the better (more efficient) unless some one timed the engine using a vacuum gauge (setting the timing at the highest vacuum reading usually results in too much initial advance and pinging and thus bearing damage). Is your distributor original with electronic conversion, or one with centrifugal advance? |
|
03-30-2019, 03:57 PM | #14 |
Senior Member
Join Date: Dec 2011
Location: SW Idaho
Posts: 970
|
Re: Valve Lash
Do you have a Motor's or Chilton. If so read about vacuum values and what they tell you. Dry plugs won't cause your idle issue, wet ones will.
|
03-30-2019, 05:31 PM | #15 |
Senior Member
Join Date: May 2010
Location: new britain,ct 06052
Posts: 9,389
|
Re: Valve Lash
Put about a pint of MMO or ATF in the gas tank and run it. Not going to hurt anything and if a valve is sticking it should free it up. FWIW
Paul in CT |
03-30-2019, 09:50 PM | #16 |
Senior Member
Join Date: May 2010
Location: Alabama
Posts: 8,099
|
Re: Valve Lash
Paul makes a good point in post number 15 . When I overhauled the engine in my roadster I installed new original type valve guides and original style mushroom stem stainless steel valves . After a while it started running so badly that I wouldn't trust it out of the drive way . I mentioned the problem here . It was said that the corn gas was probably causing the stainless steel valves to get sticky . When I checked the compression , the gauge would show good compression on all cylinders . When the engine was running I was getting slow valve action because of sticky valves . I first drained the tank and added corn free gas . I then added a small bottle of Marvel Mystery oil to the gas tank and a few ounces to the crankcase . . I then disconnected the vacume line and stuck one end in a bigger bottle of marvel Mystery oil . I started the engine and let the vacume draw the MMO into the intake and to the valves . In a short time it started smoking as the MMO made its way into the combustion chambers . I stood on the passenger side and kept the engine running at a high enough RPM that it wouldn't go dead . When the engine smoothed out and would rev I removed the vacume line from the bottle of MMO and reconnected it to the firewall . I kept the engine running at a fast idle until the smoke subsided and it was good to go for a ride . I now always add at least four ounces of MMO to each ten gallons of gas and have had no more problems with sticky valves ..
Last edited by Purdy Swoft; 03-30-2019 at 10:25 PM. |
03-31-2019, 06:37 AM | #17 |
Senior Member
Join Date: May 2010
Location: Largo Florida
Posts: 7,225
|
Re: Valve Lash
Good point. Its been long enough that I didn't give sticky valves a thought even though I've run into this issue.
|
03-31-2019, 09:07 AM | #18 |
Senior Member
Join Date: May 2010
Location: on the Littlefield
Posts: 6,155
|
Re: Valve Lash
For a while I had a slight "miss" at idle, power was ok, lugging the engine would pull evenly, I finally checked the valve clearance, had 1 exhaust and 1 intake valve at .004, .005 clearance, after adjustment the perfect smooth idle came back
i have original split guides, and original Ford stainless valves |
03-31-2019, 12:05 PM | #19 | |
Senior Member
Join Date: Jan 2019
Location: Florida Panhandle
Posts: 585
|
Re: Valve Lash
Quote:
Do you recall how much clearance you had on the other exhaust/intake valves ? PS - Use to live by Exit 13. |
|
03-31-2019, 12:46 PM | #20 |
Senior Member
Join Date: May 2010
Location: Alabama
Posts: 8,099
|
Re: Valve Lash
I run all of my model A intake and exhaust valves with .016 clearance . This includes the ones with 3/4 race cams . Good clearance helps keep the valves cooler and less likely to burn. Snyders recommended a clearance of .016 years ago and it has worked for me . Less clearance may give a fractional amount of lift . I try to stay on the safe side .
|
Thread Tools | |
Display Modes | |
|
|
Sponsored Links (Register now to hide all advertisements) |
|