|
Sponsored Links (Register now to hide all advertisements) |
|
|
Thread Tools | Display Modes |
11-03-2020, 12:45 PM | #1 |
Junior Member
Join Date: May 2019
Posts: 15
|
engine vacuum problems
i have a rebuilt 53 ford flathead engine ,ever sense i 1st started it ,it starts right up but rough idle and vacuum gauge jumps all over from 5-12"and increase rpm from 8-15"with little pops out pass. side of exh., i did a compression and cyl. leak down test looks ok, the vacuum chart shows could be leaking head gasket, put new head gasket in and the same thing, i do have new alum heads which look ok, could they be warped and causing this problem, also checked my 2x2 intake manifold and carbs with no leaks, not sure where to look now. any help out there ?
|
11-03-2020, 12:51 PM | #2 |
Senior Member
Join Date: Sep 2013
Location: Dighton, Mass
Posts: 1,230
|
Re: engine vacuum problems
sounds like tight valve lash from here....
|
Sponsored Links (Register now to hide all advertisements) |
|
11-03-2020, 12:58 PM | #3 |
Senior Member
Join Date: Apr 2019
Location: Kansas
Posts: 921
|
Re: engine vacuum problems
First I'd make sure there aren't two plug wires switched. Then I'd idle the engine and short each plug wire in succession to see if each drops rpm slightly as it's shorted. If you can isolate the affected cyls it will be easier to diagnose.
Terry
__________________
"It don't take but country smarts to solve the problem" (Smokey Yunick) '41 Merc Town Sedan / 260" 8CM engine '66 Fairlane four door / "warmed up" 302 |
11-03-2020, 01:19 PM | #4 |
Junior Member
Join Date: May 2019
Posts: 15
|
Re: engine vacuum problems
readjusted already
|
11-03-2020, 01:31 PM | #5 |
Senior Member
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 10,319
|
Re: engine vacuum problems
Sounds like a vacuum leak to me.
|
11-03-2020, 01:40 PM | #6 |
Senior Member
Join Date: May 2010
Location: on the Littlefield
Posts: 6,159
|
Re: engine vacuum problems
Sponsored Links (Register now to hide all advertisements)
|
11-03-2020, 01:42 PM | #7 |
Member Emeritus
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
|
Re: engine vacuum problems
Any kind of head gasket or warped head issues would have shown up on the leak-down test. I'm with tubman, sounds like a vacuum leak somewhere.
|
11-03-2020, 01:50 PM | #8 |
Senior Member
Join Date: May 2010
Location: new britain,ct 06052
Posts: 9,390
|
Re: engine vacuum problems
Vacuum wipers??
Paul in CT |
11-03-2020, 01:55 PM | #9 |
Senior Member
Join Date: Oct 2013
Location: Glens Falls NY
Posts: 1,267
|
Re: engine vacuum problems
I'm with others here re vacuum leak. As a possible point of reference, best my '47 with 30,000 m will do at running temp is a steady 19.
|
11-03-2020, 04:26 PM | #10 |
Senior Member
Join Date: Jul 2010
Location: 36 miles north of Albany NY
Posts: 2,950
|
Re: engine vacuum problems
Try spraying brake parts cleaner around base of manifold,carb,anyplace where you could think of where it would leak. The rpm will change when you get close. Wiper hose is another possibility, mine was all cracked, I found it when I tried to lube the wiper motor with a syringe and I had a puddle of MMO under the dash.
|
11-03-2020, 04:51 PM | #11 |
Junior Member
Join Date: May 2019
Posts: 15
|
Re: engine vacuum problems
my 53 has no vacuum wipers so i will try spraying around the intake and check for leaks
|
11-03-2020, 05:03 PM | #12 |
Member Emeritus
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
|
Re: engine vacuum problems
|
11-03-2020, 07:46 PM | #13 |
Junior Member
Join Date: May 2019
Posts: 15
|
Re: engine vacuum problems
I went by the book to adj the lifters,had holes drilled in the housing to hold the lifter in place while adjusting and they were tight locked in place
|
11-03-2020, 08:51 PM | #14 |
Member Emeritus
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
|
Re: engine vacuum problems
Which book, LOL?
|
11-04-2020, 11:20 AM | #15 |
Junior Member
Join Date: May 2019
Posts: 15
|
Re: engine vacuum problems
How to Rebuild and modify ford flathead v8 engines. maybe i should have read it twice.
|
11-04-2020, 11:43 AM | #16 |
Senior Member
Join Date: May 2010
Location: MN
Posts: 7,053
|
Re: engine vacuum problems
If valves adjusted correctly. I'd guess its the valves sticking with tight new guides. mmo down the carb till it smokes out and then drive it. Repeat.
|
11-04-2020, 11:46 AM | #17 |
Senior Member
Join Date: May 2010
Location: MN
Posts: 7,053
|
Re: engine vacuum problems
I would think a vacuum leak in the intake would just create a consistent low vacuum reading through out. Not a erratic vacuum reading, that would show a individual cylinder or valve issue.
|
11-04-2020, 06:41 PM | #18 |
Junior Member
Join Date: May 2019
Posts: 15
|
Re: engine vacuum problems
i will try mmo tomorrow, i put a little in the oil and gas tank ,but didn't do the carb
|
11-04-2020, 06:53 PM | #19 |
Senior Member
Join Date: Aug 2012
Location: Perth, Western Australia
Posts: 2,687
|
Re: engine vacuum problems
Just going to ask what cam, so we can judge roughly what vacuum it should be.
__________________
"Came too close to dying to stop living now!" Last edited by Talkwrench; 11-05-2020 at 12:58 AM. |
11-04-2020, 07:32 PM | #20 |
Member Emeritus
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
|
Re: engine vacuum problems
If you happen to have the intake off again for something I would check a couple of valves again for clearance being sure the lifter is on the cam heel for each one you check. But the issue is more likely a vacuum leak somewhere. Also, if the cam was not degreed when it was installed there is always the possibility of the cam being off or the timing gear not being marked correctly.
Last edited by JSeery; 11-05-2020 at 12:50 AM. |
|
|
Sponsored Links (Register now to hide all advertisements) |
|