Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 12-14-2016, 06:48 PM   #1
Dutie
Senior Member
 
Dutie's Avatar
 
Join Date: Sep 2016
Location: Kingston N>Y>
Posts: 121
Smile some compression testing advice

Wanna do my first compression test. Have a pretty good idea but would like to first run it by some more experienced minds. I am thinking let it warm up some, plugs out, key off, engage starter from under hood and check gauge. The car is a 31 deluxe roadster and is my avatar pic. The engine is stock with a high compression head, maybe a comp. test will give me an idea of how high. Motor has been redone in 97 and has about 2500 mi. since a full restoration. Had this car about ten years and have it running great thanks to a lot of members who have helped out from timing to corn head grease. I am an older fella but a good learner.

thanks again dutie
Dutie is offline   Reply With Quote
Old 12-14-2016, 07:16 PM   #2
Art Newland
Senior Member
 
Art Newland's Avatar
 
Join Date: Mar 2016
Location: Lynden, WA
Posts: 1,564
Default Re: some compression testing advice

Sounds like you're just checking for the fun of it? Sounds like you have it figured out, might want to hold the throttle wide open also, and cycle 5-6 compression strokes. My old engine has only 45, 50, 50, 50 PSI. I call it compression-depression, you have been warned! 8^)
Art Newland is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 12-14-2016, 07:19 PM   #3
Dick Steinkamp
Senior Member
 
Dick Steinkamp's Avatar
 
Join Date: Apr 2016
Location: Bellingham, WA
Posts: 1,163
Default Re: some compression testing advice

I have found no difference between WOT and a closed throttle on compression checks. It won't hurt to put a brick on the throttle to hold it open, however. You may want to try both ways (closed and open) and report your findings back here.
__________________
All steel from pedal to wheel
Dick Steinkamp is offline   Reply With Quote
Old 12-14-2016, 07:27 PM   #4
Mitch//pa
BANNED
 
Join Date: May 2010
Location: Bucks County, PA
Posts: 11,454
Default Re: some compression testing advice

Quote:
Originally Posted by Dick Steinkamp View Post
I have found no difference between WOT and a closed throttle on compression checks. It won't hurt to put a brick on the throttle to hold it open, however. You may want to try both ways (closed and open) and report your findings back here.
Same here no difference..... just pull the throttle lever down if you feel better having the throttle open....i usually go 3 bumps
Mitch//pa is offline   Reply With Quote
Old 12-14-2016, 07:34 PM   #5
Art Newland
Senior Member
 
Art Newland's Avatar
 
Join Date: Mar 2016
Location: Lynden, WA
Posts: 1,564
Default Re: some compression testing advice

Quote:
Originally Posted by Mitch//pa View Post
Same here no difference..... just pull the throttle lever down if you feel better having the throttle open....i usually go 3 bumps
Hey Mitch, what do you normally see on an A engine that's in good condition?
Art Newland is offline   Reply With Quote
Old 12-14-2016, 07:37 PM   #6
larrys40
Senior Member
 
Join Date: May 2010
Location: St Charles , Missouri
Posts: 1,994
Default Re: some compression testing advice

Sponsored Links (Register now to hide all advertisements)
Stock head about 55.... Might get more or less
Looking for uniformity
Larry
larrys40 is offline   Reply With Quote
Old 12-14-2016, 07:43 PM   #7
Mitch//pa
BANNED
 
Join Date: May 2010
Location: Bucks County, PA
Posts: 11,454
Default Re: some compression testing advice

One can tell just by the way an engine idles, and the sounds of it if the motor is tired.. a nice smooth running motor at a low idle the compression test will be fine.
All gauges are not created equal

Last edited by Mitch//pa; 12-14-2016 at 07:57 PM.
Mitch//pa is offline   Reply With Quote
Old 12-14-2016, 10:47 PM   #8
Tom Wesenberg
Senior Member
 
Tom Wesenberg's Avatar
 
Join Date: May 2010
Location: Mpls, MN
Posts: 27,582
Default Re: some compression testing advice

Quote:
Originally Posted by Dick Steinkamp View Post
I have found no difference between WOT and a closed throttle on compression checks. It won't hurt to put a brick on the throttle to hold it open, however. You may want to try both ways (closed and open) and report your findings back here.
Yep, the same with me. I don't worry about the throttle, but do have all the plugs out. A while back someone was checking compression with only one plug removed.

If you have a low cylinder, then do the leakdown test to see if the air is exiting out the tail pipe (ex. valve), or the carb (intake valve), or out the oil fill pipe (bad rings).
Tom Wesenberg is offline   Reply With Quote
Old 12-14-2016, 11:36 PM   #9
Y-Blockhead
Senior Member
 
Y-Blockhead's Avatar
 
Join Date: Jul 2011
Location: Redondo Beach, CA
Posts: 5,817
Default Re: some compression testing advice

Quote:
Originally Posted by larrys40 View Post
Stock head about 55.... Might get more or less
Looking for uniformity
Larry
Seriously? I get ~75 psig in each hole. Stock head @ sea level...
Y-Blockhead is offline   Reply With Quote
Old 12-15-2016, 01:00 AM   #10
Fullraceflathead
Senior Member
 
Fullraceflathead's Avatar
 
Join Date: May 2012
Location: Chillicothe, Missouri
Posts: 1,156
Default Re: some compression testing advice

I got 70psi stock head and block is sleaved back to standard bore.
__________________
"If I asked people what they wanted they would have said faster horses."
-Henry Ford

"Primitive technology is not a design flaw"


1928 Ford Model A Roadster Pickup
1930 Gordon Smith Air Compressor
1941 Willy's Pickup
1960 Thunderbird-For Sale
1964 Buick Riviera 2x4 425
1965 Pontiac GTO, 455 Super Duty
2004 Dodge Ram SRT-10, V-10 Viper
1977 Charger Jet Boat,460 Ford,Jacuzzi Jet
Front Engine Nostalgia Dragster,Supercharged 296 "Fullrace Flathead" Ford
Engine Build up on DVD ask
Fullraceflathead is offline   Reply With Quote
Old 12-15-2016, 05:40 AM   #11
Mitch//pa
BANNED
 
Join Date: May 2010
Location: Bucks County, PA
Posts: 11,454
Default Re: some compression testing advice

Post #7 all compression gauges are not created equal... CA air is also different
Mitch//pa is offline   Reply With Quote
Old 12-15-2016, 09:12 AM   #12
Tom Wesenberg
Senior Member
 
Tom Wesenberg's Avatar
 
Join Date: May 2010
Location: Mpls, MN
Posts: 27,582
Default Re: some compression testing advice

Quote:
Originally Posted by Mitch//pa View Post
Post #7 all compression gauges are not created equal... CA air is also different
Watching a Johnny Carson rerun the other night, Johnny said the smog was so bad in San Francisco that a guy actually asked a girl for a date.
Tom Wesenberg is offline   Reply With Quote
Old 12-15-2016, 09:19 AM   #13
SeaSlugs
Senior Member
 
SeaSlugs's Avatar
 
Join Date: May 2010
Location: Central, IL
Posts: 3,968
Default Re: some compression testing advice

Quote:
Originally Posted by Mitch//pa View Post
CA air is also different
does it contain lead and cause cancer? seems everything in California does according to every warning label ever made
__________________
1929 Model AA - Need long splash aprons!
SeaSlugs is offline   Reply With Quote
Old 12-15-2016, 09:32 AM   #14
DaWizard
BANNED
 
Join Date: Nov 2016
Location: Dizzyland Ca
Posts: 332
Send a message via AIM to DaWizard
Default Re: some compression testing advice

Oh, you have no idea. I am a native and I remember when there was NO smog. Sun burnt days of playing in shorts and no shirt in the summer without a care. Now they have polluted everything we have, air, water, food. It's like we are being embalmed before we die so all the funeral parlor needs do is bury us and charge more for that!
__________________
New owner of '28 Tudor
Previously owned;
'30 Sport Coupe
'28 left brake ccPickup
'31 SW Town Sedan
'28 AA Stake Bed
'30 Cabriolet
'42 Super Deluxe 4door Sedan

"If it don't fit, get a bigger hammer.
If it breaks...... ya needed a new one anyway!!"

Doing a good job here is like wetting your pants in a dark suit.
It gives you a warm feeling, but nobody notices.

Never pass up a bathroom
Never neglect an erection
Never trust a fart
DaWizard is offline   Reply With Quote
Old 12-15-2016, 10:18 AM   #15
100IH
Senior Member
 
Join Date: Dec 2011
Location: SW Idaho
Posts: 970
Default Re: some compression testing advice

Compression decreases with an increase in altitude, less air density to suck in, less to compress. When the readings are not similar from cylinder to cylinder, put a squirt of motor oil in the hole, less than a teaspoon. This will make an improvement when redoing the test on that cyl. IF the rings are bad. The oil won't improve the readings if the valves are leaking.

Last edited by 100IH; 12-15-2016 at 10:25 AM.
100IH is offline   Reply With Quote
Old 12-15-2016, 11:30 AM   #16
BILL WILLIAMSON
Senior Member
 
BILL WILLIAMSON's Avatar
 
Join Date: Dec 2010
Location: FRESNO, CA
Posts: 12,560
Default Re: some compression testing advice

[QUOTE=Mitch//pa;1399753. CA air is also different[/QUOTE]
SA Kid!!!
California air is ONLY BAD, when Buster T. & I FART in UNISON
SA Kdad
__________________
"THE ASSISTANT GURU OF STUFF"
BILL WILLIAMSON is offline   Reply With Quote
Old 12-15-2016, 01:57 PM   #17
Dodge
Senior Member
 
Join Date: Nov 2011
Location: Sonoma, CA.
Posts: 1,491
Default Re: some compression testing advice

Trying Burping and Farting at the same time Bill, it will cause a vacuum and not create
any smog saving our air.
Thanks
Dodge is offline   Reply With Quote
Old 12-15-2016, 03:54 PM   #18
Dutie
Senior Member
 
Dutie's Avatar
 
Join Date: Sep 2016
Location: Kingston N>Y>
Posts: 121
Default Re: some compression testing advice

Thanks to all the barners who took time out to reply. Will run it for a while Saturday outside, just to cold out there for me and Francis today...only 17. and real windy, afraid my top might blow off you know. Will keep in touch and thanks again Dutie
Dutie is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 06:20 AM.