Compression went South - Alfa Romeo Bulletin Board & Forums
 1Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 28 (permalink) Old 08-20-2019, 05:23 AM Thread Starter
Senior Member
Gold Subscriber
 
Join Date: Oct 2013
Posts: 661
Garage
Compression went South

Freshly rebuilt 2L spider motor, was running good about 10 hours, getting the Webers and valve clearances adjusted. Fired her up yesterday and while warming up I heard a few clunks that did not sound at all normal. Checked valve train, appears ok, 5 psi compression on cyl. #3. 160 on the rest. #3 piston is moving up and down. Engine builder is old, maybe has lost touch (self)

It appears something catastrophic happened, any ideas?
930cabman is offline  
Sponsored Links
Advertisement
 
post #2 of 28 (permalink) Old 08-20-2019, 06:54 AM
Registered User
 
classicalfas's Avatar
 
Join Date: Apr 2003
Location: New Jersey
Posts: 1,402
Garage
I would remove the cam cover and cams and look under the followers first. See if everything looks in place.
horsewidower likes this.

1966 GTA replica, 1967 Duetto, 1987 Quadrifoglio
1972, 1973, 1974 Montreal
classicalfas is offline  
post #3 of 28 (permalink) Old 08-20-2019, 06:59 AM
Richard Jemison
Platinum Subscriber
 
Alfar7's Avatar
 
Join Date: Apr 2005
Location: Pensacola, Fl. U.S.A.
Posts: 7,010
See if everything looks in place.

Like a adjusting shim not seated on the valve, holding it open

Bring # 3 to tdc so valves "should be closed. Blow air through the spark plug hole. Side that air escapes through is the cam you need to remove and check.

Richard Jemison
RJR Racing

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

"When you are dead you don`t know it.
Only those around you are distressed.
Same with stupid"
Alfar7 is offline  
Sponsored Links
Advertisement
 
post #4 of 28 (permalink) Old 08-20-2019, 07:31 AM Thread Starter
Senior Member
Gold Subscriber
 
Join Date: Oct 2013
Posts: 661
Garage
Clearance at intake #3 is .015, exhaust .020
930cabman is offline  
post #5 of 28 (permalink) Old 08-20-2019, 07:50 AM
Richard Jemison
Platinum Subscriber
 
Alfar7's Avatar
 
Join Date: Apr 2005
Location: Pensacola, Fl. U.S.A.
Posts: 7,010
Still do the air test.

You could have bent a valve turning the cams without the two being timed together..

Richard Jemison
RJR Racing

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

"When you are dead you don`t know it.
Only those around you are distressed.
Same with stupid"
Alfar7 is offline  
post #6 of 28 (permalink) Old 08-20-2019, 08:35 AM
Registered User
 
classicalfas's Avatar
 
Join Date: Apr 2003
Location: New Jersey
Posts: 1,402
Garage
Borrow or rent a borescope and take a look down the spark plug hole, look for kiss marks or dings from the valves on the piston to rule out a bent valve. My guess it’s a top end issue.

1966 GTA replica, 1967 Duetto, 1987 Quadrifoglio
1972, 1973, 1974 Montreal
classicalfas is offline  
post #7 of 28 (permalink) Old 08-20-2019, 10:10 AM
Moderator
Platinum SubscriberModerator
 
Alfajay's Avatar
 
Join Date: Jan 2005
Location: San Juan Capistrano
Posts: 9,807
Quote:
Originally Posted by classicalfas View Post
My guess it’s a top end issue.
Agree. If piston #3 is still going up and down, then there isn't much else it could be. It might be a head gasket issue, but those clunks 930cabman heard suggests valve damage.

Jay Mackro
San Juan Capistrano, CA

'65 Guilia Sprint GT
'67 Duetto
'91 164L
Alfajay is offline  
post #8 of 28 (permalink) Old 08-20-2019, 10:14 AM
Registered User
 
classicalfas's Avatar
 
Join Date: Apr 2003
Location: New Jersey
Posts: 1,402
Garage
You can do a leak down test too.

1966 GTA replica, 1967 Duetto, 1987 Quadrifoglio
1972, 1973, 1974 Montreal
classicalfas is offline  
post #9 of 28 (permalink) Old 08-20-2019, 10:29 AM
Registered User
 
genericwood's Avatar
 
Join Date: Jul 2003
Posts: 2,778
A bent valves would likely lead to excessive clearance. Could be a broken piston?

Erik
'66 GTV racecar, '71 Spider racecar, '74 GTV street car, '71 GTV project
genericwood is offline  
post #10 of 28 (permalink) Old 08-20-2019, 10:51 AM Thread Starter
Senior Member
Gold Subscriber
 
Join Date: Oct 2013
Posts: 661
Garage
Quote:
Originally Posted by Alfar7 View Post
You could have bent a valve turning the cams without the two being timed together..
Richard nailed it again.

I shot some compressed air into cyl #3 (intake valve clearance .014, exhaust .020) and sure enough air was escaping from the venturi at cyl #3.

Not sure how this could have happened, but it looks like the head will be coming off, hopefully its in the top end.
930cabman is offline  
post #11 of 28 (permalink) Old 08-20-2019, 05:27 PM Thread Starter
Senior Member
Gold Subscriber
 
Join Date: Oct 2013
Posts: 661
Garage
Pulled the cyl head off, a small metallic something found it's way into the combustion chamber. The top of the piston, underside of the head and valves are peppered with small dents. Generally I am very careful when the spark plugs are removed or when the carbs are off to make sure this does not occur. Hopefully the bottom end is ok.
Heading off to my local machine shop tomorrow to replace the damaged valves.
930cabman is offline  
post #12 of 28 (permalink) Old 08-20-2019, 06:13 PM
Registered User
 
genericwood's Avatar
 
Join Date: Jul 2003
Posts: 2,778
Also have to be careful when the carbs are on but the cleaner is off. I have seen nuts and washers make there way past the throttle plates.

Erik
'66 GTV racecar, '71 Spider racecar, '74 GTV street car, '71 GTV project
genericwood is offline  
post #13 of 28 (permalink) Old 08-20-2019, 07:03 PM
Senior Member
Platinum Subscriber
 
alfaparticle's Avatar
 
Join Date: Oct 2004
Location: Columbia SC
Posts: 12,769
Quote:
Also have to be careful when the carbs are on but the cleaner is off. I have seen nuts and washers make there way past the throttle plates
.

Been there and done that.

https://www.alfabb.com/bb/forums/eng...n-chamber.html

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
alfaparticle is offline  
post #14 of 28 (permalink) Old 08-20-2019, 07:47 PM
Registered User
 
Join Date: Mar 2007
Location: San Antonio, Texas
Posts: 4,080
A good machine shop can work wonders. Hope everything gets fixed and back together. I'm guessing your rings are OK.

Jim . . . '72 Super 1300, '70, 1750GTV, 2nd series,
'62, Lancia Flaminia Zagato3c, 2nd series
180OUT is offline  
post #15 of 28 (permalink) Old 08-21-2019, 05:35 AM
Senior Member
Platinum Subscriber
 
alfaparticle's Avatar
 
Join Date: Oct 2004
Location: Columbia SC
Posts: 12,769
Look at the before and after pictures in the link above. I did not have to pull the engine which was as strong as ever when I put the head back on. I only needed help to replace a damaged valve seat.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
alfaparticle is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Alfa Romeo Bulletin Board & Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome