Club Cobra Gas - N Exhaust  

Go Back   Club Cobra > Events > Other Upcoming Events

Keith Craft Racing
Nevada Classics
MMG Superformance
Main Menu
Module Jump:
Nevada Classics
Nevada Classics
MMG Superformance
Advertise at CC
Banner Ad Rates
MMG Superformance
Keith Craft Racing
March 2024
S M T W T F S
          1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31            

Kirkham Motorsports

Like Tree25Likes

Reply
 
LinkBack Thread Tools Display Modes
  #21 (permalink)  
Old 10-13-2021, 02:30 PM
ZOERA-SC7XX's Avatar
Senior Club Cobra Member
Visit my Photo Gallery

 
Join Date: Mar 2005
Location: Meriden, CT
Cobra Make, Engine: ERA 427 SC s/n 718, 428 FE
Posts: 1,726
Not Ranked     
Default

Quote:
Originally Posted by cycleguy55 View Post
You might try using air. Make sure all the head bolts are loose or removed. Put a fitting in one of the spark plug holes in an end cylinder (not the one with the broken valve) and pressurize it. Area of a 4.36" bore is 4.75 sq inches, so 100 PSI is 475 lbs pressure pushing up on the cylinder head.
Sounds like a good plan. However, you should leave at least two head bolts loosely attached. 100 psi is quite a bit of air.
__________________
"Paint It Black, Black As Night"
Reply With Quote
  #22 (permalink)  
Old 10-13-2021, 02:43 PM
767Jockey's Avatar
Senior Club Cobra Member
Visit my Photo Gallery

 
Join Date: Feb 2005
Cobra Make, Engine: Contemporary, FE, Tremec TKO 600
Posts: 1,946
Not Ranked     
Default

That piston is likely going to be ugly. Hopefully your cylinder walls were spared.
Reply With Quote
  #23 (permalink)  
Old 10-13-2021, 02:45 PM
767Jockey's Avatar
Senior Club Cobra Member
Visit my Photo Gallery

 
Join Date: Feb 2005
Cobra Make, Engine: Contemporary, FE, Tremec TKO 600
Posts: 1,946
Not Ranked     
Default

Quote:
Originally Posted by ZOERA-SC7XX View Post
Sounds like a good plan. However, you should leave at least two head bolts loosely attached. 100 psi is quite a bit of air.
Make sure the parking brake is firmly set, 100PSI is also enough to rotate the engine in gear and move the car.
Reply With Quote
  #24 (permalink)  
Old 10-13-2021, 04:25 PM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,773
Not Ranked     
Default

Quote:
Originally Posted by cycleguy55 View Post
You might try using air. Make sure all the head bolts are loose or removed. Put a fitting in one of the spark plug holes in an end cylinder (not the one with the broken valve) and pressurize it. Area of a 4.36" bore is 4.75 sq inches, so 100 PSI is 475 lbs pressure pushing up on the cylinder head.
Bore size is irrelevant. 100 psi from an air line into the cylinder will still be 100 psi.
__________________
Gary

Gold Certified Holden Technician
Reply With Quote
  #25 (permalink)  
Old 10-13-2021, 04:36 PM
patrickt's Avatar
Half-Ass Member
Visit my Photo Gallery

 
Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 21,889
Not Ranked     
Default

Quote:
Originally Posted by Gaz64 View Post
Bore size is irrelevant.
Uhhh, are you sure about that? Lift force (for blowing that head up through the ceiling) is found by multiplying the pressure times the area. That's why a hovercraft can get off the ground by using only 7 lbs. of pressure. Of course, you should not just take my word for it. See: https://www.discoverhover.org/infoin...ors/guide4.htm
cycleguy55 likes this.
Reply With Quote
  #26 (permalink)  
Old 10-13-2021, 04:47 PM
DanEC's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Apr 2009
Location: Little Rock area, AR
Cobra Make, Engine: ERA Street Roadster #782 with 459 cu in FE KC engine, toploader, 3.31
Posts: 4,480
Not Ranked     
Default

He’s correct - just like a hydraulic brake line. 100 psi is 100 psi. The issue might be when it’s multiplied by the cross sectional area of the bore in square inches as cycleguy55 said.
cycleguy55 likes this.
__________________
ERA 782 Running
https://www.youtube.com/watch?v=Cfge...b1-77fqwFRu7c]
Reply With Quote
  #27 (permalink)  
Old 10-13-2021, 04:47 PM
CC Member
Visit my Photo Gallery

 
Join Date: Jul 2021
Cobra Make, Engine:
Posts: 16
Not Ranked     
Default

Thanks for all of the help this far. I am sure I wouldn’t have gotten this far without it. Diagnosis spot-on Gary.

I put the plugs back in, cranked it and saw the head move. With some very light prying pressure, it seems to move a little on the intake side. However, I can’t get much more than that. I am wondering if I might be missing something. I can’t get the exhaust side of the head to budge, even the slightest bit.

Valve covers removed, intake manifold removed, headers removed, rocker arms and push rods removed (rocker arm studs and 6 of the valves still in place), 10 head bolts removed, spark plugs removed.

There are 3 large Allen head screws/plugs in the head, between the valves, which I assume are something to do with the machining process. I haven’t messed with them. Does it seem like I missed some fastening device?
Reply With Quote
  #28 (permalink)  
Old 10-13-2021, 04:49 PM
CC Member
Visit my Photo Gallery

 
Join Date: Jul 2021
Cobra Make, Engine:
Posts: 16
Not Ranked     
Default

Picture of one of the Allen bolts.
Attached Images
 

Last edited by splenderleith; 10-13-2021 at 04:55 PM..
Reply With Quote
  #29 (permalink)  
Old 10-13-2021, 05:00 PM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,773
Not Ranked     
Default

No, I don't agree.

Let's assume 5 square inches.

A typical compression test might yield 180 psi, about 12 x 1 atmosphere (14.7psi). Compression ratio and inlet valve closing point are the determining factors.

And so do we get 5 times our typical compression pressure?
__________________
Gary

Gold Certified Holden Technician
Reply With Quote
  #30 (permalink)  
Old 10-13-2021, 05:11 PM
patrickt's Avatar
Half-Ass Member
Visit my Photo Gallery

 
Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 21,889
Not Ranked     
Default

The page I referenced gives a wonderful example, including the math, but an easy way to visualize the difference is to think of a thimble full of air at x pressure and imagine how easy it would be to hold your thumb over it. Now take the same pressure and have it inside a barrel. Do you think the strength necessary to hold the lid of the barrel down is the same as the thimble even though the pressure is the same?
cycleguy55 likes this.
Reply With Quote
  #31 (permalink)  
Old 10-13-2021, 05:16 PM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,773
Not Ranked     
Default

Quote:
Originally Posted by patrickt View Post
The page I referenced gives a wonderful example, including the math, but an easy way to visualize the difference is to think of a thimble full of air at x pressure and imagine how easy it would be to hold your thumb over it. Now take the same pressure and have it inside a barrel. Do you think the strength necessary to hold the lid of the barrel down is the same as the thimble even though the pressure is the same?
Hmm, I have to ponder over this one for a bit.
__________________
Gary

Gold Certified Holden Technician
Reply With Quote
  #32 (permalink)  
Old 10-13-2021, 05:19 PM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,773
Not Ranked     
Default

Quote:
Originally Posted by splenderleith View Post
Picture of one of the Allen bolts.
I thought you said you had head bolts.

They look like studs, after nuts have been removed.

The heads will not move sideways while studs are fitted. The studs need to be removed if the head won't break free.

The hex plug is a coolant plug. No need to remove it.
__________________
Gary

Gold Certified Holden Technician
Reply With Quote
  #33 (permalink)  
Old 10-14-2021, 05:55 AM
undy's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Jul 2005
Location: Virginia Beach, Va & Port Charlotte, Fl.,
Posts: 2,280
Not Ranked     
Default

Quote:
Originally Posted by eschaider View Post
This picture is exactly what Gary described / predicted in post #15.


Ed
...or what I said in post #6.
__________________
Too many toys?? never!
Reply With Quote
  #34 (permalink)  
Old 10-14-2021, 06:22 AM
CC Member
Visit my Photo Gallery

 
Join Date: Nov 2015
Posts: 171
Not Ranked     
Default

The damage can sometimes be extensive. In 2008, #2 intake valve in my 427 dropped because both springs had broken. The piston split the cylinder wall.

When the failure occurred, and before I dismantled the engine, I knew things were bad. We were stopped on the side of the road with antifreeze running out of both side pipes.
Attached Images
   

Last edited by HTM101; 10-14-2021 at 06:27 AM..
Reply With Quote
  #35 (permalink)  
Old 10-14-2021, 06:34 AM
CC Member
Visit my Photo Gallery

 
Join Date: Jul 2021
Cobra Make, Engine:
Posts: 16
Not Ranked     
Default

I was unsuccessful in removing the head last night. I believe the air from the compression is plenty to break the seal, but the intake side seems to have a slightly weaker bond, which leads to a gap on the intake side. It seems that the air is then able to escape before it breaks the exhaust side loose.

What I think I may try this evening is to hook up the compressed air and pressurize the first cylinder to see if I can get enough space to get some plastic shims in. I believe if I can break the head gasket on the exhaust side free, I can probably pull it off.

If that fails, I will probably have to find a way to remove the studs. I think that will involve some thin jam nuts, with the same thread as the studs.

I will report back after I try option 1.
Reply With Quote
  #36 (permalink)  
Old 10-14-2021, 07:05 AM
eschaider's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2006
Location: Gilroy, CA
Cobra Make, Engine: SPF 2291, Whipple Blown & Injected 4V ModMotor
Posts: 2,628
Not Ranked     
Default

Quote:
Originally Posted by HTM101 View Post
The damage can sometimes be extensive. In 2008, #2 intake valve in my 427 dropped because both springs had broken. The piston split the cylinder wall.

When the failure occurred, and before I dismantled the engine, I knew things were bad. We were stopped on the side of the road with antifreeze running out of both side pipes.
Very impressive job there HTM101!


Ed
__________________


Help them do what they would have done if they had known what they could do.
Reply With Quote
  #37 (permalink)  
Old 10-14-2021, 08:31 AM
HighPlainsDrifter's Avatar
Senior Club Cobra Member
Visit my Photo Gallery

 
Join Date: Jul 2000
Location: Chilliwack,BC, BC
Cobra Make, Engine: F5 Roadster
Posts: 1,409
Not Ranked     
Default Pull Engine Out

The engine needs to be pulled and at least one piston replaced if it has wrecked the cylinder wall a sleeve can be installed. the connecting rod needs to be checked as it may be bent also.
Good Luck.
cycleguy55 likes this.
__________________
F5 cobra Mark 4 roadster, Ruby Wine Red with pearl,
dual 2" roll bars, warmed up 302, E Street aluminum Heads, Comp cam and roller rockers, AOD, 4.10 Eaton Possi, Power Baer/disc brakes, block hugger headers, 2 1/2" under car exhaust, F500 18" black spoke wheels.
Reply With Quote
  #38 (permalink)  
Old 10-14-2021, 11:07 AM
cycleguy55's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2014
Location: White City, SK
Cobra Make, Engine: West Coast, 460 CID
Posts: 2,844
Not Ranked     
Default

Quote:
Originally Posted by Gaz64 View Post
Bore size is irrelevant. 100 psi from an air line into the cylinder will still be 100 psi.
Bore size matters. 100 PSI (Pounds per Square Inch) has a greater overall force when applied to a greater area. It would be 200 lbs force when applied to 2 square inches, but 500 lbs force when applied to 5 square inches.

That's also why a narrow bicycle tire (e.g. 700 x 25c) needs more pressure (100-125 PSI) to support a given rider weight than does a wider tire (e.g. 700 x 38c) - which might only need 60-80 PSI.
__________________
Brian
Reply With Quote
  #39 (permalink)  
Old 10-14-2021, 11:10 AM
patrickt's Avatar
Half-Ass Member
Visit my Photo Gallery

 
Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 21,889
Not Ranked     
Default

Quote:
Originally Posted by cycleguy55 View Post
Bore size matters. 100 PSI (Pounds per Square Inch) has a greater overall force ...
I think Gaz gave up when I hit him with my thimble and barrel example.
cycleguy55 likes this.
Reply With Quote
  #40 (permalink)  
Old 10-14-2021, 12:00 PM
eschaider's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2006
Location: Gilroy, CA
Cobra Make, Engine: SPF 2291, Whipple Blown & Injected 4V ModMotor
Posts: 2,628
Not Ranked     
Default

OP,

What you have here is commonly called a blown engine. By and large you do not want to replace just the broken parts with new good parts, that is a formula for follow on failure.

There is a good chance your engine will look similar to HTM101's when you finally get it taken down. If you have one dead piston when you replace just that one piston you could find it challenging to get it to the same weight as the other seven for balance purposes. The upshot is a new set of oversize pistons, pins and rings, boring the block, individually fitting each new piston to its new cylinder and or course rebalancing of the rotating assembly.

You can frequently that find shrapnel from the cylinder with the broken valve has found it's way to other good cylinders and done damage over there also. This would likely also require other pistons being replaced. Just buy a whole new set and do the job correctly.

When you finally get the head off, if the valve head has been pushed into the port throat damaging the valve seat, while repairable, the short way home could just be replace the old damaged casting with a new one. The exception to this would be a head casting that had significant additional work done on it for example like a nice porting job.

If you have a cracked or gouged cylinder you can certainly bore it and put a sleeve in it. For a high performance engine however, I might begin looking for a replacement block. For FE engines with all the availability issues they currently have, this will certainly become more challenging, especially in the current economic and supply chain impacted climate.

When a valve spring breaks there can be certainly two and sometimes three or more pieces. Your broken spring has many pieces. This could be an indicator that the engine was operated for some time after the initial break because the failure was not apparent to the driver. If that is the case then there is the possibility for broken spring pieces to have found their way into the oil system and done additional damage elsewhere in the engine.

Bottom line this is an R&R for the engine with a complete rebuild not just a cylinder head repair.


Ed
Gaz64 and cycleguy55 like this.
__________________


Help them do what they would have done if they had known what they could do.
Reply With Quote
Reply

Tags
valve spring, valves

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 On
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -7. The time now is 12:30 AM.


Powered by vBulletin® Version 3.8.0
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
The representations expressed are the representations and opinions of the clubcobra.com forum members and do not necessarily reflect the opinions and viewpoints of the site owners, moderators, Shelby American, any other replica manufacturer, Ford Motor Company. This website has been planned and developed by clubcobra.com and its forum members and should not be construed as being endorsed by Ford Motor Company, or Shelby American or any other manufacturer unless expressly noted by that entity. "Cobra" and the Cobra logo are registered trademarks for Ford Motor Co., Inc. clubcobra.com forum members agree not to post any copyrighted material unless the copyrighted material is owned by you. Although we do not and cannot review the messages posted and are not responsible for the content of any of these messages, we reserve the right to delete any message for any reason whatsoever. You remain solely responsible for the content of your messages, and you agree to indemnify and hold us harmless with respect to any claim based upon transmission of your message(s). Thank you for visiting clubcobra.com. For full policy documentation refer to the following link: CC Policy
Links monetized by VigLink