The Ford Barn

Jack 34pu · 05-19-2011, 10:39 AM

Well, another issue with the '50 Merc engine. I layed an EAB head on the freshly machined block and it appears the valves clear OK but the EGGE pistons bump the head up about .025" (no gasket). It seems I remember someone else having that problem. Is there a solution that isn't going to break the bank?

Those $5k complete engines are looking better all the time!

Bruce Lancaster · 05-19-2011, 10:45 AM

Do these pistons have a sort of conical shape to the dome rather than the section od a sphere look of Ford ones??
We just had a lengthy analysis on the HAMB, which included a measured mapping of the dome shape...the cone of course gave different clearances all the way across, so that even if clearance was adjusted there was no way to get any approach to even or tight clearance across the chamber. The piston shape just did not make sense.

Bruce Lancaster · 05-19-2011, 10:52 AM

The discussion: http://www.jalopyjournal.com/forum/s...ical&showall=1

Scroll down to the mapping of the shape...very poor relationship between curve of piston and that of the chamber. Clearance was obtained, but I don't think there was any way he could have gotten a tight chamber at all points.

Walt Dupont--Me. · 05-19-2011, 11:08 AM

I think you'll find the heads have been milled. I've found alot of those EAB heads that the pistons hit the heads. It's hard to find a set of those heads now that haven't been milled. Thay don't stand much milling. Put the gasket on and lay the head on, if it don't hit put a couple of bolts in and then clay the piston and see what you have forn clearance. I've got some out there with .025 over the over the piston and they have a lot of miles on them with no pinging. Walt

Jack E/NJ · 05-19-2011, 11:27 AM

If worse comes to worse, just use a double set of headgaskets with plenty of grease smeared on all surfaces. Torque and re-torque often. Not the best solution, but it can work without breaking the bank. 8^)

Jack E/NJ

Charlie ny · 05-19-2011, 11:46 AM

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Jack,
I had the same problem. I cleaned everything real well then
sprayed the top of the pistons with white paint. I installed the heads
using four studs and gravity. What I saw was the pistons on the right
bank contacted the comb chambers at 3 o'clock and those on the left
contacted at 9 o'clock. I relieved the comb chambers very carefully
a little at a time grinding only the witness mark left by the paint....
grind the witness mark...repaint...check and grind etc. When I no
longer had any witness marks the comb chambers were quite uniform in
appearance and all 8 cc'd about 70.
About 6 hours each.
Charlie ny

Jack 34pu · 05-19-2011, 11:51 AM

I cc'd the EAB heads early on and they came in around 64cc so I don't think they were machined. I have another set that came in about the same.

I put one original 8CM head on and got a .002 bump from one piston which would not be a problem once gasket is included. I think the domed head on the EGGE pistons is the problem. Too late to return them, they have been balanced so the are some spot drilling on most of them.

I know the 8CM is the worst head to use but if the EGGE piston is higher, wouldn't that give me a boost in compression. I could install 8CM with old gasket and cc one cyl if someone else had a cc volume to compare to.

One other note, the machinest took a very light cut on the deck surface because of pitting. Not deep enough to get rid of all of it so I know it was a light cut.

Bruce Lancaster · 05-19-2011, 12:41 PM

There are maybe two issues on compression...actual compression and sensitivity to knock. The issue is that the close match between dome and chamber serves as a quench area and source of turbulence in the chamber as the charge is squeezed out...good activity here makes engine less sensitive to the potential troubles of high compression and allows engine to tolerate higher compression and its benefits.
With pistons paid for and balanced focus moves to chamber...Charley's excellent technique would be worth exploring to see precisely where the problems lie, both too close and too far, and hence whether chamber work is a reasonable solution.
Also, look at Swissmike's chamber mapping on the Egge problem over on the HAMB. Both would help you see if simple relieving in limited areas is a way to make things good enough.
Lots of shops used to have a cutter replicating Ford chamber dome, used to get clearance back on milled heads, but that is a scarce thing now...and I suspect it would not be useful because piston shape is somehow different than chamber shape with some Egges. I have heard of Egges too high in the middle, almost becoming a cone, several times over the last few years.

Jack 34pu · 05-19-2011, 01:20 PM

Thanks guys - please keep following this post as I can use all the help I can get.

UPDATE: I took a used head gasket and tightened 5 or so bolts down to make sure it was seated somewhat - then backed the bolts back a bit. No interferance on the EAB head with the gasket (thkness measured approx .053").

So, I like Charlie's suggestion as a touch here and there may cure the problem. I wonder if someone else has a different idea than spray painting the piston tops? What else could I put on top of the pistons to transfer a mark. How about some hard grease in a thin layer which could be wiped off later? Any suggestions??

Bruce Lancaster · 05-19-2011, 01:27 PM

Anything that transfers and can be seen will do the job. It helps to use something that can be quickly blasted away with a squirt of carb cleaner to make re-marking easier as you progress.
For studying the dome, little pills of aluminum foil or strips of wire solder are useful.

Jack 34pu · 05-19-2011, 02:37 PM

UPDATE 2

I took your advice and improvised strips of aluminum foil and tacked them to each piston with a little hard grease.

RESULTS:

With used head gasket - I did cyls 5 thru 8.
cyl 5 = .0225 at thinest spot on foil
cyl 6 = .0229
cyl 7 = .0260
cyl 8 = .0290

It is close at the quench area that you were talking about a flycutter being used. Fairly even so the piston dome does match the head curvature fairly close. I'll check the other side tomorrow.

What say? Is .0225" too close (detonation?) I would say the measurements avearge out about .028-.030 in the thicker areas of foil.
Valves are not even close.
Please give me some feedback.

Jack 34pu

Bruce Lancaster · 05-19-2011, 03:02 PM

Curve matching well is good news, meaning that you don't have to compromise with poor fit to clear worst places. See WD's post, #4, on the numbers. I suspect your numbers are a bit daring but not suicidal.
I believe there are suppliers out there making non-standard gasket thicknesses...someone here or on HAMB will know that. A slightly fat gasket would be a great solution.

Ol' Ron · 05-19-2011, 05:42 PM

I've been building my engines with .050" piston to head clearance. However, recently we've been tighting this up abit. In 37 Dons engine we;re alittle less than .040", Engine has several thousand miles on it with no problem. One reason for the clearance issue is that back in the 40's and 50's the old Janns Pistons were quite heavy and rod streach caused some piston to head contact at hi RPM. Modern engines have much less clearance. I'm using Egge pistons in the economy engine and had to mill .030" from the EAB heads to get ,035" clearance. Keep it under 4K

Ol' Ron · 05-19-2011, 05:54 PM

I just checked the HAMB site and found it to be very complet and informative. I will follow some of the suggestions when finishing the heads. A note here the first heads will be the Modified EAB heads. Then a set of Offy heads with relocated spark plugs and 9:1 CR, providing we can run this on 87 oct gas. Keep on putzing untill it's over.

hotcoupe · 05-19-2011, 06:18 PM

What else could I put on top of the pistons to transfer a mark.

lipstick works well - pasty,visible,easy to remove.

Karl Wolf · 05-19-2011, 08:42 PM

I am using a block that has a defect that is very deep, decking the block about .025"... The heads that I am using 59A (not AB) were the wrong dome shape, and there was not enough piston to head clearance... I made a template of the shape of the 3 5/16" pistons that I am using, and cut that same shape onto an old piston...
I have an old run out block on end on the floor... Hung a 59A head on the block on a couple of studs, twisting piston in bore against head, graphite spray on the piston to find high spots... Using a die grinder with a burr, then the sand paper rolls for porting, knock down the parts with graphite marking... I put the head on the assembled block, measuring to see how far the new pistons push the head up from the block... (no gasket, count on new gasket compressed thickness of .055")...

LOTS of work, patience, I hope that I have a uniform dome surface that matches the shape of the pistons I am using, with clearance of about .040"... Haven't fired it, but I live in high hope.... Karl

40 Deluxe · 05-20-2011, 02:12 AM

When messing with piston to head clearance, what about eliminating the "dead zone" on the side of the head furthest from the valves? Seems like there's a pocket there that is basically isolated from the rest of the camber around TDC so doesn't burn properly. Is it feasible to angle mill the heads while we're at it?

JWL · 05-20-2011, 05:27 AM

Actually, getting the dome-to-head match is less important than getting the outside fitted closely. If you read my book you will learn about angle milling and see some methods for performing the operation.

Jack 34pu · 05-20-2011, 09:42 AM

I called Speedway as someone suggested. They have a copper big bore gasket that compresses to .062" so that would give me approx .032 - .034" clearance at the tightest spot which I feel is still too close?

With out a tear down, it appears I have 2 choices

1. Put double big bore Best gaskets with the EAB heads which would give me .072 - .074 clearance. Possibly defeating the higher compression advantage?

2. Go back to the 8CM heads with one big bore gasket which would give me about .048 - .050" clearance.

A little frustrated at this point. What advice at this point?

Russ/40 · 05-20-2011, 10:36 AM

Jack, If I were you, I'd use the thicker copper gasket you describe and, by hand, knock a few thousands off the top of the pistons a be done with it. For the street, you're never going to suffer any consequences. Use an abrasive disk on a flex-pad and take off .015 or so off the problem area.
It's not an offenhouser, it's a flathead.

05-19-2011, 10:39 AM	#1
Jack 34pu Senior Member Join Date: May 2010 Location: State College, PA Posts: 362	EGGE pistons hitting EAB heads?? Well, another issue with the '50 Merc engine. I layed an EAB head on the freshly machined block and it appears the valves clear OK but the EGGE pistons bump the head up about .025" (no gasket). It seems I remember someone else having that problem. Is there a solution that isn't going to break the bank? Those $5k complete engines are looking better all the time!

05-19-2011, 10:45 AM	#2
Bruce Lancaster Member Emeritus Join Date: May 2010 Location: Madison, NJ Posts: 5,230	Re: EGGE pistons hitting EAB heads?? Do these pistons have a sort of conical shape to the dome rather than the section od a sphere look of Ford ones?? We just had a lengthy analysis on the HAMB, which included a measured mapping of the dome shape...the cone of course gave different clearances all the way across, so that even if clearance was adjusted there was no way to get any approach to even or tight clearance across the chamber. The piston shape just did not make sense.

05-19-2011, 10:52 AM	#3
Bruce Lancaster Member Emeritus Join Date: May 2010 Location: Madison, NJ Posts: 5,230	Re: EGGE pistons hitting EAB heads?? The discussion: http://www.jalopyjournal.com/forum/s...ical&showall=1 Scroll down to the mapping of the shape...very poor relationship between curve of piston and that of the chamber. Clearance was obtained, but I don't think there was any way he could have gotten a tight chamber at all points.

05-19-2011, 11:27 AM	#5
Jack E/NJ Senior Member Join Date: May 2010 Posts: 2,173	Re: EGGE pistons hitting EAB heads?? If worse comes to worse, just use a double set of headgaskets with plenty of grease smeared on all surfaces. Torque and re-torque often. Not the best solution, but it can work without breaking the bank. 8^) Jack E/NJ

05-19-2011, 11:46 AM	#6
Charlie ny BANNED Join Date: May 2010 Posts: 3,019	Re: EGGE pistons hitting EAB heads?? Sponsored Links (Register now to hide all advertisements) Jack, I had the same problem. I cleaned everything real well then sprayed the top of the pistons with white paint. I installed the heads using four studs and gravity. What I saw was the pistons on the right bank contacted the comb chambers at 3 o'clock and those on the left contacted at 9 o'clock. I relieved the comb chambers very carefully a little at a time grinding only the witness mark left by the paint.... grind the witness mark...repaint...check and grind etc. When I no longer had any witness marks the comb chambers were quite uniform in appearance and all 8 cc'd about 70. About 6 hours each. Charlie ny

05-19-2011, 11:08 AM	#4
Walt Dupont--Me. Senior Member Join Date: May 2010 Location: Gardiner Me. Posts: 4,200	Re: EGGE pistons hitting EAB heads?? I think you'll find the heads have been milled. I've found alot of those EAB heads that the pistons hit the heads. It's hard to find a set of those heads now that haven't been milled. Thay don't stand much milling. Put the gasket on and lay the head on, if it don't hit put a couple of bolts in and then clay the piston and see what you have forn clearance. I've got some out there with .025 over the over the piston and they have a lot of miles on them with no pinging. Walt

05-19-2011, 11:51 AM	#7
Jack 34pu Senior Member Join Date: May 2010 Location: State College, PA Posts: 362	Re: EGGE pistons hitting EAB heads?? I cc'd the EAB heads early on and they came in around 64cc so I don't think they were machined. I have another set that came in about the same. I put one original 8CM head on and got a .002 bump from one piston which would not be a problem once gasket is included. I think the domed head on the EGGE pistons is the problem. Too late to return them, they have been balanced so the are some spot drilling on most of them. I know the 8CM is the worst head to use but if the EGGE piston is higher, wouldn't that give me a boost in compression. I could install 8CM with old gasket and cc one cyl if someone else had a cc volume to compare to. One other note, the machinest took a very light cut on the deck surface because of pitting. Not deep enough to get rid of all of it so I know it was a light cut.

05-19-2011, 12:41 PM	#8
Bruce Lancaster Member Emeritus Join Date: May 2010 Location: Madison, NJ Posts: 5,230	Re: EGGE pistons hitting EAB heads?? There are maybe two issues on compression...actual compression and sensitivity to knock. The issue is that the close match between dome and chamber serves as a quench area and source of turbulence in the chamber as the charge is squeezed out...good activity here makes engine less sensitive to the potential troubles of high compression and allows engine to tolerate higher compression and its benefits. With pistons paid for and balanced focus moves to chamber...Charley's excellent technique would be worth exploring to see precisely where the problems lie, both too close and too far, and hence whether chamber work is a reasonable solution. Also, look at Swissmike's chamber mapping on the Egge problem over on the HAMB. Both would help you see if simple relieving in limited areas is a way to make things good enough. Lots of shops used to have a cutter replicating Ford chamber dome, used to get clearance back on milled heads, but that is a scarce thing now...and I suspect it would not be useful because piston shape is somehow different than chamber shape with some Egges. I have heard of Egges too high in the middle, almost becoming a cone, several times over the last few years.

05-19-2011, 01:20 PM	#9
Jack 34pu Senior Member Join Date: May 2010 Location: State College, PA Posts: 362	Re: EGGE pistons hitting EAB heads?? Thanks guys - please keep following this post as I can use all the help I can get. UPDATE: I took a used head gasket and tightened 5 or so bolts down to make sure it was seated somewhat - then backed the bolts back a bit. No interferance on the EAB head with the gasket (thkness measured approx .053"). So, I like Charlie's suggestion as a touch here and there may cure the problem. I wonder if someone else has a different idea than spray painting the piston tops? What else could I put on top of the pistons to transfer a mark. How about some hard grease in a thin layer which could be wiped off later? Any suggestions??

05-19-2011, 01:27 PM	#10
Bruce Lancaster Member Emeritus Join Date: May 2010 Location: Madison, NJ Posts: 5,230	Re: EGGE pistons hitting EAB heads?? Anything that transfers and can be seen will do the job. It helps to use something that can be quickly blasted away with a squirt of carb cleaner to make re-marking easier as you progress. For studying the dome, little pills of aluminum foil or strips of wire solder are useful.

05-19-2011, 02:37 PM	#11
Jack 34pu Senior Member Join Date: May 2010 Location: State College, PA Posts: 362	Re: EGGE pistons hitting EAB heads?? UPDATE 2 I took your advice and improvised strips of aluminum foil and tacked them to each piston with a little hard grease. RESULTS: With used head gasket - I did cyls 5 thru 8. cyl 5 = .0225 at thinest spot on foil cyl 6 = .0229 cyl 7 = .0260 cyl 8 = .0290 It is close at the quench area that you were talking about a flycutter being used. Fairly even so the piston dome does match the head curvature fairly close. I'll check the other side tomorrow. What say? Is .0225" too close (detonation?) I would say the measurements avearge out about .028-.030 in the thicker areas of foil. Valves are not even close. Please give me some feedback. Jack 34pu

05-19-2011, 03:02 PM	#12
Bruce Lancaster Member Emeritus Join Date: May 2010 Location: Madison, NJ Posts: 5,230	Re: EGGE pistons hitting EAB heads?? Curve matching well is good news, meaning that you don't have to compromise with poor fit to clear worst places. See WD's post, #4, on the numbers. I suspect your numbers are a bit daring but not suicidal. I believe there are suppliers out there making non-standard gasket thicknesses...someone here or on HAMB will know that. A slightly fat gasket would be a great solution.

05-19-2011, 05:42 PM	#13
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,860	Re: EGGE pistons hitting EAB heads?? I've been building my engines with .050" piston to head clearance. However, recently we've been tighting this up abit. In 37 Dons engine we;re alittle less than .040", Engine has several thousand miles on it with no problem. One reason for the clearance issue is that back in the 40's and 50's the old Janns Pistons were quite heavy and rod streach caused some piston to head contact at hi RPM. Modern engines have much less clearance. I'm using Egge pistons in the economy engine and had to mill .030" from the EAB heads to get ,035" clearance. Keep it under 4K

05-19-2011, 05:54 PM	#14
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,860	Re: EGGE pistons hitting EAB heads?? I just checked the HAMB site and found it to be very complet and informative. I will follow some of the suggestions when finishing the heads. A note here the first heads will be the Modified EAB heads. Then a set of Offy heads with relocated spark plugs and 9:1 CR, providing we can run this on 87 oct gas. Keep on putzing untill it's over.

05-19-2011, 06:18 PM	#15
hotcoupe Senior Member Join Date: May 2010 Location: imperial,mo Posts: 694	Re: EGGE pistons hitting EAB heads?? What else could I put on top of the pistons to transfer a mark. lipstick works well - pasty,visible,easy to remove.

05-19-2011, 08:42 PM	#16
Karl Wolf Senior Member Join Date: May 2010 Location: Mill Valley,Ca. Posts: 1,509	Re: EGGE pistons hitting EAB heads?? I am using a block that has a defect that is very deep, decking the block about .025"... The heads that I am using 59A (not AB) were the wrong dome shape, and there was not enough piston to head clearance... I made a template of the shape of the 3 5/16" pistons that I am using, and cut that same shape onto an old piston... I have an old run out block on end on the floor... Hung a 59A head on the block on a couple of studs, twisting piston in bore against head, graphite spray on the piston to find high spots... Using a die grinder with a burr, then the sand paper rolls for porting, knock down the parts with graphite marking... I put the head on the assembled block, measuring to see how far the new pistons push the head up from the block... (no gasket, count on new gasket compressed thickness of .055")... LOTS of work, patience, I hope that I have a uniform dome surface that matches the shape of the pistons I am using, with clearance of about .040"... Haven't fired it, but I live in high hope.... Karl

05-20-2011, 02:12 AM	#17
40 Deluxe Senior Member Join Date: May 2010 Location: now Kuna, Idaho Posts: 3,779	Re: EGGE pistons hitting EAB heads?? When messing with piston to head clearance, what about eliminating the "dead zone" on the side of the head furthest from the valves? Seems like there's a pocket there that is basically isolated from the rest of the camber around TDC so doesn't burn properly. Is it feasible to angle mill the heads while we're at it?

05-20-2011, 05:27 AM	#18
JWL Member Emeritus Join Date: May 2010 Location: Fitzgerald, Georgia Posts: 2,204	Re: EGGE pistons hitting EAB heads?? Actually, getting the dome-to-head match is less important than getting the outside fitted closely. If you read my book you will learn about angle milling and see some methods for performing the operation.

05-20-2011, 09:42 AM	#19
Jack 34pu Senior Member Join Date: May 2010 Location: State College, PA Posts: 362	Re: EGGE pistons hitting EAB heads?? I called Speedway as someone suggested. They have a copper big bore gasket that compresses to .062" so that would give me approx .032 - .034" clearance at the tightest spot which I feel is still too close? With out a tear down, it appears I have 2 choices 1. Put double big bore Best gaskets with the EAB heads which would give me .072 - .074 clearance. Possibly defeating the higher compression advantage? 2. Go back to the 8CM heads with one big bore gasket which would give me about .048 - .050" clearance. A little frustrated at this point. What advice at this point? Last edited by Jack 34pu; 05-20-2011 at 10:05 AM.

05-20-2011, 10:36 AM	#20
Russ/40 Senior Member Join Date: May 2010 Location: Santee, California Posts: 3,505	Re: EGGE pistons hitting EAB heads?? Jack, If I were you, I'd use the thicker copper gasket you describe and, by hand, knock a few thousands off the top of the pistons a be done with it. For the street, you're never going to suffer any consequences. Use an abrasive disk on a flex-pad and take off .015 or so off the problem area. It's not an offenhouser, it's a flathead.