The Ford Barn

DJ S · 07-25-2015, 11:43 AM

So recently I've been showing interest in the possibility of purchasing a high compression head in the future... with this interest comes an internal conflict. Obviously the high compression head will increase power but what the are the negative affects of doing this or are there any (such as increased bearing wear). If increased bearing wear is a prevalent problem then is it advised to only up grade to 5:5:1 head as opposed to purchasing the 6:1 head that will clearly provide much more power for only $30 more.

PC/SR · 07-25-2015, 12:00 PM

Don't worry about the bearings. I run a 6.8 with other modifications with no problem. Others use higher compression with babbitt. Jim Brierely runs Bonneville with babbitt mains.

V4F · 07-25-2015, 12:31 PM

the casting on ford type heads give a lil boost , but they are restricted on air . I ran a 6-1 for years , then changed from stock casting to a lion 3 . you need a big bucket to carry the difference . the stock casting 6-1 will not hurt your stock motor .

Dick M · 07-25-2015, 01:03 PM

The easiest upgrade is the 5.5 head. It is acceptable to run the stock head studs with the 5.5. I have run a 5.5 head for over 20,000 miles without incident. It provides extra power when climbing hills. I am very happy with the 5.5. One item to consider when installing a head with a higher than 5.5 compression ratio is you will need to install Grade 8 head studs.

modelAtony · 07-25-2015, 01:11 PM

Quote:

Originally Posted by DJ S

So recently I've been showing interest in the possibility of purchasing a high compression head in the future... with this interest comes an internal conflict. Obviously the high compression head will increase power but what the are the negative affects of doing this or are there any (such as increased bearing wear). If increased bearing wear is a prevalent problem then is it advised to only up grade to 5:5:1 head as opposed to purchasing the 6:1 head that will clearly provide much more power for only $30 more.

I would go with the 6.1 at least. I have been running 5.9 brum since 2003 and love it, would really like the 7.1. I personally believe buying a 5.5 is throwing your money away. the reason is if you drive a correct built engine at 6.1 or close you will really notice the 5.5 is ok but you get the best bang for the buck with a little more uuummmmppphhhh. have fun modelAtony tony white Lafayette, LA

Mitch//pa · 07-25-2015, 01:16 PM

Sponsored Links (Register now to hide all advertisements)

if your motor is tired say goodbye

colin1928 · 07-25-2015, 06:20 PM

If your engine is in good condition you will have no problems with a High comp Head
If not you shorten its life
Might be worth dropping the sump and inspecting things 1st

BILL WILLIAMSON · 07-25-2015, 07:08 PM

HIGHER compression DOES put on extra load, especially, on ROD BEARINGS!!--Like, put on 60 LBS of GUT & your FEET begin to HURT.
Bill W.

Mitch//pa · 07-25-2015, 07:15 PM

other than the bearings i put an HC head on a engine and not long after the blow-by was terrible... it must have blew a piston...

Mike V. Florida · 07-25-2015, 10:37 PM

Check the clearances of the bearings, adjust as necessary. Install the HC head and enjoy. There are three things to watch for; 1) spark setting, you don't have to lower the rod as much. 2) the slow idle sound goes away (or at least changes). 3) hand cranking it harder.

harleynut · 07-25-2015, 11:55 PM

If you want to see performance difference between the 5.5 head and the 6.1 head go to Snyders web site click on HC head then look for the dyno testing results. You will see there isn't much to gain with the 6.1 head compared to the 5.5 head. I have two As....both motors are fairly fresh rebuilds. The one with the stock head has 60 pounds of compression in every cylinder. The one with the 5.5 head has 90 pounds of compression in every cylinder. I sure you will get differences of opinion on this but this is what I found.

40 Deluxe · 07-26-2015, 04:47 AM

Bearing loads from the higher compression are not the problem. The potential for bearing failure is from inattentive drivers who just yank the spark lever completely down and leave it there. Either install a distributor with mechanical advance or learn to advance/retard according to load and speed.
Don't run it too retarded either or it will overheat.

jaguar6165 · 08-13-2015, 12:34 PM

Glad this was brought up. I decided to change my oil pan gasket and found a small amount of coolant in the oil. Time to change the head gasket, which means its time to upgrade to a high compression head (been wanting to for a few years now). I have the same dilemma 5.5 or 6. I have a stromberg, header with glass pack, and just recenty installed an electronic ignition. The only thing that concersn me is that the motor is older. With the pan off and a flashlight in hand everything looks to be in great shape. I'd love to go 6-1 because it seems like that is definitely the better option for the price. Sounds like I should be safe with that, is the 5.5-1 any safer?

hardtimes · 08-13-2015, 01:41 PM

Quote:

Originally Posted by jaguar6165

Glad this was brought up. I decided to change my oil pan gasket and found a small amount of coolant in the oil. Time to change the head gasket, which means its time to upgrade to a high compression head (been wanting to for a few years now). I have the same dilemma 5.5 or 6. I have a stromberg, header with glass pack, and just recenty installed an electronic ignition. The only thing that concersn me is that the motor is older. With the pan off and a flashlight in hand everything looks to be in great shape. I'd love to go 6-1 because it seems like that is definitely the better option for the price. Sounds like I should be safe with that, is the 5.5-1 any safer?

'motor is older' ! Whatever that means, if it means that the engine is worn out, you can expect 'some' things/unintended consequences...the higher the head compression is , that you put on. That is, worn out rings...expect blowby. Worn /loose bearings...expect shorter life and noise...etc. With what you say you have, I'd first thing check compression and thereby ring conditions...dry then wet tests...etc.
Also, with what you've said about blown head gasket, I'd check for deck problems, i.e.- valves seating/good condition; cracks and uneven deck surface. Think of increased compression maybe worsening an already existing problem that caused blown gasket ?
Do you know just how old/worn your engine is ? Maybe if real worn, the cam gear (fiber)may not like...more power, etc. Good luck

jaguar6165 · 08-13-2015, 01:58 PM

Older as in I haven't gone through the internals. The car was "rebuilt" in the 80s by my father. He said he did a head gasket sometime in the past, but it could've been 30 years ago. I replaced the cam gear after that decided to lose a few teeth on me in the middle of the road about 3 years ago. I don't put many miles on it or drive it hard. I'm guessing its the head gasket because there is some, but a very small amount of coolant in the oil. It also looks like after blowing out the coolant that there is some oil in the coolant. This is pretty minimal, but I want to get it corrected.

I'll definitely run a compression test then.

If I have a faulty head gasket won't that also mess with the compression readings?

40 Deluxe · 08-13-2015, 06:52 PM

Quote:

Originally Posted by jaguar6165

Older as in I haven't gone through the internals. The car was "rebuilt" in the 80s by my father. He said he did a head gasket sometime in the past, but it could've been 30 years ago. I replaced the cam gear after that decided to lose a few teeth on me in the middle of the road about 3 years ago. I don't put many miles on it or drive it hard. I'm guessing its the head gasket because there is some, but a very small amount of coolant in the oil. It also looks like after blowing out the coolant that there is some oil in the coolant. This is pretty minimal, but I want to get it corrected.

I'll definitely run a compression test then.

If I have a faulty head gasket won't that also mess with the compression readings?

Not necessarily. You could have a minor, slow seepage of coolant when the engine is cold, but when it's fully warmed up, everything expands enough to seal up and hold compression. If it's bad enough to show low readings on a compression test, you would likely be blowing water out the radiator big time.

40 Deluxe · 08-13-2015, 07:25 PM

A couple of thoughts: First, the cam gear is totally unaffected by a high compression head. It does not take any more effort to turn the cam no what the compression.
Second, the bearings don't know nor care if the cranking compression is higher ie: if a compression test showed 60# with the stock head and 90# with the new head, it will not affect the bearings. This is because combustion pressure is a lot more than compression pressure, by several hundred pounds more.
Now, what is supporting all that pressure? Oil! There is always a film of oil between the crankshaft journal and the bearing (whether Babbitt or insert) that prevents metal to metal contact, which would mean a rapid death! But if you let pre-ignition or detonation occur (which is like hitting the top of the piston with a sledgehammer) you can squish out that film of oil and damage occurs. Same thing if the oil supply is insufficient. Bearing surface area is plenty to support the extra load of higher compression as well. So a high compression head won't kill an engine by itself, it has to have help.

JohnLaVoy · 08-14-2015, 08:43 AM

I always say that the high compression head is the best "bang for the buck" at improving performance. As to the bottom end, I have a Brumfield 5.9 on one car that is all babbitt, and a 5.5 on another where the mains are babbitt and have around 45,000 miles on the two cars with out a problem.

07-25-2015, 11:43 AM	#1
DJ S Senior Member Join Date: Aug 2014 Location: Southwick, MA Posts: 598	High Compression Head So recently I've been showing interest in the possibility of purchasing a high compression head in the future... with this interest comes an internal conflict. Obviously the high compression head will increase power but what the are the negative affects of doing this or are there any (such as increased bearing wear). If increased bearing wear is a prevalent problem then is it advised to only up grade to 5:5:1 head as opposed to purchasing the 6:1 head that will clearly provide much more power for only $30 more.

07-25-2015, 12:00 PM	#2
PC/SR Senior Member Join Date: May 2010 Location: Santa Rosa, CA Posts: 1,285	Re: High Compression Head Don't worry about the bearings. I run a 6.8 with other modifications with no problem. Others use higher compression with babbitt. Jim Brierely runs Bonneville with babbitt mains.

07-25-2015, 12:31 PM	#3
V4F Senior Member Join Date: May 2010 Location: ca. Posts: 2,524	Re: High Compression Head the casting on ford type heads give a lil boost , but they are restricted on air . I ran a 6-1 for years , then changed from stock casting to a lion 3 . you need a big bucket to carry the difference . the stock casting 6-1 will not hurt your stock motor . __________________ V4f

07-25-2015, 01:03 PM	#4
Dick M Senior Member Join Date: May 2010 Location: Ukiah, CA Posts: 510	Re: High Compression Head The easiest upgrade is the 5.5 head. It is acceptable to run the stock head studs with the 5.5. I have run a 5.5 head for over 20,000 miles without incident. It provides extra power when climbing hills. I am very happy with the 5.5. One item to consider when installing a head with a higher than 5.5 compression ratio is you will need to install Grade 8 head studs.

07-25-2015, 01:16 PM	#6
Mitch//pa BANNED Join Date: May 2010 Location: Bucks County, PA Posts: 11,454	Re: High Compression Head Sponsored Links (Register now to hide all advertisements) if your motor is tired say goodbye

07-25-2015, 06:20 PM	#7
colin1928 Senior Member Join Date: Mar 2013 Location: Australa Melbourne Posts: 878	Re: High Compression Head If your engine is in good condition you will have no problems with a High comp Head If not you shorten its life Might be worth dropping the sump and inspecting things 1st

07-25-2015, 07:08 PM	#8
BILL WILLIAMSON Senior Member Join Date: Dec 2010 Location: FRESNO, CA Posts: 12,560	Re: High Compression Head HIGHER compression DOES put on extra load, especially, on ROD BEARINGS!!--Like, put on 60 LBS of GUT & your FEET begin to HURT. Bill W. __________________ "THE ASSISTANT GURU OF STUFF"

07-25-2015, 07:15 PM	#9
Mitch//pa BANNED Join Date: May 2010 Location: Bucks County, PA Posts: 11,454	Re: High Compression Head other than the bearings i put an HC head on a engine and not long after the blow-by was terrible... it must have blew a piston...

07-25-2015, 10:37 PM	#10
Mike V. Florida Senior Member Join Date: May 2010 Location: Florida between Sarasota and TampaSouth Florida Posts: 14,054	Re: High Compression Head Check the clearances of the bearings, adjust as necessary. Install the HC head and enjoy. There are three things to watch for; 1) spark setting, you don't have to lower the rod as much. 2) the slow idle sound goes away (or at least changes). 3) hand cranking it harder. __________________ What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II Last edited by Mike V. Florida; 07-25-2015 at 11:57 PM.

07-25-2015, 11:55 PM	#11
harleynut Senior Member Join Date: Jun 2013 Location: Pittsburgh Pa Posts: 279	Re: High Compression Head If you want to see performance difference between the 5.5 head and the 6.1 head go to Snyders web site click on HC head then look for the dyno testing results. You will see there isn't much to gain with the 6.1 head compared to the 5.5 head. I have two As....both motors are fairly fresh rebuilds. The one with the stock head has 60 pounds of compression in every cylinder. The one with the 5.5 head has 90 pounds of compression in every cylinder. I sure you will get differences of opinion on this but this is what I found.

07-26-2015, 04:47 AM	#12
40 Deluxe Senior Member Join Date: May 2010 Location: now Kuna, Idaho Posts: 3,818	Re: High Compression Head Bearing loads from the higher compression are not the problem. The potential for bearing failure is from inattentive drivers who just yank the spark lever completely down and leave it there. Either install a distributor with mechanical advance or learn to advance/retard according to load and speed. Don't run it too retarded either or it will overheat.

08-13-2015, 12:34 PM	#13
jaguar6165 Senior Member Join Date: May 2010 Location: Casselberry, FL Posts: 188	Re: High Compression Head Glad this was brought up. I decided to change my oil pan gasket and found a small amount of coolant in the oil. Time to change the head gasket, which means its time to upgrade to a high compression head (been wanting to for a few years now). I have the same dilemma 5.5 or 6. I have a stromberg, header with glass pack, and just recenty installed an electronic ignition. The only thing that concersn me is that the motor is older. With the pan off and a flashlight in hand everything looks to be in great shape. I'd love to go 6-1 because it seems like that is definitely the better option for the price. Sounds like I should be safe with that, is the 5.5-1 any safer?

08-13-2015, 01:58 PM	#15
jaguar6165 Senior Member Join Date: May 2010 Location: Casselberry, FL Posts: 188	Re: High Compression Head Older as in I haven't gone through the internals. The car was "rebuilt" in the 80s by my father. He said he did a head gasket sometime in the past, but it could've been 30 years ago. I replaced the cam gear after that decided to lose a few teeth on me in the middle of the road about 3 years ago. I don't put many miles on it or drive it hard. I'm guessing its the head gasket because there is some, but a very small amount of coolant in the oil. It also looks like after blowing out the coolant that there is some oil in the coolant. This is pretty minimal, but I want to get it corrected. I'll definitely run a compression test then. If I have a faulty head gasket won't that also mess with the compression readings? Last edited by jaguar6165; 08-13-2015 at 02:04 PM.

08-13-2015, 07:25 PM	#17
40 Deluxe Senior Member Join Date: May 2010 Location: now Kuna, Idaho Posts: 3,818	Re: High Compression Head A couple of thoughts: First, the cam gear is totally unaffected by a high compression head. It does not take any more effort to turn the cam no what the compression. Second, the bearings don't know nor care if the cranking compression is higher ie: if a compression test showed 60# with the stock head and 90# with the new head, it will not affect the bearings. This is because combustion pressure is a lot more than compression pressure, by several hundred pounds more. Now, what is supporting all that pressure? Oil! There is always a film of oil between the crankshaft journal and the bearing (whether Babbitt or insert) that prevents metal to metal contact, which would mean a rapid death! But if you let pre-ignition or detonation occur (which is like hitting the top of the piston with a sledgehammer) you can squish out that film of oil and damage occurs. Same thing if the oil supply is insufficient. Bearing surface area is plenty to support the extra load of higher compression as well. So a high compression head won't kill an engine by itself, it has to have help.

08-14-2015, 08:43 AM	#18
JohnLaVoy Senior Member Join Date: Jun 2014 Location: Rocklin, CA Posts: 779	Re: High Compression Head I always say that the high compression head is the best "bang for the buck" at improving performance. As to the bottom end, I have a Brumfield 5.9 on one car that is all babbitt, and a 5.5 on another where the mains are babbitt and have around 45,000 miles on the two cars with out a problem.