08-31-2023, 08:04 PM | #1 |
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5.5 head
After blowing a head gasket I decided to replace the head also. Part of the reason was a friend blew his head gasket and took the old head to machine shop to get a clean up cut and found the head was cracked. He went through 4 heads before he got a good one and the machining bill was over $400. Well I thought to avoid all that and just get a Snyder 5.5.Well its on and running and what a difference 10 hp makes. Very pleased I went this route
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08-31-2023, 10:35 PM | #2 |
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Re: 5.5 head
There is no doubt that extra bit of compression really helps. I found the main benefit was the extra low down grunt. Now, if you improve the carburettor, you won't know yourself. Even a B carb with an enlarged inlet manifold will wake up the car. A downdraught (like a Stromberg or Webber) does even more.
Who says original is best?
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09-01-2023, 06:25 AM | #3 |
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Re: 5.5 head
Compression ratio is only part of the picture. The combustion chamber design is important too. It effects breathing and combustion efficiency. In my opinion, the combustion chamber for the racing flat head Harleys had the best design.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
09-01-2023, 10:11 AM | #4 |
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Re: 5.5 head
I have a 5.5:1 head on my Coupe and a 6:1 head on my Victoria. The 6:1 head has a noticeable increase in torque over the 5.5:1 head. To use the full travel of the spark advance lever, special tuning is necessary. Here is what I did to regain full travel of the spark lever.
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09-01-2023, 01:18 PM | #5 |
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Re: 5.5 head
This was my approach to limiting advance: https://www.fordbarn.com/forum/showp...2&postcount=23
And my 6:1 head has improved the driving pleasure a lot. |
09-01-2023, 03:28 PM | #6 |
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Re: 5.5 head
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09-01-2023, 05:17 PM | #7 |
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Re: 5.5 head
Will changing to a high compression head cause any appreciable increase in coolant temperature?
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09-01-2023, 05:26 PM | #8 |
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Re: 5.5 head
Rebuilders recommend changing out the studs on a rebuilt engine. The latest ones I bought were not straight and it made putting the head on difficult. However, after a few miles and a few re torquing, they straightened out so the head was easy to remove next time. The straightening indicates to me that there is some yielding in the steel. If you do change out the studs make sure the tapped holes in the block are clean down to the bottom. I use some anti seize except if the holes go into the water jacket, in which case I will use a sealant.
The high compression heads are more efficient so more of the fuel is converted to torque and less to heat. So, if you drive your car at the same speed as before the coolant temperature will be lower.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
09-01-2023, 05:35 PM | #9 |
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Re: 5.5 head
When I had blown a head gasket before on this car I replaced all the studs and nuts with harder ones, they were grade 8. I ran a tap through all the stud holes before installing the new studs. This time when I put the new head and gasket on it was a dream as the studs and nuts were like new despite being in the car 2 years ago. All the work to put a new gasket on before it just felt better to put all new studs. I considered the money spent on the studs was worth it
Last edited by Ordsgt; 09-01-2023 at 07:13 PM. Reason: Stud rating |
09-01-2023, 05:36 PM | #10 |
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Re: 5.5 head
As a matter of interest, what is the general opinion on maximum advance for a 5.5:1 head. I run a max of 22° for a 6:1 but I realise a 5.5:1 would be more.
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09-01-2023, 11:23 PM | #11 |
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Re: 5.5 head
Just a side note. Don't use a tap to clean up the head stud holes. Use a thread chaser.
The thread chaser will clean out the threads. The tap will cut material out of the stud holes. There are three grades of taps. Each one has a different tolerance of depth cutting. The taps most of get from the hardware store, Snap-on, Matco ect. cut a deeper thread than the taps that are used in engine manufacturing. |
09-02-2023, 12:55 AM | #12 | |
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Re: 5.5 head
Quote:
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09-02-2023, 06:37 AM | #13 |
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Re: 5.5 head
I do what Bob does by timing my engine with the spark advance 3 or 4 notches down. I have a 6.5 head. I still change my timing to match conditions but at a lower position of the spark lever. With the higher compression ratio the spark advance does not have to change with RPM as the burn rate increases with increased engine speed. I will retard the ignition one notch when lugging or driving in town and advance one notch when cruising on a level road with reduced throttle. I start the engine with the lever 3 or 4 notches down. I love to listen to a low idle and can get a really low idle with the lever all the way up and the throttle cracked.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 09-02-2023 at 06:42 AM. |
09-02-2023, 07:41 AM | #14 |
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Re: 5.5 head
[QUOTE=Dodge;2252508]Just a side note. Don't use a tap to clean up the head stud holes. Use a thread chaser.
The thread chaser will clean out the threads. The tap will cut material out of the stud holes. D.I.Y. chaser... notch a fastener to resemble a pie missing one piece and it will clear the threads without damage. |
09-02-2023, 08:31 AM | #15 | |
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Re: 5.5 head
Quote:
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09-02-2023, 12:43 PM | #16 | |
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Re: 5.5 head
Quote:
I like your approach to the problem. Approximately, how many clicks up from full advance did you place the stop on your car? From Bob’s diagram I would assume it would be 4 to 5 clicks up for a 6.0 compression head. David Serrano |
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09-02-2023, 12:55 PM | #17 |
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Re: 5.5 head
Now, advise you to get your intake bored out to 1.250 and bolt a B carburetor on it. Or get a downdraft Carb. on it. The A engine is starved for gas with the A carb.
Terry |
09-02-2023, 02:04 PM | #18 |
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Re: 5.5 head
The underside of the device is flush against the bottom and the top is filed to give the 28 degrees using the Nurex timing strip as mentioned in my post. I never looked to see how many clicks.
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09-02-2023, 03:54 PM | #19 |
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Re: 5.5 head
A little different setup as I have a Phillips Auto Advancer (original NuRex) but I have my total advance set @ 28° BTDC with my 5.5 head. I have it so I can retard the timing with the original advance control if that is too much on hills
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09-02-2023, 04:12 PM | #20 |
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Re: 5.5 head
New grade 8 studs have a much higher yield rate than the originals which were probably grade 5. They all rely on some stretch for their holding power. The grade 8 stretches less so it doesn't fatigue as fast. Most newer cars torque the heads 90-100 ftlbs and at 55 lbs the grade 8s should last many rebuilds. Has anyone tried 55+ lbs with the new bolts? My 289 HiPo would blow the gaskets at the stock torque but 5 pounds extra and the problem was cured.
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