High Compression Head - Snyder's 6:1

nellis003

nellis003

Senior Member
Hi, all--

My father and I just bought a '29 Roadster pickup with a cracked head. PO says he left water in the engine while the truck was in an unheated garage. The crack is very pronounced, right on top dead center of the head.

First and foremost, is there any way I can test the block in-car to see if there was any damage?

Second, since I'm going to be replacing the head anyway I thought I'd get a high compression one. Snyder's has one on their site that's a 6:1 ratio as opposed to the to 5.5:1. They say it's a new item. Is anyone running one of these heads, or heard about their quality?

Thanks for any information.

Nick
 
Eevery one and there mothers running a hi comp head it seems but iv herd that if your running an old warn out motor the hi comp head can bust it apart that's why I haven't gotten one maybe some one elce will confirm this cuz I don't know for sure. In regards to your motor the only way I know is to put head on and fill with water an fire up if there's no leaks and no water in the oil that's the best you can hope for
 
You will have to pull the head off and look for cracks between valves , look in valve chamber also under the water pump and the water jacket above the starter motor.

Stock compression is 4.2 as this is an unknown engine I would be tempted to use a stock head for the time being . You might be able to borrow one from a local club member. Pickup pain is right the 6.1 will damage the bearings if its tired !!!

John Cochran
 
Hm. I hadn't thought about the additional stress the high compression head would cause. While the engine is still in the frame, I can pull the pistons and rods out, and replace the rod bearings and piston pins/rings. Would that be enough to ensure that the engine would take the stress, or are the crankcase babbits also an issue?
 
I run a 6:1 head on a refreshed "worn out" motor. New rings and valve job but didn't get the bearings poured. I did however pull shims on the bearings as needed and got the clearance down to spec.

After 3500+/- miles it hasn't given any trouble, I'm not one to poke along at 35-45mph.

If you go with the 6:1 head make sure you don't use too much spark advance, with the higher comp head you won't need to advance the spark as much. I believe too much advance will pound the bearings out faster than a couple point increase in compression.
 
I have a cars with both types of hc heads. Both work great. 5.5 is around 9hp, 6.1 is supposed to be around 13hp. Can't say I can tell a big difference between the two but either of them makes a very nice improvement over the stock. Very safe on your car to use and is just a great option to use all around. Depending on your body style, I think you would be just as happy with the 5.5 head.
 
nellis003 said:
Hm. I hadn't thought about the additional stress the high compression head would cause. While the engine is still in the frame, I can pull the pistons and rods out, and replace the rod bearings and piston pins/rings. Would that be enough to ensure that the engine would take the stress, or are the crankcase babbits also an issue?
Click to expand...

UHHH, NO! These are model A's! The bearings are poured babbit. By "Crankcase babbits" I guess you mean the Mains, they're poured too.... Unless someone has bored them out and replaced them with inserts. It is possible.
For the possibility of a cracked block, I have a system to check blocks. It uses three aerosol cans . Actually it's for checking for cracks in welds. If you interested, I'll dig it out and send the name.
Terry
 
Terry said:
By "Crankcase babbits" I guess you mean the Mains, they're poured too.... Unless someone has bored them out and replaced them with inserts. It is possible.
Click to expand...

I do mean the mains, yes. I can't break the habit of calling them crankcase journals versus rod journals.

I'd love to hear about the aerosol method of checking for leaks, for sure.

Thanks,
Nick
 
I was at Snyder's two weeks ago, they said they didn't know when they would have 6:1 heads available, problem with the casting. I hope they'd have them in the next six weeks, as I having Antique Engines in Skokie, do my rebuild.:o
 
amishman said:
I was at Snyder's two weeks ago, they said they didn't know when they would have 6:1 heads available, problem with the casting. I hope they'd have them in the next six weeks, as I having Antique Engines in Skokie, do my rebuild.:o
Click to expand...
Been that way for the last 1 1/2 years.
 
I love my Snyder's 5.5 head I put on my used engine in my Roadster pickup. I was afraid I would lose the low end chug-a-lug ability but it actually improved it! It is so much better running at all speeds, makes it much more drivable and runs easier as it isn't having to try so hard.
 
Terry said:
For the possibility of a cracked block, I have a system to check blocks. It uses three aerosol cans . Actually it's for checking for cracks in welds. If you interested, I'll dig it out and send the name.
Terry
Click to expand...


The process is called Dye Penetrant Inspection. It's a non-destructive test method, relatively inexpensive and used for a lot more than weld checking. I use it often when inspecting aircraft.
Basically the concept is to apply a dye (usually red color) to test area, allow it time to flow in to any cracks that might be present. Wipe it off from the surface, then apply a white talc-like powder. Any dye trapped in a crack get's wicked-out by the powder and shows as a red line.

http://youtu.be/QpU5JyhNVgQ
http://youtu.be/yvjfeZxu_Bw

Graingers sells it, so does Aircraft Spruce. I'm sure there are others..
 
The stuff I have is called "Spotcheck" and it is made by Magnaflux . It's a three step process and as someone said, first you spray a red dye/penetrant then you spray a white talc on it and cracks show up. This is somewhat oversimplified so read and follow the instructions. I bought mine off a guy in the flea market, 3 cans for $10. so I have no idea what it costs over the counter.
Terry



nellis003 said:
I do mean the mains, yes. I can't break the habit of calling them crankcase journals versus rod journals.

I'd love to hear about the aerosol method of checking for leaks, for sure.

Thanks,
Nick
Click to expand...
 
Ross' link to Grainger's is the same stuff. But WOW!, The price! I got a deal and didn't know it! I'm sure someone is underselling Grainger, who are notoriously overpriced anyway!
Terry
 
I have a balanced ,1938 diamond "B" engine,lightened fly wheel , 60 over with cb crank ,insert rods and a "C" head .I have been thinking about getting a HC head . Do you think it would be worth it .
Appreciate your input .
 
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