Head bolts too short for High Compression Head

M

Model A Apprentice

Member
In attempting to install a Snyder 6:1 head on the 31 roadster using the standard length grade 8 head bolts that were recommended for the head, I find that the 3.5" head bolts are too short. I can order the softer grade 5 head bolts in the 3.75" length required, but am concerned about the grade.

Has anyone had experiance using the grade 5 head bolts on a 6:1 Head? I hear they have the potential to "stretch". Is there any truth to this?
 
Last edited:
Bought and installed one of Snyders 6.1 HC head last month using the grade 8 3.5" bolts. Same problem, they are too short. I am having a bubbles in the radiator problem and attribute it of lack of torque. Have not solvess problem yet. Ken
 
Did you use the 3.5" "high compression" bolt set or did you use the longer but grade 5 bolts? I am thinking of using the eleven of the 3.75" ignition studs. Longer studs but lighter grade.
 
I used the 3.5 "high compression" bot set. Snyders call it chrome-moly or something like that. I am going to order eleven of the 3.75" ignition studs and trade them out one at the time.
 
Not a bad idea if you can get the ignition studs in grade 8. Will that mean you might have to use grade 8 flat washers under the nuts ?
 
Model A Apprentice said:
In attempting to install a Snyder 6:1 head on the 31 roadster using the standard length grade 8 head bolts that were recommended for the head, I find that the 3.5" head bolts are too short. I can order the softer grade 5 head bolts in the 3.75" length required, but am concerned about the grade.

Has anyone had experiance using the grade 5 head bolts on a 6:1 Head? I hear they have the potential to "stretch". Is there any truth to this?
Click to expand...


All the studs stretch. You just don't want them to stretch too much such as when a Grade 5 (or any grade) stud is over-torqued.

Snyder's head is off 1/4 of an inch as compared to the original head for you to need 3-3/4" studs.

The most common Model A ignition stud is 3-11/16" which is 1/16" shorter than what you're calling for but 3/16" longer than the correct 3-1/2" studs.

correct nut height = 7/16"
3-1/2" x 11
3-11/16" x 1 (most common ignition stud and correct for 1931)
5-23/32" x 2
correct thread length of bottom thread for all studs (the part that screws in the block) = 3/4"
Snyder's gasket = .050" (?)








.
 
Last edited:
Is the 3-11/16" stud that you reference more commonly known and listed as the 3-3/4" in the Bratton Manual? I did not measure the exact length of the bolts in the high compresion head bolt package I received. The water outlet studs fit well. The "3-3/4 ignition bolt" would take a nut nicely. But I could just barely get a single thread to start on the "3-1/2" bolts. Not sure what I will use for the actual ignition stud. I will check the exact measurments of all the bolts when I am in the shop tomorrow.
 
Model A Apprentice said:
Is the 3-11/16" stud that you reference more commonly known and listed as the 3-3/4" in the Bratton Manual? I did not measure the exact length of the bolts in the high compresion head bolt package I received. The water outlet studs fit well. The "3-3/4 ignition bolt" would take a nut nicely. But I could just barely get a single thread to start on the "3-1/2" bolts.
Click to expand...


No, the 3-11/16" ignition stud is just what it is .. 3-11/16" and it is the correct original length for all Model A's ignitions except for AR 1928 which used a thick conduit clip and a stud length of 4-7/16". There was also another thick conduit clip which used a stud length of 4-1/16".

The 3-1/2" stud is the correct original length for all Model A's from start to finish.








.
 
Last edited:
I also recently installed a 6:1 Snyders head and used their grade 8 studs. Same issue. As I've said here before, I torqued the head to 65 lbs. and have no bubbles or leaks. The tops of the studs do not come up even like the originals so for you purists that might be a problem.
 
I have the same problem with the Snyder’s 6:1 head. I was hoping when I did my second torque after 500 miles it would be better, but it was not. (55 lbs.) Everyone points it out me, I am glad to find out that it wasn't a rookie mistake.
 
Boston Bruce said:
I also recently installed a 6:1 Snyders head and used their grade 8 studs. Same issue. As I've said here before, I torqued the head to 65 lbs. and have no bubbles or leaks. The tops of the studs do not come up even like the originals so for you purists that might be a problem.
Click to expand...


Being a purist or not has nothing to do with it. The maximum threads of the nut should be utilized for accurate torque and proper clamp ESPECIALLY on a high compression head.

Moreover, on the original head, the original stud rose ABOVE the nut a thread or two to secure maximum thread.







.
 
Last edited:
Larry Brumfield said:
Being a purist or not has nothing to do with it. The maximum threads of the nut should be utilized for accurate torque and proper clamp ESPECIALLY on a high compression head.
Click to expand...


I assume when corrrecting the problem, the proceedure would be to replace one at a time following the torqueing sequence. Is there any additional concerns I should be worried with?
 
Could the studs be threaded too far into the block? The studs cavities blown into the water jacket letting the studs enter the jacket.

Just SWAGing

GW
 
You'd think that the manuf of the new head knew it was thicker than a stock head and would have made avail correct length studs ?????
Paul in CT
 
GW

No threads were left on the studs, when hand tightened into the block. All studs are equally short. When installing I assumed the threads were at a set length for your reason stated above.

Paul
 
30ccpickup said:
I assume when corrrecting the problem, the proceedure would be to replace one at a time following the torqueing sequence.
Click to expand...


Since you just installed them (I assume) you might be able to get them out one at a time by gripping them but you'll be lucky and may just make a mess out of the studs. Of course you could also weld a nut to the stud but that's a lot of trouble and not the way to do it in this case. It's best to remove the head.


30ccpickup said:
Is there any additional concerns I should be worried with?
Click to expand...


Yes, a blown head gasket ... or leaking combustion under load and a head gasket that may not hold up for the long haul (or possibly even the short haul) with only a partial grip by the nut and 55 pounds of torque.
 
You must log in or register to reply here.
Back
Top