Engine/Transmission (1994 - 1998) the infamous allen head head bolts

[DJWyckoff]

I have posted about my head bolts and to clear up all questions they are;



grade 8 allen head bolts

12mm x 1. 75 thread pich

six are 70mm long

eight are 120mm long

six are 180mm long

washers

nine are 12mm

five are 10mm use a die grinder to enlarge the center (used between the valve covers)

six long rocker bolts dont get washers

torque

standard patern 90ft lbs

standard patern 90* "torque turn"



I have replaced the stock bolts one at a time with these front to back with no porblems as long as the engine has not seen over 32lbs boost the stock gasket will be fine. these bolts are a common thing in WV they work good they will hold the head on and are cheep if you shop around they should cost less than $80



they are curently installed in the local WV shops pull truck when he ran twins the truck would have boost #'s @ or around 100lbs the head is o-ringed but there are a bunch that are not running 55-60lbs hope this helps

 

[bgilbert]

Stock head bolts are what, 12. 9 grade? Or is this just the cheap option?

 

[DJWyckoff]

I would have answered sooner but I was in tenn for 4 days . I don't know what grade the factory bolts are. but I have seen them streach under extream boost presures and after head gasket failure (from lifting the head) some bolts were removed with with my fingers no tools required. so if these stock bolts are failing and the allen head ones are working does it matter what the stock hardness is? arp studs are around $450 these are around $80 stock bolts $? try them if you like. I will not do a head gasket with out them.

 

[SDrake]

Do you torque these bolts to a higher spec or do the bolts work because they take more load to stretch, ie have a higher strain rate?

 

[DJWyckoff]

the answer to these and all other questions are hard to answer. I'm sorry that I dont know the streach or any other caricteristics.



however there is no need to retorque these bolts so they must streach and hold good right?



and as far as torque if you install these bolts the torque is high enough that 1 name brand (snap-on, mac and matco )10mm allen head socket will not finish the job. so the torque is higher I'd say. don't you think?



I use a matco 10mm allen socket center and a 10mm shallow impact 1/2 drive.



I don't know all, but I do know I changed my bolts 80k ago and at the same time installed a trans buddy/lockup switch in my 47re and removed the torque plate from my p pump and crimped off the waste gate banks big head.



the boost #'s were in the low 40's and the smoke was so that day was night behind my truck. try them out I love mine. hope this helps.

 

[pwerwagn]

Dug up this old thread searching.....



Has anybody else ran these and had good success?? I have a contact at fastenal, so I thought I might try it out when I have to do a HG.



--Jeff

 

[Joseph Donnelly]

Two points: stock head bolts are torque-to-yield grade 12. 9 and are the lengths noted, but with washer heads. Using separate washers on the Allen bolts results in engaging one fewer threads in the block. Second, Allen 12. 9 bolts are not designed for the 90 degree turn torque-to-yield. They should be tightened to a specific torque depending on their grade. I typically torqued stock head bolts to 120 ft lb instead of the 90 degree system, and they worked fine with a stock head gasket at 60 psi boost.

 

[pwerwagn]

Did you re-use the stock headbolts Joe? Maybe I should just torque mine to 120 as it sits. Ive been running 40-42psi and havent had any probs yet (fingers crossed-knock on wood), Just starting to worry about it a little considering the mileage and abuse.



--Jeff

 

[rbshowpig]

I run these allen head bolt. I run 60 psi everyday and over that when i am pulling with 12mm bolt. if you are runnning over 60 psi go with 14mm bolt. The guy with the pulling truck in west virgnia he is running 14mm bolt. Last year he spilt the block with bolts. these bolts realy works.

 

[Joseph Donnelly]

I re-used stock head bolts, even at 800 hp. I prefer to use higher grade bolts where possible instead of going larger. It is hard to drill and tap exactly straight, and crooked would make for big problems. It is also good to leave more meat in the block. However, grade 12. 9 is about as high as you get, unless you get special stuff from ARP.