Hornet headbolt question

Unknown
Unknown
edited November -1 in HUDSON
I know that original headbolts had a 3/4 hex head and used a large diameter washer. A new headbolt can be easily purchased in a grade eight but has a small hex head of 5/8 inch and the washers currently available also much smaller diameter. My question is if these bolts will be adequate? I am talking about a 7/16 bolt application with 308 or 262 head on a Hornet - a minimal compression increase. Seems to me short of a 1/2 inch stud upgrade that the heads may need the increased area under the larger bolt head and the larger washer to adequately seal? Perhaps not, I would like to know what you have to say on this issue.

Comments

  • 464Saloon
    464Saloon Senior Contributor
    I went with the later 5/8 style and thick washers. According to the harware supply that I deal with which are mostly automotive assured me I would have even more clamping force with the thick washers that the old style. So far no problems. I believe Dale Cooper and Paul Larguette (sp???) on this forum offer the bolts with the large heads.
  • Browniepetersen
    Browniepetersen Senior Contributor
    The original head bolts were rated as a grade 5 and the torque strength was much less than the grade 5's that are available today that are built for the machine/automotive applications. However, it would not be wise to use anything less than a grade 8 bolt. The torque strength of the grade 8 bolt and the compression strencth of the matching washer is more than adequate for the Hudson head. I could give you a bunch of figures for the torque strength and the shear strength but lets leave it here for now. My concern with my 52 step down 308 engine was due to the close tolerence machining and the modification to the piston/rings that we fabricated for the engine. Our goal was to increase the horse power above 215. With this additional horse power we ran into the problem of the distance between head bolts with the aluminum heads. We trashed three good heads right off the bat. We went to the 308 steel head, heat treated it and machined and lapped the block and head to get a secure fit. Then we added the grade 8 bolts with matching washers. It works for me. We ended up with a bench horse power of 220 and an engine that runs smooth as silk.
  • super651
    super651 Senior Contributor
    Petersen, You said that you had a 308 iron head heatreated ? How was that done (did it have a Rockwell Rating ) I am intrested in that as I was going to use the Freeze type of getting the head to withstand Higher Pressures.

    I will be using the 1955 308 Iron head on my 1956 -308 engine that I am building and hope to finish this year. ( Iwill be using a T04 Turbo and a SUCK-through Carb. with boost in the 10-14 PSI range.

    Let us know about the HEAT Treated Process. Thanks RUDY
  • Unknown
    Unknown
    One thing many people forget to do is to check the torque on the head bolts thru several heat cycles - untill everything takes a set and no further torquing is needed to achive specs. That may be less of a problem with the new Best gasket available from Dale Cooper it has real adhesion to the block and head. Dale has new large size headbolts in the 7/16 s size see Nov/Dec WTN. Lou Cote
  • super-six
    super-six Expert Adviser
    I have used the Grade #8-7/16 bolt with the 5/8 head w/hardened washers and they work fine. No problems.
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