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Thread: Extra head bolts on Merlin block

  1. #1

    Extra head bolts on Merlin block

    Just wondering if it is worth using the extra two head bolts per side in the lifter valley on the merlin blocks.On the merlin block the maximum torque on those lugs is only 35ft.lbs so i didn't know if that would help very much to worry about using them.Thanks

  2. #2
    Senior Member DYNO OPERATOR
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    Use them. 35 to 45 ft lbs. Lots of luck trying to measure torque there. I use blue loctite and as much as I can pull with an end wrench.

    Start them before you torque heads down and torque them down after finished torquing all head bolts/studs/nuts etc.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  3. #3

    Use them

    Yes, use them, but I use red loctite and a box end wrench.


    gyrogearloose

  4. #4
    Senior Member RACING JUNKIE
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    I have the BBC Merlin VR345 heads that have the threads going into the 2 intake ports each side, but I dont have a merlin block that accomidates the threads, guess I need to plug them , correct?
    ><Charles
    ***IN GOD WE TRUST***

  5. #5
    Senior Member MASTER BUILDER
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    Absolutely use them if you have them. On a big block chevy, 2 of the cylinders, on each side, so, 4 total, have an inherant flaw, with a wide span between the 2 upper head bolts. The other 2 cylinders, have a bolt in between there. It is VERY common, to push the gaket out, on the 4 cylinders without that extra head bolt. I have 2 540 3300 intercooled Whipple Charged big block chevy's to re-do, as the oil is milky, and, they had very bad blow by. Turned out, the block and heads had a horrible 85B finished decks, that, combined with regular fel-pro gaskets, without those bolts, all 4 of the cylinders where the bolts were missing, were pusherd out there, leaking compression, and water from the coolent hole right by there. You could see the saw tooth pattern, indented into the fire ring, and, it wasn;t completely sealing very well. They were pretty poochy too, only like 730 hp, with the blowers. I have a naturaly aspirated marine 540 combo that makes that much power. So, picking these up by 100+hp, without being more racical, should be easy.

    So, I will be re-block truing the blocks, on the 10-V with cbn, for a smooth finish, re-cutting the heads, and using Fel-Pro MLS gaskets. Also, when I un bolted the heads, the head bolts were fairly losse. I don;t think the heads were re-tqed after the initial running. Which I will also do. I always do that. Especially with the composition Fel-Pro's, and aluminumn heads, even though, they say you don;t need to.

    I am rambling again, but, definately use them. Like was mentioned some lock tight for sure.

    Frank
    Advanced Performance
    www.get-ap.com

  6. #6
    Senior Member RACING JUNKIE
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    I have a Merlin lll block. My old heads were 074 GM that had the bolt holes in the ports but were plugged. I just bought some new Brodix...so before I put em on should I just have them drilled and tapped for the extra bolts? It looks like Brodix marked the location with a drill but didn't go all the way through to the port .If I do this do I drill all the way through or just partial depth?

  7. #7
    Senior Member MASTER BUILDER
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    head bolts

    Just a word of caution, I drilled my own on a drill press, the 2 valley bolts were at a different angle than the head bolts, had to make 4 crooked studs to make them work. :shock:

  8. #8
    Senior Member RACING JUNKIE
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    Re: head bolts

    Quote Originally Posted by topcat572
    Just a word of caution, I drilled my own on a drill press, the 2 valley bolts were at a different angle than the head bolts, had to make 4 crooked studs to make them work. :shock:
    :? How far did you throw the wrench when you realized this? I most definately would have turned the air blue.

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