check your manifold bolts......
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5.0 and 5.7 Discussion, check your manifold bolts...... in Cadillac Engine Technical Discussion; Check your engines for broken manifold bolts the next time you check your engine or work on it many or ...
  1. #1
    ocjmakaveli's Avatar
    ocjmakaveli is offline Cadillac Owners Enthusiast
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    check your manifold bolts......

    Check your engines for broken manifold bolts the next time you check your engine or work on it many or most lt1's have broken manifold bolts usually towards the rear there should be 6 bolts on each side.

    Broken bolts hurt performance and gas mileage.

    If you like preventative maintenance then upgrade your manifold bolts from grade 5 to grade 8 to avoid broken bolts which will happen because of the excessive heat and pressure build-up.

    Sometimes GM makes mistakes and we have to fix them

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    DanTheMan is offline Cadillac Owners Member
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    Re: check your manifold bolts......

    This is good advice. I checked at 100k, had 2 loose bolts and one missing. For those of you planning on doing this it is good advice but be carefult to do only one bolt at a time and make sure you sufficiently tighten them. Otherwise you'll develope a manifold leak that. If you do end up replacing the manifold gasket make sure all the bolts are thoroughly tightened and you'll have to go back and retighten them every time you drive for the first week or two.

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    The Ape Man's Avatar
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    Re: check your manifold bolts......

    It's a good idea to keep manifold bolts tight to prevent trouble. Changing to grade 8 bolts might not be the way to go. These bolts are stronger and will not strech. They will break instead. Turbocharger mounts use low grade bolts on purpose to take advantage of this. When in doubt, take a look at what Cadillac used from the factory.

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    ocjmakaveli's Avatar
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    Re: check your manifold bolts......

    Quote Originally Posted by The Ape Man
    It's a good idea to keep manifold bolts tight to prevent trouble. Changing to grade 8 bolts might not be the way to go. These bolts are stronger and will not strech. They will break instead. Turbocharger mounts use low grade bolts on purpose to take advantage of this. When in doubt, take a look at what Cadillac used from the factory.
    A lot of people with lt1's are using grade 8 bolts and none have had any broken bolts as of yet. Lt1's including fleetwood, impala ss, caprice, roadmaster, 9c1 cop car.

    "GM has TSB for upgrading these bolts to Grade-8, which has over 180,000 pound per square inch. Also Grade-8 bolt has higher alloy material, which offers superior anti rust capability. Why GM did not install Grade-8 bolts at first place? Cutting cost and passing the cost to you!"

  6. #5
    The Ape Man's Avatar
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    Re: check your manifold bolts......

    Quote Originally Posted by ocjmakaveli
    A lot of people with lt1's are using grade 8 bolts and none have had any broken bolts as of yet. Lt1's including fleetwood, impala ss, caprice, roadmaster, 9c1 cop car.
    Maybe that should read "No one has reported any broken bolts" I doubt you have had the time to verify this yourself. Imagine having to admit changing all exhaust bolts to grade 8 then having them snap.

    God bless all the small block guys who use grade 8 bolts. I wish them the best. It's your car and you can fix it the way you like. The fact remains that grade 8 will snap instead of stretch like grade 5.

    http://www.boltdepot.com/fastener-in...Materials.aspx

    I'll stick with engineers on this one.

    You never know who writes GM TSB's or just why. Do they state a specific failure that this is supposed to correct? If GM were to say something like switch to grade 8 and increase torque from 18 to 22 foot pounds then it would make sense. I don't know about you but it seems to me that there have been some pretty questionable TSB's released over the years.

    I was involved in fleet service for 8 years. We had severe duty 4.3 GMC V6's that regularly cracked exhaust manifolds. We replaced over 1000 sets of manifolds in NJ and NY using a different GM design. GM paid some of the cost. They never specified wheather to change bolt types or not. Some mechanics chose to replace with grade 8, some grade 5 and some re-used the originals. All bolts were overtorqued from factory spec as there was no way to check torque in the vehicles and the factory spec seemed too low to most of the mechanics. Result: No difference between installations. No fastener failures reported. These results represent millions of miles on vehicles that get the crap beaten out of them daily. My point here is that it didn't seem to make any difference in this application. The 4.3 is pretty similar to a SBC.

    As far as GM saving money, I'll take my chances that those old nasty cheap grade 5 bolts are there to purposely stretch while the engine literally changes size as it heats up and cools down. It might prove educational to look what some not so cheap manufacturers use like Mercedes. I'm quite sure someone on here has machine shop experience and further information.

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    ocjmakaveli's Avatar
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    Re: check your manifold bolts......

    Quote Originally Posted by The Ape Man
    Maybe that should read "No one has reported any broken bolts" I doubt you have had the time to verify this yourself. Imagine having to admit changing all exhaust bolts to grade 8 then having them snap.
    I would have known if they had snapped because they would have reported so on another forum i go to just how they reported the grade 5 bolts snapping they would have done especially so for the grade 8 and for the most part the guys using grade 8 bolts have NOS setups and superchargers even a few turbos so if its good enough for a 400 HP+ setup then its good enough for mine. Most of the guys that upgraded bolts do a lot of drag racing and autocross and since i don't do any of that it should hold up very very well. These upgraded bolts have been done since '98 I just barely got on teh forum 2 years ago and didnt see the need to upgrade because all my bolts were fine but I shouldve a long time ago to avoid the the headaches of a broken bolt.

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    Re: check your manifold bolts......

    I don't know what GM used on my 301 Turbo V8, but everytime I took the turbo off (if you want to take a valve cover off, off comes the turbo), but for me it was because I blew head gaskets, I broke the inlet to the turbo bolts.

    Well, I have a broke or missing bolt on my LT1. So I will have to deal with it soon. You would think, after oh, 60 years of Small Block Chevies, (let alone tens of millions of GM engines or more sold) they would have got this part down pat. I guess not....

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    Re: check your manifold bolts......

    If GM manufactures a million vehicles a year and saves 1 penny per vehicle by using grade 5 instead of 8, that's an extra $10,000 the company saves. The example numbers aren't right, but the idea is the same.

    Brian

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    Re: check your manifold bolts......

    Honestly, the cost "savings" can be even less than that. I call them "Micropennies", often 100th of 1 cent. But when it is placed say 50x or 100x, and you do millions, that does add up. And the bean counters are there to count it for us.

    Consider how many bolts GM buys per year. Now, consider your PO's that are going out. That want to keep the bottom line as low as possible. It stinks, we would gladly pay a few extra $ to get good quality, but, that isn't what they will let us do. I wish we could!

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