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Horsepower limits of a Service Block?

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jpnjim View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Topic: Horsepower limits of a Service Block?
    Posted: Feb/08/2018 at 8:18pm
Is there a concensus on the HP ceiling of a thick web Service Block?

Assume 4.08-4.125" finsh bore for maxium wall thickness,
and billet crank/good rods to take them out of the equation.

Studded mains, girdle and/or 4 bolt mains.

Turbo application if that matters (no blower load)

What do we think breaks first, and when?


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Lyle View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lyle Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2018 at 9:33pm
If you go by the Ringbrothers that put the Hellcat engine in the "Demon" the AMC block can hold up to 800 HP. They didn't state in the articles I've read what the weakest link was but that is why they went with the Hellcat engine to go to 1100 HP.
It should not be pistons, rods, block or heads, so I'd assume harmonics on RPM with the crankshaft. Just my guess.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaemonForce Quote  Post ReplyReply Direct Link To This Post Posted: Feb/08/2018 at 9:59pm
Is there a major capacity difference between service blocks and the Indy IC-401 block? Because I really want to use that later one for my base engine build.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 5:38am
Originally posted by Lyle Lyle wrote:

If you go by the Ringbrothers that put the Hellcat engine in the "Demon" the AMC block can hold up to 800 HP. They didn't state in the articles I've read what the weakest link was but that is why they went with the Hellcat engine to go to 1100 HP.
It should not be pistons, rods, block or heads, so I'd assume harmonics on RPM with the crankshaft. Just my guess.

I read that,
but I take it with a grain of salt since they don't claim to be AMC V8 experts,
so who really knows who's advice was taken by them to get the 800hp number.

Harmonics was something I wasn't really considering with this engine,
I know even though L6's are naturally easier to balance,
 the AMC 6 has been know for a harmonics issue at some RPM.

I'm wondering at what point the rigidity of the Service Block becomes an issue.

I understand the type of racing makes a difference,
so we'll say for drag racing for the sake of the argument.

Thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 6:24am
As I remember really bad things happen to a 258 over 6000 rpm
no matter how you prep it.

As to the block taking over 1,000 hp?

IMO....

Good strong block, a proper 4 bolt main job should make it a
doable thing in a drag race situation.

Oiling system will bite you in the butt first.

Obviously you need an after market reciprocating assemble and internal balancing.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 6:25am
Originally posted by DaemonForce DaemonForce wrote:

Is there a major capacity difference between service blocks and the Indy IC-401 block? Because I really want to use that later one for my base engine build.

I don't know,
I would say the assumption is the Indy block is much stronger,
but there was that other thread a while back where one broke in half.

Apples and oranges tho,
I'm just wondering what the "assumed" max power a Service Block can safely handle is.

Like, Small Block Fords split in half at xxx hp,
Big Block Buicks throw out the mains at xxx hp,

something like:
AMC Service Blocks break the ?? or split the ?? at xxxx hp.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 6:34am
Originally posted by Boris Badanov Boris Badanov wrote:

As I remember really bad things happen to a 258 over 6000 rpm
no matter how you prep it.

As to the block taking over 1,000 hp?

IMO....

Good strong block, a proper 4 bolt main job should make it a
doable thing in a drag race situation.

Oiling system will bite you in the butt first.

Obviously you need an after market reciprocating assemble and internal balancing.
 

Yeah,
looking for a number something like that.

Assuming everything else is addressed:

 rods & pistons appropriate for the power levels
billet crank
properly ballanced for the application,
appropriate oiling 

at what horsepower level would the block strength itself be the issue?

Assuming a properly prepped thick web Service Block,
not over 4.125".

I know it's just guessing until it happens,
but is the assumed block strength around 8-900hp,
or is the consensus closer to 1200?

 thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lyle Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 8:15am
Found this article that seems quite informative:
http://amccars.net/cgi/yabb2/YaBB.pl?num=129278929
I believe the crankshaft weight being near 90 lbs vs the hemi and other crankshafts below 70 lbs is what makes the limiting factor. That'a quite a bit more rotating mass and rotating forces.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 8:39am
Originally posted by Lyle Lyle wrote:

Found this article that seems quite informative:
http://amccars.net/cgi/yabb2/YaBB.pl?num=129278929
I believe the crankshaft weight being near 90 lbs vs the hemi and other crankshafts below 70 lbs is what makes the limiting factor. That'a quite a bit more rotating mass and rotating forces.


Thanks Lyle!

I think the last number 6 got cut off your link,
but think this is the thread:


I had breezed it years ago, but forgot what forum it had been on,
very informative Smile
thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote shootist Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 11:38am
Well since the service block is ultimately a small bore 390/401 block (to my knowledge, correct me if that is wrong) I know 800-900 is easily doable in the stock setup without even going 4 bolt mains because I have done it and a few AMC friends of mine have done it. Now if you go 4-bolt then I would say 1,000 would be easily reachable without hurting the block. What I have seen on the otherhand in 401 bore blocks and I find to be the most likely weakness is the thin cylinder walls. Out of all the block damage to the heavy webbed blocks (for which I have seen) I find blown out cylinder walls the most common. I believe this has a lot do do with mold shift causing some thinner areas but that is just an educated guess. The other types of damage I have seen have been such a mangled mess it is hard to determine what exactly happened because cranks and rods flopping loose in the crankcase at high RPM tends to destroy stuff pretty well.

Anyway, I wouldn't be at all concerned with block failure at or under 1,000 HP with reasonable levels of prep which you mentioned doing. I am putting 14lbs of boost on my 401 now with a ProCharger and there are a few others out there doing the same.
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