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Wrong direction on stroke

General engine tech -- Drag Racing to Circle Track

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Little Mouse
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Wrong direction on stroke

Post by Little Mouse » Thu Mar 19, 2020 10:51 pm

Most everyone wants to stroke there BBC people have even put longer stroke BBC cranks in the old 409. What about the 3.5 inch stroke 409 crank put in a Mark 4 BBC, anyone ever make main bearings to do that or are they still made.

Low&slow
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Re: Wrong direction on stroke

Post by Low&slow » Fri Mar 20, 2020 12:03 am

Back in the mid 80 there was a machine shop in Houston using 348 & 409 cranks in big block chevys for a certain class don’t remember the details but at the time I heard he also made his own connecting rods
My source also said those cranks had a small block size snout for the balancer and it was problematic for them
The rpm they were turning was top secret

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Re: Wrong direction on stroke

Post by Little Mouse » Fri Mar 20, 2020 12:38 am

Ya they had sbc size balancer.

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midnightbluS10
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Re: Wrong direction on stroke

Post by midnightbluS10 » Fri Mar 20, 2020 12:39 am

Low&slow wrote:
Fri Mar 20, 2020 12:03 am
Back in the mid 80 there was a machine shop in Houston using 348 & 409 cranks in big block chevys for a certain class don’t remember the details but at the time I heard he also made his own connecting rods
My source also said those cranks had a small block size snout for the balancer and it was problematic for them
The rpm they were turning was top secret
Wasn't that Reher Morrison Shepherd? Afaik, David Reher has talked openly about that plenty so there should be plenty of info out there.
JC -

SUPPORT THE RPM ACT :!:

https://www.sema.org/rpm-bill-summary

Low&slow
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Re: Wrong direction on stroke

Post by Low&slow » Fri Mar 20, 2020 12:43 am

Refer Morrison may have done it also
The place I knew of was in Houston
And I knew very little about it they were tight lipped about that deal

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Re: Wrong direction on stroke

Post by Low&slow » Fri Mar 20, 2020 12:52 am

I’m sure David rehear would tell you all about now
40 years ago probably not so much
He probably would have said hmmm never thought about that

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Re: Wrong direction on stroke

Post by GLHS60 » Fri Mar 20, 2020 1:42 am

Coincidentally, or not, 3.5", was the stroke of the original Mk II canted valve Engine.

The MK IIs, or 427 Mystery Engine as they were known, had a stroke increase to 3.65"

The original Design Engineer, Mr Richard Keinath was a strong proponent of short stroke Engines.

The 409 size bore blocks were problematic for the foundry so later MK IV Engines settled for 3.76"

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There is no logical reason to call an Engine a motor.

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Re: Wrong direction on stroke

Post by Low&slow » Fri Mar 20, 2020 2:05 am

I think the 396 version of the mark ll had 3.390 stroke iirc
All 3 versions had a 4.310 bore
Smokey wrote there was no power difference between the three in stock form from Chevy

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Re: Wrong direction on stroke

Post by Diodedog » Fri Mar 20, 2020 11:51 am

Back in the late 70s I worked in a machine shop building Pro Stock engines and we used 348 cranks in 396-427 blocks because of the cubic inch x weight factor.

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Re: Wrong direction on stroke

Post by Low&slow » Fri Mar 20, 2020 11:56 am

I heard the bottom end could take a whole lot more rpm than what the valve train could offer in those combinations

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Re: Wrong direction on stroke

Post by PackardV8 » Fri Mar 20, 2020 12:35 pm

Low&slow wrote:
Fri Mar 20, 2020 2:05 am
Smokey wrote there was no power difference between the three in stock form from Chevy
Being there back in that day, the valves, springs and cam lobe profiles hadn't caught up to the "porcupine" head design. Those first engines blew so early and often, it's doubtful if Smokey put enough dyno time on any of the three to quantify the output. He did end up with some of the 396" versions which were orphaned when GM really cracked down on racing support.
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Re: Wrong direction on stroke

Post by Low&slow » Fri Mar 20, 2020 12:47 pm

I read Chevy sent 44 of the 60 built mystery to Smokey
Junior Johnson said many years later that Smokey could get almost 600 hp from the 427
But they didn’t run very long

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Re: Wrong direction on stroke

Post by falcongeorge » Fri Mar 20, 2020 3:45 pm

Low&slow wrote:
Fri Mar 20, 2020 12:03 am
Back in the mid 80 there was a machine shop in Houston using 348 & 409 cranks in big block chevys for a certain class don’t remember the details but at the time I heard he also made his own connecting rods
My source also said those cranks had a small block size snout for the balancer and it was problematic for them
The rpm they were turning was top secret
Pro Stock, pre-500" rules. late seventies, Bernie Agaman. Might have been someone in Houston doing it too.

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Re: Wrong direction on stroke

Post by Little Mouse » Fri Mar 20, 2020 5:49 pm

Who made bearings or spacers to use the 2.5 mains back then or did they fabricate up something.

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Re: Wrong direction on stroke

Post by Little Mouse » Fri Mar 20, 2020 8:12 pm

Been reading about the new DRCE4 pro stock block and what there doing in pro stock. Ya the mains are the old 409 size 2.5, rod pins are Honda size 1.888. Cam can be from 70 to 80 mm. The 80 mm is 16 mm bigger the mains on the crankshaft, has 9 jurnals supporting it, compression rings are either stainless steel or carbon steel .021 with a titanium nitrate coating, oil ring 2.00 mm. Oil viscosity they use W02. Deck height as block comes 8.90 can be cut up to .300 lower. Crankshaft is 50lbs and I forget the mandated rule on the piston, pin and rod. Think the piston was 430 grams, pin 130 grams. Original bbc took somewhere in the 25 to 35 lb range to turn the rotating assembly. They only need an inch pound tq wrench to check theres. They have some special tool to check cylinders for roundness to 1 micron. All of GMs DRCE4 blocks and there nascar block are made by a company over in england or there more proper, united kingdom. Lol

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