All Small Six Molnar connecting rod for the 250 six

[pmuller9]

Molnar just made an "H" beam rod available for the 300 six that also can be used for the 250 six along with a custom piston.
They are made from 4340 billet steel, heat treated to increase tensile strength and shot peened and feature ARP2000 bolts
They are 6.210" long and use a .975" pin

 

[powerband]

pretty...

Could you please explain for the layman how they could be used for 250 application. Using 300 wrist pins (?) with custom pistons, is any machining needed at big end?.

thanx
. . .

 

[pmuller9]

pretty...

Could you please explain for the layman how they could be used for 250 application. Using 300 wrist pins (?) with custom pistons, is any machining needed at big end?.

The 300 connecting rod big end width is .990" and uses a 2.123" rod journal on the crankshaft.
It should be a direct fit on the 250 six.

It will need a custom piston from Autotec/Racetec or any other piston supplier you prefer.
The piston will have around a 1.300" CH depending on finished block deck height and will need a .975" pin to fit the Molnar connecting rod.
The piston will be lighter than stock and the longer connecting rod will improve rod angle.

What does the big end width measure on one of your 250 rods?

 

[powerband]

I'll check OEM rod width can't find spec , OEM Rod Length is 5.880", and the Molnar rods' @ .33"difference added length to the (custom) piston pin should improve rod angle with @ 1.300" CH ? .

have fun

 

[pmuller9]

OEM Rod Length is 5.880", and the Molnar rods' @ .33"difference added length to the (custom) piston pin should improve rod angle with @ 1.300" CH ? .

Doesn't look like much but every bit counts.

The rod length to stroke ratio is increased from 1.504 to 1.588.
Max Velocity is reduced by .5%
Side loading is reduced by 2.5%
"G" forces at TDC are reduced by 1.7%

 

[bubba22349]

Bob the builder "62Ranchero200" built his 250 Six short block using the early 300 six rods and a custom forged piston awhile back, it seems to be a really nice combo of parts for the short block. Some details for his build with the Aluminum head and cam change are here. https://fordsix.com/threads/250-w-al-head-mill-head-to-raise-compression.80506/#post-624956

 

[rocklord]

The early 300 connecting rods have the same .9122" pin diameter as the 200/250 rods and are forged. Use a piston from a 2002-04 Jeep 4.7L Modular V8 +0.40"/1.00mm (3.700 Bore, 1.24 CH, Flat top, 0.946 Pin diameter) and enlarge the small end of the 300 rod. The piston recess would be 0.064" instead of the stock 0.134".

Piston: Sealed Power H833CP 1.00mm

2001 JEEP GRAND CHEROKEE Sealed Power H883CP100MM Speed-Pro Hypereutectic Pistons | Summit Racing

Free Shipping - Speed-Pro Hypereutectic Pistons with qualifying orders of $109. Shop Pistons at Summit Racing.

www.summitracing.com

 

[bubba22349]

I think these new rods are going to be a great way to go especially for a Turbo build!

 

[powerband]

"What does the big end width measure on one of your 250 rods?"

250 rod big end width in previous picture measured @ .992.

... the vintage Jack Clifford shop built 250 in my '61 uses AMC 4.2 258 application Pistons with .070 overbore and the 250 rods..

Ford 250: bore = 3.68 / comp distance = 1.5 / dish volume = 13cc
AMC 258: bore = 3.75 / comp distance = 1.633 / D-Sump = .178(?)

... the bore at @ .070 over raises the piston toward the deck .133 . The specs list the pin diameter of the ford at .9122 and the AMC's at .9310 which can be accomodated. The 250's thin wall casting must be taken into account for high boost but my NA engine has run solidly for @ 10 years with aggressive performance.

hav fub

.

 

[chad]

"...Molnar just made an "H" beam rod available for the 300 six that also can be used for the 250 six along with a custom piston.
They are made from 4340 billet steel, heat treated to increase tensile strength and shot peened and feature ARP2000 bolts..."
o0OO la la! Nice find~