240/300 parts interchangeability

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240/300 parts interchangeability

Post #1 by pmuller9 » Thu Mar 01, 2018 1:54 pm

Cylinder heads:
240 heads have a 68cc combustion chamber.
300 heads up to 1986 have a 76cc combustion chamber.
1987 and later heads have a 68cc heart shaped combustion chamber. These are the EFI heads

Heads up to 1984 have stud mount rocker arms with slot shaped pushrod holes in the head to act as pushrod guides.
1985 and 1986 carburetor heads and 1987 and later EFI heads have pedestal mount rocker arms with round holes in the head for the pushrods.
1986 and earlier heads use a 4.810” long valve while the 1987 and later EFI heads use a shorter 4.750” valve.
All have 11/32” valve stem diameter, 1.780" intake diameter and 1.559" exhaust diameter
SI valves is the main source for 240/300 valves.

If the head is converted to screw-in rocker studs then the SBC 4.910” long valve can be used for oversize valve installation.
The 1985 and later heads will need pushrod guide plates when converting from pedestal to stud mount rocker arms.
Chevy 250 six, Big Block Chevy, Ford 460 and Ford Cleveland 1.650" length roller rocker arms can be used with the screw-in studs.

Piston and connecting rods:
The 240 rod length is specified at 6.7947” and the 300 rod is 6.2097”. They are generally rounded up to 6.8" and 6.21"
The 1965-1968 240 and 300 rods have a .912” wrist pin diameter. 1969 and later rods have a .975” pin and an oil spit hole in the big end of the rod.
All rods are .994” wide at the big and small end.
Rod journals are 2.130”

240/300 block deck height is 10.00”
240 stroke is 3.18” and 300 stroke is 3.98”
Standard bore is 4.00" for all blocks.
Rotating assemblies will interchange between the 240 and 300 blocks.

A favorite combination is to use the longer 240 rod on the 300 crank.
This allows for a shorter and much lighter piston along with a higher rod length to stroke ratio.
The .912” pin rods allows the use of Ford 302 and 351W V8 pistons.
The .975” pin rods for 352 and 390 Ford FE V8 pistons.

The small 2.100” journal BBC rods have a .992” wide big end can be used with custom pistons.
These rods use the SBC 2.100" bearings.
The 300 crank rod journals are turned down form 2.130" to 2.100" to accommodates the BBC small journal rods.
The 6.385” long small journal BBC rod is available as an “off the shelf” item.
The Eagle CRS6385B3D is the least expensive.

The 240/300 lifter is .875" and is common throughout the Ford six and V8 engine families.

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Re: 240/300 parts interchangeability

Post #2 by WorldChampGramp » Tue Mar 06, 2018 7:40 am

Well Done PMuller9. I trust others appreciate this compendium of well thought thru :idea: facts and suggestions. I certainly do and so does our machinist. Gramps

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