Paul, I know it's a sin to use Chevy parts on a Ford motor, There is probably a price on my head from the Ford crowd. But believe me, it's done a lot. For one thing, parts for Chevy motors, both small and big blocks are plentiful and cheap.
When you build a high performance motor, you want to minimize the rod angle as the piston travels through the bore. The longer the rod, the less angle you will have and as a result you will have less side load reducing bore wear. Also the longer rod will reduce piston speed as well which is also a benefit and increases the time the piston is at top dead center. The limiting factor is the position of the piston pin in relation to the oil ring (Lower ring). On an FE with 3.98" stroke, a 6.8" long rod is pretty much the maximum rod length you can have and have the piston pin sufficiently away from the oil ring. Some small block builders stroke their motor so much that the piston pin sits so close to the oil ring that the motor has unacceptable oil consumption and blow by. The drawback of having a long rod is weight, that is why I chose Oliver Nascar billet rods which are pretty much the lightest for their size without going to a titanium rod (833 Grams Each).
http://www.oliver-rods.com/products/FordBilletIndex.html This is lighter than the Ford "Le Mans" rod used in the 60's racing 427 and the 428 Super Cobra Jet. These rods like almost all Ford FE rods were only 6.488" long. Oliver rod are much stronger than any stock rod and can withstand tremendous load in top fuel dragsters and offshore racing. As a matter of fact their unique parabolic shape make them as strong as an H beam design like a Carrillo for example, but quite a bit lighter. Another advantage of the longer rod is less tendency to detonation. Since I am requesting 10:1 compression, which is the limit for a carburetted aluminum heads engine on pump gas here in the US.
Why use a Chevy rod bearing size? The FE has a rod journal size of 2.4384" but is slightly narrower than the BB Chevy. Chevy rod journal size is 2.20" in diameter but slightly wider. Racers like to reduce journal diameter because it reduces the rotational speed of the bearing. The smaller diameter of the rod big end saves weight, increases clearance to the block walls and allows the uses of a rod made for the Chevy motor which is quite a bit less expensive than a custom designed and built item. Some people will turn down a stock Ford crank to the Chevy size but the crankshaft weights have to be trimmed as well to accommodate the wider rod and crank strength and stiffness can be seriously compromised. The other alternative is to machine the rods but then a custom size bearing has to be used, not a good idea as well! This is why I think that this should only be done when using a new custom forged or billet crank.
With longer rods, the engine should have a bit more torque and reliability should be much better than if I was using stock Ford bits. We will see! When you look at the size and weight of the rotating assembly in one of these motors, (4.25" bore) you want to make sure that your bottom end is bullet proof or everything might go with a loud bang at 6,000 Rpm! After all, each rod and piston assembly weights over 3lbs.
Hopefully, the motor will stay together during the dyno run, I will publish the sheet when that happens probably in a month! The bottom end of my engine should be able to handle more than a 1,000HP with these components, the goal is to have a motor which will be dead reliable like a stock motor but can go the distance with about 500HP. Time will tell.
The FE is a wonderful motor which is seeing a resurgence in popularity. Being a full skirt block, it is extremely strong, and as a side oiler, it can withstand tremendous rotation speeds. Long ago, Shelby saw it's potential and the GT40's that won Le Mans ran virtually stock motors. It's not perfect, the rocker assembly is horrible and extensive modifications are required for the heads to breath half as well as a big block Chevy. But the motor is relatively light and compact compared to it's competition and is an icon in automotive history. With this type of engine, the Frua is virtually the fastest automobile of the 60's, 70's and maybe 80's as well, and we know the chassis is up to it! It should be a fun ride![
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Emmanuel[
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