Sucessful Improvements From A Mechanic(s) Of Many Years

Some of the improvements I have made on the 5.7 include.

Using hardened grade 9 aircraft quality head bolts. I don't know of a

national supplier for these bolts, but I found them I a local hardeware

/surplus store for .99/lb. It may be possible to order them from a whole

sale bolt supplier. They work very well in that they don't strech like the

factory bolts. They hold a true torque on the head.

This greatly improves the ability of the head gasket to keep it's seal.

Another improvement that I have done is to have the cyclinder block


This is a raceing engine trick. It involves machineing a .030 deep grove

around each cyclinder bore where the head gasget seats on the deck. A .060

copper wire is then tapped into the grove. This provides a ridge for the

gasket to seal around. This is not a complicated process and most any good

engine shop should be able to do the job, usually for under $100.00. When

I had mine machined, the shop where I had it done

also told me that there is a .060 stainless steal wire available, but this

is recomended for copper head gasgets. Which they said they knew of a

place to have custome made for 5.7s. I don't have the name of that

supplier any more. But the machine shop where I had the work done was,

Quality Engine and Machine

no. 26 16th St. S.

Fargo ND


Before this work is done make sure that the block deck has been shaved and

magnafluxed for cracks.

Another problem the 5.7 has is breaking main brg. caps. To help with


I have made straps that go on top the cap, under the bolts. This gives the

cap extra strength and added support. These straps can be made from a

piece of 1" wide by 1/4" thick tool steel cut as long as the cap and

drilled for the bolts. When this is added you will need longer bolts. I

recomend using raceing engine stud bolts. These will allow for the thicker

cap and they also screw completely into the block,

strengthing it and holding the cap more securely. These studs can ordered

for any engine from a preformance auto parts supplier, Just give them the

length and size you need.

Breaking crank shafts is also common on the 350D. There isn't much

that can be done to strenghten the crank, but the problem can be helped by

having the engine balanced. This can also be done at any good engine shop,

they will need all of the engines reciprocating parts. (crank, rods,

pistins, vibration damper, & flexplate).

This procedure makes the engine run smoother and prolongs the life of the

crank, rods and bearings. The 350DX is a stronger mained Block and does not have this problem. Another way to prolong the life of the crank is

to check the glowplugs every oil change. Yes, a burned out glowplug will

cause the engine to start hard and run rough when cold, putting undo stress

on the crankshaft.

Many people have had problems with the rear main oil seal leaking.

Many times this is caused by the breathers on the valve covers becoming

pluged, or a faulty CDR valve (crankcase depression regulater) on the

latter engines. If the seal must be replaced use a seal from a 460 ford.

This is a two piece rubber seal that preforms much better than the factory

rope seal.

Another improvement especially in warmer climates is to bypass the

oil cooler in the radiator (it should be called the oil warmer) and reroute

the lines to an aftermarket oil cooler in front of the radiator.

These are most of the affordable improvements, there are many others

that could be made, such as billet steel cranks, racing connecting rods,

forged pistons, roller rocker arms,and head porting,ect.

350 Diesel Page