hi i am rebuilding my first engine and am somewhat clueless on what to tell the guy at the machine shop what i want done.

first of all the engine is a 300 cid out of my 1980 F-250. the engine runs very strong(only 80,000 miles). I want to rebuild it because i'm looking for more performance. what i mainly want the guy to do is improve the breathing of my 300's head. I'm not 100% sure yet, but i might be getting a head off a 240 cid to increase compression.

what should i look to have done and then could you kind of give me a short explanation on what is done with each improvement so i'm not clueless when i go to the machine shop.
Also if i do rebuild the bottom end and bore the cylinders .030" or .060" do i need to get different pistons or just different rings. Any help would be great, thanks

FORDS_FORLIFE

 

Good luck on your project.

The first thing you need to do is make sure the machine shop in question is competent to do the work. I don't care how well you like them, find local references that will vouch for their work. If you can find a web forum with local drag racers, circle track drivers, or something similar they will be able to tell you which shops are capable of building a quality engine and which ones are capable of building a quality boat anchor.

Secondly, you need to sit down with your builder and discuss what you want to do. If the builder can't or won't do this you need a different builder. If they know your performance goals and how you intend to use the vehicle they should be able to put together a good engine without much more input from you.

There are several operations that are done on any rebuild. The main thing that is done is boring the cylinders to accept an oversize piston. If the engine has never been rebuilt before 0.030 is usually enough. Going further to increase displacement is not a cost effective practive on a street engine; just overbore enough to clean up the cylinders. This will increase the compression ratio slightly, maybe 0.1 or 0.2 points. Before the cylinders can be bored the block must be cleaned and it's a good idea to have it magnafluxed to check for cracks, but cracks are not likely if the engine is running now. For a performance rebuild you should select a piston before the boring is done so that the bores can be matched to the pistons. You will also need to tell them what type of rings you want: iron, moly or chrome. Iron is standard in most engines, moly breaks in faster but doesn't last as long, chrome takes an eternity to fully seat but will last forever. You need to discuss this with your builder to make sure you get what is best for you. Other common operations that are done on a block include decking and line boring or honing. Decking is a process that removes material from the deck of the block (where the head sits) to either true it up or increase compression. Line boring and honing are done to ensure that the bearing saddles in the block are in a straight line. Most of the time a machinist will check the alignment of the main bearings and they do not require adjustment. If possible, have the block torque plate honed. Torque plates for the 300 probably aren't very common, but they can probably use two for a small block and get good results since the bolt patterns are the same. Discuss this with your builder.

The crank will likely need to be ground to an undersize for both the rod and main bearings. Some shops can offset grind a crank to increase displacement and compression, but this usually isn't worthwhile. On most engines 0.010 offset grinding results in the additon of 1 cubic inch. You can also have the oil passages cahmfered to improve lubrication of the bearings. The crank should ALWAYS be magnafluxed because it has a rough life. It is actually rare to find a cracked crank because it doesn't take long to go from cracked to broken. If it is cracked you want to find out now because if it comes apart while the engine is running it will destroy everything.

The head will need to be cleaned, surfaced (like decking only on a head), and get a valve job. If it will be worked hard it would be a good idea to have bronze valve guides installed. A 3 angle valve job is usually fine for a street engine. Your builder should be able to do some port work to get the airflow improvements you are looking for. If you are going to use a fairly stout cam it would be a good idea to have screw in rocker studs and guideplates istalled.

There are probably dozens more operations that can be performed, but these are the basics. There are several good books on the subject. The first one I remember getting was "How to Rebuld Your Small Block Ford" by Tom Monroe. Another good one that comes to mind is "Engine Blueprinting", but it is for the more experienced builder. I don't know if there is a specific book for the 300 or not, but most of the stuff is pretty much the same for all engines.

 

Let us know where you are located. Someone might be able to recommend a shop. I know of a good one in western Missouri. Mark.

 

I think it said in his profile he's from Wisconsin.

 

ya, i live in central wisconsin, i like the idea of having the block decked, and the head surfaced to increase compression. i can't remember exactly who said it on a different post but that the machine work to the block and head combined with a 240 cid head produces something like 10.0-1 or 10.5-1 compression, is this correct and if it is would that require premium 93 octane gas or even possibly higher. i'm looking to get the performance somewhere in the range of 250 - 300 hp for better driveability and of course more fun. would all that work be require of an engine making hp in that range. i would also like the hp peak at a higher rpm for better cruising speeds. i don't want to skimp on the work because i want a good reliable engine but i also don't want to spend money on something that would be better for an engine making 600 to 700 hp.

FORDS_FORLIFE

 

I'm not sure where the compression would end up with that combination. There is a compression ratio calculator on the Silvolite pistons web site. 10:1 is probably too much for a carbed 300 running in a streetable rpm range.

Your hp goals are possible, but will sacrifice some of the torque you have now. The 300 was designed for torque, you are better off building it for torque and letting the hp fall where it may. If you build the torque like you want it the hp will take care of itself.

I think all the operations I mentioned (except offset grinding the crank) should be done on any performance rebuild.