i started to write a small book with all the technical details in german language and metric dimensions. For this i read the MTFCA books and the McCalley book.
But now there are some open questions. I put all technical dimensions in this book and after reading the books and the forum there are so different dimensions...so i need some informations.
1. Spark plug gap?
Motorcraft / Autolite = 0,025 inch or 0,032 inch
Champion X = 0,028 inch?
2. Connecting rod play at the crankshaft?
0,002 inch or 0,038 inch?
3. Connecting rod screws?
30 footpound or 24 footpound?
4. Main bearings play?
0,038 inch okay?
5. Piston ring gap
Top ring = 0,003 inch per inch of diameter
Middle / bottom ring = 0,004 inch per inch of diameter?
Thanks a lot for all informations and if you like send me some pictures of the adjusting the play or something i can use in the book.
Here is no technical information in german available and so i put it all together.
Thanks for any help.
My mailadress firstname.lastname@example.org
Could you please give the name of the book and page number for those references?
1. .025 - .032 (Champion recommendation vs Ford recommendation)
2. .002" - .003"
3. Tighten snug, then advance to the next cotter pin hole that aligns. Ford did not specify torques for any fastener. The bolts are extremely weak. Over torque can damage the bolts or nuts.
4. .002" - .003"
5. That sounds correct
In regards to rod bolt torque; I suggest that 30 ft lbs is the absolute maximum and I would consider 20 ft lbs to be the absolute minimum. Personally I use a "breakable thread locker compound" and torque to 25 ft lbs and forget the cotter pin. Ford use cotter pins because thread locker compounds did not exist.
I also carefully examine all rod bolts and look for any evidence of stretching. If in doubt I replace. I just use a grade 8 fine thread bolt and grind a flat on the head so it fits. After many thousands of miles on numerous engines I have never had a problem.
That being said, please do as you wish in your engine.
On bearing clearances I figure .0015 minimum to .003 maximum
Michael, some of the technical details you seek may differ depending on what is needed, fresh rebuild or the max tolerance as Ford set a 100 years ago.
eg, modern machining has the con rod and main bearing clearance for a fresh rebuild at .0015".
Piston ring gap you have is fine for aluminium pistons but not for cast iron ones.
The ring gaps are up-side down.
The top ring needs to be .018 to .020.
The center and bottom can be tighter.
The oil ring can be .015" or even .012".
They run hotter with today's gasoline than they did way back before 1990 or so.
Please let us know when you have your small book finished. I, for one, would like to get a copy.
I would say your ideal bearing clearence is about .001-.0015 if i were taking up rods or mains i wouldnt eave them at .002 or .003
remember these engines have 1.250 journals, they dont need the clearence of of a big block v8
Thanks to all of you and please if you want send more informations.
@joseph: No problem when it is finished i send it to you.