bubba22349":28lza340 said:
....The Falcon engines are a non interference engine, but let's say the timing chain broke using all your above measurements I get a .049 valve to pistion clearance if the cam was at its full lift of .512 and the pistion was at TDC, what is not accounted for in this is the coefficient of thermal expansion.
Formulas for Thermal Expansion
https://www.engineeringtoolbox.com/line ... _1379.html
The cam to conrod situation makes a US Ford 200 six and the 250 six both interference engines if the cam timing is not kept to the standard 116 degrees Lobe Center, that's Not the LCA, but the timing BTDC event.
Im an ex Mini A series guy from way back in 1993 to about 1996. The Australians used stadard BMC chain pitches, and the block is mapped out similar to the Ford 144-250 small six.
Since the Australian 200's and 250's used the same kind of Mini A series 1275 and
Mike1157's 250 conversion to 5.0 timing gear also used Holden Small Block 253/308/304 Vee-Eight and the Toyota 18R timing chain, this video will help you.
As
JackFish found, if the base cam blank is re-pitched wrongly during the cam grinding process, WHICH DOES HAPPEN, then you get rod to cam shaft contact. In the case the the USA 250 timing gear, both the 69-72, and later 73-80 timing gear, the timing can slip.
When checking the cam tiimg, drop the sump, and check for clearance. These engines are most certainly interfersnace for cam to conrod clearance in certain situations. The failure or slipping of cam timing can cause what English copy writer Graham Robson described as "
Spectacular Disarrangement's". This was a referenace to an old Dutch Spyker term for Serious Terminal Cam to Crank Contact.
Take a little time out to preview this. The A series ran either a twin row chain, or single row chain, later on, with a tensioner, as yall will know, in serive wear is huge with the Ford single and twin row timing gear set, of any type. Its the nature of a pushrod engine, and Ford, like Morris and later BMC/British Leyland and then Austin Rover, they worked the tolerances on making a Bad Idea Work Well...
https://www.youtube.com/watch?v=rad7cdJ ... e=emb_logo
https://www.youtube.com/watch?time_continue=rad7cdJmT6k
[bbvideo=560,315]https://www.youtube.com/watch?v=rad7cdJmT6k[/bbvideo]
Part 2 of 2.
Then go through the basics, this post below is on the 200, but the same principals apply.
See
viewtopic.php?f=1&t=75618&p=582243&hilit=CAM+TO+CRANK+CONTACT#p582243
You don't have to go so far or worry too much, but just Be Aware that Ford packed a lot of cubic inches in a very small space in the 144-170-187-188-200-221-250 small sixes, and the weakness is that timing chain wear
then causes cam to con rod contact.
This is only on the Short deck 187-200 7.803" and tall deck 250 cubic inch 9.38-9.469" engines.
The short deck 200 and all 250's were factory Stroker engines. The rare 187 Argentina engie is an overbored 170 with a four bearing 200 crank, same issue.
Not and issue with the USA 7.803" deck 144, 170 (1960-1964, and 1960-1973)
the Argentina and Australian Medium Deck 8.425" 3.1 liter 188, 3.6 liter 221 (1968-1996 Arg, 1968-1970 Australian)
or tall deck 9.38" Australian 200 (1971-1992).
The 200 and 250's are the ultimate economy engines. Ford didn't make a mistake, they just designed them as inventory filler engines for those who didn't want SBF V8's like the 221, 260, 289, 302, 351s, 400's or gasp, the little 255 4.2. Every year from 1962 to 1983 for the 200, and 1969-1980 in the USA and Canada for the 250, they existed to fill a cost effective gap, and man, where they ever an inexpensive engine to make.
In Argentina and Australia , they were Y block 292 and Windsor 289/302/351 and Cleveland 302/351 step down options.