250CID Custom Adjustable Timing Gear Danger?

Good Evening! I just want to first say this is my first post and I will make sure to show you all my journey as i learn from all of you on how to properly do a classic inline 6 justice.
I have a 1970 Ford Mustang Coupe that had a 250 cid engine. I am doing a tri carb set up, ordered a camshaft from claysmith cams via vintage inline, shoutout mike from vintage inlines thank you for all your assistance if you are reading this, and a bunch of other things. I wanted to degree my camshaft and I have noticed there are no adjustable timing gears available for the 250 cid, specifically the crank gear with multiple slots, unless someone knows where? So I went on ahead and had my machinist machine out 2 more extra slots that were directly correlative to advancing and degreeing a couple degrees. I got as close as possible at a degree off, interesting enough my intake and exhaust open exactly where the timing card is set. Regardless, this is the closest I can get but i was told by the same machinist, after all was said and done, that he had several street racers back in the day that asked to do the same thing I did, which is machine extra slots in the crank gear, and they all failed within a couple of months to a year. This obviously worries me but since i couldnt find any adjustable gears i didnt have any choice. With that being said, has anyone ever machined their own slots so they can degree their camshaft correctly? Should I be worried? Im not trying to go race or go fast. Im just trying to have fun with my car, for the sake of the build. If anyone can give some insight and some experience on this that would be much appreciated.

Re machining a new keyway at a new spot helps performance, but it has a very short span and is not deep enough, and will shear under the stress of a valve soring with more than 150 psi at wide open. Its not a performance part in any way, hape or form because Ford didnt want to cut the crank snout back. It needs about 50 taken off tge shoulder to make a SBF 302 sprocket and a twin roller Dido chain from Melling fit. Ford decided the cost of a remachined crank to suit the SBF wasnt worth it, and there were Noise Vibration and harshness issues when a twin row timing chain was used.

The early and late US 250 timing gear sets arent as strong as even an aftermarket 200 twin row timing set. All this defined from Ak Millar , who decided the stock early 250 chain was okay, but the keyway is a failure point. Ford decided to use the 1.375 crank snout on the US 250, not the smaller 1.248, so the whole crank was used to make a new 250 only timing gear set based on the 351 Cleveland tooling. It was changed in 1973 to a far inferior timing set.



FoMoCo reasoned that the 250 would only ever be a sub 100 hp net engine, with about 150 pounds of valve spring tension at fully open......so like the thinwall blocks and cast iron rods, it didnt need to make a Maverick 250 engine able to stand up to a 450 hp Weapons Grade Attack.

The early timing set crank sproket had a small amount of retard built into it. The later
250 chain and crank sprocket have more.

The later 200 got cam sprocket retard and cast iron rod downgrades too.

This means that US 200s and US 250s share no common timing processes...they are different families with totally different parts and timing philosophies. Advanced to the casting dvision, Engineer Bill Gay was asked and given the task to "reduce" inventory sharing, and down grade the machining and parts to suit the horsepower of these engines. It was totally different in Australia at the time.

The loss of twin row timing chains "we" found on Aussie 200 and 250 sixes was a US cost reduction initiative to use simplified tooling. The rules of production expediency are that a dollar saved is a dollar earned, and a new part that is cheaper is fine. A one size fits all part was suddenly deamed "bad" in the Bill Gay economy.

The downgrade in parts strength and design, it started in 1969 and by 1976, all in line 250s had the cheaper block, timing gear and rods to suit an engine that made about 99 hp net. It happened in yhe economy engines...the 2300 turbo got rod upgrades, forged pistons, but all the 1975 to 1982 V8s got downgraded and shared parts with the 351 heads downgraded for emissions systems simplicity, yet the passenger car and truck 351 M and 400s got an upgraded block, and the seriously good 4bbl 4180/4190/4195 series Holley carb got drip feeded into the 351 W and 302W....yet the 255 became the 250 replacement engine.

Ford had to practice a give with one hand, take with the other system to maje ends meet on the production line.

The keyway often fails, then the 250 chain.

Will and Kelly Does10s/TurboChicken and Mike1157 decided to get a stock 200 twin row and 302 twin row chain and remachine the crank snout shoulder 300 thou further in like the Race 351 Cleveland crank. That allowd the use of a 56 link Holden 253/304/308 and Toyota 18R chain to run the camshaft. It is essentially the 200 twin roller chain (BMC 1275 Mini/ Frog Eye/Aussie Ford Falcon 200 aftermarket ) with another 6 links and the Small Block Ford 302 twin roller crank sprocket. Some after market 302 Small blocks use it, similar to the Cloyes, but its a special British Leyland pitch used first on the Mini Cooper 1072 S and then the Austin America 1300. Then the Ohc 18R Toyota and the 1969-1971 253/308 Holden V8 used in the Torana and Monaro.

That is a 100% reliable system with good keyway and a 600 mile endurance race tested cam chain that has one about 10 endurance races from 1975 to the late 80s in 350 to 460 horsepower Holden and Ford Mustang V8's....its the same whitebox part made for GM, Toyota and Ford by a now US Melling owned Indian company.

See

viewtopic.php?f=1&t=72053&p=553333&hilit=sbf+timing+gear#p553333

And

viewtopic.php?f=95&t=71986&p=552768&hilit=sbf+timing+gear#p552768

others usea offset woodruff key to advance a few degrees (4*)

Oh wow. After reading all that, you went through a lot of trouble! Thank you for your guidance and wisdom. I guess I am going to be seeing a failed crank gear soon if I don't do some more machine work on the crank and cam snouts. ARGHH. I had just assembled everything too! Now that I know I might be rolling the dice in terms of crank gear failure, anyone have any experience of it actually failing after machining your own crank gear?

Once again, thank you all for your guidance!

Offset keys can and do shear off with disastorous results. The 250 stock chain has enough issues without adding a sheared key to the list.

In everyway, the changes made the 250 US engine a nasty retrograde step. Be carefull if you are loading it up on valve gear. If the keyway shears, the rod and cam can touch.

The issue is that the oem crank sprocket is powdered metal ,it wears well but very hard and brittle...Cutting new slots adds to the problem.
Some replacement sprockets are made out of steel but I don't know they if still do or who.

I see. I am using the v8 valve springs courtesy vintage inlines with a closing pressure of 80 lbs. My intake and exh duration @0.050 is 214 degs, lobe enter 109. Honestly, doesnt seem agressive at all for it to be a problem but, ive never had to machine my own key ways on a oem crank gear and worry about it failing. Anyone think I can live with this temporarily till I have the time to open it up again and machine my snouts down like xctasy has? I really liked what you did there by the way.

as for the replacement sprockets being steel, I think i actually saw that somewhere being sold? Id have to double check. Just kinda bummed that I might have to open this back up and spend more money. Nevertheless, I hope this is all worth it!

The heavy duty roller timing gear isnt needed if you need less than 150 pounds open. The early or late kit is your choice. FalconSedanDelivery ran 14s with the early chain and gearset. Just be aware that your cam timing might not be perfectly set, and dont let a few degrees out break your sanity.

Mike1157 and Will made 400 hp plus with turboed engines, not me.Read Will (Does10s) early posts. He was making well over 400 hp with a reindexed stock chain and sprocket, so despite what I said, in your case, Relax a little. After youve understood the matters, get some other advice, not just.mine.

Do some long term planning latter on.

First things are first man

Thank you for the positive reinforcement. I appreciate it truly.
I guess since Im not running an aggressive valve train I should not worry too much. Atleast for the short term.
Ya im not too worried with the timing being a couple degrees off, I just dont want to drive this bad boy one day and hear my engine go because I had machined multi slots to get as close as possible to what I needed.