Valve timing
 

I,m building a 276 engine in my shop, I am using a stock Ford cam and lifters,
Good used Ford timing gears,
Today I checked the valve timing,well not the actual opening and closing times but the overlap method by measuring the amount off the seat (equal amount) when the exhaust is shutting and the inlet is opening,
I,m using two valves with the heads machined down so they will go down inside the seat and sit on the lifters with NO clearance, a dial indicator on each valve and a degree wheel on the crankshaft, tdc set via a positive stop and dial indicator on the piston.
I am sure this point of overlap should be at TDC, BUT is 3 deg after TDC.
This engine will be going in our 33 and spend most of its life towing the caravan ,so mostly around 2500 rpm, stock 97 carb and 33 manifold.
Should I take the time to correct this ??
I think a few more hours wont mater as I just spend two days fitting up the floater bearings.(we are stuck home with the Virus so time is not a problem)
I think I read some where that timing like this after TDc makes for better higher RPM and before TDC makes for more torque
what do you think.
Ron, JWL,Gofast,Pete, and others
Lawrie

Re: Valve timing
 

Cam specs are usually opens x degree BTDC closes at x degree
Since intake opening is stated at 0 and exhaust closing at 6 doing it your way maybe thats why you end up between thoose 2 values...
And it should be measured with the correct gap at lifter...or you get "happy" values of duration and lift.

Re: Valve timing
 

Lawrie since you have the time to do it why not determine the actual valve timing events then you would know exactly where the cam is located. You have already determined TDC and have the valve to lifter at zero clearance which is the correct way to do it figuring out the rest and determining the C/L will give you the correct information. Setting the cam at the overlap position is always a good starting point when checking for the unknown. What you come up with would be very interesting to see what the stock Ford cam and gear will actually give you especially for economy.
Ronnieroadster

Re: Valve timing
 

I just did a 59AB can. It had around .300 lift and I measured it at 1* advance. You are correct about advance and retard.

Re: Valve timing
 

Zero lash, brings in the opening and closing ramps. Kinda doesn't tell the whole story. On My 280 I putz around with the EAB cam, can't remember where it actually landed, but I like the split overlap method. However I checked compression befor the engine was started and it was between 155 and 165. I allllso used milled EAB heads

Re: Valve timing
 

Tilden's site shows .5* retard for the Ford cam.

Re: Valve timing
 

Ok
I mapped out the cam this morning
I actually did a graph of the whole cycle.
But these are the figures .taken at .050 lift
inlet opens 14 deg After TDC
inlet closes 32 deg After BDC
inlet max lift .292 in

exhaust opens 32 deg Before BDC
exhaust closes 9 Deg Before TDC
exhaust max lift .302 in

the opening of both valves is very slow until .020 lift then it ramps up quickly.
I mapped the full open and closing of both valves in increments of .020 lift ,except from the first movement of the valve until .020,I did it at .005 increments.
I have the ford service books ,but they dont show what lift the figures are taken at.
I will have a look and see if I can work out what the have used.
SO, should I change the timing to be the same lift at TDC for both valves?
Lawrie

Re: Valve timing
 

I have no idea as to what stock cams are like, so really can't comment on the timing numbers. Can tell it doesn't have much duration!

Re: Valve timing
 

Lawrie something doesn't seem correct in your cam timing numbers. If I am reading what you posted correctly you have the intake opening 14 deg AFTER TDC. An intake valve needs to be open before TDC or at TDC at the latest. You wouldn't want the piston moving down on the intake stroke with the intake valve closed. The intake normally is opened before TDC. You would also normally want to keep the exhaust valve open until at least TDC, don't want the piston still moving up the cylinder and the exhaust valve closed. Timing events for the exhaust want to remain open past TDC to allow the flow of exhaust gas movement even after the piston has passed TDC. There should be some overlap when both the intake and exhaust are open.

I wouldn't think measurements at .050 would move the timing that much. The 8ba numbers I have are intake opens 5 deg BTC and closes 44 deg ABC, exhaust opens 48 deg BBC and closes 9 deg ATC. But, as you stated, not sure what amount of lift these are taken at.

This would say (using the 8ba timing just as an example) that it is taking 5 + 14 = 19 deg to get to .050 lift and 44 - 32 = 12 deg on the closing. And on the exhaust side 48 - 32 = 16 deg and 9 + 3 = 12 deg. Would need the actual timing spec's for the cam year you are using to really mean anything.

Re: Valve timing
 

OK, the only way I can get anywhere near the factory specs of EXH 48 and 6 and the inlet of 44 and 0 is to use .015 lift as the point I take my readings. then I get EXH 50 and 6 and the inlet at 2 and 6
Maybe I try another cam and check that
Lawrie

Re: Valve timing
 

If you still having 0 valve lash that explains why you get the correct readings at .015.

Re: Valve timing
 

Man , I have just spent the whole afternoon looking at this.
I tried a really nice 8ba cam that by the ford books has the same timing , ( I would use this ,but it would need the longer chev type valves and I already have my new valves,plus I,m using the original lifters.)
Books says inlet 0--44 ,I get 0-43 .close enough.at TDc both valves have .022-.023 lift,
Exhaust book says 6-48,I get 6-48.
,So I refitted the cam I want to use and left out the two bolts that locate the gear and just put in the ones with the larger holes,set it up and shifted the gear around ,and ended up with at TDC both valves open by .017,(exh closing and Inlet opening) close to what the 8ba cam was at .022-.023.
I think I forgot to then check the actual opening and closing figures,
so will do that in the morning when I,m fresh,
Lawrie

Re: Valve timing
 

Knowing the timing should be at 0°. Your degree wheel should be there between .010 & .0125 (factory lash setting) of cam lift. If your lobe is a little worn, your .015 may be right.


I would also recheck the TDC mark, by taking degree readings at .100 before and after TDC, then the average of the two readings, for true TDC.


I don't know if it applies to the early Ford's but, the SAE standard for valve timing is at .006 lift. If the TDC mark is off, you might also try it by adding that in.

Added:
Both .100 reading taken in a clockwise rotation. But, I've never been down there, maybe your engines run anticlockwise ;)

Re: Valve timing
 

If I am understanding this, 3 degrees either way will be totally unnoticeable.

Re: Valve timing
 

I'm not exactly sure where you've ended up. In order to compare any sort of timing numbers, you'd have to know at what amount of lift they were taken at. Do you know what lift the 'books' numbers were generated at?

If not - then the exercise is futile. Also, make sure you have a timing cover on and that the cam backlash is correct - in that it is very easy for the cam to walk in/out and the timing to move along with it. For most engines, having the cam advanced a bit - is more desirable than having it retarded a bit.

In many modern camshaft grinds (for OHV setups) they'll instruct you to install it 4 degrees advanced (for those with adjustable timing sets). Also, many camshaft are ground with the advance built in (as many backyard engine builders don't know how to degree a cam and don't have the necessary tools, so by grinding them 4 degrees advanced and having the installer just install them with stock timing gears/chains, they are close enough to the goal).

Re: Valve timing
 

The Ford cams were speced at .015 lift.

Re: Valve timing
 

It would not surprise me that the original "book" numbers were NOT taken at .050 profile lift. I've seen a lot of timing numbers generated at closer to .020 lift (back in the day). It seems the .050 "standard" for comparing cam timing is something that became much more common from the 50's onward. (Pete can probably give us some insight on that!).

Truth is that comparing timing numbers at .050 is still a very basic method of comparing any two camshaft grinds - as it is early in the lift ramp and tells us nothing about the rest of the timing/lift curve (which is where the majority of the action really is anyway).

Re: Valve timing
 

Well, after the whole day today ,I finally found the problem ,
The two holes in the cam gear that the fitted bolts go in,were worn about .010 over.PLUS the the fitted bolts that hold the cam gear on were.worn .005 undersize,
So I went through my cam bolt supply and came up with a set that were.3125 diameter,then fitted a new alloy cam gear( I didn,t know this was in my stock), this fixed the problem and checked it again, with my checking using no lash it then came in VERY close to the ford specs in my info.
So its all bolted up and waiting for me to make the full flow stuff and finish the assembly.
I learned some stuff this last few days.
Wife Carol said I wasn,t allowed in the shed tomorrow as I was to worn out after the last few days.
Lawrie

Re: Valve timing
 

Good update Lawrie . . . glad you sorted it out and also that you learned a bit about cam degreeing and timing. I have about a 24" degree wheel and I use it all the time . . . and it is depressing how some of the "big name" cams are way off their advertised timing and you can't "fix" it as the intake might be one way, the exhaust another - just ground incorrectly during manufacturing.

Re: Valve timing
 

Glad you figured it out Lawrie!