Timing a pinto cam

[Group4_Mark2]

Hi,

This is not how I time a pinto cam but I found this link on U-TUbe on it. Can someone explain the calculation to determine the lift on the inlet. .

http://au.youtube.com/watch?v=yJXKzaq_5GUYouTube - How to set the cam Timing on a ford pinto Engine.

Regards

[Graham]

dunno, im still thinking about how he arrived at the figures in the first place as thats not how i do it either,

i used to do it by meassureing full lift degrees method, but now days i usually set the cam before bolting the head on the block so its easy to use couple of DTI gauges to get both valves to equil lift, bolt the head on with the bottom end at TDC, fit and tension the cam belt with the vernier loose, then tighten the vernier,

the last few engines ( both pintos and BMWs) i did i marked the vernier so i knew exactly where it was before it went on the rolling road, and found in all cases after the rolling road had "swung " the cam timing it ended up exactly where i had set it in the first place

[Group4_Mark2]

I had initially though that he was trying to set the cam so that the lift was equal at TDC so he measured the lift on both inlet and exhaust at TDC and then did the calculation to make them both equal be the final number is not what I would be using. I would have thought that the final number would be more like

215 - 96 = 119
119 / 2 = 59.5
96 + 59.5 = 155.5 (half way between the two)

But I am only guessing here

Tom

[Miniliteman]

I had initially though that he was trying to set the cam so that the lift was equal at TDC so he measured the lift on both inlet and exhaust at TDC and then did the calculation to make them both equal be the final number is not what I would be using. I would have thought that the final number would be more like

215 - 96 = 119
119 / 2 = 59.5
96 + 59.5 = 155.5 (half way between the two)

But I am only guessing here

Tom

Tom,

that's how I do it: determine point where lift of inlet = lift of exhaust.
His sums: lift of inlet measured = 215. Lift of exhaust measured = 96. Do determine at what lift true TDC is you can do it like you wrote it or: 215 + 96 = 311 (like the vid).
To find the middle: 311/2 = 155.5 same answer as you.
But in the vid he does 311 x 3/5 = 186 (first divide by 5 they multiply by 3).
So basicly he doesn't use equal lift of inlet and exhaust on TDC but a tad more lift on the inlet which is advancing the cam a bit.

Leon.

[Group4_Mark2]

I see what you are saying here. But would not the calculation depend on the difference between the two in the first place. If the difference was much less then the calculation would give a different answer. Would it not be better to find the middle and add something to it to advance the cam.

Tom

[Miniliteman]

Whatever the numbers are (and so whatever the difference between the 2 is) your method of calculations gives the same answer as mine.
Say inletlift = a ; exhaustlift = b .
You: subtract b from a and divide by 2 add that number to b;
this equals to (a-b)/2 + b or a/2 - b/2 + b = a/2 + b/2 .

As you can see this is the same as Me: (a + b)/2 .

For this measurements to give the proper TDC both inlet and exhaust valves must be well "off the seat" if you know what I mean.

Leon.

[Group4_Mark2]

I totally agree with your calculations and thank you for the clarification. I was suffering from some brain fade for a while when I submitted the last post.

I had another calculation regarding the optimum shape of a curved pipe to aid flow around the bend. The calculation came from Nasa originally but it drove me mad for a while trying to get the calculation to work. I must try to find it again and post it here as it was very interesting for anyone into porting cylinder heads.

Regards
Tom

[profit]

Do you set the cam timing with clearance or with out???
as all the figures on a cam card are with no lash.
I have been setting mine up as I have no timing specs only 278deg advertised duration and .289 lobe lift.
one method i was using is equal lift then plus .015 lift on the inlet then there is add the inlet lift to the exhaust divide by 5 and times it by three both methods are giving me about the same result within a couple of thou so about .070 lift atdc

[Graham]

you would set cam ting with lash correct, not zero