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Discussion and questions related to the course How to Degree a Cam
I have a weird situation dialing in my kelford 272 cams on my evo 7 engine. I found true tdc, measured my valve timing events and found that my EV opens 10 degrees too early having 1mm of lift at 36 degrees bbdc. Funny thing is it closes right where it should having 1mm of lift at 0 degrees tdc. Same situation the other way around for the intake valve. I have 1mm of lift 7 degrees btdc which is correct but am adavanced 10 degrees while closing 1mm of lift at 30 degrees abdc which should be at 40 degrees abdc. Valve lift at tdc is correct with 1.52mm for the IV's and 1mm for the EV's. I have the feeling it could have to do with my valve lash. Built solid lifters from old hydro's which are adjusted to ~0.2mm of lash on the intake and ~0.15mm on the exhaustside because i didn't want to push the valve open while installing. Do you guys think valvelash could be the problem? I dont think kelford delivered me a set of cams where the lobes on both cams are bad anglewise. Maybe someone can help because i am pretty stuck right now:D
Greetings to all from Germany:)
Hi. It's normal to see that the actual numbers don't match the advertized ones. I've seen it on Kelford camshafts, Power-devision cams, Cosworth as well. Moreover, i found on enternet similar case when one US guy also tried GSC camshafts and was very surprised to find them "off the specs". I couldn't understand it just like you and i wrote to GSC addressing my frustration. The answer i got from them explained that manufacturers have very precise equipment comparing to common wheels and dial indicators and this is where difference is usually coming from. That is why i personaly use lobe centerlines figures. Having said that i wouldn't be 100 percent sure that in your particular case something didn't go wrong - to me it's worth while double checking with manufacturer.
Was that everything GSC had to say about that? :D
I'll definetely do it with the centerlines tomorrow but i'm a little bit afraid that my timing events will still be off after adjusting the cams to the correct centerline...
Yep, that's all they said).
Just to give you a tip the stock evo 7 centerlines are 109 atdc intake and 110 btdc exhaust. It makes it so much easier to dial camshafts with that method. For Kelford 272 camshafts intake is 107 and exhaust is 113, so basically you turn counterclockwise intake camshaft from straight position 1 mark on the sprocket ( 2 degrees of crankshaft) and also retard exhaust camshaft 1.5 mark on the sprocket (3 degrees on crankshaft).
I love hearing someone is taking this level of care with their build and look forward to hearing the outcome.
I’ve had kelfords match the card, but anything is possible. Have you spoken to them about it?
Hey guys unfortunately i did 2 hours more on other peoples cars today which is why i only managed to dial in the exhaust cam on my evo... But the good news is that the centerline method worked out great and i will definetely do that again. I managed to get the exhaust cam centerline to 112.75 degrees which is good enough for me as it should be 113 degrees:D
Didn't have the time to measure opening and closing events so far but i'd definetely recommend georg's way to do it it is really fast in
deed because you don't have to turn the engine over 100 times. Tomorrow i'll do the rest of the work and then tell you about the results:)
Ps: i didn't speak to kelford about it because i was pretty sure that it has to be my fault:D
When i'm finished and the centerlines are correct but the opening and closing events are not i will propably reach out to them...
Sounds great Marius!
Hey there buddies
Sadly i only had the time to dial in the intake cam yesterday. So today i rechecked the centerlines for both cams came out as a 112.5 for the exhaust and a 106.75 for the intake cam, which is pretty much on point.
While checking the centerlines i obviously checked the opening and closing events and they were off...just as expected.
EVO was 38°bbdc which is 8° off
EVC was 2.5°btdc which is 2.5° off
IVO was 2°btdc which is 4° off
IVC was 32.75°abdc which is 7.25° off
Right now i feel like leaving it just as it is and simply contact Kelford with my issue. I just feel confident in the centerline method and it can't be that off when the centerlines are correct can it? :D
Pls give me some input if i'm right at that point or if i should do it all over again:D
Btw thanks to Georg for providing me with that tip:)
The "split" method for timing only really works where the valve lift is symetrical and follows the cam' profile - in short, direct acting flat followers on (D)OHC engines or on any pushrod engine.
The problem is that while the rocker pivor point is fixed, and the rocker tip moves in a consistent arc, the point where the follower contacts moves in relation to them and this changes the rocker ration on the leading and trailing sides of the lobe. This means that if checking it at different lift points it's going to move the "split" through a few degrees as the cam' is rotated.
There should be a specified cam' lift for checking the split given on the cam' spec' sheet.
Alternatively, if it has a specific angle for the TDC point, you should be able to use that.
If i understood you correctly measuring the opening/closing events on a roller/rocker engine is worthless because of the different offsets i get either side of the lobe. When using the lobe centerlines i guess this error becomes irrelevant because you have it in the equasion for both sides of the lobe (i could be wrong here:D).
Or is the only valueable method using the lift @ tdc then?
A friend of mine once had his new 4g63 engine put together and his mechanic installed new Cosworth camshafts using dial gauge and degreeing wheel. He asked me to double check if the camshafts were set up correctly. I found specs for those cams and told him how they should had been dialed using centerline method and the actual cams positions were right on the money - that's how i know this method is really working particularly for 4g engines as all manufactureres make their camshafts symmetrical in 99.99 percent of cases.
Ah, my apologies, I was thinking of using the valve travel, rather than taking it directly off the camshaft - must have been missing out on my morning cuppas.
With a roller rather than a pad, the thrust line may not be significant - If someone is looking at a way to pass a few hours, it may be enlightening to plot the valve lift against crank, or camshaft, degrees. It's not difficult, just time consuming with a DTI and degree wheel - but I don't have one to check for myself, and settle it one way or the other.
@ georg: i also think that your method works great as is said it worked out for me too and i think i'll leave it like that.
@ gord: now i'm confused i don't get your point can you explain what you meant i the beginning or if i'm right at what i said regarding the roller/rocker issue with cam degreeing?