Yep, I ran the straightedge and just gave it the ol eyeball test. The waay out measurements were caused by the rocker stud measurement tool. I'm quittin for the day. Tomorrow, degreeing the cam and valve to piston clearance.
how in the hell do you put a straight edge across a bbc head with canted valves? this thread is getting nuttier by the post
That's not hard at all. It's a good quick reference. If you can't figure out how to lay a straight edge across the valve tips, I'm worried about you. :jawdrop:
I'm gonna pick this apart, Rio. Nothing personal.That's an understatement!
Putting a straight edge across the valve stems doesn't tell you anything anyway. Sure it does. It'll tell you right off the bat if you've got a decent valve job or a shitty one. Tear the heads apart and measure the valves by themselves. Measure what? The length? The dia? the stem? The margin?Then put the heads back togather and measure the highth with only a weak spring installed, at the retainer when you have made sure that the spring height is correct. Hmmm. Measure what height? If you've already gotten the spring height correct, then what are you measuring? You can measure retainer height off the spring pad without shims, but that dosen't tell you anything either. Spring pads can be all over the place up and down. IF your machinist was worth a sh*t all heighths should be the same meaning the valve seats were all ground the same depth. (this sounds like where your problem lies). This is exactly right, but very few "machinists" even know how to check this, or how to achiev it. If all the measurements come out correctly then you can check your valve to piston clearance. Nothing here has anything to do with valve to piston clearance. A rocker being overtightened can definately cause a valve to hit a piston, but not valve length or seat depth. (A deep valve job just moves the valve further away from the piston) Your choice then would be to disassemble motor and cut pistons, or you could change cam lift by differing timing, rockers ratio, or the entire cam. Sounds like starting from the beginning is in order.
It almost sounds like this is your first engine build(we all have to start somewhere) and a few important steps were missed along the way. I heard that!!:sqeyes: Rio->
:idea: :idea: :idea: I just had a brain wave!!!
I've got a half a dozen sets of Manton pushrods setting on the shelf so why don't I just send them to you and you can check each hole and just use the length that works for that hole. If you have a piston/valve contact then just use a shorter pushrod, if the clearance is okay then use a longer pushrod for more valve lift. Then you can just send me back what you don't use.
Valve depths are pretty important, and the only way they can be measured is to somehow reference the depth of the valve seat to the deck. This is usually done when the seats are cut on a machine with a dial indicator that's referencing off the deck. A measurement is determined, and then each valve seat is cut to that same measurement; usually (hopefuly) within a couple thou of eachother. A special valve can be made to check the seat depths using a depth mic when grinding seats, (again, measuring off the deck), but the same valve has to be used in each seat to get consistant measurements. Unfortunately, you need a bunch of different valves for all the different int. and ex. sizes. Checking the overall length of a valve can be misleading, because if a valve has been ground (faced) enough times, it's overall length won't change (unless it's tip is also ground to compensate) but it's face to tip length will increase, causing an increase in installed height of the spring and a taller valve tip height. Installing all the valves and measuring from the retainer to the spring pad can also be misleading since the spring pads aren't very consistant themselves.
These are the "little" details that really need paying attention to in good cyl. head preperation. Having all your seat depths the same means more consistant chamber volumes and shapes, and also insures more consistant valve train geometry. Both of these things = HP.
Just my .02
Hey Steely, I think you've been gettin picked on too much lately cuz you're wound too tight. If you slowly read what I posted it's just about what you posted however the way I go about doing the measuring is assbackwards from yours. I'm sorry I wasn't more specific about what part of the valve to measure as when I set up a head the valves are basically new and of the same length for the most part. What I was getting at was this sounds f&cked up from the beginning.
I know this is your area of expertice and that's why I'll let you do the heads for my next motor but don't go gitten all technical on us upside down mechanics cuz once in a while we do slap togather a motor thats starts if we get lucky.
Now, If I use a shorter pushrod with a rocker with a larger ratio(ya know, sorta like more overdrive) will that give me more clearance so I don't put the valve thru the piston? Been workin on this all week.
Rio
LOL...Rio, Rio, Rio,
I was just uzin your post as an opportunity to 'splain some things. Read at the top...nuthin personal!
To answer your question, no. A shorter pushrod isn't going to change how far the valve is lifted. Just like a shorter connecting rod dosen't change the stroke on an engine. The cam lobe is what it is, and that determains the lift at the lifter. The pushrod only transfers that lift from the lifter to the rocker arm. Now if you add rocker ratio, you're going to add lift by moving the valve further. That dosen't sound like what you want. Pushrod length dosen't have anything to do with this. The pushrod needs to be a certain length for the right geometry. Period.
Hey, BTW..I've thrown a few junkers together myself. Some not so lucky on, either.
If you need some help, PM me your number, I'll call ya.
A shorter pushrod isn't going to change how far the valve is lifted.
steel,
I know what you are getting at, but in case this is misread...
The length of pushrod will change the amount that the valve is lifted, by over arcing or under arcing the rocker.
Yeah, I'd appreciate it iffin you'd pop down to Big River in the morning and set the timing at about 32 degrees an take it for a test run since it just got put back togather. It's gassed and ready to go cept for the timing. Cyclone an his playmates will be down there so you shouldn't be lonesome.
Rio
Sounds like there's going to be plenty of loose nuts down there.
You'll just have to have fun without me.
I gotcher 'pushrod length'...
Sorry guys...aphishal drunk poscht!!!
I'm gettin some of this. If you change from a 1.7 rocker to a 1.8 , what changes? What part of the rocker is different?
I'm gettin some of this. If you change from a 1.7 rocker to a 1.8 , what changes? What part of the rocker is different?
I may get corrected but I believe it is the distance from the fulcrum(pivot point) to the tip of the rocker. The longer the distance the higher the ratio I think.(It's been awhile, but if I'm wrong someone will tell me)
Sleeper CP
Big Inch Ford Lover
Moving the pushrod cup closer to the pivot point of the rocker increases the ratio.
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