Do I need longer pushrods? (Pics)
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Joined: Dec 2007
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From: Redmond WA
Do I need longer pushrods? (Pics)
Hello guys,
So I'm installing a pair of new 170cc summit aluminum heads with my stock cam and hydraulic lifters, I might get a little longer duration and lift cam in the future.
I took these pics with the valve fully closed and fully open.
As you can see, at fully closed position the rocker roller is well into the right side(the picture wasn't taken on a perfect perpendicular angle which makes it look even more far to the right, look at the roller position on the valve stem instead.) and at fully open is barelly past center.
Should I consider putting a longer pushrod to have it more even or is this close enough? The cyl head manual doesn't say anything.
Thanks,
Fábio.
So I'm installing a pair of new 170cc summit aluminum heads with my stock cam and hydraulic lifters, I might get a little longer duration and lift cam in the future.
I took these pics with the valve fully closed and fully open.
As you can see, at fully closed position the rocker roller is well into the right side(the picture wasn't taken on a perfect perpendicular angle which makes it look even more far to the right, look at the roller position on the valve stem instead.) and at fully open is barelly past center.
Should I consider putting a longer pushrod to have it more even or is this close enough? The cyl head manual doesn't say anything.
Thanks,
Fábio.
Last edited by FabioSan; Apr 26, 2009 at 04:18 PM. Reason: Moved the image to photobucket
Le Mans Master
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From: McHenry Illinois
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Checking and making a determination based off just the top or bottom of the stroke isnt the way to do it.. You want to check the entire "sweep"..
The best thing to do is put something on the top of the valve stem so the rocker will leave a witness mark.. Then turn the motor over a few times to see where the "sweep" is from the rockers.. The sweep should be even on both sides of the valve stem from center.. If the sweep is not even on both sides, then you will need longer or shorter Pushrods. If the sweep marks are more toward the inboard side of the motor, you will need longer pushrods and if the sweep is more on the outside, then you will need shorter pushrods.. If the sweep runs across the entire length of the valve stem, then you have other issues but thats usually rare..
If you find you need a different pushrod length get a pushrod length checker..
The best thing to do is put something on the top of the valve stem so the rocker will leave a witness mark.. Then turn the motor over a few times to see where the "sweep" is from the rockers.. The sweep should be even on both sides of the valve stem from center.. If the sweep is not even on both sides, then you will need longer or shorter Pushrods. If the sweep marks are more toward the inboard side of the motor, you will need longer pushrods and if the sweep is more on the outside, then you will need shorter pushrods.. If the sweep runs across the entire length of the valve stem, then you have other issues but thats usually rare..
If you find you need a different pushrod length get a pushrod length checker..
Last edited by Fishndude; Apr 26, 2009 at 05:43 PM.
Thread Starter
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Joined: Dec 2007
Posts: 79
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From: Redmond WA
The manual says to to find the full open crank position, full close crank position, find the middle point on the crank. The rocker should be at the center of the stem then.
Full close
Middle
Full open
Seems that I need to be a tiny bit longer. Will get a lenght checker tomorrow.
Fábio.
Full close
Middle
Full open
Seems that I need to be a tiny bit longer. Will get a lenght checker tomorrow.
Fábio.
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Melting Slicks
Joined: Jul 2006
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From: Salmon Arm, BC
To me it looks like they could be a bit longer. In the picture of the full closed position, the centreline of the rocker seems to far off to the right. As you said, get a length checker and that will help you find the correct ones.
Melting Slicks
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From: Florida
Thread Starter
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Joined: Dec 2007
Posts: 79
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From: Redmond WA
And then you see a bored sw engineer with his cameras, remote shutters, lighting, angles of incidence and everything else be totally defeated by a Sharpie pen. 
They should teach experience in school! Thanks Jim it makes a lot more sense, its much easier and nothing can be more accurate than that. Here are the results:
Intake is spot on, exhaust seems to be too short? Is that a dual pattern cam? Let's confirm the reading on Cyl#4:
And as you can see exhaust look a little short and intake... Intake?? No intake!!! Yes that's a wiped out cam right there. What a joy!
I had no clear signs of it when the car was running, after warming up could tell that the engine sounded slighly uneven, I thought it was the oil going down the worn valve seals as it warmed up. Maybe this was related, maybe not. The bottom of that lifter looks ok, I wonder how, when, why this happened...
Well at least I have a good reason to replace the cam, and a hundred new questions. I'll create a new thread for that.
Thanks guys for the help. The sharpie hint should be a sticky note on the forum.
Fábio.
They should teach experience in school! Thanks Jim it makes a lot more sense, its much easier and nothing can be more accurate than that. Here are the results:
Intake is spot on, exhaust seems to be too short? Is that a dual pattern cam? Let's confirm the reading on Cyl#4:
And as you can see exhaust look a little short and intake... Intake?? No intake!!! Yes that's a wiped out cam right there. What a joy!
I had no clear signs of it when the car was running, after warming up could tell that the engine sounded slighly uneven, I thought it was the oil going down the worn valve seals as it warmed up. Maybe this was related, maybe not. The bottom of that lifter looks ok, I wonder how, when, why this happened...
Well at least I have a good reason to replace the cam, and a hundred new questions. I'll create a new thread for that.
Thanks guys for the help. The sharpie hint should be a sticky note on the forum.
Fábio.
Last edited by FabioSan; May 4, 2009 at 04:39 PM.
Thread Starter
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Joined: Dec 2007
Posts: 79
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From: Redmond WA
I wasn't planning to touch cam now to keep this a small project. I try to break my projects into 1-2 days big projects so I can do them over a weekend and still drive the car to work. Also to keep it on a budget, I know that if I go all out the vette will suck all my money in a heart beat.
Its a damn bottomless money pit. But you know that
Fábio.
Last edited by FabioSan; May 4, 2009 at 04:33 PM.
Racer
Joined: Feb 2009
Posts: 343
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From: San Diego CA
Now that's a good Q 
