solid lifter cam lift
my 1963 has solid lifters but I can not determine which cam is installed so do not know what to set the valve lash to. I bought a dial indicator to try to measure the cam lift at the push rod end of the rocker arm. This is almost impossible given the small difference in the lobe lift in the 3 GM cams not to mention all of the after market cams. Any suggestions about measuring the lift with out taking the cam out? I am currently using the 1963 specs for the 097.
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Re: solid lifter cam lift
That's a tough one.
I would do the "best guess".
See how it runs with the .024 and do it again at .030.
See how it runs and sounds.
If everything else is stock I would give you good odds it's stock.
Aftermarket intake and a Holley? I would assume the worst.
Could be anything given the staggering amount of SBC camshafts out there.
If you need the facts you might have bite the bullet and disassemble the motor. -
Re: solid lifter cam lift
Jeff,
Do not do the Best Guess Method as it will end in failure of the presently installed camshaft. In the 1963 Corvette Shop Manual there is a procedure on Engine Mechanical page 6-19 that outlines how to check Camshaft Lobe Lift. Simple to follow the instructions.
I agree that it is probably the 097 camshaft but it's better to know and easy to check.
The 097 Camshaft has a lift of 0.382 and 0.386 with a 0.012 and 0.018 valve clearance.
JRComment
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Re: solid lifter cam lift
You should be able to determine if the cam is GM because the lifts are different enough to determine with careful measurement.
Rocker ratio does not come into account because you are effectively measuring gross lobe lift INCLUDING the clearance ramps.
Gross lobe lift, inch, inlet/exhaust:
Duntov .2625/.2665
LT-1 .3067/,3233
30-30. .3233/.3233
If your measurements don't ID an OE cam, determine the upward inflection point from the constant velocity clearance ramps, and multiply this number times 1.37. It's best to use a degree wheel and take measurements about every ten degrees and plot them, but it can be done without.
DukeComment
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Re: solid lifter cam lift
Jeff, If you have a vacuum gauge use it to determine how many inches of vacuum your engine is putting out at idle.
My 63 FI car puts out 16" at 900 RPM. It has the old TRW cam now sold by Federal Mogul. CS113 R. I the old days it was TP113.
If it has a 30-30 cam vacuum varies depending on valve lash, manufacture, etc. 10-12" or so.
The tighter the valve lash the less vacuum.
Now listen to the gurus. JohnComment
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Re: solid lifter cam lift
My '63 FI car, just freshly tuned, has 13" at 1000 rpm. I am sure it has the stock cam and configuration. My '64 fuelies vary from 11-12" at 1000 rpm, but they have a much more healthy cam......
Big Tanks In the High Mountains of New MexicoComment
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Re: solid lifter cam lift
13" @ 1000 jibes with my recollection that the Duntov cam is about 12" @ 850. I set up 365 HP engines with 30-30 cams to about 10" @ 900, but sometimes FI requires 100-200 more idle speed to get reasonable idle quality and the higher idle speed means higher vacuum.
I don't know how JD got 16" @ 900 for a Duntov cam, and I don't agree with it.
BTW, Michael, you are probably aware that the 375 and 375R units are setup up for ported vacuum advance. You can achieve better idle quality and other benefits by converting it to full time, but you will also have to swap the OE 201 15 VAC for a B28 because the 201 15 doesn't pass the Two-Inch Rule.
DukeComment
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Re: solid lifter cam lift
Michael. Here's a tip I learned from Jerry Bramlett. Could be your PCV valve leaking big time vacuum. You should have more than 13. Block it off and then check the vacuum. John D.Comment
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Re: solid lifter cam lift
That is where I put the vacuum gauge to measure it, at that fitting off the FI doghouse, PCV disconnected. My other FI cars have even lower vacuum, as they have the '64 cam. Remember I am also at 8000' elevation.Big Tanks In the High Mountains of New MexicoComment
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Re: solid lifter cam lift
That doesn't make any sense at all.
Idle vacuum must be checked with the engine in the normal configuration, which includes the PCV system and vacuum advance. It's amazing how many guys try to check manifold vacuum by disconnecting the hose from the VAC and connecting the vacuum gage to the hose, thus no vacuum advance, so idle revs and vacuum drops... same result if you disconnect the PCV and connect to the open hose.
That's why the gage must be connected in parallel, not series, so you tee into the VAC hose or any other vacuum source that feeds something else. The only time you can connect a vacuum gage directly is when there is a vacuum source that is normally plugged and doesn't operate any other engine control device.
DukeComment
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Re: solid lifter cam lift
Duke, I went back and put a "T" in that fitting, so PCV was still hooked up, I still got 13".Big Tanks In the High Mountains of New MexicoComment
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Re: solid lifter cam lift
Without looking at a 375/375R FI unit I'm not sure how you can tap into manifold vacuum. You can't use the VAC signal line because it's ported. Does the ratio lever have an external line you can tap into?
You can use the PCV system, but would have to get an adapter with a nipple for the vacuum gage that is connected to the plenum adapter that will accept the valve on the downstream side. Is that how you did it?
DukeComment
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Re: solid lifter cam lift
My '63 375 has a large, 90 degree fitting on the upper right (passenger) side of the doghouse, shown in the picture, connecting into the PCV valve and hose. I tapped into that with a T, it is full manifold vacuum.
Footnote: The ported vacuum off the air meter is 10" at 1000 rpm.Big Tanks In the High Mountains of New MexicoComment
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Re: solid lifter cam lift
Interesting that your "ported" VAC signal line shows significant manifold vacuum, but I think I know the reason whr.
Due to your 8000 foot altitude the lower air density requires more idle throttle opening to maintain acceptable and stable idle speed.
So the throttle valve is open enough to partially expose the ported vacuum advance orifice, but not quite enough to show full manifold vacuum
Engine behavior at idle and typical low speed driving should improve with full time vacuum advance and a B28 VAC.
DukeComment
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Re: solid lifter cam lift
Thanks all,
I am getting 14" at 800 to 900 rpm so I am going to guess it is the correct 097 cam.Comment
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