-
-
Re: Hydraulic Lifter Lash Adjustment (Cold Engine)
CHRIS-
The hydraulic lifter itself is actually an oil pump and the tolerances are taken up by the oil in the lifter. If you take your time and set the lifters and than go back and double check your "cold" rocker adjustments you should'nt have any issues as long as you follow the service manual. I just got done with my 74 L-48 about 8 months ago and still as quite as a church mouse and the motor runs great.
Marty -
Re: Hydraulic Lifter Lash Adjustment (Cold Engine)
my advice on doing hyd lifters is to only install one push rod and rocker as you adjust because i have seen where the rocker that was not adjust yet collapsed that lifter while turning the rotating assy and sticking in the collapsed position and you can not get a correct setting if this happens. this is why i like to do hyd lifters before i install the intake as i can see the push rod cup moving in the lifter when i adjust the rockerComment
-
Re: Hydraulic Lifter Lash Adjustment (Cold Engine)
Are you absolutely positive that the cam is a hydaulic lifter type? Do you have the mfg./part number and have you verified the specifications?
If it is a hydraulic lifter cam, your "engine builder" screwed up. With hydraulic lifters the pushrod should always be under slight "compression" from the lifter plunger spring so none of the rockers/pushrods should be "loose" as some will be if the cam is a mechanical lifter type and properly adjusted.
Follow the shop manual procedure for adjusting 8 at TDC #1 and 8 at TDC #6 if it's an OE equivalent cam. (You didn't mention the engine option or whether the cam is an OE replacement.) You can also adjust each cylinder at TDC of the compression stroke if you wish, and I recommend this if the cam is some unknown aftermarket hydraulic type. In production this procedure was done in a matter of seconds. It's not rocker science!
Loosen the nut while wiggling the pushrod up and down. As soon as you detect any clearance, apply the 1/2 to 1 turn. If you can't make up your mind how much to use - just do 3/4 turn.
Wear in the valvetrain will cause the lifter plunger to rise, but engine oil pressure keeps the cavity below filled with oil while the lifter is on the base circle, and a check valve keeps the oil from reverse flowing when the lobe begins lifting the lifter, which increases pressure in the oil chamber. Since oil is essentially "incompressible" the lifter will be in "hydraulic lockup" with zero clearance in the valve traiin.
Three-quarter to one full turn from zero lash will usually allow the lifter to compensate for all normal valvetrain wear over the life of the engine.
If you spend a little time typing some details about the engine configuration and something more specific than "runs like crap" to characaterize the operating characterisitcs we might be able to help you determine the problem. Think of this Board as a "service advisor" at a dealer when you bring your car in for a problem. Can you tell him something more specific than "runs like crap"?
Have you discussed any of these issues with the "engine builder"? What did he say?
DukeComment
-
Re: Hydraulic Lifter Lash Adjustment (Cold Engine)
Comp Cams "151" 327/350 equivalent. Comp Cams hydraulic lifters are confirmed. I've got the receipt somewhere, but can't find it now.
Newly rebuilt 327 motor with approximately 9.5 to 1 compression ratio.
Engine builder is a friend. Can't really push on him. His initial reaction was that the valves need adjusting.
Engine runs rough between 1000 and 3000 rpms. (I've only operated it between 1000 and 3000 rpms.) I don't think it's a miss. Just rough. Won't idle below 1000 rpm. Vacuum is 13-15 at 1000 rpms. Unsteady needle. Not jerky. Wanders between 13 and 15. I've checked the routing of the plug wires 3 times and the timing 10 times.
I know the distributor needs re-curving. But now I've adjusted the initial mechanical advance to give it 24 degrees at 1000 rpms and 36 at 2400. If I retard it more than this, the idle speed decreases. It seems to want more advance at the 1000 rpms at which I do the timing. Connecting the vacuum advance only adds 4. Carb is an AFB that was stored dry, and ran fine 2 years ago. I'd suspect the carb if it only ran badly at idle. But the engine also runs badly at higher rpms.
I'm looking to rule out causes now, so that I can do a decision tree, and decide if this is something I want to pursue. Or, if this is something that I need to bring to somebody else. I'm reluctant to bring this to somebody else because that just kicks off another set of problems.Comment
-
Re: Hydraulic Lifter Lash Adjustment (Cold Engine)
Christopher,
If it's a 327/350HP clone, the idle should be approx 750 and 14" vacuum. Set the inital timing at 10 BTDC with the vacuum can disconnected at the lowest idle you can get, then see if it runs better.
There may be a vacuum leak somewhere.Comment
-
Re: Hydraulic Lifter Lash Adjustment (Cold Engine)
Chris - 1000 is too high for idle, and 24* initial is WAY too much initial advance (if it's really "initial" - you probably have some centrifugal in that 24*). The vacuum advance should add 15* or so when you connect it - check it out with a Mityvac.
For setting initial timing (vacuum advance disconnected), it should idle around 600 or so to give you a true reading - set it at 10*-12*, then see how much centrifugal advance it adds with increasing rpm (vac advance still disconnected) for "total timing".Comment
-
Re: Hydraulic Lifter Lash Adjustment (Cold Engine)
I can't get it to idle at less than 1000 rpms. And if I retard the timing any more than where it is now, the rpms fall off, leading to a stall. I had the distributor re-curved, and I believe there's too much centrifugal advance coming in too soon. I agree that 24 at 1000 rpms probably has much centrifugal advance. But I can't get it to idle lower in order to determine the advance curve below 1000. At 24 at 1000 rpms, it doesn't "ping" on acceleration in 4th. Although at starting, the engine initially cranks slowly - just like an engine with too much initial timing. My setting it at 24 at 1000 is as much retarding as I believe I can do. The engine wants more advance. The rpms increase at that setting when I advance it, and decrease when I retard it.
This is perplexing. Which is why I want to go back to basics and eliminate possible causesComment
-
Re: Hydraulic Lifter Lash Adjustment (Cold Engine)
Christopher,
I would start by verifying the TDC mark on the engine balancer. Do this with a piston stop but be careful to not damage a piston, the spark plugs should be removed so the engine can be turned by hand. That will tell you exactly where the timing is. If you post #'s on the vacuum advance can someone may be able to tell you the specs.
If the distributor has been recurved then return it to be checked and give them specs you want for the curve or check it yourself with a timing light. These specs worked well for the 350 HP distributor I restored. 0*@800 - 20*@2000 - 26*@3100 and set inital at 12*, the VAC is napa 1765 which gives 15*@12". The engine idles at 750 RPM with approx 14" vacuum.
If the camshaft is a 350HP clone, are you sure the valves are adjusted correctly. May be time to remove the valve covers and start over, and once again verify TDC mark before any adjustments. The service manual gives valves to be adjusted at #1 TDC and #6 TDC but if damper marks are not correct???
Comment
-
Re: Hydraulic Lifter Lash Adjustment (Cold Engine)
That assumes it has a correct VAC for the installed cam, which has not been established.
More info is needed from the OP. We're flying blind! It has an AFB, which probably means it was not originally a L-79. What's the year and original engine configuration? What's the VAC ID number?
What's the cam part number, what other components were replaced during the rebuild?
The way I figure it, the "engine builder" ought to be willing to help sort this out. What does he say?
DukeComment
Comment