LT-1 soild/hydraulic lifters, cam

[Ted K.]

Long story abbreviated. Bought 71 LT-1 year ago. Engine was out of car and partly rebuilt. Took engine to my guy and had it rebuilt. Cam, lifters, pistons and crank were in short block. He took it apart and replaced what it needed. After about a year I finally got it installed and it runs like crap. At least 1000/1100 rpm at idle 5-6' vacuum and needle shaking like crazy.. First thought was it had a monster cam in it. The rebuilder said the cam and lifters (HYDRAULIC) looked good and he reused them. Too long ago for him to remember the lift of the cam. His suggestion was to back off on the hydraulic lifters until they clack and see if it runs any better. If it does it should probably have solid lifters with that cam.
It does run better with loose hydraulic lifters than with them adjusted properly.
Does it make sense to change them to solid lifters to solve my poor low end performance or is it possibly something else?
Ted

[Joseph K.]

Re: LT-1 soild/hydraulic lifters, cam

Ted,

I found this. I hope it helps. I would start with a compresion test first. I know that there is a diagnostic chart some were on the web that tells you the reason for diferent vacum readings.

Compression tests

Internal combustion engines depend on compression of air/fuel mixture to maximize the power produced by the engine. The upward movement of the piston on the compression stroke compresses the air fuel mixture within the combustion chamber. The air/fuel mixture gets hotter, as it is compressed. The hot mixture is easier to ignite, and when it is ignited it generates much more power than the same mixture at a lower temperature.
If the combustion chamber leaks, some of the air/fuel mixture will escape when it is compressed, resulting in a loss of power and a waste of fuel. The leaks can be caused by burnt valves, a blown head gasket, worn rings, slipped timing belt or chain, worn valve seats, a cracked head and more.



An engine with poor compression or even low compression will not run correctly and cannot be tuned to factory specifications. If initial engine diagnosis suggests that the cause of the problem may be poor compression, a test should be performed.
A compression gauge is used to check the cylinder compression and is a good indication of the overall health of that particular cylinder. The typical compression gauge indicates pressure in pounds per square inch.
Most compression testers have a vent valve that holds the highest pressure reading on the meter. Opening the valve releases the pressure when the test is completed. The steps for conducting the cylinder compression test are included with the gauges. Specifications can be obtained from a good auto repair manual.
Vacuum testing

Measuring intake manifold vacuum is another way to diagnose the condition of an engine. Manifold vacuum is tested with a vacuum gauge. The downward movement of the piston forms vacuum during the intake stroke. If the cylinder is sealed well a maximum amount of vacuum will be formed.
Vacuum gauge readings can be interpreted to identify many engine conditions, including the ability of the cylinder to seal, the timing of the opening and closing of the engines valve train, and correct ignition timing. Ideally each cylinder of an engine will produce the same amount of vacuum.

Therefore, the vacuum gauge readings should be steady and give a reading of about 18-20 inches of mercury. If one or more cylinders produces more or less vacuum the needle of the vacuum gauge will fluctuate.
The intensity of the fluctuation indicates the severity of the problem of the leaking cylinder. For example, if the reading on the vacuum gauge fluctuates between 10 and 17 inches of mercury you should look at the rhythm of the needle. If the needle seems to stay at 17 Most of the time, but drops to 10 and quickly rises this reading is probably caused by a problem in one cylinder.
Fluctuating or low readings can indicate many different problems. For example, retarded ignition timing or incorrect valve timing might cause a low steady reading. A burned intake valve might cause a sharp drop in vacuum at regular intervals.
Other conditions that can be revealed by a vacuum test are weak valve springs, faulty PCV, EGR valve operation, compression problems, worn rings or cylinder walls, leaking head gaskets, a manifold vacuum leak, and restricted exhaust systems will also cause low vacuum readings.

[Joseph K.]

Re: LT-1 soild/hydraulic lifters, cam

Here are some more sites

<LI class=g>Engine Diagnosis Basic Test Procedures | Auto-Facts.org

This basic engine diagnosis will give you a good indication of the true condition of your engine. Performing a compression test and an engine vacuum test ...
www.auto-facts.org/engine-diagnosis.html - 23k - Cached - Similar pages
<LI class=g>ENGINE VACUUM DIAGNOSIS -- Tracy Performance Auto Service

Mar 3, 2002 ... We Offer These Suggestions For Vacuum Diagnosis. Proper engine operation should result in an even vacuum reading from 15 inches to 20 inches ...
www.tracyvette.com/enginevacuum.html - 12k - Cached - Similar pages
<LI class=g>How to diagnose your Ford engine using a vacuum gauge

Mar 3, 2007 ... Diagnosing car engines with a vacuum gauge. A vacuum gauge gives a quick and cheap (under $15) indication of engine problems. ...
www.fordf150.net/howto/diagnoseengine.php - 17k - Cached - Similar pages
<LI class=g>Engine Testing With A Vacuum Gauge

Even with modern computer controlled engines a vacuum gauge is still a valuable tool for diagnosing engine and transmission problems.
autorepair.about.com/cs/troubleshooting/a/aa112401a.htm - 23k - Cached - Similar pages
<LI class=g>Engine Vacuum Gauge Diagnosis | MILEPOSTS Garage (Tech Tips)

A vacuum gauge can indicate the condition of your engine, and how well it is tuned. This chart shows you what the various gauge readings mean.
automotivemileposts.com/garage/vacuumgaugereadings.html - 5k - Cached - Similar pages
<LI class=g>Engine/Fuel Pump Vacuum/Pressure Gauge

Engine/Fuel Pump Vacuum/Pressure Gauge. ... Helps to identify and diagnose system vacuum leaks and problems in the engine, and the various vacuum-operated ...
www.automotive-diagnostic-tools.com/Engine-Fuel-Pump-Vacuum-Pressure-Gauge-p/inn3620-ast.htm - 27k - Cached - Similar pages
<LI class=g>Engine Vacuum Leaks

But oftentimes, a vacuum leak will disguise itself as an ignition or fuel problem that defies diagnosis. Either way, an engine vacuum leak is bad news ...

[Ted K.]

Re: LT-1 soild/hydraulic lifters, cam

Joe, Great info. I'll have to do some reading.
Still wondering about the lifter impact on vacuum.
Thought my Uncle Joe was responding with the similarity in the name.
Ted

[Dick W.]

Re: LT-1 soild/hydraulic lifters, cam

Lt-1 came with solid lifters.

[Duke W.]

Re: LT-1 soild/hydraulic lifters, cam

Like Dick said...

You can use a dial indicator to take the lobe data. Mechanical lifter cams have very long constant velocity clearance ramps of about .0002" per crankshaft degree, so they are easy to differentiate from hydraulic lifter cams.

Your "guy" sounds like he's going through life without a full sea bag.

Duke

[Vincent F.]

Re: LT-1 soild/hydraulic lifters, cam

I've never heard of anyone installing hydrolic lifters with a solid lifter cam shaft. I would think you could seriously damage something.

[Ted K.]

Re: LT-1 soild/hydraulic lifters, cam

My problem is I don't want to go through all the trouble to pull the cam to see if it requires solid or hydraulic lifters.
It seems that hydraulic lifters do not work with a solid lifter cam.
Will solid lifters work with either cam?
I am thinking of changing the lifters to solids and don't want to have a similar non-compatibility problem.
Ted

[Duke W.]

Re: LT-1 soild/hydraulic lifters, cam

I give up...

[Steven B.]

Re: LT-1 soild/hydraulic lifters, cam

My problem is I don't want to go through all the trouble to pull the cam to see if it requires solid or hydraulic lifters.
It seems that hydraulic lifters do not work with a solid lifter cam.
Will solid lifters work with either cam?
I am thinking of changing the lifters to solids and don't want to have a similar non-compatibility problem.
Ted

Hi Ted! The '70-'72 LT-1's came with solid lifters/cam. Solid lifters require a solid/mechanical cam and hydraulic lifters require a hydraulic cam. The package (heads, intake, carb, timing, etc.) is designed for solids. You need to be certain the cam and lifters "match".

Cams and lifters are cheap compared to engine damage repair. You really want to make certain you have the solids. Pull the cam and lifters and replace as necessary to protect your special engine.

Steve

[Dick W.]

Re: LT-1 soild/hydraulic lifters, cam

You can either follow Duke's instructions, Steve's instructions, or live with what you have. Throwing parts together that are incompatible is a recipe for disaster

[Wayne K.]

Re: LT-1 soild/hydraulic lifters, cam

I give up...

Perhaps he didn't read your post but please don't give up. Your knowledge and willingness to share it on this board is much appreciated and I think I speak for the majority here.

Wayne

[John M.]

Re: LT-1 soild/hydraulic lifters, cam

Ted,
I agree with Stephen; if it's hydraulic take it out of there and replce it with the correct cam and lifters. If you do it yourself it's $300-400 and peace of mind and satisfaction with a job well done. If you're not sure what's in there find someone who can tell you for sure; all you need is a dial indicator and some time.
It's a special car and you won't be happy till your sure it's right.

[Jim L.]

Re: LT-1 soild/hydraulic lifters, cam

My problem is I don't want to go through all the trouble to pull the cam to see if it requires solid or hydraulic lifters.

Hmmmm..... if you are unwilling to go to the trouble to do it right, then are you willing to go to the trouble to do it over?

Jim

[Ted K.]

Re: LT-1 soild/hydraulic lifters, cam

I have changed the hydraulic lifters to solid lifters and adjusted them following the Hinckley/Williams adjustment procedure. They were set cold at .023/.023. They seem to me to be pretty loose and are fairly noisy, in fact noisier than any solid lifter engine I can remember.
Would that be considered normal for the LT-1 or should the valves be set at a different clearance?
Ted