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Learning Engines

I had an uncle who owned his own shop. I also had a cousin, his son, who also was a mechanic. I got help from both. I then went to work in a dealership after high school. Took a votec class on engine rebuilding. Had a very good teacher. Wish I had continued but didn't. It's all about the money. At that time diesels were still being developed and that is where the money was at. I didn't want to mess with diesels. I got my hands on a spare long block and basically tore it down and rebuilt it myself and some book reference and my cousin helping me when I got stumped. After gaining income, I got into drag racing. Learned the most there. When you're trying to run consistent times and figuring out the game trying to shave off tenths of a second here and there and dropping 60 foot times, it involves certain components over others and then you get into the meaning of things like springs rates, valve lift, overlap, lobe seperation angles, why you can run a taller cam if it's a roller over flat tappet etc. You gain an understanding of where torque and horsepower comes from and how to develope one over the other depending on application. Also gaing knowledge of the reslation between bore and stroke adding up to cubic inches. Operation of heads and intakes and how they affect the performance of and engine and their relation to torque and horsepower. There is a ton of info. I only scratched the surface. Drag racing is learning gearing, engine, suspension and driving ability. It's a sum of everything. Off roading is the same thing. You will learn all this stuff over time.

I would recommend getting into an engine rebuilding class. Then befriend your local off road shop guy or speed shop guy. You can pick up good info there. Then just do research into each component independently. It gives you a better understanding of WHY things work the way they do. Once you figure this out, it helps you make decisions on what would be better for your application if you're building say and engine. It just takes time.
 
1979bettywhite said:
Have done that one already. #2 is my problem child. Over 10% away from the others. And I know that there is some blow by in that one so the rings may be shot. That plug gets fairly well oil covered pretty quick. Here are the numbers when I did the compression check last:

1 - 128
2 - 125
3 - 135
4 - 148
5 - 135
6 - 138

I think #1 was a little higher the 2nd time I ran it. But #2 was unchanged.


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There could be a few things leading to low compression readings. Could be rings. Could be valve seats. To test your rings, hook everything up for a compression test, pull the spark plug for that cylinder and put just a little bit of oil in the cylinder. I'm talking just a little, do not want to hydro lock it. Crank it over. If the rings are shot, the compression should build then drop off again. Anyone else second this?


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Those readings aren't bad at all. All 6 cyl are within 20 psi. How many miles on the engine? I would hook up a vacuum gauge and see how steady the needle is.
Also-Take a wrench to each manifold bolt.
I would switch spark plug wires and spark plug around to see if the burn in #2 cleans up. Have you confirmed that all the SP gaps are the same, especially #2?
Maybe a cap/wire/rotor/spark plug issue.
Does your dizzy cap have brass or alum terminals? Brass is the best......
LG
 
Make sure your engine is properly vented. Depending on how long the engine has sat and how much you drive it, you may want to drive it a few hundred miles to make sure the rings are not sticking a little in the lands.

Does the engine smoke any? Also make sure it's not filled over capacity on oil also.
 
Have had the jeep since July and put plenty of miles on it since then. Have had to do a number of maintenance related items on it since I got it, but nothing out of the ordinary. Has had a tick since I bought it that has not gone away with any of the remedies I have tried. But the engine runs smooth and strong for being the age it is with the miles it has (111k per the odometer).

The only other issues I notice on it is that it will knock at a very low idle after it has warmed up. When I mean low idle, I mean 500 rpm or less, so that is rarely in play. Also, it will exhibit some of the same knock when I slow down fast and come to a stop. Soon as I am stopped it goes away.

LG, I will pull the dizzy cap and check things. I believe all the gaps are correct on the plugs. I will get a new set and check/set them.

At startup with 10W30 I get 50-60 lbs of oil pressure. At fully warm and idle I get 7-10 lbs. I have also pulled the PCV and given it a good shake. Seems to be operating just fine.

The other symptom is that I feel the oil dirties fairly quickly and burns about 0.5-1 qt per 1000 miles (or leaks it out, lol). I have a leak at the dipstick tube. Fixed the valve cover gasket leak. May have another leak at the rear main, but nothing substantial at either place. I just keep a good eye on all fluid levels all the time.

The only thing I have heard is that you want to have all the cylinders within about 10% of the highest reading. So in my case that would be 133 on the low end. So #1, and #2 would be outside that range. LG, you still think my numbers are acceptable for the age of the engine?

I plan to take it to a reputable mechanic here as I want to know that I either am towards the latter stages of life before a rebuild or whether I have a decent amount of time left before I have to do it. Just want to know what I can plan as far as trips go this summer! And whether I can wheel it with some confidence, don't want to get stranded if I can avoid it!

JD
 
For the age of this engine & mileage. I think your fine.
That knock you hear at 500rpm could be from low oil pressure. One thing you may want to try. Is one blue bottle of STP. YUP-My flame suit is on-:D
Also, if this is the OEM oil pressure gauge. DON'T TRUST IT!
No reason to get new plugs. Just check and confirm gap. You want a wire feeler gauge for this. I also suggest a dab of copper anti-seize on the plug threads. Rub some dielectric grease on the porcelain area where the wire boot makes contact.
Fingers crossed. :notworthy:
LG
 
Last edited:
Thanks LG.

I learned a long time ago that a dab of anti-seize on threads makes a world of difference. I thank Dad for that one.

I think that knock has to be from low oil pressure. And I have an aftermarket sunpro mechanical pressure gauge in the Jeep, so I believe it is accurate.

I have a bottle of Restore in the current oil, but I will look into this blue bottle of STP. I guess the only other option would be to replace the OEM pump? I believe from what I have heard that can be a pain and fairly expensive and may not even help things.

Was not so concerned with the low idle knock, but the one slowing down gave me more concern. I think that maybe with the quick drop in speed and rpms maybe the oil isn't getting back down to the bottom end quick enough?

Will get a feeler gauge and test out the current plugs.

JD
 
Give the STP a try........
Make sure the oil level is at the top mark if not just a bit above the top mark on the dip-stick.
LG
 
So if I am currently at the top mark with 10W30 and a can of Restore, you think I should wait to add the Blue Bottle STP with the next oil change, or go ahead with it now?
 
Are you at the top mark now with the Restore??? If so, add the STP. These 6's won't mind.....
FWIW: I play in the notches a good bit. Have'n the oil level a little bit higher just makes sure you don't suck any air when laid over about 35* on your side.
LG
 
Ha ha. Will consider adding it. Going to see what the mechanic has to say.

I will say that this is my first inline six and I am impressed with this engine so far, even in its tired state.

Threw it in four low the other day and crawled up the driveway at low rpms. Plenty of torque. I have 3.54 gears and 31s. I can only imagine what a better gearing would be like with these little cjs. Climbs like a goat.


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For that low speed knock........check your timing. And also check that Carb if it has the low idle elec. pod on it.

And a leak down test will tell you if you have issues in the overhead , like a head gasket, valve guides or valve seats...........valve guide leakage is common on those.........likewise if it's rings it will also point to them.............you do need an air compressor to run the leak down test. Good Luck!
 
Bet your "mechanic", will say not to use it. :laugh:
LG
 
Back to the original topic, Learning engines... a neverending story for me. Got my start with a '66 Chevy Malibu. Traded my (then) Levis '77 CJ5 for it, sellers remorse?
That car was lightning quick off the line and so I was really taken with that trade...at first.
Turned out one of the pistons had a hole in it's crest so had to keep feeding it oil until one night after a party out in the woods at a friends cabin heading home she ran out of oil and I was hoping to limp it home as I had just run out of the fresh case I kept in the trunk.
Called my friend that lived at the cabin and we chain pulled the Chevy back to his cabin. Turns out, in his youth he used to build SBC's and dirt track race in tri 5 chevys back in the '60's.
When we pulled the motor while I knew it had a solid lifter cam I learned from him that it was a 30/30 Chevy racing cam stuck into a stock, 2 bolt main 350. This accounted for the quickness of that ride.
He passed on his knowledge to me through the various rigs I had back in those days when I had the money for such.
Different story these days, regretably.
 
Got her back from the shop today. As I already knew, pretty extensive blow by in cylinder #2. He said he would really do nothing until I am ready for a rebuild. Just keep a couple extra plugs with me in the jeep as well as some oil. But it doesn't burn that fast. It only seems to dirty a little quicker. I think I can keep using either Restore or STP in it to try and keep the compression up.

On the other hand, finding a body shop that wants to take on my recent collision damage is hard to come by. Pulling the tub back straight seems to be a "lost art" as most new cars and trucks are thinner metal and panels are just replaced.

Hopefully I can get someone to take it on soon.

JD
 
Run the next step hotter spark plug.
What plugs are you run'n now?
LG
 
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