oilleaker1
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Post by oilleaker1 on Sept 18, 2022 6:35:54 GMT -5
I've been suffering with low compression/power , all while running a Kaiser Supersonic high compression head. When out running trails, tired engines can drive around me with more power and mine is all new. I can add in fuel going up hill until it loads up like it's choke is pulled. I checked the cam/crank gear timing and it's correct. Verified it with two other cam gears. So, I pulled the head and found carboned up exhaust valves. I re-ground the valves and seats and checked contact patterns over and over. Like beating a dead horse. No change on compression ( 90 lbs. ) readings before or after. Vacuum reads 16 and no change from before. Tried advancing the timing, no help. Checked timing with my light and it is advancing fine when revved up. Two carbs, two distributors, two vacuum gages, 3 compression testers, two intake and exhaust manifolds, no change. It read 90 pounds across the board with only one or two pounds difference between two. The engine runs great, starts perfect, and responds to carburator adjustments. So, my next move is to pull the head. I'll go back and compare the combustion chambers with a stock head first. If it does indeed look smaller on the Supersonic, then all that is left are the pistons and rings. Vacuum gage says late ignition timing. It's not late. I plan on checking piston skirt clearance , and pull some compression rings and check end gap. I have a feeling that I saw excessive ring end gap when I assembled the engine 4 years ago and left it on the engine stand. Now the question, if the pistons are fine but the ring gap is bad, can you buy .030 over rings and fit them to the current .020 over pistons and cut the ends down for correct end gaps? ? Seems you used to buy over size rings for loose but OK pistons during a overhaul. Any experience here? A stock engine should have around 110 lbs of compression. 90 is absolute low end. With the Supersonic head, I would think 120. None of my other engines have ever done this to me.
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Post by rickg on Sept 18, 2022 10:10:54 GMT -5
can you buy .030 over rings and fit them to the current .020 over pistons and cut the ends down for correct end gaps? ? No real experience with this but.. it seems to me that a hardened ring, mfg to a certain spec .030, with ends cut then squeezed into a smaller bore may become out of round and not contact the cyl wall full circumference.
Muley
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Post by Scoutpilot on Sept 18, 2022 10:36:58 GMT -5
What is your idle RPM? Have you tried rebalancing the carb air/fuel mixture? Heavy carbon deposits? What do the plugs look like?
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oilleaker1
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Post by oilleaker1 on Sept 18, 2022 15:59:58 GMT -5
Idling at 650 to 700. Plugs are fine unless you have your foot buried in it going up hills. It does not have enough power due to poor compression. What muley said is what I was wondering on the rings being oval. I'll ask my machinist about this. A professional engine builder would know. My gut is telling me ring end gaps are not good.
Idle mixture screw is 1.5 turns out. Both carburators I tried ran identical. It starts perfect. Better than the Jeeps around me. If I had compression, I'd not consider touching it.
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oilleaker1
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Post by oilleaker1 on Sept 19, 2022 8:31:56 GMT -5
OK, end gap should fall between .008-.013, piston skirt clearance on thrust side is .003. Rule of thumb is .0015 gap per inch of bore.
I'm pretty sure mine is way too large on the end gaps. It's not apart yet.
You also need to check for taper. Anything over .007 means it needs to be bored. The constant squeezing and releasing of the rings as the piston goes up and down will eventually break the rings. So, check the end gaps low and high in the ring travel zone.
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oilleaker1
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Post by oilleaker1 on Sept 19, 2022 13:32:20 GMT -5
The motor machinist said that yes you can order the next oversize ring set and cut to fit. Guys building race engines do it all the time to get theirs exact.
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Post by rickg on Sept 20, 2022 7:59:58 GMT -5
The motor machinist said that yes you can order the next oversize ring set and cut to fit. Guys building race engines do it all the time to get theirs exact. Hmm, learn something new every day. I wonder about longevity issues for rings during heating and expansion while compressed beyond their design limit.
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oilleaker1
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Post by oilleaker1 on Sept 20, 2022 11:56:31 GMT -5
Had another talk with the machinist. Going to pull the head and measure the bore to confirm it's indeed .020 over. Then order new rings and try again. All else is in order.
I also ordered the ring carbide end filing tool. Hand filing the ends is a bit crude.
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oilleaker1
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Post by oilleaker1 on Sept 21, 2022 5:24:48 GMT -5
One more thing to check. The machinist said to re-check compression by running the engine!!!!!!! Never have done it that way. Make sure you have a 1/2 inch reach adaptor. A bent valve could happen.
He basically said from my description he is skeptical it's the rings. I'm grasping for straws right now. I've never had a engine do this to me.
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oilleaker1
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Post by oilleaker1 on Sept 21, 2022 14:14:02 GMT -5
Still could not see why no compression or vacuum. BW mentioned to try the test that the manual describes to check valve timing. I thought: but I already checked the gear index marks. Ok, so you set number one intake valve tappet clearance to .020. Rotate the engine in running direction and watch until number one is beginning it's compression stroke. The manual (I have several) says the gap should close and touch the valve stem when your timing mark is at 9 degrees before top dead center. About double your 5 degree mark. I closed the gap and looked. Sure enough, the pulley mark was about 5 degrees after TDC. Late valve timing. The index marks were correct on the gears, I double checked. Engine is coming out and going on the stand. I have everything all polished so it will zing apart again. I know which wrenches to grab before hand. I already ordered a new camshaft. I have two real nice cam gears. I'm still going to re-ring the pistons. Hastings rings are coming. When all done, do it two more times for good measure.
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Lee
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Post by Lee on Sept 21, 2022 17:57:45 GMT -5
Excellent plan 👍🏽👍🏽👍🏽
Lee😉
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oilleaker1
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Post by oilleaker1 on Oct 15, 2022 18:32:23 GMT -5
The engine has awakened. New cam and rings fixed it right up. A word of caution, if your valve timing is off and the gear markings are correct remove the bolt and thick washer from the cam gear and shine a light up the keyway of the cam gear. If you reused the old cam cause it looked good, be sure that the DFPO did not forget to install the half moon key. You've heard of harmonic balancers shifting on a bad rubber right? My gear shifted on the cam. Education is expensive. Do you suppose there is a Biden fund that will cover my education expenses? Oops, it's a hybrid, burns oil and gas. Nope only for electric cars. oh well, time to get back to the trails. Oilly
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Post by rickg on Oct 15, 2022 19:45:29 GMT -5
.. Attachments:
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oilleaker1
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Post by oilleaker1 on Oct 17, 2022 18:20:12 GMT -5
Today I drove Hullet like it should be driven. drove over to Spearfish and had lunch. From there up Higgins Gulch to Iron Creek Lake. Then cross country to Roughlock falls. Zinged up Spearfish Canyon to Cheyenne Crossing store which by the way is closed due to a kitchen fire. Pulled the large hill (quite well) up and over to Lead. Then down through Deadwood and back over the hill to Crook City. The Jeep has never driven so well since I bought it. Very pleased with the engine now. People waved all day at us. Lots of smiles. The half cab with roll up windows was so nice, I never put on a jacket. Pretty plush ride. ( for a 74 year old Jeep that is)
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Post by Scoutpilot on Oct 17, 2022 18:27:41 GMT -5
Bravo!
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