the sucker king Posted December 3, 2011 Share Posted December 3, 2011 I had an ea81 built for my hatchback with delta cam and ea71 pistons. I got it in and it ran great. I ran the motor, did not drive the car. I tuned the carb and timing by ear, never revved it above 3k. After I ran it to get it up to temp for maybe 20 minutes (this was the next day afer I got it running), It purred like a kitten for 20 minutes and suddenly went from purring like a kitten to running like crap and backfiring through the carb. This happened in an istant. It was a rythmic backfiring, Like one cylinder repeating. There is a total of probably a little under one hour of running time on this engine, Zero miles. Today I tested compression. These numbers are cold, as I didn't want to run the car for twenty minutes with it backfiring twice a second. 1. 90 2. 100 3. 120 4. 125 I am also at 5500 feet altitude, and should expect around 10 pounds lower than nurmal, but these numbers are way lower than the 125 to 175 than HTKYSA manual says is normal, especially when you figure in the ea71 pistons. I also put a gun on the timing and set it to 8 degrees. pop pop pop still. A little additional - just went and started the car and pulled the #1 wire, the backfiring stopped. with that wire still out, I pulled #2 and it didn't significantly stumble, so it's running on just the two. Any thoughts on what happened? Quote Link to comment Share on other sites More sharing options...
Caboobaroo Posted December 3, 2011 Share Posted December 3, 2011 I would start by checking the advance in the distributor to make sure its working properly. I have a vacuum pump with a gauge I use but you can also use a piece of vacuum line and suck the opposite end of it and see if its holding. Quote Link to comment Share on other sites More sharing options...
naru Posted December 4, 2011 Share Posted December 4, 2011 1 Leaky intake valve maybe? Try putting compressed air into #1 at TDC and listen at the carb. Might be worth checking valve clearance too. 2 Vacuum leak 3 Carb trouble 4 Ignition crossfire(seems unlikely) Look for moisture or carbon tracks inside the disty cap. Quote Link to comment Share on other sites More sharing options...
the sucker king Posted December 4, 2011 Author Share Posted December 4, 2011 I would start by checking the advance in the distributor to make sure its working properly. I have a vacuum pump with a gauge I use but you can also use a piece of vacuum line and suck the opposite end of it and see if its holding. I thought that at first when the timing was suspect. Now the real concern is low compression Quote Link to comment Share on other sites More sharing options...
the sucker king Posted December 4, 2011 Author Share Posted December 4, 2011 1 Leaky intake valve maybe? Try putting compressed air into #1 at TDC and listen at the carb. Might be worth checking valve clearance too. 2 Vacuum leak 3 Carb trouble 4 Ignition crossfire(seems unlikely) Look for moisture or carbon tracks inside the disty cap. Again low compression seems to be the key here, but the leaky intake valve thing is where I am with you, It ran fine at frst. My worry is if a valve bent slightly that could explane the backfire, but now why two cylinders? I am just kicking around ideas, what if the cam was not ground right and it took out two valves on two different cylinders. Does anyone know how the temperature of the engine effects the compression test? All I can do to get it to running temp and retest run it is let it run on 2 cylinders, but is it okay to let all that fuel get dumped into the one and two cylinders without burning any off? Don't want to do any further damage. I would pull the wire on the number one so it didn't backfire the whole time. Quote Link to comment Share on other sites More sharing options...
MilesFox Posted December 4, 2011 Share Posted December 4, 2011 with my experience, backfiring out the carb has been due to spark plug wires routed improperly. firing order is 1-3-2-4, counterclockwise. The #1 cylinder is the fornt on the passenger side and 3 behind it. Those cylinders fire almost simultaneously, and then the other side (2 and 4) Quote Link to comment Share on other sites More sharing options...
the sucker king Posted December 4, 2011 Author Share Posted December 4, 2011 with my experience, backfiring out the carb has been due to spark plug wires routed improperly. firing order is 1-3-2-4, counterclockwise. The #1 cylinder is the fornt on the passenger side and 3 behind it. Those cylinders fire almost simultaneously, and then the other side (2 and 4) I apreciate the help, but please ubderstand the problem. The car ran Great for an hour. Like a finger snap it ran bad. The ignition wires are routed proper. The cap and rotor are like new. The compression is bad. Quote Link to comment Share on other sites More sharing options...
the sucker king Posted December 4, 2011 Author Share Posted December 4, 2011 I think part of the problem with how this thread is going is that people read the title and backfire through the carb = ignition timing or wires. But if you read the (entire) initial post, it suggests something quite different. Quote Link to comment Share on other sites More sharing options...
Crazyeights Posted December 4, 2011 Share Posted December 4, 2011 (edited) Pull the valve covers and make sure ALL of the rockers are moving when you turn it over by hand. It sounds like it might be a valve train problem. Perhaps a pushrod jumped out somehow causing one valve to stay shut or you lost a lobe on the cam. Edited December 4, 2011 by Crazyeights Quote Link to comment Share on other sites More sharing options...
the sucker king Posted December 4, 2011 Author Share Posted December 4, 2011 Pull the valve covers and make sure ALL of the rockers are moving when you turn it over by hand. It sounds like it might be a valve train problem. Perhaps a pushrod jumped out somehow causing one valve to stay shut or you lost a lobe on the cam. I'm thinking more along the lines of an intake valve is staying a little OPEN. That would explain both low compression and the backfire through the intake. Why this is happening is the other story and then also why the second dead cylinder? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 4, 2011 Share Posted December 4, 2011 You have low compression - fine. Now you have to find out why. Next step is a leak-down test. I really can't understand why no one sugests to continue with the proper testing methods. We can guess at this all day - won't get you anywhere. GD Quote Link to comment Share on other sites More sharing options...
the sucker king Posted December 11, 2011 Author Share Posted December 11, 2011 Thanks for all the suggestions, First off forgive me I work slow, the car is outside and it's winter and gets dark early, really I only have weekends to work on this. Did a leakdown test and the results were horrid, 45% leakage on the two "good" cylinders and 65% and 75% on the two bad ones. today I took the valve covers off and crazyeights is our winner, a pushrod jumped ship. The pushrod was damaged and the cup on the rocker assembly was damaged too. The damage was not the reason for the failure, but the result. valves all need adjusting on both sides too. So I got a replacement pushrod and rocker assembly and will put it all back together in the morning, then adjust valves. Hopefully up and running again. Why did this happen? Again this is a fresh rebuild, read first post. Did a valve come so far out of tune that the rod popped out? If the cam grind was wrong I guess this will happen again. Quote Link to comment Share on other sites More sharing options...
the sucker king Posted December 11, 2011 Author Share Posted December 11, 2011 forgot to give some details on the leak down test. i could hear it in the crank case and in the intake, I couldn't listen to the exhaust. fixing all the valve issues should take care of that, but what about the air i heard in the crank case, do you think only having run for an hour the piston rings aren't seated propper yet? Also the engine was cold. Quote Link to comment Share on other sites More sharing options...
Crazyeights Posted December 11, 2011 Share Posted December 11, 2011 Don't worry about it yet. I would just fix the valve train problems and CAREFULLY adjust the valves to specs. You may never know exactly why this happened, but over the years I have seen it a number of times on engines that were just assembled. Also, IMO there is no way the rings are seated properly yet after only an hour of run time. That could take 1000-5000 miles depending on exactly what was used. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted December 11, 2011 Share Posted December 11, 2011 Yeah - the final leakage rate determination will have to wait till the rings are broken in. The only way a push-rod can come out is if it's bent or there is MASSIVE play in the valve train (valve stuck open, etc). Check the make sure you don't have a sticky valve stem. GD Quote Link to comment Share on other sites More sharing options...
Dirk Posted December 11, 2011 Share Posted December 11, 2011 Just a thought about 2 cylinders being affected. The cam shaft only has 4 cams that are shared by opposing cylinders. Sadly there is no quick way to inspect the cam shaft but I wonder if as you have already suggested the cam grind is suspect? Quote Link to comment Share on other sites More sharing options...
Dirk Posted December 11, 2011 Share Posted December 11, 2011 Hydraulic lifters? Quote Link to comment Share on other sites More sharing options...
Quidam Posted December 11, 2011 Share Posted December 11, 2011 (edited) the sucker king;106490 Thanks for all the suggestions a pushrod jumped ship. The pushrod was damaged and the cup on the rocker assembly was damaged too. The damage was not the reason for the failure, but the result. valves all need adjusting on both sides too. So I got a replacement pushrod and rocker assembly and will put it all back together in the morning, then adjust valves. Hopefully up and running again. Why did this happen? Again this is a fresh rebuild, read first post. Did a valve come so far out of tune that the rod popped out? If the cam grind was wrong I guess this will happen again. Hth, just some thoughts on cams and lifters being different animals than HLA's. A lifter contacts the cam lobe, a LA doesn't. With a reground cam it's best to use new lifters, as you're rolling the dice as to whether the cam lobes will get wiped out. And I've witnessed two camshafts getting wiped out. I'm a gambler if I like the odds, but I lost the bet with those two. You adjusted the valves, ran it, then this happened. You said the valves needed adjusted again when you surveyed the damage. You could check the clearance again to help diagnose what happened. Compare your initial valve lash with those lash readings. How much difference between the two? Again, just HTH. Doug Edit: If you don't have a magnetic drain plug, I suggest you stick a strong magnet to the bottom of the oil pan. But, I suggest you install a magnetic drain plug, insurance. Edited December 11, 2011 by Quidam Quote Link to comment Share on other sites More sharing options...
the sucker king Posted December 12, 2011 Author Share Posted December 12, 2011 Hydraulic lifters? Solid lifters I am told were modified by delta. The pushrods were unlike any I've seen, was told they are the late year hydro pushrods. they did not have the caps on the ends like the others I've seen and no knurl marks. Just a thought about 2 cylinders being affected. The cam shaft only has 4 cams that are shared by opposing cylinders. Sadly there is no quick way to inspect the cam shaft but I wonder if as you have already suggested the cam grind is suspect? This is still my biggest fear, time will tell.... So anyway, here's where it's at- So I got it running again. I re-torqued he heads, replaced the damaged pushrod and rocker arm and adjusted the valves on both sides. Fired it up and let it run for 25 minutes or so. After a few minutes the valves got noisy, but that doesn't worry me so much as I don't have that much confidence in my valve job, having just reinstalled rocker arms on both sides, the pushrods are hopefully nicely seated now in their new homes. I'll readjust the valves and go from there. With it running now, I can take it down to my shop (I rent an industrial space for my business) and park it inside to work on so now i have weeknights to work on my car. Check the make sure you don't have a sticky valve stem. GD How do I check this? ................ Quote Link to comment Share on other sites More sharing options...
the sucker king Posted December 12, 2011 Author Share Posted December 12, 2011 (edited) . Edited December 12, 2011 by the sucker king Quote Link to comment Share on other sites More sharing options...
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