Downshift caused backfire then broken engine
 

Took the car out for a quick spin, nothing hard, started fine, warmed up a little at idle then cruised to the highway. The water temp was coming up by the time I was on the on ramp. Jumped on the highway at a casual acceleration came upto 65-70 mph for a 3 miles then got off. Came to a stop at a stop light, left casually when it turned green only to get stopped by the next light 300 yards down. I downshifted the car backfired out of the exhaust (it does this sometimes but I thought it was an exhaust leak) This one sounded different. As I came to a stop at the light something was not right out of the right bank. Engine noise at idle is the same, bu there is a strange sucking sound coming out of the exhaust, like an exhaust leak but not a cracking sound more sucking. I limped it home ~1 mile. I didn't get on it to see if I am down on power but something is not right. Any ideas?
I opened the hood at idle and it looks like some blow-by might be coming out of the valve cover breather (but I'm not really sure).
The engine only has 1400 mile on it and less than 40 hours of run time. I guesing a stuck/bent/not working valve BUT I don't know...

...man it was suppose to be a simple cruise!!

If it's a Keith Craft motor, I'd give him a buzz first before posting. He can walk you through whatever you need to check.

Pull the Valve Cover Off...
 

... and I bet the problem will be obvious.

I agree, pull the valve cover(s).

Look to see if you blew out a piece of the exhaust gasket if you do not see anything in the valve train.

:D

You need a couple of testers
 

Rwillia4 Before you pull valve covers, check out the basics of spark and injector pulse at all cylinders. Make sure that the distributor cap and rotor are OK. Check the center contact for being there. Pull the valve covers after doing this first. I would ALSO call Keith and ask what he wants you to do next?? Did it sound like you lost 1 cylinder or the whole bank went? It's funny that some motors will run on just 4 cylinders. What was the oil pressure in the motor if you got it to start? DON'T run the motor more than 10-15 seconds. If no or low oil pressure, it's internal like a lifter out of a bore or pushrod damage. If pressure is good, fine out which cylinder or cylinders are causing the problem. Again call Keith. You don't want to go from a minor issue to a major destruction problem. Get some guys to help you with these basic checks. 6 eyes are better than 2 sometimes. Get a spark tester and a Noide light to check injector pulse. These are 2 good tools to keep in the tool box for future overnight trips. You can also write them off on taxes too.%/:rolleyes:;) Rick L. Ps if the motor is backfiring when coasting down, it's either a burnt out gasket or a timing issue. If the gasket is blown you will feel it at idle with an air noise. Another tool you may want is a stethoscope. They are great for finding noises and hear sounds and locating them without lossing a finger, ear drum or eye. Just the hose will help you find any air leaks going into or out of the motor.

You didn't lose a spark plug??

Dom

Start simple. I like the spark plug idea!

Brilliant!

Thanks for all the tips. I haven't done anything yet. I want to talk to Keith first. Then I will start simple like spark plug checks, compression checks,... to find which cylinder is bad. Talk to keith again with the results and go from there.

I actually had a spark plug come out before. Made one he!! of a noise.

Terry

Are you sure the headers are tight to the head and the exhaust is tight to the headers? I've had mine loose and it causes nasty backfires. That could be the source of all your noises.

If you want to pull the valve covers, you can visually inspect the rocker arms and pushrods. If a valve is messed up, you'll likely see a rocker arm thats also messed up or not holding it's pushrod.

Sounds like you've gotten good advice on what to check. I know it might sound cool to downshift and use the engine as a brake, but it's not good for the engine. The engine is for go, the brakes to slow down and stop. Just my 2 cents.

Talked to Keith. I inspected the plugs, they were all there and looked good (a little on the rich side). I did a compression test and cyl 1 & 2 were not reading pressure AT ALL. I might take of the valve cover tomorrow, but I'm moving to the east coast from the west coast and my path just happens to take me by Arkadelphia, so I may just stop by KC and have them take a look.

I re-torqued the heads around 600 miles but with two cylinders low makes me think it could be a head gasket but I would expect more issues with oil and water.

It could have blown the head gasket between cylinders 1 & 2 and not show any water/oil cross contamination.

Hence no compression in adjacent cylinders.

Put cylinder 1 on the compression stroke and fill the cylinder with air via a leakdown tester, you'll probably hear air out of cylinder 2.

how does the oil look >? milk-shake or >? coolant system hold 10 PSI >?

-- Steve

Oil and water looks as good as the day I put them in, no milk shake.
I got the car loaded into a 6.5' wide trailer... yes it was tight!! I had a good inch to spare.

John Chestnut, your comment is in great company. That was the basic philosophy of one of the greatest driver/engineers ever to come along-- Mark Donohue.

Stopped by Keiths yesterday. His guys did an amazing job breaking down the engine after they found no compression in 1&2. Once the head was off it was obvious the head gasket was the problem. It "coughed" about 1 inch from #2 into #1. They clean up the surfaces and put everything back together in a few hours. Then took it for a drive to tune it for the exhaust and air cleaners (it was running pretty rich). Now it is all fixed and ready from some summer fun. It wouldn't have happened the direct help of Kendell and Henry. Many thanks to those two for taking the time out of their day to help me out.

...can't figure out why it happened.

Great story of first class customer service!!

I went with a Roush motor, but was very close to pulling the trigger on a Keith Craft motor. He responded to every question I had via email and is a class act.

I was going to say it may be a open stuck valve, as it can be sucked in and will produce a pop sound on the next exhaust revolution. This happened to me once, and it also bent the push rod 90 degrees. The guide was too tight of tolerance. (good lesson)
She sounded like a sick puppy, but still got me home.