Cavalier 96, Severe Spark Knock

Perfect answer and a GA from me.

He should hope that he has not cracked a piston in the process......usually not, but you never know......pistons can take a big knock.

After rebuilding an engine, I fill it with oil and turn it over by hand several times and then with the ignition disconnected, but plugs in, I run the starter motor to get oil into every nook and cranny.

Then I start the engine.

He would have heard the knocking if he had done that first before starting.............

Will this cure the spark knock? The plugs are the A/c plugs called for in the Hayes manual, but I will check it out. Thanks.

Never ever ever trust specs in any Haynes manual without checking second source. Haynes are poorly researched/proofed/written and illustrated. (And the mfrs don't respect that publisher so are sometimes reluctant to provide them data). Right now (for example) I'm preparing to invoice that publisher for over $500 in repairs (damages) necessitated by use of their manual. What's amazing...if you bring an error (even a totally incorrect (and ludicrously conceived) procedural error) to their attention, they will continue to insist that their procedures are correct in spite of all evidence to the contrary. Even Ford Motor (and, I presume, other mfrs as well) no longer seem to offer Haynes manuals in their parts departments.

I sure have to agree with you on that. If you go to the spec page and look up the spark plugs, they show the same plugs for all years. The only difference is the gap. I went to sparkplugs.com and looked up plugs for 1996 and 1999 Cavalier and they listed 2 different part numbers for the plugs.

Sorry, I was guest with spark plug commet.

I doubt its actually spark ignition knock but rather spark plug collision knock! Your lucky you didn't punch holes through your pistons!

I saw a vehicle in the college auto tech lab room some years ago where some kid put long plugs in his car and then drove them right through the top of the pistons when he cranked it over!

Its been in the back of my mind ever since and I always think of it every time I change spark plugs on anything!

Some vehicles have combustion chambers with enough room for a long plug to fit in and work without problems but many newer ones don't.

First of all , you said you changed the block , does this mean you used the original head ( short block ) or did you change the head too ( long block ) ???

Please be specific , it is very frustrating when folks ask for help but offer little info. for us to go on .

Spark knock is one thing but slamming pistons into sparkplugs is something else !!

Please come back with some detailed info. as to exactly what you have done so far.

I changed out the short block with a used 99 short block. The head came from another engine. The original head from the replacement block, I thought was bad because I had the same problem with spark knock and overheating. Looked at the head and it had some bad wear around the water passages. I figured this was the cause of the overheating and spark knock due to water getting into the cylinders past the head gasket where the wear was. I then found another good used head and replaced the original head and changed the plugs with the recomended plugs from the Hayes Manual and gapped them to .060. The auto parts store also showed these plugs as the correct plugs. They were A/C plugs. The Hayes Manual shows the same plug number for all years up to 2000. The manual also shows different gap settings for different years. So I gapped the plugs at .050 and still had spark knocking so then I set them to .045 but still had spark knocking. I don't think it's a plug problem. I believe it may be a timing issue. When I looked up part numbers for the cam sensor, crank sensor, crank and cam for the 96 and 99 motors, the only difference was the crankshaft part number. Do you think this could be the problem? I don't have any specs on the cranks to compare. I think this may be the problem. Do I need to take the car to someone and get the timing checked and set with a computer? Sorry I wasn't detailed enough earlier.

Timing will not effect piston impacting spark plug and is difficult to understand why only two cylinders would be effected.

Could be a repair were conducted of those two cylinder head spark plug threads, rendering the thread shoulder at an incorrect height allowing the spark plug to extend into the pistons path.

Using a length of wire with the end bent at a 90° angle allowing you to gage the distance between the outer spark plug seat and the inside edge of the combustion chamber and use a dial indicator to measure the distance from the spark plug seat to the top of piston @ TDC.

Does the possibility exist a few small bits of metal or nuts may have found their way into the combustion chambers of cylinders #3 & #4?

Well, those of you that predicted doom and gloom can pat yourselves on the back. Started the car after regapping and reinstalling the plugs and it was running really rough this time. Removed the oil fill cap from the dipstick tube and had severe blow by. I don't think the spark plug deal was the initial problem with this motor. I never had any issues with the plugs bending before I changed the head the first time. The old head was spark knocking before the plug problem. Maybe the plugs were hitting the pistons and not bending on the old head making the spark knock sound, but I don't think so because I could not find any issues with the plugs and I have heard spark knock before on other cars whenever the timing was retarded or advanced to much. I will tear down the motor and let you guys know what I find.

Gees Man , sounds like you have wrenched on this head and block enough , why tear it down again ? If you have severe blow by why waste any more sweat on this motor ? My suggestion is to go to a reliable wrecker who offers complete motors with oil pres. and compression test results on the motors . They also grade motors for sale in other ways to inform the buyer of its condition . The motor you are dealing with is one of the most common ones out there and you should have no trouble finding a solid replacement for your car for $ 3-400.00 .

Keep us informed and ask for help if you need it .

Seems the OP want to do it themselves, the engine's life expectancy is about 250,000 miles and the OP should be able to handle a rebuild.

Possibly a re-configuration is in mind to take advantage of an alternative fuel. The window of opportunity is open...NG fueling points are out there but without knowing the location no help of this nature can be provided.

have you checked fuel pressure egr control and flow timing advance sorry no way to change timing if timing advance is off you have to change controller (computer,ecu,powertrain control module,etc)

I possibly stand corrected.

Thanks to the pin head engineers that cant keep using s good reliable design for more than one year to the next unless held at gun point we are al plagued by the lack of interchangeability of parts from one year to the next on many devices. American made vehicles are some of the worst ones for that.

Very likely you do have a more complex mix and match induced problem!

GTO , you said plugs 3 and 4 where bent flat ? If this is the case you have more problems than timing . I suggest you take the numbers off the head and go to your local Chev. dealer and ask them to identify your head and what plugs go with it . You should do the same for the block. Its sounding like the head and block are possibly incompatible. Are you using the proper head gasket and torquing it correctly .

I also dont understand why only two plugs where bent and not all of them , something dosent make sense here.

Best of luck , keep us informed .

Hey everyone, it was the crank shaft. The reluctor wheel on the 99 crankshaft was timed different from the original block's crankshaft,the timing was off by about 15 deg. This caused the spark knock. Too bad I didn't find out sooner, I could have saved the engine. When I tore the motor down, all 4 pistons had busted ring lands and scored cycl. walls.