Rebuilt my m20 and oops???

[Bmr]

So my plan was to rebuild the motor and put a cam in the head.

Had the head decked just below max clearance. I think 18 thousand was shaved off. Pretty close. Head was tanked and other stuff.

Put my nice shrick 288 cam cam in. Actually was my seconds cam first one i opened the ups package and dropped on the floor. Broke in half. Oops. lol

Bought this adjustable cam gear for the head since I'll need to change the timing a little now.
Check the block, pistons were good block was flat.


I decided to do a little painting while the engine was out. kinda random paint scheme i guess.



After this i put the engine in the car and got it going. Ran great over the weekend. Man that cam made the car sound mean!

[CHIF8008]

glad she is running good. hope that white wasn't a poor choice in color

[Bmr]

So on my way to work the following Monday I get on the freeway and just as i hit the 70 sign i give it a little gas, not 10 seconds later, i heard breaking and the car died. Luckly i was able to coast the the off ramp and get a tow truck to the shop. I pull the sparg plugs to find this???



That is one fubared spark plug!!! So i pull the head to find this

OH hey valves, glad you could hang out.
Then i turn the head over to see this!!

Carnage!!!!

Blocks still good, minus this hole n stuff.


!!!!!!

[CHIF8008]

spoke too soon. :( sorry to hear man. guess 18ths off was too much. maybe should have used a thicker HG?

[Bmr]

spoke too soon. :( sorry to hear man. guess 18ths off was too much. maybe should have used a thicker HG?

Live and learn. I'm not sure what exactly happened. Was using a thicker head gasket from VAC. Had the cam gear adjusted right. Car ran great for 2 days before hand, tons of power. Was running miller maf conversion with 19lb injectors and chip.

[mbonanni]

oh no man ):

[PNWDan]

Live and learn. I'm not sure what exactly happened. Was using a thicker head gasket from VAC. Had the cam gear adjusted right. Car ran great for 2 days before hand, tons of power. Was running miller maf conversion with 19lb injectors and chip.

Almost looks like the timing belt jumped or the gear moved judging by the marks in the other piston(the one without the hole)

sucks man

[whodwho]

Almost looks like the timing belt jumped or the gear moved judging by the marks in the other piston(the one without the hole)

sucks man

From valves touching pistons

"Had the head decked just below max clearance" + "Put my nice shrick 288 cam cam in" = "Carnage!!!!"

That is a big cam and would need the piston to valve clearance checked ;)

[digger]

schrick 288 has about 1.5mm to 2mm additional lift at TDC and just eitherside compared to stock, there is a reason why certain members always recomend checking PtoV clearance..........

[LJ851]

schrick 288 has about 1.5mm to 2mm additional lift at TDC and just eitherside compared to stock, there is a reason why certain members always recomend checking PtoV clearance..........

Truth. When building a non stock engine there are many things to check or you can roll the dice as you did....

[jlevie]

Since the engine ran fine for a while, my guess is that your adjustable cam sprocket moved. Which is something I've seen happen before. I won't use one and if cam timing needs to be adjusted I'll make an eccentric bushing to go into the cam sprocket. There is no way that can slip.

[digger]

Since the engine ran fine for a while, my guess is that your adjustable cam sprocket moved. Which is something I've seen happen before. I won't use one and if cam timing needs to be adjusted I'll make an eccentric bushing to go into the cam sprocket. There is no way that can slip.

could also be that it was so close that as things loosened up, timing belt stretched a little under load, even a lack of valve control caused a kiss, tipped it over the edge.

Did the OP check PtoV? what valve springs?

[TobyB]

If you didn't check valve- to- piston clearance, that'd be my vote-

they CAN kiss for a while, then... well, my condolences, anyway, that sucks.

t

[e30trooper]

For every ten thousandths of decking you retard the cam 20 degrees. SO you should have went 36 degrees retarded so you dont have valve slap.

I still need to do this. I had my head decked ten thousandths and have my cam on TDC. SO far i dont hear shit but still better safe than sorry. Reason why you have an adjustable cam gear o_O

[jlevie]

For every ten thousandths of decking you retard the cam 20 degrees. SO you should have went 36 degrees retarded so you dont have valve slap.

I don't know where you got those numbers, but they are way too big. If you deck the head to the max (bottom of the limit dimples) offsetting the cam sprocket index pin 3/16" will bring the cam back into time. That is way, way, less than 20deg.