what could cause the valve seats to brake? this is the second time that one of them brake. the frist time I lost the engine, when some of the seat small pieces(after onley small piece broke(about 1/4 of an inch)) fall down and hit between the cylinder head and the piston and brake the head to the water port and the piston crown. then scrach the cylinder wall.
the seats were machined twise before the first time when they did the usual stone miling. the scond time with my rebiult when I asked for 3 angle job.
after changing the short block and one head the old head broke down.
in both times intake valve seats broke.
could it be that they mix out these two valves when the install them.(they still hand lap the valves when they install them so they should find out that they wont seal because of the marks the laping make on the seats)
I have cca 306 cam + 1.6 roller tip rockers with cca dual springs and no shims at all under the springs. they use to be with shims on the first engine(so I don't think it's excessive seat pressure caused by the springs)
on both engines I use to get the rocker arms spin around the valve tips untill I install guide plates.(what cause this too)
just ignore my comments and tell me what the **** is wrong
both engines have less then 2000 miles

 

The valve seats doing what they are doing is being caused by overheating or sustained high-speed driving. I know that some of the the higher speed roads in the ME are "lightly patrolled" if you are driving 120+ for hours at at time there may be high heat loading of the seats causing them to break apart. You may need to get a better cooling system or harder seats. If the car gets over 220 at high speeds, you need a bigger radiator.

You need to be kind of careful with the seat pressure as well. It should be no more than 120 PSI with that cam setup. If you are putting too much pressure on the seats you could break them. Give us some more details....

Good luck and Salaam.

David

 

Thanx David for reply
the car never over heats before only when Ihear it clicking for the second time and saw the water coming from the exhausts. the car were Idling when I just start it then
since those were new engines I never do more then 70 miles even my plans were to race it mostley and drive it to car shows only and the race (wich never happen
I got 12.2 cc pistons that I did not reprogram for it yet and the engine were knocking alot. on last engine I have 10.4 cc with the engine programmed for th 306 with no knockig and it did it.
I did full porting my self at home and I hit the seats down to the bowl area when I was porting. may that cause them to brake apart
I did step by step what it says at this link
http://www.sa-motorsports.com/diyport.htm
tomorrow i will take some pics and post them
if you need more info please ask

 

hear are the pics
http://www.geocities.com/amjadalgaro...nderheads.html

 

please help me, at least post any reply to keep the topic at the top. I want as many people to see it to help me. it is 1:34 am lockal time and I dont know the best time to post.

 

thi is the fourth day please help. new pics link http://www.geocities.com/amjadalgaro...alveseats.html

 

That's an unusual problem. Not sure what to tell you, but this will bring your post up to the top.

 

Technically, the valves never slam on the seat.

Maybe your heads were a bad batch?

I used to race big block Mopars and had that problem. I bought some heads and was running 11.3's first time out. Then I started to lose ET for no reason. Pulled the motor and the seats were crapping out on me. Junk seats were the problem. Fixed it and ran low 11's after that.

Hope it might help.

 

bleave or not that almost what happend to me. when I start it it runs low low 12s N/A then it start loose pwoer. the seats were stock.
a freind told me today too tight rockers may do it is he right on that.
I don't know may be the rokers wre tooo tghit.

 

Are the springs sitting on the castings or are they in cups to prevent walking. If they arnt in cups maybe your valve guides are worn allowing the valve to wobble....just a thought I may be way off.