Oversized valves discussion

[Blackcrow64]

Ok guys, I donno how many of you had seen my last update but all my intake valves got bent... I'm running 1mm oversized valves with 272 cams.

The problem I am trying to figure out is if there is a clearance issue with running oversized valves. On my pistons you can clearly see where the valves hit outside the top edge of the valve reliefs. The head was ported out and machined to fit the larger valves, however I'm questioning if something else still needs done...

I didn't find much info here about oversized valves, but I did find a good bit on tuners. I don't really like tuners though cause everyone is a smartass there and tells you to search without helping you. I found out that some are running the 1mm valves with no clearance problems and some are. Some have had their blocks and heads decked and that is part of their problem. I don't think anything needed done on mine, so I should still be sitting at factory specs in that aspect... I'm also running the MLS headgasket which adds a slight amount of extra clearance, which was the solution for some on tuners.

I still believe this occurred when the oil pump sprocket broke and it possibly jumped the timing. Although, my dumbass never once thought to check that before taking off the timing belt. I still have my head off and just got my new valves today in the mail. I don't really wanna put it all back together and bend more valves if there is a clearance issue here...

So pretty much I'm hoping you guys will have some input on the situation or some info I haven't read online yet. I've pretty much searched everywhere and have yet to find any direct answers to this type of problem...

I've been looking for another 6 bolt head too in case this can't be corrected and I have throw everything into one with stock valves instead...

Help? lol

[toddman67]

I use moldeling clay to check clearences. Put it in the valve reliefs and install the heads only snug or use an old gasket. Remove the heads and measure the clay thickness with a micrometer or caliper. Don't forget to substract the gasket "crushed thickness" compared to the original gasket thickness. As with many gasket makers, there may be several different thickness gaskets to obtain the clearence that you need.
The correct method here would be to have pistons with reliefs that accept the valve size.

[Blackcrow64]

Ok, I may have to give that clay trick a shot here just to see where I stand with it...

I am using a MLS head gasket so that'll give me an extra .051" of clearance over the stock head gasket. I'm hoping that'll be enough clearance for these valves.