i was planning to run 2.055/1.60 valves in my 5.3 heads for my new motor. i took them to a machine shop today and he told me he wouldn't be able to put in 2.055 valves that there wasn't enough room for the valve to clear the wall. after i left i called smc performance and he said he had a set of 5.3s sitting in his shop right now with the exact valve sizes i need. what gives? he should be able to machine the 5.3s to accept the 2.055 valves right? will they need new valve guides/ valve seats or anything like that? or should i just get a set of ls1 heads and forget about the 5.3s?

 

I'm not an expert on 5.3, but I believe the bore is just under 3.8", and some would agree that 2.055" intake valves are getting big on the 3.9" bore that the LS1 engine has. I could see where he might have some reservations about it, but I woulnd't say it's not possible.

I would ask if you were putting these heads on a stock bore, or a modified displacement engine, if so, I would probably steer you towards a smaller valve. I would probably want to know more about the buildup before I gave a strong answer.

 

The machine shop that I use, said that anything bigger than a 2.02, would not leave enough meat on the seat. It will cause the edge of the seats to crack and finally break.

 

the motor is a 6.0 block with a .030" bore. i guess i could have him do the extra machine work needed to fit the 2.055" valves, it wont really be that much more(100ish.) guess i have a decision to make.

 

When I did my 5.7 heads, I had the shop compleatly remove the factory seats and replace them so I could put larger valves in. This protects against my seats lossening over time. You can usually get away with the next size up valve in the factory seat but thats about it.


Chris