bigdsz

iTrader: (1)

I want a bigger cam but I think I'm screwed, when I put a dial indicator on the top of the valve stem and zero it when the valve is resting on the piston, and then lift the valve up into it's seat I only have .175". I now have a TR224/224 .563/.563. How am I going to fit a bigger cam with that close a tolerance. I have AS 5.3 Stg 2 heads 11/1 CR with 978 springs. The other bad thing is the spring install height should be 1.850, it's only 1.830 on the intake and strangely 1.870 on the exhaust. What could be the reasoning for that?

MichLT

When the heads were machined for the larger valves on the intake side they weren't "sunk" enough. Usually if a shop opens the seats up just enough for the seat to come in on a 5.3 the valves will sit ~.050 low.....I think the .040 difference you're seeing falls in line. Probably one of the reasons so many people think that 2.02 valves in 5.3s have P/V clearance problems....It's not the fault of the valvesize....It's how the valvejob was done..

CAT3

iTrader: (9)

Take your .175 and subtract the difference b/w cam lifts new - current and you get your final clearance.

My cam with your specs for example.
Intake Valve (thats all you gave right?)
.6307 my cam
- .5630 your current cam
= .0677

.1750 clearance
-.0677 difference
= .1073 Thats quite excellent still actually.

So you can go with way more cam, but you have to consider the duration and events as well. Above was just a mathmatic representation based off increasing only your lift.

Good luck,

Charlie

bigdsz

iTrader: (1)

My problem is the cam I want to install is 228/228 .588/.588 112+2. My TDC measurement is .175, I am told by one of the sponsors that I need a minimum of .200 for safety. I guess that includes the minimum .080 for intake valves.

Mike TexaSS

iTrader: (2)

Actually, PTV needs to be checked on the intake side 8* - 12* ATDC and PTV needs to be check on the exhaust side 8* - 12* BTDC.

GueSS Who

228/228 will fit fine.

bigdsz

iTrader: (1)

Mike , I totally agree, however how do I know if the new cam will fit unless it's already installed. I plan on degreeing and checking clearances ~ .010 ATDC. My dilemma is I want a minimum of 228 .588 on the intake side but with my clearances will it fit?

bigdsz

iTrader: (1)

GueSSwho, I appreciate your support more than you know, can you give me hard numbers how it will fit ? This is absolutely driving me nuts, Ijust hate to buy the cam to find it Ain't gonna work. My wife is already really pissed at me about the money I've already wasted on mods that produced poor results.

racer7088

YOU need to look at the lift at TDC and multiply that by your rocker ration and then subtract that from the free drop data you measured. The valves are closest 10 BTDC on exhaust and 10 ATDC degrees after on intake. Most lobe cataloques show your lobe lift at TDC at at least two centerlines.