TR2/3/3A TR3...Mild street cam....valve gap?

[karls59tr]

I'm running a "mild street cam" on my TR3. I was told to run .016" for the valve clearance. The stock spec is .010" intake.....012" exhaust. Anyone running a modified cam? What do you set your valve gap at? I dont have the exact cam grind specs handy but I'll try to find it in my papers. Apparently its a very common cam grind for "street" to give the car some extra grunt.

 

[martx-5]

"Who" told you to set the valve clearance at .016"?? If it was the cam grinder, then that's what you set it for. Each manufacturer has it's own specs for each grind. If it was your buddy down the street who told you to set it at .016", then I would call the cam grinder or whoever you got the cam from to verify what the clearance should be.

 

[JFS]

Art is right on!

 

[karls59tr]

Well the cam grinder ,Shadbolt cams from Vancouver said to set the gap at .016" and I have no doubt he's correct. But are cam manufacturers familiar with 40 year old brit motors? I was wondering if any TR3 owners on this site had experimented with valve gap to find optimum gap and where they had there's set at.

 

[swift6]

I think its pretty common for reground cams to have larger gaps. My GP3 regrind from Goodparts calls for .017-.018 gap.

 

[TRTEL]

Karl, As much as anything the larger gap assures that the points of opening and closing are matched as much as possible. Which is to say the more you close that gap the more likely you will encounter variations on the profile of the cam lobes. One intake might open a degree or more before another does. If you want to take the time to experiment pull your plugs, take all the gap out of the rocker arms on the backside of the cam lobes (just twist the adjustment screw very lightly till contact is made), use a dial indicator to detect open and closing, turn the engine over slowly by hand with the fan and mark the open and close points on the pulley. I used to use typing 'white out', that stuff's probably history. Out of four cams on the shelf in the garage, two ( an Isky and a Triumph D are pretty accurate though not perfect but the other two really do need that extra gap the allow all cylinders to breathe equally. On a rolling road dyno decades ago, we never saw anything in the way of significant output changes from making minor changes in the valve clearances.

Tom Lains
TS8651 & 58107

 

[karls59tr]

So .016" for all intake and exhaust would be way better than the stock .010" that I set them at after the rebuild? My car had lots of power but I got the feeling that when I let off the gas it seemed to run rough. I have heard that at idle with a modified cam it will never idle smoothly. The car pulled strong after about 3000rpm. I've got about 100km. on the rebuild and new cam so I think in the Spring I'll open up the valve gap to .016" and see what happens. Karl

 

[Simon TR4a]

The cam in my TR4a is "not so mild", and Kent cams specifies clearances of 22 thou. intake and 24 thou. for the hotter exhaust valve.
It seems extreme, to the point I thought it might be a misprint and sent them an email to ask, but they confirmed it is correct.
Simon.

 

[YankeeTR]

The old Corvette FI cam was called a "30-30" as that was the specified valve clearance...