I ran my valves from 20/10 to 18/8 yesterday. Are there any downsides to running them tighter? I'm very impressed with the improved throttle response, especially around town. A quick run to the governor in 3rd reveals a much happier engine above 2200. Now I'm thinking cam thoughts

 

I don't know about these engines but on a gasoline engine you would risk a burned valve. I have heard of people adjuting them tighter on our engines but have been chicken to try mine.

 

No personal experience here but I thought wanna said something about doing this and getting better top end and response like you said. If it's ok with him, it's ok with me

 

Just keep a close eye on them.

 

Will do, Dave I've got about 100 miles on the adjust and it really does help with driveability and max boost. For as much as I 'want' twins, I'm thinking I'd be $$ ahead with a cam and a 'good' single. I hear that holset H1/HX series are old tech and that, for instance, an S300 variant would be far more efficient, even given similar dimensions. Thoughts?

 

sorry to ask on this thread, but didnt wanna start a new one. I'm not sure when the last valve adjustment was done on my truck, so I probably need to do one soon. Whats the difficulty on this, etc. also, how much will I benefit and how?

 

Greg, there's no substitute for airflow. The guys I've talked to who sell both of them say that the cam is a good complement to the big single or twins, but not a substitute.

DieselSmith, the valve adjustment info is in the sticky at the top of the 1st gen page.

 

Going from the recommended 20/10 to 18/8 should hurt it a bit. I wouldn't go much tighter than that if you have a daily driver or working truck as you risk burning a valve or hurting the cam. Fortunately these engines have fairly heat stable materials in the overhead, so they don't expand and contract as much as other materials so 2 thousandths shouldn't cause any problems.

 

I understand how tightening the valves could increase performance but I can't figure out how it could cause burned valves? Is it because they don't contact the seat in the head for as long to dissipate heat?

 

As every thing get hot, the 20/10 gap gets smaller and if it gets hot enough or the gap is set to tight(valve adj is set with a cold eng)the the valve is held sightly off its seat, or open causing a torching affect on the valve and seat.


With that said, i thing 18/8 is safe............if it's your first time adj valve, I would stick with the .020 ex. and .010 intake!

 

I've been told that .0085 is ideal for the intake, and lacking a .0085 gauge, I just run .009 and .019. I noticed little differences, nothing huge, but 30-50deg reduction in EGT, a psi or more boost, etc.

Daniel

 

Yeah, always adjust when the engine is stone cold. I know mine was, as it was 35 degrees out when I did it...brrr! I set it to a pretty loose 8/18, just to be safe, but it was also set at a loose 20/10 as well, so I sure I'm getting the full 2 thousandths benefit.

 

I can't find it! but there is a spec out there to check the valve to see if thy need to be adj, that said some thing like.......don't quote me but seam like if the ex. valve was between........ .018 to .022 and the the intakes was some thing like .008 to .012.


The 10 and 20 were middle speck

 

.006 and .015 and still running.

 

When i had my valve springs installed my buddy went ahead and set the valves at .08 and .18. No problems at all so far.