Valve Adjustment Method For Duntov Cam
 

I need the correct and most accurate method for adjusting valve lash on my '61 283 with the Duntov cam. I have heard that it differs from other solid adjustments. Thanks

Its the same as the rest, ICE-EOI.....:cheers:

I thought the Duntov 30/30 should be adjusted running after the engine is warmed up. I think there is another way but it seems it isn't the standard TDC adjustment.

Wally, Just so I understand the abbreviation. ICE= Intake closed adjust exhaust. EOI= Exhaust open adjust intake. Correct?

Here is what I use...all the time with NO problems or hassle. You only have to move the engine twice. This works perfectly for the Duntov cam...the 30/30 cam is a different matter because of the grind on the lobes..

If you want the MOST accurate then you have to adjust the lifters "hot" ... meaning with the engine running and oil splashing everywhere...good luck with that..

Yes,

It will put you right on the heel of the lobe your adjusting. The lash is a little controversial on the 097 however. I know its been mentioned as 12-18 but I seem to recall 08-18 somewhere..... but its been a long time since my 61 was around.

The first two sentences in the document I attached above explain the valve lash change in specs on the intake. It was supposedly tightened up for 'weekend racers'...

Thanks Wally and Frank! Great illustration on the Duntov, Frank. :cheers:

I took this out of the Vette Vues Magazine about 20 years ago. If you can read it, it's the easiest, clean easiest and almost fool proof way to adjust your lifters. I takes about 10 to 15 minutes. I've been using this for years on my 65' 365hp.


http://i25.photobucket.com/albums/c9...Adjustment.jpg

Enlarged it a little but this is the way I do it as well.

Works great. :thumbs:

http://i242.photobucket.com/albums/f...justment01.jpg

Basically, the same method that I use except you are turning the engine over more.
Its also prob harder to hit exactly 180 deg from TDC if you don't have timing tape around the balancer than just hitting TDC twice where it is clearly marked.

Believe me I've tried different methods and mine is the simplest, especially if you don't have the big bolt on the front of the cranshaft pulley to help turn the motor easily (which I don't) !!
I have to 'bump' the starter and then bust a gut on the generator fan belt to get the motor positioned just right so moving it only twice makes me very happy.

TDC does not put the lobe on the base. Best method is the "opposite" from full lift. For example, to adjust #1 intake you bring #6 intake to full open position, then adjust #1. You match the opposite in firing. Use the following. Works the same for both intake & exhaust, i,e, adjust #1 exhause when #6 exhaust is at full valve lift. You can work around in the normal firing order, just go to the opposite.

1 - 6
8 - 5
4 - 7
3 -2

Other methods get close, but not at full base of lobe

Check this link out...very good info

http://www.lbfun.com/warehouse/tech_...n/SBvlvadj.pdf

I'm telling you that if you don't have the 30/30 cam then the method I use is as accurate as any other except a hot valve lash adjustment.

I have done it this way and then went through the agony of measuring lash with the car running and hot and it was dead on.