Expert Engine Builders Part 2 - Brain Teaser

[Jerryl]

Exhaust valve spring retainer bottoms out around 0.435 travel
Cam spec: 0.456 lift with 1.55 rockers.

Stock rockers and retainers installed
Installed height 1.660 (Spec 1.700) for Comp 980’s

212/212 Comp Cam
Cam lobe lift verified to be correct at 0.2930

So the correct install height will give 0.040 additional valve travel before bottoming out resulting in 0.020 clearance between the retainer and valve guide. (Too tight right?)

Valve train geometry is correct and lifter pre-load is all 0.030-0.040.
(Should not effect this measurement at this point.)

Had a constant radius valve job done on the heads and stock valves are installed.
Someone who installed 1.65 rockers must have had similar issues.

According to GNTTYPE stock specs are:
Advertised Duration : 258/262
Duration at .050" lift : 192/196
Lift .384/.408

First question; “Why” do you think this is happening with stock parts and “replacement cam”? (Hot Air heads set-up for different lift?)
Second question; Anyone know which retainers I can use that have about a 0.050 offset?

 

[turbodave231]

The picture looks like you have replacement guides. If the bottom of your retainers are hitting the top of the guides, machine the top of the guides down. Any competent machinist can do this. Problem solved?

Dave

 

[Jerryl]

The picture looks like you have replacement guides. If the bottom of your retainers are hitting the top of the guides, machine the top of the guides down. Any competent machinist can do this. Problem solved?

Dave,
Thanks for the response.

I know for a fact (from doing the bowl work) that these are not replacement guides.

Anyway ....... Went out to take a picture fpr posting ..... and remembered ;
The machine shop had replaced the retainers ...... So I replaced the retainers with the ones form my spare head ....
Installed height is now 1.740 (Hard to see the difference in the picture)
Think I got it and on to the next opportunity! :biggrin: Thanks!


Edit:
Note the open garage, the sunshine and 70 degree weather Jan 7, 2006.

 

[Jerryl]

Thought I would post this pic. You can clearly see the difference (About 0.040). Could have REALLY messed up a new motor with a "drop in cam"! Proves again you can NEVER EVER take ANYTHING for granted with these motors. Hopefully it can help someone someday.