Leaderboard

It will be interesting to see if your order gets canceled due to them being out of stock. Keep us posted.

To put the sidetrack about airflow anomalies to bed, I just did a couple of things I should have done before wasting everyone's time. First, I arbitrarily clamped the intake valve at .400" lift, close to the maximum of an '89-'90. Nominal valve lift for intake is .400" '89-'90 and .433" for '88. I ran both the untouched head and the ported head on the bench and the results are much more in line with expectations. Untouched head, 160cfm on the dot, ported head, 175cfm, a useful increase without a lot of work. I then pulled out my records of the last heads I did, the '88's I received from Daves89. That was a more serious porting attempt, partially due to rust issues, but with just a scrape and brush of the intake port, .400" flow was right at 160cfm, after porting, there are several readings of 182-185cfm at the same lift as I was experimenting with back cutting valves. There are also notes about the port with no valve, just as I have been doing now. Result: stock 194, ported 202.🤢

I also found them in stock here for $7 less. I went ahead and ordered 2 because I will need to replace mine sooner than later. There were some other GM parts sites that were labeled as "discontinued" so there probably aren't many of new stock still out there. https://www.gmpartsonline.net/oem-parts/gm-shock-absorber-19166882?c=Zz1yZWFyLXN1c3BlbnNpb24mcz1yZWFyLXN1c3BlbnNpb24mbD0xMCZuPUFzc2VtYmxpZXMgUGFnZSZhPWJ1aWNrJm89cmVhdHRhJnk9MTk5MCZ0PWJhc2UmZT0zLThsLXY2LWdhcw%3D%3D

They actually have them in stock here it looks like: https://www.gmpartsstore.com/oem-parts/gm-shock-absorber-19166882?c=Zz1yZWFyLXN1c3BlbnNpb24mcz1yZWFyLXN1c3BlbnNpb24mbD0xMCZuPUFzc2VtYmxpZXMgUGFnZSZhPWJ1aWNrJm89cmVhdHRhJnk9MTk5MCZ0PWJhc2UmZT0zLThsLXY2LWdhcw%3D%3D

I did take the bench unit apart to check for the correct measuring orifice and look for a stray mouse nest and everything looks just fine. A few fasteners could be snugged up a bit but nothing out of the ordinary found. Tried both heads on the bench again and going back and forth between them a couple times the results repeat so that is a positive. Ordinarily I test with the valves in place and go through the lift progression, so the large increase in flow without valves made me question myself. Below is a pic of an intake valve inserted into my 200cfm calibration plate. It is a knife edged hole in an aluminum plate, dimensions are on the plate. Our intake valve nominal size is 1.72”, so it almost passes right through the orifice plate with only the valve margin showing. It graphically illustrated to me that a hole that size is capable of the flow rate I am seeing. In any case, the only item limiting air flow through the intake valve opening into the chamber is the valve stem. Indicated flow is 196 cfm that increases to 200cfm if the valve stem is withdrawn to be flush with the valve guide. At some point I will go through the calibration process on the bench but at this point I am confident it is working consistently for my present purposes. With that in mind I copied my original reshaping to the other two intakes in the first head. One other item for the heads is to see about reshaping an old exhaust valve to use as a tool to narrow the exhaust seat.