edwardb
06-20-2015, 04:08 PM
This is one of my "Ask me how I know" moments. If you want, I can save you some time reading this thread by just saying read and follow the directions when installing your AFR heads. But if you don't read them closely enough (like I didn't), here's the whole story.
This is about the AFR #1388 185cc aluminum SBF Renegade Heads I installed on the DART 347 in my recently completed Mk4. From the very beginning, I detected that I had a potential oil consumption issue. At first I just monitored, hoping it was a new engine break-in issue. After a few hundred miles and no change, decided to dig deeper. The symptoms were lowering oil indication on the dipstick, occasional puff of blue smoke from the exhaust mainly at startup, and signs of light oil fouling on all eight plugs. Nothing terrible, and mostly not noticeable. But clearly not quite right.
DART blocks are known for having a lot of oil in the top end (maybe too much in some cases) so my first thought was I was pumping oil through the PCV circuit. I confirmed the valve covers were properly baffled, and then installed a catch can/oil-air separator to see what might be happening. Confirmed this was not the issue.
Fearing the worst, I pulled all the plugs and did a compression check. The results were excellent. Strong numbers within just a few pounds across all cylinders. What I would expect from a new not inexpensive motor. Granted something could be going on with the oil rings and still have good compression. But decided to keep looking.
My next thought was valve guides and/or valve stem seals, since the symptoms were consistent with a problem in this area. Not something I would expect with brand new heads, but decided to check anyway. Pulled a couple rockers and valve springs. Seals looked good and no discernible play in the valve stems. So did more digging, and found this statement in the instructions: "*WARNING* ROCKER STUDS ARE INSTALLED FOR SHIPPING PURPOSES ONLY! THESE STUDS MUST BE SEALED AND TORQUED TO 60 FT/LB. BEFORE RUNNING THE ENGINE." Emphasis on sealed is mine. Guess what I didn't do? I used some anti-seize when I installed the ARP 7/16 inch studs, but no sealant. Oops. Checked further and found that on these heads, typically the hole for the rocker stud on the intake side penetrates the head, e.g. is open underneath the top of the valve.
So, yesterday I went through all 16 valves, removing the rockers and studs, and sealing them with ARP PTFE sealant. Not a small job. Confirmed, as expected, that the intake side stud holes did in fact penetrate the head. All 8 intake stud threads were wet with oil. The anti-seize I had used during assembly was completely washed away (unlike the exhaust side) and there were clear signs of oil flow. I had ordered new valve stem seals (only .87 each) and since I was 90% there, went ahead and replaced all those too. But likely wasn't necessary. Put everything back together and reset all the valve lashes. Cleaned up the plugs and confirmed the gaps. This morning I did a 60 mile or so cruise down to a Saturday cars and coffee. Clearly a difference. No blue smoke. The car was running really good before, but the difference is noticeable. I guess oil added to the intake cycle is not a good thing. Pulled #1 plug after back home and it was cooled down. Plug was clean and dry, with zero signs of oil. I know that's not many miles, but I'm positive I found the problem. Before it would already be wet with oil. My final punch list item for the new build is finally signed off. Now off to London next week.
I don't know if this is common with other head brands, or even any other size AFR heads. Or maybe you experts out there are shaking your heads thinking everyone should know rocker studs need to be sealed. I didn't before, but now I do. Regardless, the moral is the same. Read the directions!
This is about the AFR #1388 185cc aluminum SBF Renegade Heads I installed on the DART 347 in my recently completed Mk4. From the very beginning, I detected that I had a potential oil consumption issue. At first I just monitored, hoping it was a new engine break-in issue. After a few hundred miles and no change, decided to dig deeper. The symptoms were lowering oil indication on the dipstick, occasional puff of blue smoke from the exhaust mainly at startup, and signs of light oil fouling on all eight plugs. Nothing terrible, and mostly not noticeable. But clearly not quite right.
DART blocks are known for having a lot of oil in the top end (maybe too much in some cases) so my first thought was I was pumping oil through the PCV circuit. I confirmed the valve covers were properly baffled, and then installed a catch can/oil-air separator to see what might be happening. Confirmed this was not the issue.
Fearing the worst, I pulled all the plugs and did a compression check. The results were excellent. Strong numbers within just a few pounds across all cylinders. What I would expect from a new not inexpensive motor. Granted something could be going on with the oil rings and still have good compression. But decided to keep looking.
My next thought was valve guides and/or valve stem seals, since the symptoms were consistent with a problem in this area. Not something I would expect with brand new heads, but decided to check anyway. Pulled a couple rockers and valve springs. Seals looked good and no discernible play in the valve stems. So did more digging, and found this statement in the instructions: "*WARNING* ROCKER STUDS ARE INSTALLED FOR SHIPPING PURPOSES ONLY! THESE STUDS MUST BE SEALED AND TORQUED TO 60 FT/LB. BEFORE RUNNING THE ENGINE." Emphasis on sealed is mine. Guess what I didn't do? I used some anti-seize when I installed the ARP 7/16 inch studs, but no sealant. Oops. Checked further and found that on these heads, typically the hole for the rocker stud on the intake side penetrates the head, e.g. is open underneath the top of the valve.
So, yesterday I went through all 16 valves, removing the rockers and studs, and sealing them with ARP PTFE sealant. Not a small job. Confirmed, as expected, that the intake side stud holes did in fact penetrate the head. All 8 intake stud threads were wet with oil. The anti-seize I had used during assembly was completely washed away (unlike the exhaust side) and there were clear signs of oil flow. I had ordered new valve stem seals (only .87 each) and since I was 90% there, went ahead and replaced all those too. But likely wasn't necessary. Put everything back together and reset all the valve lashes. Cleaned up the plugs and confirmed the gaps. This morning I did a 60 mile or so cruise down to a Saturday cars and coffee. Clearly a difference. No blue smoke. The car was running really good before, but the difference is noticeable. I guess oil added to the intake cycle is not a good thing. Pulled #1 plug after back home and it was cooled down. Plug was clean and dry, with zero signs of oil. I know that's not many miles, but I'm positive I found the problem. Before it would already be wet with oil. My final punch list item for the new build is finally signed off. Now off to London next week.
I don't know if this is common with other head brands, or even any other size AFR heads. Or maybe you experts out there are shaking your heads thinking everyone should know rocker studs need to be sealed. I didn't before, but now I do. Regardless, the moral is the same. Read the directions!