largecar379

while reading my new copy of PCA's Panorama, I stumbled upon a tech question from a 928 owner about sludge in his (928's) oil----4.7L engine.

As you may know, John Venniger is PCA's 928 tech answer guy.

re: 4.7L 928 head gasket change, page 71 Panorama, Jan '08

the questioning went along the lines of trying to find out about changing out the head gaskets and such, but the last question really caught my eye:

"Also, can I install 16 valve heads on my block?"

Mmmmm..........last time I looked, 4.7L engines were equipped with 16v heads....

John went on to reply:

"The 16V heads will fit on your block, but cause other challenges to run. You will need to modify the pistons to achieve the correct valve clearance, and also compression ratio.The intake system will also have to be changed. It would be much simpler to purchase a complete S4 motor vs. modifying the 16V to use 32V heads"


This is either a case of lousy editing by the staff of Panorama, or somebody has got their engines/heads all mixed up---------hopefully not the owner needing the help, and hopefully not John......


I sincerely hope that John didn't make this mistake, as he is a well respected, knowledgeable member of the 928 community.

Just goes to show, sometimes you can't trust what you read. Maybe John will read this, review what was printed in Panorama and correct it in the next issue.

--Russ

Tom. M

Well...in the old 4.7 motors...each head has 8 valves..for a total of 16...now the later 5.0 liter cars have 32 valves..eg. 16 valves per side...

Later,
Tom
89GT
82 Track car with 16 valve heads on each side..

John Veninger

Think the misunderstanding is when we take about a 16V motor vs. a 16V head.
The S4 engine uses heads with 16 valves. The 4.7 and earlier engines uses 8V heads. When you add it all up, you get a 16V motor and 32V motor.

This part of your quote is not what was written:
This is what was written:
" Would be much simpler to purchase a complete S4 motor vs. modifying the 4.7 to use 32V heads."

Charley B

Sorta True. But each head had 8 valves making it a 16V engine.

I think the questioner was asking about installing heads with 16 valves per head, and that is the way John answered it. His response could have ended with "16V heads" to be slightly more accurate but I think most people understood what he meant.

atb

You're not alone Russ, I had to read that through a couple of times before I caught on as well on the 16v motor vs. 16v head distinction .

Mike Frye

I read it to mean he was trying to upgrade, since he was starting out with the 16v OB motor, the question only made sense that he was trying to 'upgrade' (sorry OB owners ) to the newer heads.

Great answers John, I've seen your name on there, but I think most people with 928 tech questions don't want to wait for the next pano to come out so they just go here. So you probably don't get as many inquiries as some of the other technical advisers.

John Veninger

Mike,

The volume on the 928 questions is way less than the 911 guys. Either due to volume of cars or maybe they just have more problems

You would not believe the amount of folks that call me or write an actual letter!
Many do not go to websites, are challenged by email, and some are not on-line at all.

The Q&A in Pano is generated by the questions from the web site. Questions asked are answered and emailed to the person asking the question and anyone else subscribed to the Tech group.

So if you would like to see Q&A before it hits Pano, subscribe to the Tech group
http://www.pca.org/tech/tech_qa.asp

Mike Frye

Aha! Thanks John.