In a recent thread I noted that the ports on my 1.7 turned 2056 heads are 47x37.5mm. I don't know what the valve size is.
Is the valve size usually the same size as the port, or smaller?
The heads are installed and I don't want to remove them unless I need to, but the engine is about to come out for conversion to EFI. The engines PO had the headwork done and I don't have all his notes.
If the valves are the same size as the ports I am going to pull the heads to have proper fitted valves for my engine.

Would too large a valve size lead to higher head temps? The PO said when I bought the motor that it ran warm and I have noted this myself even after rebuilding the bottom end in 2009. Its manageable but I do have to take care climbing hills on the freeway.

Hi Zach, just got back to the computer and got your PM.



A properly sized intake port will be ~ 85% of the diameter of the valve.

Those port sizes sound extremely large, and very unlikely to me. They are probably valve sizes. A 47mm intake port would be appropriate for feeding a 55mm valve.

Hey Zach,

Did you get your car back from Tony yet??

Its in my garage.
I need to get the engine dropped.

Zach

Not to make you roll your eyes....
BUT

47mm intakes may explain many of your issues.
The heads and 2056 displacement cant support that....and it will make tuning it very hard.
You may really want to look for the notes, or pull a head and take a look.

I thought you rebuilt this at some point in time???


Rich

You and me both, I need to get the 2056 put togeather before I try to drop mine. Im running out of room in there

Take a picture and show us where you're measuring.

Rich, I rebuilt the entire bottom end in 2009. I did not touch the heads as the PO had them done not long ago at a shop in VA. I SHOULD have rebuilt them at the same time. I agree, if the valves are as big as my notes seem to indicate that could be a key to the running issues I have been having.


I will. Is it not obvious where I should measure the valve diameter?

Zach

Nah, just one of those, checking the basics first things.

Theory...

n/a engine: ports should taper down from the port opening to the valve. This increases velocity as the air travels into the cylinder. Added velocity helps the mixture and speeds up the intake process.

Forced Induction: Ports do not need to taper. Ports should be as large as possibe to help flow the forced air into the cylinder.

True; til you get to the short turn radius and bowl area beneath the valve. 1.8 & 2.0 914 intake ports twist rather than taper as a way of enhancing mixture quality. That is a method that has gained much popularity with the high-end V8 race head crowd.



That is a popular misconception. The dimensional relationship between port and valve is still critical. The intake/exhaust flow ratio needs to be increased to around 85% for turbo engines as compared to around 75% for NA engines.

And....
Bigger is far from better. Finding "just right" takes about a decade.

I finally pulled the heads off the motor yesterday.the intake valve measure at 45mm. Looks like I need to rebuild them.

*grumble*