Another QV engine nearing completion

That looks like a fun and nicely detailed project. May I ask about the pistons. Are they the stock 81mm bore? The reason I ask is if the sleeves are bored oversize, did you re-apply the nikasil coating?

I ask because I have a Qv engine torn down and am contemplating the next step. Thanks.

CJ

 

I am really interested in what you did here. Thanks for the thread.

One thing that impresses me more than I thought it could is a proper flow adjustments on the intake side of an engine. My Alfa Spider's head was set up by Sperry back in the 90's and my Scirocco's 16V by Techtonic about 10 years ago.

The difference between what they did and any other "port and polish" is they had extensive research under their belt for THOSE engines specifically. The difference is unbelievable.

I want the same for my QV at rebuild time but I am afraid of actually making it worse unless I find the correct diameters, etc, and cam profile that gives the best overall increase in street performance without losing driveability. Somewhere out there someone knows EXACTLY what to do to wake up a QV motor - however much or little - thru the intake and head without destroying it's daily driving style at the same time.

What are your thoughts?

 

Sure, those look pretty. But pretty doesn't mean anything if it doesn't run well! That's my car in post #11, and I have to say... It runs awesome. I couldn't be happier with the results of the engine rebuild. David is truly a master.

 

You know Dr, that's a very good question. I've spent a lot of time modeling and running CFD or computational flow dynamics on the 2v and 4v heads, first I had to get the model to closely match real world flow. Then I could do what no bench is capable of, simulate piston and cam events for reversion and dynamics.

the 2v head is BAD, no way to sugarcoat it. The 4v is much better. the thing to keep in mind though is that the cam profile really controls a lot of the dynamics of the flow. also more lift can actually hurt, in the 2v case the increased protrusion of the valve beyond 11mm lift into the cylinder caused mixture problems and slowed velocity down significantly. to offset that you'd have to reduce the valve face dia but then you'd trade off for lower velocity and flow below max lift, push-pull everywhere. the 2v flow can be helped with reducing the 'bubble' in the roof past the stem where a low pressure zone builds and slows velocity down.

I haven't yet gotten to modifying the 4v ports and running the numbers.

All that aside, the BIGGEST improvement is getting rid of the CIS fuel system, purist may not like it but the hydrolic fuel pressure system is exceptionally restrictive and slow to respond. The ignition maps for the US are awful as well.

The other area in need of a redo is the exhaust system. I think that for the 4v before head work is contemplated there are some other areas that can be sorted to increase the efficiency of the engine.

just my 2cents...

 

I know I am resurrecting a thread from 2012 but do current owners of 328;s still have the yellow clamps paint marks on there cars engine still from the factory?

 

Bump...