Best means of port matching??

DaviesDJ · Post by **DaviesDJ** » Wed Jan 30, 2013 7:49 pm

Hi Guys! Have got my engine dismantled now, turns out that noise was not a valve drop at all, it was a sheared flywheel bolt, crank going to my mates for repairs, so as any self respecting tinkerer would do, while the engine is off am going to make some improvements, was going to change pistons - but with my TVR 500 rods its not a practical option, but am going to trim 20 thou off my block deck to bring pistons to the top for better squish etc, may shave a bit off the heads to up the CR a bit ( will measure this properly first) and lighten the flywheel a touch. My heads are stage 3 but I did not properly match the ports during the first assembly, so I want to do it properly this time:-) So how do I do this most effectively??? Was thinking about putting a dole in the heads and through the valley gasket and then into the manifold (edelbrock performer) and match them nicely with the drummer etc. How do you guys do it, what's the secret to really well matched ports?? Am all ears...

DaviesDJ · Post by **DaviesDJ** » Wed Jan 30, 2013 9:12 pm

When I said "dole" I meant dowel - a dowel peg - Sorry - bloody predictive spelling

mgbloke · Post by **mgbloke** » Thu Jan 31, 2013 7:57 am

Really you need to start with engine assembled & the manifold bolted up in place on the heads.
Drill a very small reference hole at each end of the manifold and each side.
Now take it all apart. Lay suitable cardboard or similar over the inlet ports and push a couple of drill bits through the cardboard into the small holes.
Now tap around the ports with a rubber mallet. I then use a stanley knife blade to cut out the holes. Write manifold side on the cardboard and remove.
Now fit the drill bits into the holes in the manifold and fit the cardboard over them with the writing facing down. You will now see the difference in the port matching and it is possible to get an exact match with some work.
Obviously you need to have your block decked and heads skimmed before to can start as this will change the alignment.
Mark

kiwicar · Post by **kiwicar** » Thu Jan 31, 2013 10:08 am

Best way, try and "match" as best you can just by tapping the inlet manifold from side to side and back and forth before you drill the dowel holes and try and end up with the port face holes all the same size once matched. but esentially the doweled cardboard template is the best simple way I know of.
Best regards
Mike

topcatcustom · Post by **topcatcustom** » Thu Jan 31, 2013 2:07 pm

I'm pretty sure David Vizard has written in one of his books I have, that (tested too) port matching is not worth the effort, if you just put a small radius on the engine side ports, say 1/8".

I will check, but he never says anything like that unless he has evidence to back it up.

kiwicar · Post by **kiwicar** » Thu Jan 31, 2013 3:00 pm

Hi Tom
I remember it as . . . not worth the effort unless you have done pretty much everything else, and often not worth it if you end up making the size ot the port too big where the head meets the inlet you can do alot more harm than good, and that it is often possable to get virtually as good results with just a radius on the faces, especially if oyu leave the gasket in place. It is one of those complex things, alot of people like to do it as it is something that you can do without a flow bench. I will point out here I have not done my inlet ports and just radiused the head face but I have used port plates on the exhaust side (the complex way of port matching and lots of work).
Best regards
Mike

DaviesDJ · Post by **DaviesDJ** » Thu Jan 31, 2013 3:17 pm

Thanks guys, can you use the gasket to match instead of cardboard??? Putting a dowel/drilbit through this?? Do you fill the holes in after this??? What does it mean leaving a radius??? sorry to ask a dumb question

kiwicar · Post by **kiwicar** » Thu Jan 31, 2013 4:46 pm

Hi
No matching to the gasket on the rover is exactly why most people say you should not try and match the manifold to the heads, what you end up with is the port at the face of the head too big for the rest of the head and it tapers to quickly causing alot of turbulance, also you lower the port floow way to far and make the flow on the short turn side worse than the standard port. even worse to match the inlet manifold to the gasket you make it taper the wrong way stalling the flow into the port and creating even more turbulance. Really either do it by taking the absolute minimum off the manifold and head using the cardboard method or radius as Tom says or leave well alone, but do not match to the gasket.
Can I just stress here on a £6.5k+ methanol 650+ bhp 7800 rev drag race motor I have not bothered to match the inlet ports to the heads but I also have not done anything that I think might risk reducing flow.
By leaving a radius Tom means that instead of having a 90 degree edge between the runner and the gasket face and the inlet port and the gasket face you put a curve on it as if you were running a router around with the bed of the router on the gasket face and running a 1/4 circle tool around the edgeof the port. Like a flair on a trumpet.
Best regards
Mike

DaviesDJ · Post by **DaviesDJ** » Thu Jan 31, 2013 9:55 pm

Ahh got you, I have the speed pro series book on power tuning cylinder heads', it does not go into anything like this sort of detail. Do you know of any good books on this?? Thanks for that advice, a real learning point

DaviesDJ · Post by **DaviesDJ** » Thu Jan 31, 2013 9:57 pm

And when putting this radius / curve on the head port, you
Smooth the gasket surface also?

kiwicar · Post by **kiwicar** » Fri Feb 01, 2013 10:34 am

Hi
There ia an excellent book by david Vizard on head porting http://www.amazon.co.uk/Port-Flow-Cylinder-Heads-Design/dp/1934709646/ref=sr_1_3?s=books&ie=UTF8&qid=1359714260&sr=1-3it is basically technique and theory and one of the best books I have read on the subject, Having read it you can confidently do a basic clean up job knowing you will not make anything worse, or you could geta flow bench and develope race heads with it as guidence, it really is that good. It is also very well written, he has a style that leaves you confident you can do what he does once you have read it.
I have had this for years, many like it, and it is good if they have covered the engine you have http://www.amazon.co.uk/Build-Modify-Cylinder-Speedpro-Series/dp/1903706769/ref=pd_sim_b_3 but I really don't think it is anything like as good as the Vizard book, it is too specific but not suficiently detailed on any head to see how to develope an head.
Best regards
Mike

topcatcustom · Post by **topcatcustom** » Mon Feb 04, 2013 10:32 am

DaviesDJ wrote:And when putting this radius / curve on the head port, you
Smooth the gasket surface also?

Generally the gasket holes are bigger than the port sizes, so are not affected by a small radius around the port. Infact that makes me wonder- once you have spent time matching the ports, you will still not have a perfectly smooth flow because you will have around 1.1mm gap between manifold and head (with a composite gasket) as the gasket is not tight to the ports.

I'd be surprised if you saw any noticeable difference between port matched and radiused ports, unless you had a wild cam making power at 7000rpm, custom gaskets and good runs on a track.

I may be wrong, just my thoughts!!

kiwicar · Post by **kiwicar** » Mon Feb 04, 2013 11:09 am

Hi Tom
I do not have exhaust gaskets on the Chevy. . . If I did match the inlet ports the first thing I would do would be make gaskets the same size as the ports, or chop some of the bottom off the inlet manifold so as to eleminate the gasket all together and use thin smear of silicon sealent.
Best regards
Mike

topcatcustom · Post by **topcatcustom** » Mon Feb 04, 2013 4:01 pm

Mike, I was just referring to the standard RV8 inlet set up, where the composite valley gasket is required to seal the valley and manifold, I don't image you have much exhaust back pressure to worry about

kiwicar · Post by **kiwicar** » Mon Feb 04, 2013 4:32 pm

Hi Tom
Oh yes I had forotten about that arrangment!

it really is a bodge and a half. . . I'm sure there must be a market in a proper valley cover for the rover so you can close the thing up properly. . . you just need bit of 16 gauge ally and a bead roller, couple of self tappers and some 90 degree clips got to be better than using the gasket to do the job.
Best regards
Mike