To polish and match ports or just clean and fit ?

[comper88]

Hi to all,
Any thoughts on polishing and port matching, is it a usefull and time consuming way of gaining small or large amounts in horsepower ,or am i just going to spend large amounts of time in the garage with the mini grinder set ?

The lump i'm rebuilding is a running 3.5 R/R motor which is going in an off road L/R 90, with standard flapper Efi injection system, i'm planning a full rebuild and replacing the standard heads with new 4.6 heads and Hot cam from real steel given to me by a good mate who is giving up racing, with these heads being later will dressing them be worth all the effort,

Any thoughts would be good.

Thanks

Nige

[demo2]

In a fast street car then yes i wud say its worth the effort, but not in a 4wd, u wudnt even notice the differance.

[Eliot]

I would check that the flapper manifold matches the inlet of the 4.6 heads - and perform blending in that area. (typically on the inlet manifold)

It wouldn't hurt to clean up any obvious casting flashes - but i wouldn't spend a whole lot of effort on it.

I have re-edited a long document on tuning the rover V8, which can be found here:
http://www.mez.co.uk/TuningTheRoverV8-intro.html

[kiwicar]

There are a few posts on this site touching on this subject at the moment. , a basic clean up is well worth it and a mild port to manifold match (may be not as far as a full gasket match and dont go too far into the port), and opening up the valve seat throat is well worth doing, don't "polish" the port though, the surface should be slightly rough otherwise you get fuel sticking to the surface (the port should opperate with a very thin turbulant boundry layer) laminer flow does not work on a changing section like a port. Smooth, blend, remove casting flash, don't do anything to change short turn radius unless you know exactly what you are doing.
Good luck
Mike

[comper88]

Thanks for all the thoughts ,will just clean and put on i think,should go ok and will save me many hours in the garage,cheers

[mikeinatruck]

Intersting read, I was thinking of doing the very same thing as I have another manifold to go on mine, but going by your responses I think i'll just change it and not bother..