DIY porting an N42.

[luvemfast]

oh and im sure you've head this already but: DONT TOUCH THE BASE OF THE PORT OTHER THAN TO POLISH IT!! or you will kill all flow (I hear)

When you say base of port, do you mean at the valve seat?

[Zeddophile]

When you say base of port, do you mean at the valve seat?

 

I'd say he means the whole floor - from entry into the head all the way to the valve seat.  Quite common for lowering the floor of the port to cause a reduction in flow, it's to do with the turn down into the cylinder from memory.  Alfa twincam heads actually flow better when you ADD metal to the bottom of the intake ports....  Of course, every head is different, and whether this applies to Zed heads, I would have absolutely no idea.  That's what research is for... or alternatively, a scrap head and a flowbench.

[luvemfast]

gotcha 

[C.A.R.]

Read here: http://www.performanceforums.com/forums/showthread.php?t=67240840&highlight=Datto

Here: http://www.performanceforums.com/forums/showthread.php?t=67239162&highlight=Datto

&

Here: http://www.performanceforums.com/forums/showthread.php?t=67227917&highlight=Datto

 

Pay particular attention to the posts made by 'TK'.

[kolonelklink]

I think the valve curtain on the exhaust represents the single greatest impediment to flow on the L-head... again this is only opinion and collected snippets of wisdom.

it's a bitch but I'm not sure how much port work on the exhaust benefits flow without a higher lift cam and/or a larger valve seat

[dazzed]

I did a similar thing to my N42 head, spent a lot of time (12 hrs) on the extractors too which were a terrible fit. Also i have a fully ported head which is still at the shop. De-shrouding the valve stems is a good start as you can take off a lot of metal there without going anywhere near the water jackets (which is why the other head is still in the shop) if you can wait a week i can get some good pictures of the other head.

Just bear in mind that if you hit a water jacket it will cost a bit to fix.  Mine cost $150 to get fixed but i bought i like that. Good part was the repair comes with a warranty.

12 hours? dont you think you over exerted yourself a bit??

[Scoota G]

I never doubt anything i've done to the car when it's singing at 5000 rpm or just burbling at the lights making the passenger jiggle. The difference in the exhaust note was noticable indeed  :)

[peter mc]

no need to change valves thay are more than capable of flowing good numbers 225cfm at28in intake in a n42 with lots of port work..

[kolonelklink]

care to elaborate further on this? source, pictures etc

Furthermore... any experience with the exhaust side modification?

 

Cheers!

-pete

[peter mc]

Hi, You are a clever man.

The exhaust port is the one that needs all the work.

You need to spend alot of time in there, standard valves are ok.

You can get 155 cfm from the exhaust port on an N42, no welding just lots of porting.

I do have pictures but i like to protect the work i do on my customers engines for them.

I am more than willing to port a cylinder head for you.

[gav240z]

It's been a while since this post was last updated. I'm wondering how this went in the end and if you had any results to share?

[peter mc]

not mine but its a good help

[peter mc]

some pics of n42 some mine some off the net

[peter mc]

more n42

[jamo240]

Cylinder head porting is a very specialised business, with experimentation on a flow bench required to validate the value of your changes. To just buy a die-grinder and a few burrs and flap rolls and fly into it is a waste of time. You'll never know if you've improved them, or if each cylinder is balanced doing that. Best to give the job to someone who's got the knowledge, experience, tools and equipment to do the work properly, and most importantly, be confident through test results that the modifications have achieved the objective. It's not a DIY job.

 

Jamo

[peter mc]

heheh yep some times i make a mod to the port and find its lost 10cfm and i thought wow i thought that would have been great  , it take lots of work and experience to do it right and you have to test all your work to make shore your doing the right thing ,,,, and that's only part of the job making the chamber work and having a pro cut the seats the right way and having the right valve to make it all come together  ... then being able to make changes to the port when you get the flow sheets ,it take lots of experience to read the sheets and know what part of the port does what  ..... its not a DIY job that's for shore .