signs of over porting a head?

[Justin86]

just drop in a new head I P&P and it won't idle. I have the throttle calbe riged so it idles about 1500 I have the ignition advanced all the way and the TB idle adjust all the way out and it doesn't help much. If I startt to die which it does I have tp go WOT for about 2sec before it brings the idle up. It bogs really bad below 2000, but above 3000 it just tears the tires up. The only thing I changed was the head and I only thing that makes sense to me is that I over ported it.................. any ideas?

[MattsAccord]

Please figure this out Justin, I really wanted to ride with you in Eugene while you tore riced out civics new ones. If you need my expert advise let me know. :D

[Oldblueaccord]

just drop in a new head I P&P and it won't idle. I have the throttle calbe riged so it idles about 1500 I have the ignition advanced all the way and the TB idle adjust all the way out and it doesn't help much. If I startt to die which it does I have tp go WOT for about 2sec before it brings the idle up. It bogs really bad below 2000, but above 3000 it just tears the tires up. The only thing I changed was the head and I only thing that makes sense to me is that I over ported it.................. any ideas?


Well by your title i was gonna answer "when you hit water"

But i'd go with vacuum leak someplace maybe the intake to the head.


wp

[Justin86]

well vacum leaks will cause eratiac idle not no idle at all. 1200-1500 it runs smooth but once it gets below that it will drop to 100 then die.

[Oldblueaccord]

well vacum leaks will cause eratiac idle not no idle at all. 1200-1500 it runs smooth but once it gets below that it will drop to 100 then die.

1500 rpm aint really an idle. You just got enough fuel with no load. Its worth a look. I put a carb on once with a spacer...... backwards. Ran it a few days but didnt like it. When I took it off i realized that I put it on wrong. I could fit 3 fingers in the gap that was not blocked off into the intake.

wp

[thegreatdane]

What cam specs do you have? You said you adjusted the idle screw in the TB all the way out. You have to adjust it all the way in to get the lowest idle, but I dont think that it will cause it to die below 1500rpm even if you have it all the way out.

[86LXItooFAST4me]

i was thinking the TB idle screw also. but thats just a guess on my end

[Justin86]

It's a 272 grind. With the TB screw when I turn it in it will start to lower but when it gets to about 1200 it will drop down to 100 and die. Samething thing when I try to set the timing it will drop the idle way down and kill it.

[86LXItooFAST4me]

thats crazy, i would just triple check the emmissions and vacum lines man. but that sounds like a real head scratcher. you have the valves lashed right and all im guessing. and have you checked the timeing with a timing light just to make sure? and plug gap? computer throwing any codes?

[Chicane]

Were you getting this flow tested? removing the most metal does not equal teh best performance... I'd say signs of overporting a head= when it doesn't flow as well.

[A20A1]

Too large a port lowers the intake charge momentum durring mid to lower rpms, this effects how good the motor is at filling the cylinders and reduces power.

For street use ( Minimum port cross-section = 0.85 x Valve area )
For race use ( Minimum port cross-section = 0.90 x Valve area )

It's not just port size that affects velocity though, cam timing, displacement, rpm, manifold design, and exhaust system design, compresion ratio, and more all effect the velocity.


Where did most of the meat come off?
Top
Sides
Bottom

[Mike's89AccordLX]

My instructor once told us when we were learning to P&P heads that not to over port b/c you will lose your bottom end performance but gain top end. Sounds like it was ported too much IMO. Just use some nitrous to get you above 3k ;)

[Justin86]

the ignition I have it advanced all the way just so that it barely idles, if I try to set it at 18 it will kill it.
The head I couldn't get flow tested cause no one close by has one.
I opened it up mostly at the opening and slow took off les as I move towards the valves. Around the valves I took off very little, just enought to clean it up. I adjusted the cam gear to 5deg advance and that has helped my lower rpm throttle response and the idle it a bit better, but still eratic. It will be at 1500 or it will drop to 150-300.

Yea that what I'm thinking mike, cause te only thing different is the port job, and over porting it makes sence to loose low end power and idle.

[Elijah]

If you got know power till 3k+ then you are right. You over did it. In the end your making more power but you have to wait till 3k+ to get there

[A20A1]

If you got know power till 3k+ then you are right. You over did it. In the end your making more power but you have to wait till 3k+ to get there
:lol: it's like my motor with my cam... I gotta go to 4k to reap the benifits... vroom vrooom. :D

[Oldblueaccord]

Can you get us a vacuum reading at all maybe at 1000 RPM that would tell us some on what the motor is seeing. Sometimes big cams and MAP sensors dont mix to well. The signal pulses to much.

I wrote this before my car wont idle at all until a drive it 30 miles if i unhook the battery for any lenth off time somethinig with the computer.



wp

[Justin86]

well this cam has never given me problems before, but I do love my top end power now. If I had a vac gauge I would, I'll put it on my list of gauges to get.

[Oldblueaccord]

well this cam has never given me problems before, but I do love my top end power now. If I had a vac gauge I would, I'll put it on my list of gauges to get.


OK so this cam has been run before with your EFI set up and is OK. Thats tells us its not the cam size per say.

What exactly did you port? P+P meansalot of things and nothing to me.

If you didn't touch the intake runners then there shouldn't be a vacuum leak there for some kinda mismatch.

Can you do a compression test maybe even a leak down and see what cylinder pressures were dealing with?

Did you use templets when you ported?
Did you get the head flowed before and after?
Is the head been milled?


wp

[Justin86]

well I was trying to do a simple port......... removed about a 1/8" in the begining and slowly worked it in the port until about half way. Around the valves I pretty mch just cleaned up the ports not trying to remove much.
templates, lol this is getto head porting
flow bench, if I knew on one close by I would have had it tested
compression I'll check tomorrow
the head was milled, valve/seat regrind, new valve guides.

[Chicane]

So you ported it without a flow bench???

[A20A1]

You make it as if it hasn't been done before or it isn't a good thing... Pocket Porting is a do it your self port job and doesn't envolve flow bench testing since most peopole don't have an in home flow bench... You take a spare head and work on it a little then go out for a run... come back in and work on it again taking off a little more then going for another run... sure you run the risk of over porting or messing up the shape... but thats the risk do it yourselfers take... I'm sure if money was no object then people would let a shop do it.

[Oldblueaccord]

You make it as if it hasn't been done before or it isn't a good thing... Pocket Porting is a do it your self port job and doesn't envolve flow bench testing since most peopole don't have an in home flow bench... You take a spare head and work on it a little then go out for a run... come back in and work on it again taking off a little more then going for another run... sure you run the risk of over porting or messing up the shape... but thats the risk do it yourselfers take... I'm sure if money was no object then people would let a shop do it.


Your right he took a gamble and maybe he rolled snake eyes is what were trying to say.

I really hope not.

Maybe the head milling has made your timing belt to loose now. It changes that distance remember. I'm wondering what your cylinder pressure is atm also.


Flow benches are to heads what a dyno is to a motor. Its the judge/ yard stick to show if you have improved or .............not. But they are expensive and head porting is time consuming thats why it cost so much to have a well known guy do a head. If it was easy we'd all be doing it right?


Good luck hope it works out.


wp

[Oldblueaccord]

http://www.theoldone.com/articles/The%5FSoft%5FHead%5F1999/


pretty good little article about head porting in general.

wp

[shepherd79]

i think your problem is in timing.
you advanced the timing too much.

i would still check the picton compression to make sure you have nice high compression. and i would check for any vacuum leaks.

[NXRacer]

Justin, i think this is directly related to the EGR problem. I'm having pretty much the same problem and i dont have shit done to my engine.

[Justin86]

and the faking ECU. Yea I read that article, but that involves many many hours of shop time and many thousand dollors, ok for a race car with a sponsor, but not the average person.

[Mike's89AccordLX]

Justin you removed an 1/8" of material from the ports? Yeah you're gonna need a different head. P&Ping is not about removing material like most people seem to think. It's about getting rid of those sharp corners, edges, and lips. Smoothing everything with a nice radii.

This is what I use for porting and polishing. Various De-burring bits with different sized shanks. (3" and 6" shanks)

Then I use the polishing kit (sandpapers, and other polishing tools)

I prefer using a varible speed drill electric. That way I can control it a lot easier than using air tools. If anyone buys those de-burring tools make sure and get the ones for aluminum. There's aluminum bits and then steel bit. If you use steel bits on aluminum it will get the aluminum stuck in the bits and possibly ruin them.

Cheapest place I know is on ebay for this stuff. Or use the schools stuff like I do :)