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^ thats sold :(
 

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:wink:
 

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A good post on essentially head porting - copy and pasted as you have to be a member of the forum.

p.s. like how im the only contributor to this thread so far ;)

timdog said:
Ok so i intended to put this thread up quite some time ago but just haven't had the time.
Anyhow, i bought myself a uk 2000 model black dc2 last year. It had a problem with the engine according to the seller but apart from the the car was fine. I gave it a quick drive and the engine had a light knock and also the gearbox synchros were shot to hell.
So i pulled the motor out and stripped it. Here are the details of what i did along the way with pictures. If anyone has any questions don't be afraid to ask.



Now to pull the motor out.






The stock cylinder head ports.





Next i stripped the gearbox. The synchro's were shot, the selector forks worn, quite a few of the gears a bit chewed out on the synchro teeth. On the rebuild the gearbox had several new gears, all new synchros, new selectors, new bearings, new seals. I did order a close ratio gear kit from spoon uk originally but they screwed me over and took 12 weeks to delivery the wrong stuff then it turned almost to a legal battle before i got a refund. So in the end i opted to put a 4th and 5th gear out of an EG civic to really close the last 2 gear ratios up.






Stripping the motor i found the cylinder 4 had done a big end. The rod had got hot and the crank had a crack in it. So i ordered up a replacement eagle crank and rod kit from a supplier in the states. I decided to also run a Darton liner kit in it too and get some CP pistons. 12.5:1 CR at 84.5mm bore size. The stock bores were a bit tired and not entirely round anyhow plus i hate open deck blocks. You can see here the stock liners being machined out and the finished item with new liners installed.









Next came the hard bit. The cylinder head.






Ok so my verdict on the head. Inlets port - way too big, like huge. Exhaust ports too much dead space. Combustion chamber a pile of poop. Valve angles canted too much towards each other. The ports and chamber i can do something about. I put the head on the flowbench and then put all the data into my engine modelling software and calculated that the stock ports have enough cfm to support 250bhp on the engine size i will be running. So the ports must be made more efficient not made to flow more.
I'm not a fan of the recessed chamber you can see clearly in the 2nd picture. I know many shops just skim the head to remove it but you loose a load of piston to valve clearance doing this. Also i didn't like the valve shrouding and because i'm going up on bore size by 3.5mm i decided to make some big changes.







I marked and then scribed the chamber for the new bore size. Now it is time to remove the old valve seats and start to pre-machine the chamber ready.






Now i can start to weld. This is the point where you look at the next pictures and either laugh or cry. See how i am filling where the previous step in the chamber was front and back with a lot of weld. This is so that the head does not need to be skimmed a lot. Also i build up the sides of the chamber a lot. You will see why in a minute.





Ok now the weld is in i can start to machine. First i use a cutter to machien the chamber shape then i put the head on the skimmer to see where i'm at. Then the seat bores can be cut ready to have new seat blanks dropped in.





Now that the seats bore are done i fit new valve seat inserts. Then are like 10mm thick washers and then have to be machined down to the valve seat you are used to seeing. I fitted larger seat inserts than stock to put more heat dissipation and better stability into the seat. Also not i welded the underhang in the exhaust ports under the old seat to remove it. The plan was to later on fit larger valves.




New seats fitted and valve job put on. Not the final valve job, just sort of 80% the way to give me something to work to. Then here now is the final chamber shape finished.




Ok now its time to look at the ports. Lets start with the exhaust port. The port shown here upside down so rotate it in our head. The floor of the port had a load of dead space when i checked it on the flowbench. Air speed was not happening. So if its dead, remove it or its wasted volume. Time to pull out the tig welder again. I also wanted to extend the port divider and make it sharper.




 

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Part 2
timdog said:
Now that the exhaust is D-shaped and finished i can move onto the inlet port. Air speed in these was pants. I mean crap. No wonder these engines have no midrange at all. Also the port divider is too short, the bowl too big etc. Time to pull out the chemical metal. Stock port shown first for comparison.






Then i put the final valve job on, skim a little off the head, check it all on the flowbench once more and now its time to build it.




Last job, i wanted to modify the stock intake plenum. I cut the back of it, flow the runner a little and smoothed the intake inside then welded it back up.




Final compression ratio was 13.62:1 with the 12.5 pistons and my combustion chamber work. Squish a little over 40 thou.
For the cams i designed my own profiles. The stock low and mid vtec cam are platypus poor so i put some more duration into these and just over 1mm more lift on both. For the big cam i only went up 0.3mm/0.5mm on in/ex put threw some more duration at it. Sure this will cost some midrange but i'm hoping to still keep the vtec point high and make it rev. New springs to my spec and stock itr valves and cotters and retainers went back in it.
The engine went back in the car. I fitted a hondata s300 ecu and a innovate wideband although the first week i used a motec plm i had here so i could watch the afr in the car more easily. The exhaust system and intake including air filter all stock apart from a used set of 4-1 headers a friend gave me to see if they fitted.
I heat cycled the engine 3 times then took it for a drive up the road, watching the afr closely and listening for knock.
Straight away the ignition for a stock itr from hondata was way too hot. Good sign, means my combustion chamber was working well along with the high CR. So i trimmed that down a lot in the end only running around 25 degrees instead of the 40-odd that a stock motor needs!!
Fuelling was good and i made trims as i built the revs up.
Brought the car back with some light load logging. Let it cool. Redid valve clearances then went out again. Built revs up a bit more slowly whilst stopping every 5 minutes to adjust the fuelling. After half hour or so i was up to the limiter with it. Felt strong, especially down low. A bit strangled up top but good none the less.
So a few days later i dropped up to a customer that has a car dyno and threw it on. Showed 195bhp. A bit low but i knew the exhaust was wrong. But at least it was running.

Next job, take the stock exhaust system off, modify the headers which were the wrong length with a bad join and a choke and then build myself a new system in 2.5" stainless. This took quite a few days to get right. Hey i'm an engine builder, not an exhaust guy!! but once done it looked mint and was not noisey. Time to revisit the dyno. 36bhp gained!!





As you can see from the chart which shows the motor at this spec but a before and after of stock exhaust to my new exhaust, its got huge torque down low. They are normally really poor down at 3k but this has some real poke around town i can tell you. Really happy so far. I tried removing the airbox lid and air filter seperately on the dyno. Was only a couple bhp here and there. Still on stock fuel injectors too.


Ok so next plan was to build a larger plenum, shorten the plenum runners and fit a larger throttle body.





Here you can see the finished items. I also upgraded the stock fuel injectors to rc 440 at the same time. Out on the road, the ignition needed changing. Power around 6-7k was improved a bit and up top it revved on slightly better but when i got back to the dyno it really was not improved any significant amount. A bit of a disappointment but a lesson learnt i guess.

Next job, pull the head and stick in some bigger valves.




The port divider seemed to be wetting and the piston looked a little odd on the inlet side. So i decided to cut the port divider back a little to stock position and deshroud the chamber a little more. The seats i recut for the larger valves and blended the ports back in again.




Got it all up together again the other week. Went back to the dyno. About the same midrange and peak power moved over a bit to the right but no more outright peak power. Ok so big valves did nothing!!!

Anyhow, that was about a years worth in between all my other work. In case you haven't guessed, i do cylinder heads and build race engines for a living :) Not sure what to do next. Considering changing pistons and fitting an evo 9 mitsi turbo to it. Not sure yet. The one turbo supplier says he can hit me up with one of the specials we use on the evo racecars but it will give me like 600bhp all up high which is a waste of time on the road where the car spends most of its time accelerating from 10% throttle opening!! I'd rather have 300 and loads of boost from nothing. But i have a mate wants the motor for his civic and i'm real busy so maybe i'll drop a b20 turbo in instead. Who knows. Will keep you posted.

As i said, any comments or questions welcome but i am real busy so can't reply all the time. Just thought it would be nice for you all to see a proper build for a change rather than read dull posts about what wheels should i run or what air filter is best etc. Enjoy.
 

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Great post on the Honda !
 

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