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All righty, first post. I'm not entirely sure this belongs in this forum, but be that as it may...

I've got a long-time friend who has a 2001 EX, and he wants to get some headwork done in prep for a turbo engine. Since he's on a serious budget, he's asked me to do the porting for him, since I've done other 4 valve 4-banger heads and I'm cheap.

I want to post my impressions of the head design and ask for suggestions past what I know I need to do.

Impressions:
The good:
The intake port, good cross-section, excellent flow potential. Very little work required.

The bad:
The exhaust port has a fair cross-section, and good flow potential. The problem here lies in the short turn. It's too sharp, then drops to what I can only describe as a flat floor, which creates a stagnant zone that kills exhaust velocity. Material addition and careful reshaping can make it flow up to it's potential.

The ugly:
Whoever designed the combustion chamber needs to go back to school. The valves are so close to the chamber sides that they are seriously shrouded right there and there is virtually no quench area. Shrouded as much as they are at chamber edges, it kills the intake and exhaust charges at low and mid-lift. The lack of quench makes it advantageous for a F.I. application, however, for N/A, you'd need to add material to the chamber to increase turbulence and improve the combustion.

What I want to do:
Match intake side to a D16Y8 intake manifold(since we have one and are going to use it), smooth the port, blend the bowl.

Exhaust port, weld material onto the bottom of the port, reshape for a smoother exhaust path, blend the bowl, polish to a mirror finish.

Since we're overboring the engine anyway, for the combustion chamber, open the chamber to the stock overbore size of 75.8 mm, thus unshrouding the valves, polish the chamber to prevent detonation.

Other work, back-cut oversize valves, valve seat radiusing. I am asking directly, what angle would you suggest for a back-cut on the valves?

Suggestions? Comments?

Thanks,
-Jim

 
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" Whoever designed the combustion chamber needs to go back to school". Honda motor designers need to go back to school

 
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the head was designed like that for a reason. You just will have to figure out why.

 
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well id would pretty much agree with you on what you say except that the head was not designed for race purposes, so you cant really critisize honda for making it that way. My plan on porting my Turbo D17a2 head are this (not much but enough): If you have the valves out and are looking at the combustion chamber on one side of all of the intake ports there is a lip that obstructs a minimal amount of flow. I will remove some of this and blend/polish everything in, hoping that it should finish off the pretty descent intake side. Of course it has already been mated and matched to a Y8 mani, which works excellent I might add. As for the exhaust side, I do want to open up the ports a bit but I really decided on anything more. You can get quite a bit out of these heads left alone, as stupid as that sounds after you look at the head lol. I think extreme/drastic changes on a well engineered piece is just not the way to go, but thats my opinion. I dont dare mess with much without access to a flowbench. We are making well over 400 whp on our h22 accord with no head work and factory cams and it revs to 8k plus all day long as a daily driver. Also if you look at the specs on most honda's the compression ratios are respectively higher than most cars and they run on the same fuels, most of the time with better gas mileage. A lot of that has to do with efficient head design. Maybe they dont look typical but one thing I have learned; Honda Engineering is where its at. OK enought raving, Im out

 
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It is a nice open chamber, which is perfect for the F.I. app we're planning. With the exception of valve shrouding, the combustion chamber designer has a mind for F.I., and I do tend to approach combustion chamber theory from a N/A viewpoint.

Good tip on that lip. That's exactly the kind of feedback I was looking for. I'll take a better look at the head when I get it back(currently at a shop for cleaning).

I will gasket match to the turbo manifold, however, I try for the smallest port that will flow the fastest. Velocity is where it's at. I'm not aiming for a massive reshape, just following the advice an old pro gave me when I started on my first head, "The difference between the professional and the ameteur is the ameteur will only remove material to try to make it better. Often he removes too much. A Professional will add material and then remove some of it to get the port to do what he wants it to."

Having said that, I am no professional, but I try to do a professional job, keeping his advice in mind.


-Jim

 
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Ok, it's back from the cleaners and boy oh boy.

Second Impression:
Intake:
Same as initial Post: Very good Port, little work needed. I like the asymmetrical port design, it promotes good turbulence as the Air-fuel mix tumbles out of the port into the Combustion Chamber. Bigger cam needed IMO.

Exhaust:
Still too sharp a short turn. Judicious material addition and carving would optimize it.

Combustion Chamber:
With the lack of quench it's no surprise to me the engine doesn't make more power stock. Valves are still too shrouded by chamber sides. Previous post about the 'lip' correct, We'll have to smooth that out, radius the seat, and blend the bowls for maximum flow past the valves.

-Jim

 
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Sorry to interupt.

Would dropping the compression ratio of the pistons help with the quenching problem?

Also there is a company that makes cams for the D17. Gude.com


Is there any way you could do a 3 way on the intake valve, the a 5 way on the exhaust?

Just wondering

 
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Quench simply means quench pad. A quench pad is a flat area on the cylinder head in the combustion chamber. As the piston reaches TDC(top dead center), the air-fuel mix between the quench pad and the piston is forced out into the chamber. You do need a gap, usually headgasket thickness, between the piston and the pad, otherwise you'd end up with cracked pistons and/or head.

Anyway, it makes for a more compact and homogenous mix of air and fuel, allowing a hotter flame and better burn characteristics, thus increasing power. A combustion chamber with lots of quench pad is called a closed chamber. Honda seems to be fond of designing an open chamber, which has little to no quench pad.

I'm not worried about it with this head as it will be going on a turbo engine. For a naturally aspirated engine, I'd add as much quench pad as possible by welding in material and then carving it down to keep the valves unshrouded.

The stock 3 way job is very good, I don't think I could improve on the angles used(especially with my equipment), however, all I'm doing is smoothing out and rounding the seat for gains in low and mid-lift flow.

Like I said, I'm no professional, and don't have access to 1/10 the tools I want, but I'll do the absolute best job I can with what I have.

-Jim