First I have a 2001 civic d17a2 I/H/E vafc2 and a hi flo cat. I recently had my head ported. They opened up my exh ports considerably. The header I have now is too small for the size of the exh ports in my head. I matched the header as much as I could with a die grinder but I am sure its still too small. I dyno'd and got somewhat weak numbers. 125 hp and 110 tq. How bad is reversion? any ideas on how much hp is being robbed?

 

Well just finish the job. also exhaust ports should smooth not rough. If the ports on the header are off alot gains lost can be noticeable.

 

if you can. try to open the header port more then the opening on the exhaust side. like alld16a if its not smoothe try to smoothe it out. the ehxaust side should be smoothe not like the intake side. who ported your head?? what kind of header do you have jus wondering? from what i believe reversion would increase your torque and lower your hp. i also think it lower nox and cylinder temps but that stuff doesnt matter.

 

yea i forgot to say u can also port the header gasket a lil more to help out with reversion. here ill show a pictor from T.O.O



there trimmed .05"

 

The soon to be replaced header is DC. The gasket has been matched to the port size. I had....dare I say it.. DH racing do the head work. <flame suit on> It was a good deal and they supplied a core. No complaints.

 

The #'s arent bad. Port the exhaust manifold aggresive seems to work. Also cleaning up some of the casting from welding in the manifold also helps. Also daves heads from my experince require a cam gear and a ported intake manifold to really do the #'s he claims.

 

How can increasing torque lower power? Maybe I am retarded or something. The formula for figure HP is TourqeXrpm/5252. My calculator is such a POS. Everytime i enter in a higher torque number and use the same RPM, i get more power. WTF? What brand calculator are you using? Maybe your using scratch paper which would explain your error.

 

alld16a are you dave . it just seems that you are dave but wut do i kno... mexi guy get a big motor and put a small exhaust on it increase torque decreases hp because of the reversion.... modified for mexiguy didnt read his post. i dont know if wut i say is true that is why i said i believe.


Modified by zad5 at 7:30 PM 6/29/2004

 

Why because I know that the manifold needs to be ported? I have owned/dyno tuned numrous dhr heads thats why

 

You should definately either open up the header ports bigger than the exhaust ports,or get a header with larger primaries.Having that step will help with anti reversion.With reversion,the exhaust can get forced back into the combustion chamber and polute the fresh air,causing the power stroke to be weaker,which will lower power numbers.

 

thanks for the info. hopefully the larger primaries will get me to the 130 ish range.

alld16a Have you noticed that DH tends to mill most of the heads they work on?

 

Well all heads should be milled for proper headgasket sealing. Dave takes off very little for selaing purposes unless you asked for milling to increase compression.