haha.. DOHC vtec conversion to start later? seriously hard to start if you start fixing your D series.. and I'm not saying this to belittle you.. seriously.
If you were serious about modding, I'd suggest getting a car riddled with engine problems that will make it necessary for an engine swap.
I had a D16 engine in the civic that I bought.. and it only saw use for a day after I bought it. It misfired, burned engine oil like nobody's business, and the dashboard rattled like it was an earthquake or something. I didn't care, because I planned the swap from the beginning, and I bought it at a price just a little over 20K.
What do I want with an EG with engine problems? Throw in a B-series and all relevant parts from a halfcut. It'll be cheaper in the long run if you search carefully for a (relatively) low mileage halfcut.
Now, to answer your question.
If you want servicing, just perform a compression/leakdown test, and you'll immediately know why your FC suffers, it will cost just a little cheaper to fix that problem as opposed to a straightforward B16A swap with a competent mechanic.. and then if you opt to fix it, the DOHC conversion will head straight for the drain. I've friends that went down that route already, even after telling them that it's simply not worth it.
Example: Guy services his D series. Change gaskets. fine for a while, then start burning oil. Service engine again. Engine now ok with new pistons and rings. Then the A/C compressor dies. Change A/C. Then distributor dies. change distributor. With the amount he spent for those repairs, half of his B-series swap budget already gone.. and the sad thing is, he bought it for 36K just a little earlier than me because everything was 'working fine' when he bought it.
The thing is, the current civic you and I are driving have been in existence for at least 11 years. Even the most careful of owners would have accumulated some serious mileage by then. So you can see why it's not a matter of 'if' your engine is having problems of not.. but rather 'when'!
A B series swap will need some minor fixups depending on the condition of the halfcut, but you end up with a lot more horsepower than the D, so it's money well spent.
Good FC for the D series is pretty simple.. as long as the gaskets, pistons,rings and bearings are okay.. you should see good FC depending on how you drive.
the original honda stuffs are the best for stock engines. You'd be wasting money trying to put expensive oils like motul and redline on an engine that's not in mint condition.
