I have a 91 dx civic with a 1.5 motor. My question is can a si head fit on a dx block? And if it does. how much horse power will I gain. If not ,will a si motor just bolt right in. One more question. Will a dx clutch fit in a si ? Thanxs

 

Yes, the SI head will fit on with no problem. BUT, you will not notice too much of an improvement. The biggest difference is that the SI is multi-port fuel injection, and the DX is only dual. Check out www.hasport.comfor a ton of usefull info on DX to SI swaps.

 

the dx and the si have the same head and block - just different pistons, cranks, and cams. like they said, just do the quick swap into mpfi. the clutches are the same (as was discussed in a previous forum), and the tranny's are the same, except for maybe the final drive in the si is taller. you are better off with the dx pistons, since they have higher compression than the si. if you really want better compression, drop in a set of 1.6 integra pistons - you don't even have to bore out the block, they are both the same bore.

 

Actually, the block is different- it has a smaller main journal size and deck height. The tranny has a much shorter final drive. The only difference in the heads is the cam. Switching to port injection made the biggest improvement. If you want- you can use an Lx trans - its final drive is between the dx and si-

 

also 88-93.25 1.5L got lighter valve springs. In early 93 Honda ran out then inventory and started using the Si valves springs in the 1.5L 16v motors.
BTW the Si springs are now the updated replacement one for the 1.5L motors.

 

listen to dohc dx i just did it the timin is not set correctly yet cause i had work but its faster and my friend did it to last week went 15.5 and before he went 19.3 i was beaten his with 18.5 i have an 88 std b18 is goin in in december hopefully untill then i did this with the four speed manuel it pulls alot but im throwin a si tranny all for free i might add my friend swaped a zc into his si hehehe hes pissed he can only run a 16.0 and my friends crx ran the 15.5 against his car with his old ecu in it funny as hell i cant wait to get to the track tuesday

 

Are all the parts just bolt in or do I have to some modifying to get them to work. What other thing can i do to get more horse power. What type of clutch is everyone have and what works best, performance wise? thanxs

 

dude, if your friend only ran a 16 flat in his si with a zc, he either a) can't drive for ****, or b) doesn't do regular maintenance or make sure his engine is running properly before he goes and rags on it at the track.

 

i think he got a bum zc i cant see wut is wrong except for shiity spark plug wires but i dunno why he can drive it pretty good i cant wait to see wut i run i just put an si exhaust on the pooper today from the motor back mad bigger than std so now i just need to put the 5 speed in and ill let u guys know wut happens with the 4 speed on tuesday

 

another option is converting to a z6 or y8 head. The y8 is the best sohc vtec head, but the z6 works pretty well and is much cheaper. Either one would mount to your engine. The hard part being the wiring.

liam

 

yeh the intake manifold and distributer are bolt on and u only have to run 4 wires from the ecu and run a resister box to the injecters took a day of work and bullshittin around

 

Well, my coming project is to put a 2000 DX head and '90 Si manifold/injectors/ECU onto my D15B1 (STD hatch engine - 70 hp stock!). So I actually expect much better gains than that!

With the cheap azz header I got and the AEM warm air I bought (for the later B16 swap actually), I hope to be in the 100-110 range. I'll be posting pics and some other stuff when I do it over the week of Thanksgiving (taking it off for car stuff).

 

the si motor has 102 so that doesnt make much sense the d15 with the si injection can beat a si so theres some info

 

thanxs for the info everyone.