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Anyone know if the engine block and crank from the 86-87 Civic DX and Civic Si are identical? I currently have one of each torn down and can't see any real difference. The Honda manuals list 4 part numbers, but all start with GW- (I think). Just want to make sure I'm legal for ITC.
I want say C/R are lower on the FI engines. I know the head is diff, but the piston could be diff too.
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Allen
I believe the blocks are the same between DX and SI but the SI crank is forged while the DX is not. I am not sure about pistons.
The cylinder heads are definitely different and cannot be interchanged legally in IT.
Si & DX engines have the exact same crankshaft, Honda P/N 13310-PE2-020 and exact same connecting rods, Honda P/N 13210-PE1-000.
The engine blocks are identical except the Si block has the bolt-on oil cooler adapter, and the oil pan was different. Since oil coolers and oil pans are free, I would suspect this would be legal, but somebody might split hairs over this. The bore/stroke/weight/ of everything else is identical. Flywheels might be different but the DX unit should be a direct bolt-on swap.
The main difference, as others have noted are the pistons and head design. The Si had pistons with a very pronounced dish and the lowest CR. The DX had a modest dish and a higher CR. The HF had a different dish/dome config to give the highest CR of all three. HF conn rods are also very different than the DX/Si rods in that they are much lighter but are too weak for racing, and are not legal. HF pistons had one less oil control ring as well to reduce internal friction. Keep in mind, the HF was designed for economy, not HP!
The heads are completely different.
The Si had the best head for making power with a true 12V head. The DX had 12V plus the CVCC prechamber auxiliary valve. Some HF's had 8V plus prechamber. All three are very easy to spot by pulling the valve cover.
Note: Canadian DX heads don't have the CVCC prechamber and make a lot more power than US heads but are definitely not legal! A quick way to spot a cheater head is to note the angle of the spark plugs. The Si and CDN DX heads are similar in that the plugs install at a near 45 degree angle, while the US Dx head the plugs install at a shallower angle since the plugs protrude into the prechamber and not in the actual combustion chamber.
[This message has been edited by Greg Gauper (edited April 11, 2005).]
Thanks Greg. I did notice that the heads and pistons were different. I have two good SI heads now in my garage and cannot use either. On the other hand, I have 4 CVCC heads and three have the #2 bearing blown out.
Thanks again for all of your advice Greg. If I am faster this season, a part of the credit goes to you. I'll send you the car from the top of my first trophy. http://ITForum.ImprovedTouring.com/smile.gif
One other question. Any preferance on exhaust headers. I've found OPM, Headman Chikira and Pace Setter. I have the Headman on the car now but its getting pretty crappy. I also have a Pace Setter in the pile of spares. Any other brands I should be looking at or there's really not much differece for ITC?
If you can find an original Mugen header, that's about as good as they get.
The OPM unit is a very good unit designed by Walt Pucket ?sp?
That's what I'm running on my G-Prod.
DC Sports to make a Mugen 4-2-1 clone, and it was a decent unit, but they are no longer made and hard to come by.
Keep in mind that most headers will be designed for the Si motor, and they will bolt up directly to the CVCC head and work fine, but you will need the Si oil pan in order to get clearence between the pan and the header. The Si header will also clear the Moroso baffled oil pan in case you are interested (That's what I run on the GP car).
You can always sell those Si heads to an ITB or G-Prod racer! Now that the older Si's are reclassed to ITB, I suspect there will be more coming out to play.
Or hang on to them and convert your car to GP specs in a couple of years http://ITForum.ImprovedTouring.com/smile.gif
I just received these headers from Dave to test with my "Bullet Proof Racing Engines" D16A6 CRX/Si (both in ITA and GTLite configuration). The are quite well build and look like he took the time to manufacture them correctly.
I expect to have test results compared to the Puckett in a few days.
http://www.sbmsinc.com/photos/SMSP_Headers
(Excuse the shop floor, but I have to teach my slave labor to paint)
Tom Blaney
SBMS Racing
http://www.sbmsinc.com/race_shop.html