Inverted Honda engine

Brian Clayton

Well-Known Member
Dec 7, 2012
Ivey, Ga and Centerville,Tn
Today I picked up a 1.7 honda engine. I have been wanting to see if a late model engine could be inverted for use as a direct drive engine in the 60-80 hp range. The core I found is a D17a1 engine. Its a aluminum block and head non vtec 24valve sohc engine out of a 2005 Civic. About 105 CI, 115hp @ 6100/110tq @ 4500. I will post pictures when I get a chance. For the time being, I have some preliminary stripped weights (before lightening) and some observations I have made along with some information I have found. The block. 42lbs stripped, including main caps/bolts. The block is a interesting piece. All of the oil galleys and water passages (other than around the cylinders) are external castings, making it very easy to access and modify them. There are 4 large oil drain backs from the head to the pan along the perimeter of the block, aligned between cylinders 1&2 and 3&4. The good part about this is that it will be super easy to drain the oil from the base of the cylinders back into the sump. The mains are oiled by directing oil internally thru the one piece main cap girdle. I am not crazy about this setup, but considering I am only shooting for 60-80 hp at 3000 rpm or less, its probably not a issue. The factory water pump is driven off of the timing belt, with only the drive/impeller being removable. The rest of the pump is machined into the front of the block. The factory oil pump is driven off of the crank, right behind the balancer. Whether it will get used will have to be seen as this progresses along. The head. 36lbs stripped externally, but including cam, and all valvetrain. SOHC, 24 valve. Aluminum adjustable rockers, non roller. There might be enough room for a 2nd plug in the head, casual inspection says maybe. Custom grind camshafts seem to be available for this engine or I can just have the stock one reground if needed. Crankshaft. 24lbs. Forged unit, reliable to 600 hp. Seems to be able to lightened about 7 lbs for a race engine, perhaps more this application. I am not opposed to a billet shaft, if modifying a stock one starts to approach the cost of a new one. Rods and pistons. 4lbs set. While the stock rods are supposed to be good to about 220 hp, a set of new aftermarket rods rated to 800 hp are only about 350.00. I look at it this way, by the time you buy aftermarket bolts, floating bushings, check the rods and have them remachined.....75.00 or so each for new rods is cheap. And from looking, I don't think the pin ends have enough material for bushings anyway. Misc parts. 19lbs. I was lazy.... water pump, oil pump, all the bolts, valve cover, oil pan, thermostat housing, timing belt parts..... it was all still nasty in the plastic tote, so I just weighed it all to get a general idea. I was not looking for a finished weight yet, just wanted a idea of what was here. The block will loose a fair amount, once it gets introduced to the bandsaw and mill. There are quite a few mounting bosses that can be removed and a large portion of the bellhousing flange. The head, not too much to loose, but I am sure a pound or so can be found with some constructive pocket milling. Total of the rough weights so far is 125lbs. More to come once everything meets steam cleaner for the first time in a while. I welcome them, but......Please keep comments related to inverted aircraft/automotive engines......