Anyone know what the stock compression ratio is on a twin cam 88? Have thoughts of purchasingthe Andrews tw37b cams. Was wondering if stock comp ratio was high enough to really make much of a diff?

 

My service manual says my '05 TC had 9.0:1 stock. That's higher than I thought.


CN

 

in a stock 88 with no head work (lowering the head cc's) and without a thinner headgasket the cmpression will be too low for a 37 to perform well. I know 3 or 4 people that put 37's in thier stage 1 bikes and were disappointed. Harley might claim 9 to 1 but in reality it is probably closer to 8.4 to 1. If you want to change cams 21's or 26's will be a better choice in a stage 1 88.

 

how much would have to be taken off the heads for it to run properly? I'm having head work done right now. Where do you get a thinner gasket?

 

http://www.bigboyzcycles.com/TwinCamComp.htm here is a great resource to see what cc your heads need to be for your desired compression. Cometic is the supplier of the .030 head gasket. any dealer or indy should be able to order you one or you can order direct. If someone is doing your heads they should have the knowledge of what your heads should be set at to run with 37's if they don't have the knowledge then you might want to find another head porter.

 

23 champ a bud just put 37's in a 03 road king and go 80 hp 83 tq with hooker slipon's.. I just put a set of hq 0034 in my 06 and got 84,89 with v&h td on it.. If yor gonna leave it 88 I would run the 26's or the hq0034's.. the 37's are lazy without any compression.. I really like my 34's but they want a little more comp. also.. I'm gonna take the heads off and set them up for 83cc and run the0.030 gaskets.. I can say that the 34's are a great cam!! slimm

 

so are you guys lowering the cc by milling the heads down?If so, how much are you taking off, like 10 or 20 thou? How muchvalve clearencedoes that leave you with stock pistons?

 

23champ I'm going to cc my heads this weekend. rule of thumb is 7 thou per cc.. I will talk it over with wfo larry to see what he suggest's for piston to valve clearance.. if I can go more than 83cc I will.. you just have to know what he tdc. lift for the cam you choose.. then a good porter already knows how much to remove.. slimm

 

The amount you shave off is totally dependant on how big the volume is to start with. If your heads are 89cc's (some are mine were) then you might have to take 40 thou off to get to 83cc. If you are staying 88 you might need to go smaller than 83cc.

 

well, I've got other issues now. I had already ordered the tw37's before anyone replied to thisthread (not a big deal, it's not really that big of a deal to pull the heads off). Unfortunatly I have already assembled the motor and fired it up, only to discover that something is not right with the rear cylinder. The exhaust sound is a little on the strange side. sounds like its echoing in the pipe??? Very strange, dont really know how to describe it. Front pipe sounds good. If you put your hand over the end of the pipe (on the rear cylinder, while running) it wants to suck on your hand, instead of blowing it back. Front pipe is good, blows your hand back like normal. I thought at first perhaps the cam timing is off...I checked it, and it was. One tooth off from the crank shaft to the rear cam.After correcting that problem, and checking to see it the dots on the cams lined up (which they were). I fired it back upwith the same results, funky sounding exhaust sound out of rear cylinder. So now I'm thinking I have a bent valve. Plug a compression gauge on it, and come up with a little over 150psi on each cylinder. That should mean the valves are sealing correct? Whats going on here?..Got me scratchin my head.