S&S 79 cc heads on TC88, need some help

[SwedishMeatball]

Greetings from Sweden,

I have a 2002 FXD with TC88 engine, currently in stock shape apart from S&S 509 gear drive cams and an S&S exhaust.

I recently happened to buy a nos set of S&S "super stock" heads, 79 cc chambers, 1.940" intake and 1.575" exhaust valves, 0.650" beehive springs.

My first plan was to use them with the stock 88" pistons, this would give around 9.3:1 comp ratio, around 190 psi ccp with the 509 cams. I figured increased compression and better flow would produce a nice power gain.

But then I started thinking maybe the ports and valves are too big for 88 cui with those mild cams, and I might end up losing low rpm torque. The intake port is 45 mm vs 42 for the stock heads, an with a little "shark fin" on the floor of the port.

So on to plan B. I am on a quite tight budget so I try to buy cheap parts on Ebay, so now I have a set of Andrews 55G cams and Wiseco 95" pistons with 4.6 cc dome. This will result in around 10.5:1 comp and 195 psi ccp. Should be fun but with the cost of boring the cylinders I'm kind of stuck with the stock CV40 carb, and I think that is too small for the setup I'm going for.

So, I am in need of advice

Is it possible to run these heads on a stock displacement 88" with good results or is going to 95" and high comp my only option?

And if I go for 95" will my small carb ruin everything?

These parts are insanely expensive here in Europe right now so I can not just buy other cams or carb, I'm kind of stuck with the parts I have.

The bike already has a Dynatek ignition module, and I have installed electric compression releases in the heads.

All help is much appreciated

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[Colvinb]

Yeah you seem to be in the middle in both situations.  Both would workout but wouldn't be ideal.  I'd say those heads would be a little much for the 509 cam in an 88.  But that Carb in a 95 with 55h cams would be a little restrictive.  We're talking best case scenario setup.  Both setups will run and run decent.  Neither will take advantage of the parts until thier respective drawback it corrected.  My vote, I would definitely go the 95 route and run it with the smaller carb until you can afford the next step up and then it will be a total ripper.  The "too small" carb which is subjective would only really hinder you on the top end.  Where as too much air in the other setup would hinder your low end/mid setup which is mostly where you ride.

BTW you did an amazing job with that little TC chopper! Looks killer its tough to pull off but you nailed it!   

[Ohio HD]

I would also agree that 95" is the way to go. That opens up more cam choices for you. Maybe look at the T-man 590PS-2. Many have very good experiences with those cams. As well they're suitable in the event you wish to do more with the motor later.

[Hossamania]

I run the 55G cams, be aware that they are a cam that likes engine rpm, the opposite of the 509 cams. If you like to chug along at 55 mph (88 kph) in 5th gear and roll on to accelerate briskly, they are not the cams for you.

[Finn]

TW55 rpm range appear to be listed from 2600 to 6000. If that is correct it is quite high.

[Hossamania]

TW55 rpm range appear to be listed from 2600 to 6000. If that is correct it is quite high.

My 95" build and heads were set up for the 55 cams. Very soft power below 3000 rpm, especially in 5th gear. They do well at 3000 rpm. At 4000 rpm they come alive. At 5000 rpm they really rip. It's hard to keep 1st and 2nd gear off the rev limiter when leaving the line hard, gets there fast. At 55 mph I usually run 4th gear, even just cruising one up, to keep them in the beginning of the power band. Surprisingly, gas mileage is often better than using 5th gear, as less throttle is needed to keep speed. This with 3:37 gearing. It was worse with the 3:15 stock gearing.
I knew what to expect going in, as this bike was set up for 1/4 mile hammering (the actual parameter I asked of the shop was, I can't beat everybody, but I have to beat my friends!). 2 up going thru the hills requires working the transmission to stay in the power band, and might mean 3rd gear at 55mph to keep speed uphill, especially steep hills, which is fine with me.
Just wanted to let you know my experience with them.
Gear drive setup with over 100,000 miles on them of hard, hard riding, and still going strong.

[Ohio HD]

You know, looking back at this bike. It should have a final drive ratio of 3.15:1, And it being an FXDX is a pretty light package. The Andrews 55's with the compression set at 10.5:1 should do alright in lower RPM's.

I had a set of the 55's in a touring bike, a 107" with compression at 10.5:1, and stock heads. The low end was really ok, it didn't feel like it was lacking anything.

[Hossamania]

I should mention that when I said soft power in the low end, it's no worse than stock 88" and stock cam, and probably better, just seems soft to me because it makes such good power once in the midrange.

[Ohio HD]

I agree, the cams are designed to pull from the midrange. But the results in a lighter bike should feel good I think. Lower gearing and less weight helps a lot.

[Hossamania]

Definitely a lighter bike (and probably rider) compared to what I'm running. Also, my compression is probably not as high using flat top pistons.

[jsachs1]

I had a hand in the development, and testing of the TW55 cams. They always performed the way I expected them to. Used a lot of them back in the day.
John

[Hossamania]

Thanks for your work on them John, they bring a smile to my face every time I ride!

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Is it possible to run these heads on a stock displacement 88" with good results or is going to 95" and high comp my only option?

And if I go for 95" will my small carb ruin everything?

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I think either would be an improvement but I'm guessing you're already leaning towards plan b because you bought pistons. I'm running 40cv (bigger jets, mixture screw maxed out) on 95" and it's ok. One day I will get a bigger carb.
Your air cleaner looks pretty cool but I reckon it's a bit restrictive. I would upgrade that as part of the build.

[SwedishMeatball]

Thank you everybody for your great replies.

I think I will go for the 95" setup and run it with the CV40 until I can afford a bigger carb.

I think I will be getting a Mikuni HSR. Not sure if a 42 or 45 is the better choice?

[Ohio HD]

I'd stay with the HSR42. It'll better suite the changes you're making.