S&S 640 Compression?

[Badger711]

Currently building a 117" in my 07 dyna, acquired pretty much all the parts and am about ready for the machine shop. Shooting for 140-150hp. I'm currently torn on what to set compression at for this 640 cam. Pretty confident ~11.5-7:1 is where I'm going to go with it but still want to get some more input before finalizing the decision.

Build list is as follows-

Factory 4.375 Crank Trued and Welded
Axtell 4.125 Cylinders bored .010 over
Factory cases, bored
KB Super Duty .010-over dome pistons (9.8cc)
S&S 640 EZ start
SE110 Heads, will be getting MVA intake valve and port work
Wild Things 57mm Throttle Body
Feuling 6.2 Injectors
Big sucker style breather
JBV Guppy exhaust (originally for a softail, retrofitted for dyna) w/ 3" louvered baffle.

Deck height calculator puts the pistons 5 thou in the hole, using a .020 base gasket and .030 head gasket, static comp figures @ 11.58:1 if I cut the heads to 93cc. This is currently the plan, but I'm a little worried about the 640 feeling soft on the bottom but being on a light bike I'm hoping that setting at 11.6:1 it'll help make up for it.

I know heads are realistically going to determine where it tops out, but I'm shooting for as close to 150 as possible while staying on pump gas and without having to pull stupid timing out to keep from pinging. From what I've read i'm toe-ing that line at 11.6 but a lot of guys seem to have ran at 12:1 and had good results.

Input?


Thanks in advance,
  -Dalton

[Baddyna]

150 hp and + 6000 rom with a factory -07 crank,,,

[Hillside Motorcycle]

Currently building a 117" in my 07 dyna, acquired pretty much all the parts and am about ready for the machine shop. Shooting for 140-150hp. I'm currently torn on what to set compression at for this 640 cam. Pretty confident ~11.5-7:1 is where I'm going to go with it but still want to get some more input before finalizing the decision.

Build list is as follows-

Factory 4.375 Crank Trued and Welded
Axtell 4.125 Cylinders bored .010 over
Factory cases, bored
KB Super Duty .010-over dome pistons (9.8cc)
S&S 640 EZ start
SE110 Heads, will be getting MVA intake valve and port work
Wild Things 57mm Throttle Body
Feuling 6.2 Injectors
Big sucker style breather
JBV Guppy exhaust (originally for a softail, retrofitted for dyna) w/ 3" louvered baffle.

Deck height calculator puts the pistons 5 thou in the hole, using a .020 base gasket and .030 head gasket, static comp figures @ 11.58:1 if I cut the heads to 93cc. This is currently the plan, but I'm a little worried about the 640 feeling soft on the bottom but being on a light bike I'm hoping that setting at 11.6:1 it'll help make up for it.

I know heads are realistically going to determine where it tops out, but I'm shooting for as close to 150 as possible while staying on pump gas and without having to pull stupid timing out to keep from pinging. From what I've read i'm toe-ing that line at 11.6 but a lot of guys seem to have ran at 12:1 and had good results.

Input?


Thanks in advance,
  -Dalton

If 150 hp is your goal, might want to eyeball the .675 also.

[Badger711]

150 hp and + 6000 rom with a factory -07 crank,,,

Trued and welded...We've had justin's turbo bike at 245hp turning 8k and its held up fine

[Badger711]

If 150 hp is your goal, might want to eyeball the .675 also.

We already had the 640EZ's on hand and this is a somewhat budget build so i'm sticking with them but I had the same thought. I feel like it would definitely feel soft on the bottom with the 675's though as well.

[SB107]

I run the TW-68 at 12:1 which closes a tad earlier (2°) and have no issues whatsoever. I believe you're safe at that compression in terms of PMS. The guppy is a LOT of pipe for a 117, you're probably going to be soft on the bottom whether you use the 640 or 675. My dyna is soft on the bottom but its so light it doesn't really matter, mine also has a 30t comp sprocket which helps. The Boarzilla will hold back HP but the tq curve will hit earlier.

Side Note: My custom pipe is 1-7/8 off the head and stepped 4 times with the collector right after the transmission. I will be doing a baffle to mainly quiet it down and I think the low end will benefit as a result. My dyno sheet is in the dyno section. It may or may not be a Guppy baffle....

[Badger711]

I run the TW-68 at 12:1 which closes a tad earlier (2°) and have no issues whatsoever. I believe you're safe at that compression in terms of PMS. The guppy is a LOT of pipe for a 117, you're probably going to be soft on the bottom whether you use the 640 or 675. My dyna is soft on the bottom but its so light it doesn't really matter, mine also has a 30t comp sprocket which helps. The Boarzilla will hold back HP but the tq curve will hit earlier.

Side Note: My custom pipe is 1-7/8 off the head and stepped 4 times with the collector right after the transmission. I will be doing a baffle to mainly quiet it down and I think the low end will benefit as a result. My dyno sheet is in the dyno section. It may or may not be a Guppy baffle....

Good to know, appreciate the info. And yeah, it's got some large primaries but being a little soft in the bottom may be beneficial as far as launch goes. We cut down a 3" baffle we had laying around and it definitely helped the curve. Ignore the clutch slip line on the sheet, that was previous pipes and didn't have the pro clutch in at the time.

This has been a pretty budget build, a lot of the parts are stuff we had laying around the shop (guppy included). And i think it's fun to do one-off type stuff and see the results so we'll see how the sheet turns out.

[Badger711]

It's also worth noting I'm getting caught up in the dyno sheet and not how it's actually going to feel on the road. If there's not a real noticeable difference between 11.5:1 and 12:1 on the @ss dyno then I don't feel like it'll be worth the extra potential aggravation

[turboprop]

Currently building a 117" in my 07 dyna, acquired pretty much all the parts and am about ready for the machine shop. Shooting for 140-150hp. I'm currently torn on what to set compression at for this 640 cam. Pretty confident ~11.5-7:1 is where I'm going to go with it but still want to get some more input before finalizing the decision.

Build list is as follows-

Factory 4.375 Crank Trued and Welded
Axtell 4.125 Cylinders bored .010 over
Factory cases, bored
KB Super Duty .010-over dome pistons (9.8cc)
S&S 640 EZ start
SE110 Heads, will be getting MVA intake valve and port work
Wild Things 57mm Throttle Body
Feuling 6.2 Injectors
Big sucker style breather
JBV Guppy exhaust (originally for a softail, retrofitted for dyna) w/ 3" louvered baffle.

Deck height calculator puts the pistons 5 thou in the hole, using a .020 base gasket and .030 head gasket, static comp figures @ 11.58:1 if I cut the heads to 93cc. This is currently the plan, but I'm a little worried about the 640 feeling soft on the bottom but being on a light bike I'm hoping that setting at 11.6:1 it'll help make up for it.

I know heads are realistically going to determine where it tops out, but I'm shooting for as close to 150 as possible while staying on pump gas and without having to pull stupid timing out to keep from pinging. From what I've read i'm toe-ing that line at 11.6 but a lot of guys seem to have ran at 12:1 and had good results.

Input?


Thanks in advance,
  -Dalton

I have a TC124 with S&S 640 cams at 11.9 that makes 158h SAE through a modified G carb, AC and JBV Guppy exhaust. The dyno sheet from the break in tune at Zippers is in the dyno section.

[SB107]

Good to know, appreciate the info. And yeah, it's got some large primaries but being a little soft in the bottom may be beneficial as far as launch goes. We cut down a 3" baffle we had laying around and it definitely helped the curve. Ignore the clutch slip line on the sheet, that was previous pipes and didn't have the pro clutch in at the time.

This has been a pretty budget build, a lot of the parts are stuff we had laying around the shop (guppy included). And i think it's fun to do one-off type stuff and see the results so we'll see how the sheet turns out.

Track oriented, the guppy wins hands down. I don't blame you for using the guppy, as that would be my choice 10/10 times with this type of setup. Brian has a new 4" baffle that I will be using on mine since it is a completely open meg.

I 100% agree with you about the launch. you have such a small time window where the low end actually matters. Even during the point it matters you're trying to avoid lighting up the tire or doing a wheelie. After that you want more tq between shift points. Win/win.

[rigidthumper]

The 640 with 90cc chambers/9.8 domes/.030HG/zero deck on top notch heads should get you close (gonna depend on the heads/intake combo). Static CR just a tic over 12:1, corrected compression just under 9.9 should be manageable.

[Badger711]

Appreciate the input all!

[Don D]

It is a 117" so realistic expectations would be ~150/140 at 12:1+ if the heads are working right. Want 150/150 from the 117? That is a lot bigger task NA. This will not be a big torque producer until 3K is passed. I have done the same with a build posted in the dyno section here a few years ago, it was a dyna on Wes's dyno.

[Badger711]

It is a 117" so realistic expectations would be ~150/140 at 12:1+ if the heads are working right. Want 150/150 from the 117? That is a lot bigger task NA. This will not be a big torque producer until 3K is passed. I have done the same with a build posted in the dyno section here a few years ago, it was a dyna on Wes's dyno.

Being in a dyna I'm after horsepower numbers, I'm alright with not making 150 square. Cubic inches limits that for sure.

[kd]

Back to the basics, I would consider cutting the barrels for zero deck.  Then the .030 gasket is being used properly to control the detonation. (presently .038 total quench with deck at .008 in the hole) There are plenty of folks running 12:1 with a good tuner device like TTS and someone that knows how to tune for performance.

The later close of the 640 will probably never be noticed on a Dyna and in fact be a benefit on the street. My experience in the 145 - 150 square realm is it can be dangerous on some road surfaces or when wet.  As said previously any launches at the track (or street  ) will not be happening below that 2500 - 3000 rpm level anyway.  If it is a little soft, you can use that to your advantage in a parking lot or sneaking through the neighborhood at night or early morning.    

That's my impression of what I would consider to get the most out of the free stuff. Gearing considerations will have a huge effect and must not be forgotten. The head work, intake choices and tuning will set the stage for the performance.

[1workinman]

Back to the basics, I would consider cutting the barrels for zero deck.  Then the .030 gasket is being used properly to control the detonation. (presently .038 total quench with deck at .008 in the hole) There are plenty of folks running 12:1 with a good tuner device like TTS and someone that knows how to tune for performance.

The later close of the 640 will probably never be noticed on a Dyna and in fact be a benefit on the street. My experience in the 145 - 150 square realm is it can be dangerous on some road surfaces or when wet.  As said previously any launches at the track (or street  ) will not be happening below that 2500 - 3000 rpm level anyway.  If it is a little soft, you can use that to your advantage in a parking lot or sneaking through the neighborhood at night or early morning.    

That's my impression of what I would consider to get the most out of the free stuff. Gearing considerations will have a huge effect and must not be forgotten. The head work, intake choices and tuning will set the stage for the performance.

Good advice . I driven the 640 with both compression ratios and the higher ratio seems a lot more responsive . I have not experienced any more problem with the higher cr than the other one

[Don D]

The head work, intake choices and tuning will set the stage for the performance.

Yep and especially the pipe.

[Badger711]

Thanks for all the input guys.

Headwork is going to be done by Jim Robinson at Head Hoggers, he's a great guy to deal with and I trust his work.

Intake is up in the air currently, and I'm confident in our tuning. Looks like i'm leaning towards getting deck to 0 and running with 12:1.

[SB107]

I wont speculate what power numbers you will make because dynos and how the bike is dynoed vary. However, if you're not  240lb like myself, you should be able to get into the 10s with practice with this recipe.

[Badger711]

I wont speculate what power numbers you will make because dynos and how the bike is dynoed vary. However, if you're not  240lb like myself, you should be able to get into the 10s with practice with this recipe.

10's are the goal, I'm sure I won't be able to ride it into the 10's right off the bat but hopefully with practice I will be. And it will be a street and strip bike so i'm leaning towards being soft down low to be a benefit not a curse now.

[SB107]

10's are the goal, I'm sure I won't be able to ride it into the 10's right off the bat but hopefully with practice I will be. And it will be a street and strip bike so i'm leaning towards being soft down low to be a benefit not a curse now.

My tq curve is ugly, but the bike is stupid fast. I havent even intentionally gone to/past peak tq. Only time I did was when I did a pull in 4th, hit a bump, and lit the back tire up at 65mph (cold tire didnt help).

[CVOKing]

I ran a 124 crate at 11.8 on a heavy bagger. On a hot rod dyna. Id want to get it to 12to1 on a 640. This cam isn't that soft on bottom when set up proper. The biggest thing with big cr is you really need a skilled dyne tech 

[Badger711]

I ran a 124 crate at 11.8 on a heavy bagger. On a hot rod dyna. Id want to get it to 12to1 on a 640. This cam isn't that soft on bottom when set up proper. The biggest thing with big cr is you really need a skilled dyne tech

Sounds good. I'm confident in our tuning so we should be alright there.

[kd]

Like Don said, the pipe goes without saying and you have that.  The clutch and basket will be weak links at that power if you plan on punishing it. It may be a good time to consider the EVO Industries basket and a 49 tooth sprocket to get your gearing down.

[Badger711]

Like Don said, the pipe goes without saying and you have that.  The clutch and basket will be weak links at that power if you plan on punishing it. It may be a good time to consider the EVO Industries basket and a 49 tooth sprocket to get your gearing down.

Running a Rivera pro-clutch so basket should be alright, I'm thinking. Gearing may be in order though.