S&S 475

[08flstf]

Anyone run the S&S 475 in anything other than stock compression engines? From what I've seen it works well in 107-117 stock motors, but I'm looking at Axtell's 117" piston kit at 10.5/1 comp. Was wondering if anyone knew if that would be too much compression for this cam or if it would still be a good fit. I've looked on S&S website but can't find any info on compression ratio for this cam. Thanks

[Nastytls]

I would like to know this as well. Running it currently in stock 107'' and have considered a bump to 117-120''.

[Jamie Long]

The 475c works very well with moderate compression

[08flstf]

Thanks Jamie.

[To The Max]

The 475c works very well with moderate compression

Jamie would that be about 10.7 .

[Jamie Long]

Jamie would that be about 10.7 .
[/quote]

You can run it up to about 11.0

[1FSTRK]

Is 11.0 to 1 moderate compression for the new M-8 engines?

[Nastytls]

Is 11.0 to 1 moderate compression for the new M-8 engines?

Is 11-1 not moderate in a TC?

Not being a smartass, it's a legit question.

[rigidthumper]

Is 11.0 to 1 moderate compression for the new M-8 engines?

Is 11-1 not moderate in a TC?

Not being a smartass, it's a legit question.

I believe the M8 can tolerate greater corrected compression (Because of the dual plugs) than the TC can.

[Jamie Long]

M8 engines run at significantly higher cylinder pressures than Twin Cam engines due to the design of the 4 valve M8 dual plug cylinder head. Stock M8 engines crank over at 240+ CCP. I would consider moderate static compression to be about 10.7-11:1 in most applications however in the end it really comes down to the specific cam & engine combination.

[Don D]

Jamie in your experience what is the top of acceptable corrected CR and have the calculators been accurate at predicting the outcome based on all the measurements plus intake close?

[To The Max]

Jamie would that be about 10.7 .

You can run it up to about 11.0
[/quote]Thanks Jamie but one more question . our best pump gas is 95 ron  is it still worth going to 11.0 with that fuel . Max

[HD/Wrench]

just get a real tune on the bike and all will be well  here is the 475 in a 117 . Specs are at the bottom of the sheet ,

2018 cvo 117 475 by GMR Performance, on Flickr

[1FSTRK]

M8 engines run at significantly higher cylinder pressures than Twin Cam engines due to the design of the 4 valve M8 dual plug cylinder head. Stock M8 engines crank over at 240+ CCP. I would consider moderate static compression to be about 10.7-11:1 in most applications however in the end it really comes down to the specific cam & engine combination.

Thanks for the reply.
I understand the why, I was just wondering where the number were settling in at for the M-8's with those that are doing the testing.

What does 11:1 with a 27.2 IVC timing yield for CCP?

With the stock engines coming with a CCP of 240+ what are you using for a target CCP on performance touring builds?

How about on hotrod street builds?

[Don D]

Exactly what I was wondering

[sfmichael]

Is 11.0 to 1 moderate compression for the new M-8 engines?

Is 11-1 not moderate in a TC?

Not being a smartass, it's a legit question.

Not an expert by any means but I would consider anything over about 10.5:1 to be above moderate. I've been building car engines for many years and know that once ccp exceeds 200psi in an old school 2 valve motor, tuning gets tricky and timing tables and fuel quality become very important.

I am surprised (pleasantly:) that the M8 cranks 240ish (STOCK!!)...no wonder they deliver such strong, early torque.

I am really hoping HD can fix the shortcomings of this platform because it's obvious to me that this engine holds enormous potential.

Thanks to Fuel Moto (and some others) leading this development I am excited about owning one of these in the future.

[HD/Wrench]

220-235 depending on cam installed .  I would have to look at my notes in teh shop but the 475 in a 11.1 117 was 228 if i recall

[HD/Wrench]

Is 11.0 to 1 moderate compression for the new M-8 engines?

Is 11-1 not moderate in a TC?

Not being a smartass, it's a legit question.

Not an expert by any means but I would consider anything over about 10.5:1 to be above moderate. I've been building car engines for many years and know that once ccp exceeds 200psi in an old school 2 valve motor, tuning gets tricky and timing tables and fuel quality become very important.

I am surprised (pleasantly:) that the M8 cranks 240ish (STOCK!!)...no wonder they deliver such strong, early torque.

I am really hoping HD can fix the shortcomings of this platform because it's obvious to me that this engine holds enormous potential.

Thanks to Fuel Moto (and some others) leading this development I am excited about owning one of these in the future.

The timing is one that you need to be on top of . Funny  tune a stage 1 and the timing is overly aggressive in my opinion , but again 108 and humidity is not your friend for high ccp and aggressive timing. 

swap a tq cam for hp and they still do very well the M8 is a tq monster with a simple bolt in cam

[To The Max]

just get a real tune on the bike and all will be well  here is the 475 in a 117 . Specs are at the bottom of the sheet ,

2018 cvo 117 475 by GMR Performance, on Flickr

Thanks that's great to know