[1993FLHS]

Got my engine parts back from the machine shop. He needed to go .020" over to straighten the bores out, and did a mild port job. No decking of jugs or heads was needed or performed. He recommended and fitted cylinders with 10:1 Wiseco pistons and swapped my cam gear on a new EV27 cam.

Maybe I'm reading too much, but I'm concerned this combo is going to have trouble starting and with detonation if I use the "standard" .040" Cometic head gasket.

By installing a .060" head gasket, how much will my compression drop?

Thanks.

 

[Mattbastard]

I have the same dilemma, EV27 and 10:1 Wiseco's. I have a friend with a mill, we knocked the dome from .154" down to .080". I figure this will take it down to around 9.2:1. I'm just not interested in hard starting, or detonation. I looked into gaskets and even with the thickest I could find it didn't drop the CR that much.

 

[shovelbill]

the only way to know what you actually have is to cc your setup. i don't remember the exact number, but somewhere around .068" is one compression point on a 3 1/2" bore........so .020 would be 1/3 of a point...........in theory.

why put in 10:1 pistons only to "rework" it? your changing the squish that way.......set it up correctly from jump street.....isn't "10:1" a little high for an EV27?

 

[cernunos]

Halloo. Agree with everyone else here. Going to a thicker gasket will most likely mess up the quench area. And the EV27 will probably drive you up the wall with 10:1 c/r. Angel, older Softail, has 10:1, and with a Crane 300 cam (comparable to the 27) I was having starting issues, detonation, blah blah. Ran great up to about four grand, but just not worth the hassles. Why not just go a bump up on the cam specs?

C......

 

[1993FLHS]

Thanks for the replies. The concensus I'm hearing is I need a cam with intake timing greater than 40 to make the 10:1 happy. Would EV46 or EV51 be a better choice for a heavy bike?

 

[cernunos]

Halloo. Angel is fairly heavy I would say. I am about 850 full fuel, bags packed, and me with a full stomach. The good thing is the compression ratio will take some of the "sag" out of the bottom end with the bigger cam. If you are wanting more oomph on the bottom I would think the EV46 should give it to you. It seems a lot of people are getting good torque figures from around 2K on up to 6K with it.

C.......

 

[tussuck]

Agree with above... An EV35 or 46 would be great. I suspect that the EV51 may be a little lumpy for that build.


Sent from my Motorcycle iPad app

 

[JamesButler]

Before doing anything, you should have your heads examined. :redrolf: To paraphrase, you wrote that they were mildly ported and decks were not shaved. As such, your cylinder head volume might have actually gained one or two cc's, which would have decreased your original mechanical compression ratio. In addition, at .020" over, your cylinders now measure 3.518. Going with a .060" head gasket is unnecessary in this case and never the way to go, imo. Stay with at most a .040" head gasket for squish and other reasons. Get the heads flowed and cc'd to get their volume, but let's assume they're at 85cc. You're Wiseco 10:1 pistons have a 12.9 cc dome volume. If you want @ 9.0:1 Corrected Compression, then with the 36 intake close of the EV-27 cam, you should now be at @ 8.99:1 Corrected Compression, according to the BigBoyz calculator. :woohoo: So, for now just make sure you're at zerO deck height and measure the volume of your heads. More cylinder volume = less compression. Less cylinder head volume = more compression, in which case you'd have to shave a little material off of the piston dome.

 

[JamesButler]

To answer your original question though, switching from a .040" head gasket to a .060" would lower compression @ a quarter of a point (.26).

 

[1993FLHS]

Really appreciate all the replies.

I just placed an order for a EV46 and I'm sticking with a .040" MLS head gasket. Once I get the cam I'm going back to my builder so he cam swap my original cam gear from the 27 to the 46. I will ask him if he cc'ed the chambers. Again, neither the jugs or heads had any milling performed.

I plan on running a external Dyna or Twin Tec ignition. The EV46 should also allow me to get more aggressive with the advance curve.

Thank you all again.

Glenn

 

[mor pwr]

You will not have any starting problems with 10:1 compression with an EV 27 cam. I have built many of them for my customers.

 

[Side Burns]

10:1 comp with an EV27, there are a zillion of those running around with no detonation problems. (Maybe only a million...) Probably need to check your timing or adjust your VOES to retard sooner, 7inHg? Stock FL is around 6inHg.

 

[Thermodyne]

Why not just go with what you have and then work the ign curve to fix the spark related problems?

 

[1993FLHS]

Too late...already have the EV46 set up with my cam gear.

Thanks for the replies.

Glenn

 

[cernunos]

Halloo. Glenn, be sure and let us know what you think of the '46 and 10:1.

C......

 

[1993FLHS]

Will do! Just got another couple inches of snow here in Metro Detroit, so it'll be awhile.

I ride 1-up about 90% of the time, and I weight about 180, so I think bottom-end torque will be just fine.

Thank you!

 

[claydbal]

typical. ...................why not design the motor to work?

 

[1993FLHS]

So clearly you don't feel 10:1 and a EV46 is a good match?

 

[cwilks]

So clearly you don't feel 10:1 and a EV46 is a good match?

thats what I'm running along with a nice street port from Bean...runs awesome...its in a '90 FXRP

 

[Side Burns]

10:1 with an EV46 is a good choice for a softail or dyna. I think Claydbal's point is that it's not a great cam for a heavier FL. An EV27 should run just fine at 10:1, and if it does not in your case, you should investigate as to why instead of just throwing a later intake closing cam at it. An EV46 in your case probably will feel a little soft at lower rpm's. Thicker head gaskets to lower static compression will make things worse, not better. Good luck.