[pozza1450]

I'm Marcello from Italy and I'm running a Underground build with this setup:

95” SE cylinders
SE domed forged pistons
Underground Heads decked at 83cc (CR=10:1), Crane spring 155
Cometic .030" head gaskets
Andrews TW 37b
Crane Adjustable Chromemoly Pushrods
JIMS Big Axle "powerglide"
SE adjustable map ignition system
Mikuni HSR42
SE Big-bore manifold
SE air cleaner
V&H Pro-Pipe

I contacted Colin of Underground Performance and asked him If in the future i would swap to gear drive which are the best cams that works with this kind of heads.
He reply to me that the TW-5G cams will give me more performance than what i have, and there are no problem with the lift because my heads will accept TW-6HG cams and those are .590 lift so the TW-5G cams will work well.
What do you think about? are TW-5G a good choice.
Any advice will be greatly appreciated.
Thanks in advance for your help.
Marcello

 

[SILVER BULLET]

If your heads are 83 cc and you are running S.E. domed top piston's ,then you are at more than 10 - 1 comp. Put the 6HG in there ! Do you have dyno # now ?

 

[pozza1450]

Sorry, but i don't have a dyno, also Colin said to me that with my compression TW6Hg+4 degree key will be fine but this cam is too much radical, noise and will cause more faster wear.
I’m looking for a reliable cam that give me excellent low end torque with an eye at the top end.

 

[GRock]

IMO, you will not see real seat of the pants difference with the TW5 over the 37. You will gain a bit more TQ and have it come on a couple hundred RPM sooner, and maybe, MAYBE 2 to 3 HP. But the TW5 is a sister to the 6HG as if you look at the numbers they are all reduced proportionally from the 6HG. Same aggression on the ramps and proportionate LSA's. That cam was made by Bob Wood to fit the SE Performance heads .575 lift capacity because his TW6H would not. Want a suggestion?? Put a +2 key in with the 37 and continue to enjoy a smooth, strong, and reliable ride.

PS. The Bullet is right, if you are running 83 CC, .030 HG, and domed pistons, you are around 10.4 to 1 comp.

 

[pozza1450]

Are you sure that i'm around 10.4:1? I calculated the CR ratio with the excel sheet, are something wrong?

Corrected Compression Ratio
Bore = 3.875 inches
Stroke = 4.000 inches
Rod Length =7.66 inches
Head Gasket Thickness = 0.030
Head Gasket Bore = 3.950
Head Gasket Volume = 0.3676
Cylinder Head Volume = 83.000
Deck Height= 0.00
Piston Dome Volume = 3.500

Calculated CR (cold) = 10.0386 :1
Calculated CR (hot) = 9.2894 :1

Putting a +2 degree key increase the cylinder pressure and i think that will give me some pinging problems!

 

[GRock]

Are you sure that i'm around 10.4:1? I calculated the CR ratio with the excel sheet, are something wrong?

Corrected Compression Ratio
Bore = 3.875 inches
Stroke = 4.000 inches
Rod Length =7.66 inches
Head Gasket Thickness = 0.030
Head Gasket Bore = 3.950
Head Gasket Volume = 0.3676
Cylinder Head Volume = 83.000
Deck Height= 0.00
Piston Dome Volume = 3.500

Calculated CR (cold) = 10.0386 :1
Calculated CR (hot) = 9.2894 :1

Putting a +2 degree key increase the cylinder pressure and i think that will give me some pinging problems!

You're actually less than 10.4, but your figures are wrong for a domed SE piston. I get into enough tiffs with guys over here over this crap, so I don't intend to get into it overseas. Arividerci, my Italian friend!

 

[pozza1450]

GRock, thanks a lot for the replies, but i don't understand what do you mean with "your figures are wrong for a domed SE piston".

 

[disco]

Pozza,
I assume you are running 22868 SE pistons with 3.5 cc domes.
Let me know if I'm off base here. I run the same set up as you
except I have .04 Cometic gaskets. I can make mine ping if I get
lazy with the gear shift on a hot day riding two up. My heads are
also 83 cc. UG heads are spin dropped. Does that result in slightly
higher compression?? :dunno: Any one?? I've been adding a little
fuel and removing a little timing advance with my PC3USB but I'm
not sure how much I can retard the timing safely. It was tuned
with Dynojet direct link and makes excellent power (94/104) so I
don't want to mess with it too much.
Grock, if I'm out to lunch here let me know.

Thanks

 

[pozza1450]

Disco, yes i'm running 22868 SE pistons with 3.5 cc domes
, the 37 worked good and the motor ping only at low rpm if i open wide throttle, my SE adjustable map ignition setting is CS=2, SA=-3 (Total advance retard= -8°) and i running with standard Mikuni setup.

 

[disco]

Pozza,
Where are you located in Itay? I spent all of June touring your country.
Traveled from the south all the way to Switzerland and both east and west coasts. Loved every minute, Italians know how to enjoy life!!
Many times on the autostradas I was traveling 160 KMH (100 mph) and vehicles would blow by me like I was parked. I understand why you would look for more top end power.

Disco

 

[pozza1450]

I live in Treviso, near Venice. Italy is a beautiful Country and i love USA also, i went in Calivornia for the second time last march and i went in Florida in August of 2001.

Marcello