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Posted by: Headrage Jan 27 2006, 05:10 PM

I have a possible line on a set of Venolia P/C's running 10:5 to 1 compression to put on my 2.7.

What I'll end up with is 40mm webers, late "S" cams and 10:5 to 1 compression.

What do you guys think about the combo???

Posted by: joea9146 Jan 27 2006, 05:11 PM

I think with !0.5: 1 you may have to Run Twiin Plugs.... That compression is pretty High

Posted by: Aaron Cox Jan 27 2006, 05:12 PM

I think its gonna suck.....
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when a cop busts you! LOL 200+ hp?

Posted by: rick 918-S Jan 27 2006, 05:23 PM

And that's a problem because?

Posted by: Eric_Shea Jan 27 2006, 05:25 PM

Twin Plug or Different Ignition (Crankfire??)

Posted by: J P Stein Jan 27 2006, 05:27 PM

Webers & S cams are OK in a race motor as is 10.5:1 compression with race gas. You gots a race car?

Posted by: Headrage Jan 27 2006, 05:49 PM

Change of plans. Mechanic says compression is too high for what I need.

Going with Mahle euro P/C's. Shooting for 9:0 to 1...

Posted by: J P Stein Jan 27 2006, 05:55 PM

'E' or Solex cams are a far better choice for a street car.

Posted by: olav Jan 27 2006, 06:04 PM

Posted by: Eddie914 Jan 27 2006, 06:12 PM

Great combination - lots of power, and fabulous throttle response, it will even lighten the car via your wallet since you will be paying$6.00 to 8.00 per gallon for race gas (100 low lead or 110 octane leaded).


10.5:1 is a bit high for pump gas. 9.5:1 is about the limit for single plug applicaitons with pump gas (depending on the quality of the pump gas ... pump gas is not the same in all parts of the country). You might be able to reduce the compression ratio with additional cylinder base gaskets, grinding of the piston crowns or grinding of the combustion chambers. It all depends on the price of the Venolia P/Cs and the amount of custom work you are prepared to do (or are prepared to pay to have done).


Eddie

Posted by: SLITS Jan 27 2006, 06:18 PM

Venolias were gone....actual pistons were Forged True with a CR of 11 to 12.5:1 depending upon installed height....

Well, back to the drawing board.............

Posted by: TimT Jan 27 2006, 09:20 PM

I used Venolia Pistons on the first 911 engine I ever rebuilt. It was 2.2, when my dad and I measured the bores they were ovaled and tapered.. so we had them bored.. An outboard motor guy we knew hooked us up with Venolia.. the engine, after all was said and done was 2.35L The CR was 10.1:1 when measured...

It was a screamer that engine.. Yikes almost 25 years ago LOL I drove it for a few thousand miles, then balled the car up.

10.5 Is probably the max CR unless you commit to high octane, or twin plug heads..

QUOTE

Shooting for 9:0 to 1...

go for a measured 9.5

Posted by: brp914 Jan 27 2006, 09:49 PM

what happened to your engine? last I heard, it torqued down ok and you were on the road.

Posted by: Headrage Jan 27 2006, 09:57 PM

QUOTE (TimT @ Jan 27 2006, 07:20 PM)

go for a measured 9.5

That's my goal...

Posted by: Headrage Jan 27 2006, 10:00 PM

QUOTE (brp914 @ Jan 27 2006, 07:49 PM)

what happened to your engine? last I heard, it torqued down ok and you were on the road.

Didn't work. Head was leaking for a long time and eroded the cylinder.

One thing I learned is that unless you are a very good /6 guy (or girl), you will not know how to determine a head leak by ear....

Posted by: J P Stein Jan 27 2006, 10:04 PM

We (myself & another guy) rad 14.5 :1 Venolias in a 301 Chebbie back in the 60s.....drag racin'. We had to to run 2 compression washers on the plugs to keep em' off the pistons.

I ain't a big fan of trimming the deck height of 911 motors. Tain't worth the trouble for about .5 compression.....which don't give much bang for the buck. Even a point more would be worth maybe 10-15 hp & torque tops..better to get new pistons, me thinks.

Posted by: sixnotfour Jan 27 2006, 10:10 PM

QUOTE

I ain't a big fan of trimming the deck height of 911 motors. Tain't worth the trouble for about .5 compression.....which don't give much bang for the buck. Even a point more would be worth maybe 10-15 hp & torque tops..better to get new pistons, me thinks.

His heads are gonna need a cut because of the loose cyl/ heads /errosion.

Posted by: Headrage Jan 27 2006, 10:11 PM

QUOTE (J P Stein @ Jan 27 2006, 08:04 PM)

Even a point more would be worth maybe 10-15 hp & torque tops..better to get new pistons, me thinks.

Thanks for the advice.


Mr. Make me spend more money....

Posted by: J P Stein Jan 27 2006, 10:16 PM

QUOTE (sixnotfour @ Jan 27 2006, 08:10 PM)

QUOTE I ain't a big fan of trimming the deck height of 911 motors. Tain't worth the trouble for about .5 compression.....which don't give much bang for the buck. Even a point more would be worth maybe 10-15 hp & torque tops..better to get new pistons, me thinks. His heads are gonna need a cut because of the loose cyl/ heads /errosion.

Yeah, but that can be shimmed back up at the cylinder base.
If not, you gotta cut the chain boxes to suit the heads, right?
Then you can get into chain length problems which can be cured by oversized idler sprokets...I'd pass.