Hot rod Engine choice...2.7 or 3.0??? - Page 2

cmcfaul · cmcfaul's Garage

wax up the skis, you are now on the slippery slope of while I am in there.

Enjoy the ride :-)

Chris
73 911 E

cnielsen · 11-19-2012, 10:16 AM

Oh, I'm VERY familiar with those slopes!

shbop · 11-19-2012, 10:42 AM

Quote:

Originally Posted by cmcfaul

wax up the skis, you are now on the slippery slope of while I am in there.

Enjoy the ride :-)

Chris
73 911 E

Too funny! I had the same thought. This is the time when "buckle-up" takes on a whole new meaning.

jeffs9146 · 11-19-2012, 11:43 AM

The 911 and 914 901's turn different! If you put a 911 901 into a 914 you have to flip the R&P otherwise you will have 5 reverse and 1 forward gears!

I have a 914 with a stock, rebuilt, 901 and an 83sc 3.0L Fuel injected motor! I love it! I don't use 1st gear and in second it pulls very strong all the way up the power band!

I don't feel like it is stressing at all and I have put about 10k on it so far! I have been told that once you push the 300hp mark then things start breaking!

cnielsen · 11-19-2012, 11:59 AM

Thanks, I would not use a 914 transmission. The two early transmissions I have are from '67 and '69...both from 911's.

al lkosmal · 11-19-2012, 12:02 PM

Chris,
I've considered twin plug vs. single plug etc. I do not have experience regarding the driveability etc. ...others have way more experience than I do. But, one of the things that I was considering was/is the increase in HP per compression point. Here is a link to a handy compression/HP calculator. I've included a sample of the results for a 250 HP engine at 9.5:1 and the results of bumping the comp to 10.5:1. Does this jive with real world results? Hopefully, Steve and other experts in the field will check in and let us know. At the time I was considering this, I decided that the increased complexity of twin plugging was not worth it for a street car and I went single-plug and 9.5:1 JE's.

That's just me....I could be wrong

Compression Ratio HP Determination Program

Bowling's Compression Ratio -> HP Calculator
Computation Results:
Engine Horsepower (peak) is 250
Old Compression Ratio is 9.5
New Compression Ratio is 10.5
Computation Results:
Computed New Engine HP is 257, a 3 percent change

jeffs9146 · 11-19-2012, 01:16 PM

Quote:

Originally Posted by rfuerst911sc

Is there a difference in the 901 in a 911 vs. the 901 in a 914 ?

The 911 and 914 901's turn different! If you put a 911 901 into a 914 you have to flip the R&P otherwise you will have 5 reverse and 1 forward gears!

I have a 914 with a stock, rebuilt, 901 and an 83sc 3.0L Fuel injected motor! I love it! I don't use 1st gear and in second it pulls very strong all the way up the power band!

I don't feel like it is stressing at all and I have put about 10k on it so far! I have been told that once you push the 300hp mark then things start breaking!

cnielsen · 11-19-2012, 01:36 PM

Wow Al, you sure know how to make a convincing case for the 9.5:1 pistons and a single plug ignition. Seems I would be chasing the last couple horsepower with thousand dollar bills!

cnielsen · 12-02-2012, 09:17 AM

If been accumulating parts for the 3.0L rebuild and if I'm ruling out the 10.5:1 CR pistons, should I just stick with the stock CIS pistons and go with a Webcam 20/21 camshaft? Seems to me the 9.5 pistons would only get me 3% gain and cost a fair amount of money.

Certainly not trying to be cheap here but if that saves me $2K then I can invest the money into other parts of the car...LSD, trans up, suspension etc. sounds like more bang for the my buck.

I need to keep reminding myself that this is NOT a race car...never was and never will be.

al lkosmal · 04:16 PM

Chris,

As you said...3% can cost a bit...............the ROI is weak.

Bowling's Compression Ratio -> HP Calculator
Computation Results:
Engine Horsepower (peak) is 180
Old Compression Ratio is 8.5
New Compression Ratio is 9.5
Computation Results:
Computed New Engine HP is 186, a 3 percent change

If I ran across a nice set of 9.5:1 JE's or 9.3:1 Euro's... I'd consider it and then go with E-cams....but for a nice street car, it would have to be a smoking deal (I.E. making the ROI mo-betta). Otherwise I'd get the most (drivable) cam I could use with CIS pistons, SSI's, Webers, recurved dizzy, sport muffler and call it real. That will be a really nice, solid, relatively unstressed, mild street-rod motor. I think that this combo will push around an early, light 911 ........convincingly.

regards,
al

Tooth911 · 12-02-2012, 04:54 PM

Hi all
I have a 77 911s that has been set up for track day at PIR.Started out stock 2.7l.Had the motor redone and now a 2.8l single plug and 9.5cr JEs. nickys, Jeff Hines did the rebuild and now has 27k on engine and trans still a fun car.
Chuck

Ived moved to Walla walla now and dont get a chance to do track time anymore

rbogh901 · 12-02-2012, 06:29 PM

Back to the CR calculator:
Interesting, it looks like you get a simple 3% HP increase for every 1.0 increase in CR. Now I know. And if the CR is high enough you need to consider twin ignition. $$$
Calculating HP/displacement is easy too. Correct me if wrong, 2.7 to 3.0 is @ 10% so 10% increase in power, other things being equal (ish).

Which brings us back to the old "displacement is king."

Tooth911 · 12-03-2012, 07:13 AM

Yes I went down that slippery slope of expenses. And Ended it up doing RSR front suspension tarretsways and so on it's a great track car but now I miss something street friendly. I run premium fuel at the pump . On a positive note I ended up shedding a lot of weight as well car weighs about 2600 with me in it and the 2.8 L plenty to move it around the track.