Calling all experts!! Algorithm for 2.7L race motor to attain 300HP??

speed4sport · 08-14-2007, 02:11 PM

OK, I've jumped out of big bore Corvettes into a 911 'cause I've always wanted to and it will make me a better racer. Here is my baseline assumption - GTU (SVRA & HSR) class "magic" competitive number is 300HP.

Here's the engine I am currently running:
* '77 2.7L, stock crank & rods
* RS p&c's, ~9:1 CR
* Nice head porting / flowed, single plug
* S cams
* Weber 40IDA's, venturis & intakes opened to 38mm
* MSD 6AL ignition
* Race headers 1.625" primaries into 2" collectors
* 110 octane race fuel only
* Dynoed at ~240HP peak at 6900RPM

So what do you recommend for a next move? All of the below or a la carte???
* Big bore kit to 2.8 or 2.9?
* CR bump to 10:1?
* PMO carbs - 46/50?
* Different cams?
* Twin plug?
* Abandon 2.7 platform and start over with '78-'83 3.0?
* Other?

Obviously each decision has a cost versus benefit, and until I win the lottery, decisions must be prioritized. So need some help so I can stay ahead of the Nissans and Mazdas!

Thanks in advance...

Henry Schmidt · Henry Schmidt's Garage

To see 300 hp with a 2.7/2.8 you will have to make hp all the way to 8000 rpm and beyond.
The 2.7 crank will not survive at those RPMs for long.
The mag case will also offer some challenges.
It's best to start with a 3.0 and build from there. Stronger crank, better heads and the aluminum case make the 3.0 the core of choice.
Even with a 3.0 platform, 300 hp is no easy task.
Ports
cams
compression
46 PMOs or more
Think RPM and start shoveling out the cash.

This 3.0 engine had all the goodies and only made a little over 280hp.

kenikh · 08-14-2007, 07:16 PM

C'mon Henry, tell him about the short stroke 2.8!

shbop · 08-14-2007, 08:18 PM

Quote:

Originally Posted by kenikh

C'mon Henry, tell him about the short stroke 2.8!

And, another photo wouldn't hurt either.

speed4sport · 08-15-2007, 03:15 AM

Henry, thanks for the feedback. Your engine is a thing of beauty. I may shift gears and live with the 240hp, and put the car on a diet, stuff more tire under it, put an LSD in, etc....and buy a lottery ticket today.

Thanks!

speed4sport · 08-15-2007, 04:19 AM

Henry, just read the thread on your SS 2.8L. Nicely done - I definitely think your idea of putting together the ultimate and keeping it "old school" is just cool. Hmmmm, I have a survivor '77 930 sitting in the shop....

ael911 · 08-15-2007, 08:08 AM

Sorry to hijack this thread a bit, but Henry, is there a way to build a short stroke 2.8 without using a 3.0 carrera or turbo case? I have been searching for awhile for one of those and it's virtually non-existent out there. Also, what kind of possibilites do I have if I use a 7R case with a 66mm counter crank?
Thanks,
Andy

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by shbop

And, another photo wouldn't hurt either.

Pictures? You want pictures? You can't handle these pictures!
oops, channelling Jack again

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by ael911

Sorry to hijack this thread a bit, but Henry, is there a way to build a short stroke 2.8 without using a 3.0 carrera or turbo case? I have been searching for awhile for one of those and it's virtually non-existent out there. Also, what kind of possibilites do I have if I use a 7R case with a 66mm counter crank?
Thanks,
Andy

There are two ways to build a 2.8 SS without a 3.0 Carrera or 3.0 Turbo case.
First, find a 66 mm 962 crank. They are out there and will generally cost around $2500.
The other option is to make a crank. That is what we are doing. They also cost around $3000. The benefit of making a crank is better material, improved oiling and of course they are new.
With a mag case 2.7 you can build a 2.5 (66x90) or a 2.6 (66x92) and have a very nice little engine but life expectancy of any mag case engine is reduced when high RPMs are encountered.
High RPMs is the reasoning behind short stroke engines.

ael911 · 08-15-2007, 11:47 AM

So it looks like I will have to spend at least $3k either way for a donor turbo or carrera engine or buy the appropriate crank. I do like the idea of the new crank though. Thanks Henry, and keep us posted on your new developments.

shbop · 08-15-2007, 12:14 PM

Pictures? You want pictures? You can't handle these pictures!
oops, channelling Jack again

Well, you're right. That just cost me about a half hour of unproductive daydreaming. On second thought, maybe not unproductive. Thanks Henry!

kenikh · 08-15-2007, 12:23 PM

One positive for new cranks is you can spec the journals for modern NASCAR type bearings. Of course then you need custom rods.

Good stuff.

dd74 · 08-15-2007, 01:35 PM

Quote:

Originally Posted by Henry Schmidt

...but life expectancy of any mag case engine is reduced when high RPMs are encountered.

About what RPM would that be, where it is high enough reduce life expectancy?

ael911 · 08-15-2007, 02:48 PM

Quote:

Originally Posted by dd74

About what RPM would that be, where it is high enough reduce life expectancy?

That's a good question, maybe I shouldn't rule out making a short stroke out of my 2.7 just yet. Help us out Henry...

Henry Schmidt · Henry Schmidt's Garage

There are so many factors that effect longevity, but as a 70.4mm stroke I would say sustained 7400-7600 would create a problem.
66mm stroke would live closer to 8000.
Reciprocating weight will play a huge role in longevity at higher RPMs.
Ti rods (light weight)
Lightened pistons
Counter weights
Shuffle pins
Controlled harmonics
All play a tremendous role.

dd74 · 08-15-2007, 03:17 PM

Quote:

Originally Posted by Henry Schmidt

There are so many factors that effect longevity, but as a 70.4mm stroke I would say sustained 7400-7600 would create a problem.
66mm stroke would live closer to 8000.
Reciprocating weight will play a huge role in longevity at higher RPMs.
Ti rods (light weight)
Lightened pistons
Counter weights
Shuffle pins
Controlled harmonics
All play a tremendous role.

So with a standard mag 2.7 case, sustained 7400-7600 begins to effect longevity. However, lightweight pistons, such as JE might mitigate some of the damage of such high revs?

Oh, and as always, thanks Henry for the help.

ael911 · 08-15-2007, 08:12 PM

So Henry, I can build a 7R, 66mm crank motor with all the goodies you mentioned and expect decent life out of it if I keep it under 8K rpms?
Thanks for all your expertise.

dd74 · 08-20-2007, 01:34 PM

Quote:

Originally Posted by dd74

So with a standard mag 2.7 case, sustained 7400-7600 begins to effect longevity. However, lightweight pistons, such as JE might mitigate some of the damage of such high revs?

Oh, and as always, thanks Henry for the help.

Henry - any input into this question?

BTW: sent you a couple PMs.

Thanks.

cstreit · cstreit's Garage

Algorithm for 111HP/liter? Here it is. $ + engine = 300 HP.

Seriously though, you'll have to turn a lot of revs for that.

HawgRyder · HawgRyder's Garage

And here I am rebuilding my 2.0L "S" with perhaps 90mm barrels, using an aluminum case and very large oil pump (got it off Ebay about 4 yrs ago).
The original idea was to build something with less compression so I could use lower octane gas.
I have been told, if I just use the 90mm barrels, without decking the cylinders or the heads, I will drop about 1 1/2 points on the C/R.
I have looked at the sets of 90mm barrels, and I notice that they have a groove at the top for a sealing ring?? perhaps.
Henry..can I use my S heads on these barrels...or am I now looking for heads as well?
Bob