small bore, high revving 6, anyone running one now? |
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small bore, high revving 6, anyone running one now? |
DanT |
Dec 18 2010, 10:12 AM
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#1
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Going back to the Dark Side! Group: Members Posts: 4,300 Joined: 4-October 04 From: Auburn, CA Member No.: 2,880 Region Association: None |
I have the chance to acquire an 2.0L 6 case and have thought about building a small bore 2.0-2.5L high revving 6.
Anyone out there running such a combination right now? This would be a street/AX motor. Prefer to do single plug. Most likely use Webers, since MFI parts are getting hard to come by . What combinations of Pistons/cams are you folks using? Pictures of motor builds would be appreciated. Just sliding in a 2.7L CSI motor is also a consideration if the small bore motor becomes too much of a pain. (IMG:style_emoticons/default/biggrin.gif) |
jjackson |
Dec 18 2010, 10:31 AM
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#2
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Member Group: Members Posts: 219 Joined: 5-October 10 From: maumelle, arkansas Member No.: 12,246 Region Association: None |
I have the chance to acquire an 2.0L 6 case and have thought about building a small bore 2.0-2.5L high revving 6. Anyone out there running such a combination right now? This would be a street/AX motor. Prefer to do single plug. Most likely use Webers, since MFI parts are getting hard to come by . What combinations of Pistons/cams are you folks using? Pictures of motor builds would be appreciated. Just sliding in a 2.7L CSI motor is also a consideration if the small bore motor becomes too much of a pain. (IMG:style_emoticons/default/biggrin.gif) We ran a 2.4L 10.5/1 single plug motor for a while.Built on a 5r case (strongest small bore case) with carbs.We only turned up to 7200 rpm.To run more RPM than that, you need aftermarket rods in my opinion.Made 220 + HP on S cams.Motor was rock solid.J |
messix |
Dec 18 2010, 10:59 AM
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#3
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AKA "CLUTCH KILLER"! Group: Members Posts: 6,995 Joined: 14-April 05 From: between shit kickers and pinky lifters/ puget sound wa.north of Seattle south of Canada Member No.: 3,931 Region Association: Pacific Northwest |
are you sure you want small bore?
a small bore will not make an engine a high rever. how ever a short stroke engine will. the short stroke has a slower piston speed compaired to a longer stroke engine per rpm. [distance the piston travels for each revolution, hence stoke]. this puts less stress on the crank and allows for higher rpm. so for a long stroke 2.5= long stroke x small bore short stroke 2.5 = short stroke x large bore |
ME733 |
Dec 18 2010, 11:23 AM
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#4
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Senior Member Group: Members Posts: 842 Joined: 25-June 08 From: Atlanta Ga. Member No.: 9,209 Region Association: South East States |
The ..2.0 six...had a short stroke...66mm.(same as a carrera 4 cam)., most also did NOT have a counterbalanced crankshaft....using a counterbalanced crank is essental for hi revs with reliability....titanium rods were used in the race engines, but carrello has excellant rods also...In my opinion the 911-S- cams are way too "peaky", and a better engine can be made with with other cams...get the bruce anderson book... "Porsche 911 performance handbook".read it, study it, then you can make some informed choises.
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campbellcj |
Dec 18 2010, 11:39 AM
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#5
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I can't Re Member Group: Members Posts: 4,557 Joined: 26-December 02 From: Agoura, CA Member No.: 21 Region Association: Southern California |
IMO you would not want a peaky small six for street or autox. Depending on the build specs and tune you might only make decent power between 4500-7000rpm's or so and regardless the peak torque would be modest compared to a larger displacement.
I have significant (18 years) experience driving 2.2 sixes and while they are gems and sound glorious, it can be challenging to keep them moving at a good clip. Short gears help. |
campbellcj |
Dec 18 2010, 11:39 AM
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#6
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I can't Re Member Group: Members Posts: 4,557 Joined: 26-December 02 From: Agoura, CA Member No.: 21 Region Association: Southern California |
IMO you would not want a peaky small six for street or autox. Depending on the build specs and tune you might only make decent power between 4500-7000rpm's or so and regardless the peak torque would be modest compared to a larger displacement.
I have significant (18 years) experience driving 2.2 sixes and while they are gems and sound glorious, it can be challenging to keep them moving at a good clip. Short gears help. |
J P Stein |
Dec 18 2010, 11:49 AM
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#7
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Irrelevant old fart Group: Members Posts: 8,797 Joined: 30-December 02 From: Vancouver, WA Member No.: 45 Region Association: None |
My old 2.7L would pull 7300 with all Porsche parts.....you want more, bring money.
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sww914 |
Dec 18 2010, 12:57 PM
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#8
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Advanced Member Group: Members Posts: 2,439 Joined: 4-June 06 Member No.: 6,146 Region Association: None |
They say the last 800 to get to 8000 will cost you $8000.00
That said, Henry Schmidt, a common sight on the Pelican board and a 911 engine builder for many years with much success says that the 2.5 short stroke is the best engine that Porsche never built. That's a 66mm 2.0 bottom end with 2.7 90mm pistons & cylinders. You can't really use the 2.7 CIS pistons because the dome shape is designed for the CIS swirl, it gets in the way of the valves if you run a good cam and their compression is too low. You have to use some JE or other A/M pistons to build that engine. It would probably respond really well to twin plugging as well. |
brant |
Dec 18 2010, 03:23 PM
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#9
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914 Wizard Group: Members Posts: 11,646 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
I put 100 racing hours onto a 2.0/6 with an aluminum case
it was all S spec, real 67S heads, cams, Counter balanced crank, pistons-cylinders, stock 2.0S rods it was great and only 9.8 compression (factory) 147hp to the wheels at 5000ft of altitude on a 104F day is not anything to sneeze at for a stock motor We would usually shift between 7200-7500 and loved it the quick revs (5lb tilton clutch and flywheel) are awesome I really like the small bore stuff and its so "right" sounding new motor is a small spigot 7R case (these are kinda hard to find, but slightly stronger than the 5R cases) I haven't driven it yet, but can't wait 66 counter balanced crank, big valves, 81mm pistons of just under 11:1 compression, twin plug, Pauter rods, lots and lots of head work with race cams shooting for a little over 200hp and probably will shift at 7500rpm (although the safe zone is somewhere around 8,500 rpm) builder said that rpm is only dependent on how long you want it to last I'm a huge fans of the small bore motors used to have an SC 3.0, and the motors are nothing alike.. really love the small bores. Attached image(s) |
GeorgeRud |
Dec 18 2010, 03:41 PM
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#10
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Advanced Member Group: Members Posts: 3,725 Joined: 27-July 05 From: Chicagoland Member No.: 4,482 Region Association: Upper MidWest |
The 66mm crank with the 90 mm piston bore does make a great sounding, high revving engine, but it will cost money to do correctly. They were popular in the early 70s as it could be used in the under 2.5 liter racing class.
Though they're usually maligned, the 2.7 does give nice grunt and revs quite well compared to the later, larger engines. In an autocross engine, I think that high torque should be the primary objective. That is achieved most easily with a larger displacement engine. |
Mark Henry |
Dec 18 2010, 05:20 PM
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#11
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
If you're rebuilding all sixes work out about the same price in the end.
Even if you get a cheap core it's a pay it now or pay it later type of deal. |
MikeSpraggi |
Dec 18 2010, 05:51 PM
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#12
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Senior Member Group: Members Posts: 781 Joined: 7-February 05 From: Silver Spring, Md Member No.: 3,570 Region Association: MidAtlantic Region |
Haven't driven it yet, but I've had a 2.2L six built for my track car I plan to run in vintage racing. Built on a 7R case, 84mm JE 11.3:1 pistons, Solex cams and reworked Zenith carbs. Oh yea, a little porting on the stock heads. Using a 2.0l non-counter weighted crank. Elected not to go with a lightened flywheel since the consensus was that I would not really see any gains.
I'll let you know how it turns out, say in April! |
d914 |
Dec 18 2010, 05:59 PM
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#13
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Advanced Member Group: Members Posts: 2,331 Joined: 12-July 03 From: Atlanta, ga Member No.: 904 Region Association: South East States |
I had a 2.5 liter short stroke six... loved it for the track,,, I even had fun on the street... auto cross not so much.. 220 at crank with 138 ft lbs.. The only thing that made it go was revs!!!! and lots of them... get caught low in a gear and your dead meat...
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Cap'n Krusty |
Dec 18 2010, 07:54 PM
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#14
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Ahem! I have an aluminum case, a long block, and a core motor. All are for sale. The core comes with a good regrindable counterweighted 2.0 crank. Bring money. I'm probably gonna use Cunningham rods in my 2.5.
The Cap'n |
J P Stein |
Dec 18 2010, 08:23 PM
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#15
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Irrelevant old fart Group: Members Posts: 8,797 Joined: 30-December 02 From: Vancouver, WA Member No.: 45 Region Association: None |
Ahem! I have an aluminum case, a long block, and a core motor. All are for sale. The core comes with a good regrindable counterweighted 2.0 crank. Bring money. I'm probably gonna use Cunningham rods in my 2.5. The Cap'n Hay Cap'n, have you priced U/S rod & main bearings lately? Bring money indeed. |
jfort |
Dec 19 2010, 07:35 PM
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#16
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Senior Member Group: Members Posts: 1,137 Joined: 5-May 03 From: Findlay, OH Member No.: 652 Region Association: Upper MidWest |
Have a 2.5 short striker with E cam and short gears. Quick and the sound is glorious
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Mark Henry |
Dec 19 2010, 08:17 PM
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#17
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
There's a set undersize rod bearings on the bird classifieds right now and I know of another set at a good price. First under size on some of the rods isn't that big of a price, the mains are a different story.
$1200 for set of SC first under mains...cheaper just to find a standard crank. |
koozy |
Dec 19 2010, 08:41 PM
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#18
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Senior Member Group: Members Posts: 651 Joined: 21-July 07 Member No.: 7,931 Region Association: None |
(IMG:style_emoticons/default/shades.gif) Hmmmmmm..... Whatcha doooooin??? (IMG:style_emoticons/default/idea.gif)
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Eric_Shea |
Dec 19 2010, 09:56 PM
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#19
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PMB Performance Group: Admin Posts: 19,279 Joined: 3-September 03 From: Salt Lake City, UT Member No.: 1,110 Region Association: Rocky Mountains |
I have Greg's 2.5 now. It will be twin plugged soon. That said; autocross motor? I would find something with torque.
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DanT |
Dec 19 2010, 10:22 PM
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#20
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Going back to the Dark Side! Group: Members Posts: 4,300 Joined: 4-October 04 From: Auburn, CA Member No.: 2,880 Region Association: None |
Mike,
I have always wanted to try a high revving 6 with the proper gearing to keep the motor up on the cam, plus they sound marvelous... Just dreaming a bit... (IMG:style_emoticons/default/biggrin.gif) Ken has some interesting combinations he has used over the years. need to check my source and see what he wants for the pieces (IMG:style_emoticons/default/sad.gif) |
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