911 "Muscle Car" engine possible?

[911 tweaks]

I have been thinking lately, AND THAT CAN BE DANGEROUS and often costly, I was wondering how, if possible to build a 911 engine that is a monster!! a fire breathing, tire squeeling, rubber burning, torquey stump puller.

Please keep these parameters in mind when suggesting your build sheet specs: normally asperated engine - minimize or preferable no custom made parts - run on pump gas i.e. 93 octane - engine will be for a street car (sleeper boulivard rocket car) may see some track/de but only for fun, not racing...

Is it possible to make such a cruiser that is reliable?

My guess is that there is no replacement for displacement... HOWEVER, Henry and others swear by Porsche's 2.8L w/66mm crank as 'THE BEST ENGINE PORSCHE EVER MADE!"

Is the set-up that is quick revving and nimble better than a huge monster 3.8~4.0L engine that may be sluggish getting going since it is soo big and not a forced induction set-up??

Based on your inputs I want to start collecting parts for the "monster build" of which will be posted and detailed here on the board.

I anticipate many wondering...well...what is the budget?? It is my hope that by using stock parts the cost will be reasonable. Maybe some will say to buy a used 3.8 RSR and be done with it...maybe others will be recommending a tolerable semi-high strung 2.8 or a 3.0 or a 3.2??

Thanks guys!! I look forward to the discussions and recommendations we can come up with. Maybe we can create a unique class of 911/engine combo for an annual track event of the future???

[onlycafe]

i want to hear more about this.

[ischmitz]

make sure you plan part of your budget for transmission parts. IMHO it'll be a challenge building a transmission that'll live through frequent dopped clutches and burn-outs

[BURN-BROS]

"THE BEST ENGINE PORSCHE EVER MADE!" It is actually the best engine Porsche never made....but should have. The 2.8 SS, best to my knowledge, never was raced or made for that matter.

That said, what do you want? Torqey stump puller thats good to 6500-7000 rpm or an 8000 rpm screamer. I personally perfer the high rpm screamers as thats what i think a Porsche should be.


Here is one that you may be interested in.
3.6 case
3.6 heads
3.6 pistons/cylinders( or substitute 3.8 RSR)
3.0 SC crank
3.0SC rods
RSR sprint cams or more
Carbs or MFI

This will make a 3.3 SS or 3.4SS(quick guess) or a 3.6 SS with the 3.8 stuff. This wont spin like the 66 mm stroke but will make up for it with lots of displacement and better rod stroke ratio than the stock 3.6.

[911 tweaks]

Thats a nice set up Aaron. Any idea on what hp those would make?

As far as longevity goes, do you think a quick revving(spinning) 2.8 would last as long as the other, I am guessing, slower revving?? 3.3, 3.4, 3.6 engine set ups would be??

Once the engine is spec'd, the trans will need to be worked out. You are right that if clutch dumping is to be happening, either a special (thicker or different mat'l) clutch will be needed. Maybe will have to live with dropping the trans frequently to replace clutch, pressure plate & t/o bearing. I worry about the half-shafts surviving. Maybe something used by the x-country buggy ridders will work??

Bob

[Facey]

i don't think starting with the 3.6 case is the way to go.
as far as i know the strongest case is the 3.3L turbo case.

and i know you can open it up to accept 100mm P&C's and maybe even 102's.

if you combine 100mm P&C's with a 70.4mm crank you have a 3.3SS. This is the engine (i believe) that chris streit uses in his NASA GTx (4?) race car , it made something like 290rwhp with 46mm webers and a race profile cam.


if you go witht he 74mm crank you then get my engine, which is (IMO) the stump puller, gobs of torque, 278rwhp with a street cam and 46mm webers, tones of power from 2000rpm upwards, no bucking or risk of stalling EVER.

the last step IMO would be the gt3 crank with 102mm P&C's into the 3.3L case with the turbo oil pump. that yeilds some serious discplacement, and it will like to rev. I do not know the details of the gt3 crank, however if i remember correctly with some customs rods it does fit the package.... the gt3 oil pump is good too, and cheaper if i remember.

cams will make a big differance in the character of the engine, whether it is a stump puller or a high rpm screamer...and IMO there is something in the middler.

in the 2L engine the early s-cam is all high rpm, yet when you put that same cam in the 3L it is a little move even.

i use a midly adjusted early s-cam in the 3.5L (semi-SS) and like i said above, GOBS of torque and it honestly jumps to redline, first gear is as faster then i can shift, especilly with an aggressive start. - and sometime when i get a little to into it, it does yeild a fun, squirmy start (this is at auto-x), and exiting a hairpin turn , even in second full throttle will quickly result in some tail out behaviour.


i am not saying the 3.5L is the engine your looking for, however i beleiev the 3.3L is the case your looking for, and you'll want at least 100mm P&C's with twin plugs.

i'm far from an expert, simply re-laying some experiences. the 3.3SS i described should be 100% built proof (i believe chris has a mis-shift which took him to ~8000+rpm and upon opening and checking everything was perfect still). my own engine (knock on wood) has been flawless.

i'd love to see a documented big discplacement build up...

and wouldn't mind hearing whats wrong with my ideas listed above. like yourself i think i am an n/a guy, and i like lots of power, knowing the best combo for future plans would be nice.

[BURN-BROS]

Bob,

This configuration as with most Porsche configurations can get up to 110 hp per liter depending on state of tune and amount of money that you throw at it. With stock components 7000 maybe a little more and probably around 85 to 90 hp per liter will make a dependable and fun motor. 8000 rpm can be had with custom rods, 935 crank etc.

There is no weak case as far as the 9 bolt aluminum cases are concerned but there are weak cylinders which a 3.0 or 3.2 punched out to 3.5 will give you. I would perfer the 3.6 because of the extra cylinder wall material and better mating surfaces. The 3.6 heads are already twinplugged and the ports are healthy as is. the 100 mm cylinders work but ovality is always a problem with them.

The lifespan of an engine is directly related rpms. The more you spin the less life you can expect. Compounding this is poor rod stroke ratio which a stock 3.6 has and a 3.2 for that matter. Back in the day Carrillo had an issue with their rods breaking at the small end for 3.2/3.3 applications. They had to beef up the small end for their product to work. This is just an example of the sideload issues these particular engines have. I don't know how much you intend to drive the car but for a recreational vehicle that gets weekend work I wouldn't sweat longevity due to rpm.


You can build this with stock parts with little to no modifications bringing the price of machine work way down and parts as well, which I am sure is something you can appreciate.

[911 tweaks]

great Aaron and Facey!! Maybe as our starting point, which I clearly remember from Henry's 2.8 "Best Porsche Motor specs" that rod to stroke ratio is "KING" in the personality of what the motor will and can be. THUS, should we find that ratio and apply it to these build options and start their with spec'ng the monster??

As we progress in this build discussion lets keep summarizing the parts that we have to date and with the addition of what ever new part, we will be able to clearly review the already established parts and see if something may need to change to work with what ever the new part is, thus, I believe it makes sense to start with this rod to stroke ratio...unless that is thrown out the window with large hp/engines??
Bob

[Facey]

well, if i remember the engine porsche never built is 66mm x 95 mm = 2776cc's

what is the rod/stroke ratio for this engine?

[BURN-BROS]

Well you are pretty much stuck with the ratios Porsche handed out, unless you are looking to order custom parts. To keep your project heading in the right direction you should think about how much money is in your budget.

If you are heading down the 66mm stroke route you will need to find the 3 turbo case for the 6 bolt crank.....that is a tough one to come by. A Factory 9 bolt race crank that is 66mm, again tough to get and expensive to boot. Custom 9 bolt crank costs about the same as a Factory race crank. Im am not familiar with how far you can bore out one of these early turbo cases but there may be a problem there.

The 3 liter stroke is a nice stroke and a decent rod/stroke ratio. The parts are readily available and importantly replaceable. Something to think about.


Facey, thats right. The factory never made one, but the ratio is the same as all 66mm stroke engines. 130mm rod/66mmstroke= 1.969 Which by the way is very good.

[911 tweaks]

I found the info Henry posted...it was on the Short Stroke 2.8, 10.28.06 @ 2:19 PM. The following is from Henry:
"for the 2.8ss: the better rod length to strok ratio reduces rod angularity and increases piston dwell.
Net result: more power, higher functional rpm's and less destructive forces produced by the pistons."

Henry went on to say: "Big bore/small stroke engines for a given displacement (all other things being equal), produce more hp. This is why F1 rules specify displacement and max bore, not stroke. Current F1 rules state 2400cc and a 98mm max bore. If you do the math thats a 39mm stroke (rough guess).

The reason you have not heard of the 2.8ss before is because its "THE BEST ENGING PORSCHE NEVER BUILT".

They came close with the 959 (95x67) and same 956/962. These were special because they had used 9 bolt racing cranks (rare but still avail) instead of 6 bolt crank."

Should we apply this methodology to the monster spec'ng or are there other design specs/issues to begin discussion with?

Bob

[Porschekid962]

How much stump pulling power do you need? My dad's car has a short stroke 3.3 that put down nearly 300lb ft of twist at the rear wheels. Total HP was sacrificed but it pulls from a dead stop all day long.

If you want a monster torque motor get in touch with 9m in the UK. They have a bespoke stroker crank just for that. There is a multitude of engine combos when dealing with Porsche air cooled. As for the 3.3 turbo case being the strongest from what I know the 964 case is a bit beefier and the GT3/GT2/996,997turbo/GT3RSR/DP case is the strongest. The latter is based on the 964 turbo case, just check out the casting number.

There are plenty of different engine combos I would like to build but simply do not have the money for it. The 3.3 short stroke was a compromise and a starting point for a 3.5L motor.

As everyone else has said you need to set yourself some goals, what is it you wish you engine to do. Rev to the stratosphere, make monster torque, ultimate hp, turbo or na? Budget, can you afford custom parts, do you want off the shelf factory or aftermarket? Think of the cost of a basic rebuild and then decide how much you are willing to spend above that. There are so many combos and variables when building a motor its crazy.

Other issues to deal with would be, the overhyped stroke/bore ratio/rod length. Valve sizes, intake and exhaust port dimensions, intake length and dia., exhaust length and diameter, cams, valve springs, retainers, valve guides, pistons (brand, design, weight, metalurgy), rods, cylinders, poil pump, often overlooked bearings (main and rods), oiling requirements, fan dimensions, pulley ratio, and on and on it goes.

Then what kind of car is it going in, stripped street rod, dedicated track car, street/track, weekend warrior, full interior, lightweight, you can get away with less power and torque on a lightweight car with proper gearing than you can with a full interior ac'ed stock car. FWIW my father's car in its initial form could easily hang with a 993s but it weighed 2200lbs and had a 3.0, stock.

Figure out a budget, what you are willing to deal with or without and go from there. In most street cars weighing around 2300 lbs, anything over 250hp and 200lb ft with proper gearing and tire sizes is a hoot. My father's car with 300lb ft, 2200lbs, later 915 and slightly smaller tires than stock its a huge kick in the pants. It still isnt dialed in properly but I doubt many "modern" sportscars could give it a challenge. Once the suspension is done properly, the engine is rebuilt and with the new induction it will be quasi supercar status.

The slope is coated with DLC coating and is slicker than anything you can imagine. Once you are over the edge there is no coming back but its one helluva ride.

Cheers

[Facey]

sorry about the strongest case comment, i guess i wasn't thinking about the gt cases, and didn't know that the 964 was an improvement (thought it had its own issues).

given a reasonable budget, and not huge $$$ the 3.3L turbo case is a good starting point, especially if it comes with the 930 oil pump.

i've had good personal experience with B&B headers, and am presently trying out georges euorpean racing headers...once i have results i'll let everyone know.

he did state that he's looking for the n/a muscle car 911 engine.

if your thinking 396/402/454/460 is the normal hot rod engine for american cars, that you just buy and drop in , then the 964/993 3.6L is the porsche hot rod engine.

however it is still a VERY civil engine, not at all pushed to its limits, and its power output can be matched or exceeded by built up engines.

the 3.5L is more like the 383, which is generally a more wild engine, especially if you combine with with a higher lift cam , lots of air and a healthy c/r.

all of which you control when doing a build up.

however if budget isn't an issue, then by all means start off with a gt case, use 9m 4L (=502/515) cyclinders, haltec or some other very high end engine management, BIG throttle bodies or an adaptation of a vario-ram system...seems un-realistic to even talk about to me...lol..

i was on a tight budget looking for big n/a power. talked with my mechanic, read wayne's how to rebuild and modify porsche 911 engines, and the quote is something like " one of the best n/a engines to build" its what i built...and it is a beast.

[911 tweaks]

thanks Porschekid. Please explain the details of your dad's engine so we can see what you did.


thanks also Facey. What beast did you actually build and what are the details?

Bob

[Facey]

porschekid's rebuild is very nicely documented here on the forum, though i do not remember the end results. hsi choice of fan colour is my favourite, and i would copy it if it would not be so obvious.

very nice build though.
mine

internals:
a 3.3L block
opened up to accept 100mm Mahle P&C's
74.4mm crank
carallio rods
raceware rodbolts
new headstuds (name is escaping me)
3.2L fly cut the heads (too much as it turned out)
everything was balanced and put together with new gaskets and such from our host or if rare from EBS
re-ground a early s-cam
46/40 int/exh ports
valve springs & retainers from Mr.Woods

everything else:
rebuilt 46mm weber IDA's with 42mm venturi's (K&N filters)
electromotive twin plug ignition, 6 coils
had the valve covers, intake manifold, timing chain covers all powder coated a black crinkle

had: 1 3/4" B&B long collector S.S. headers
now: 1 5/8" georges euorpean racing headers, will be ceramic coated.
had: custom M&K 2/2
now: well, havn't seen it yet, but a more "classic' design M&K 2/2

-ended up using double thick head gaskets, (we were alittle close at first), and given its a street engine were willing to go from 11.x down to 10.x and gain some reliability.

broke it in over the first month with redline at 6200, then pushed her up to 6500 for 3 months, then 6800 for a while, until the dyno session.

first run pulled something like 258rwhp, a nice starting number, we advanced it from ~18 to 21 and there was a nice jump up to 266rwhp, and then after a thrid near identical pull just double checking some 02 readings we advanced it to 23 degress and made 278rwhp, and close to 300lb-ft.... i believe hp peaked at 6200rpm, though it did not fall off at all. looked at the resulting tables there is more hp to be had with some weber tuning and whatnot. I am also now switching to the racing headers and expect some gain from them as well, got my fingers crossed.

and in my car which weighs a less then 1100kg's it really pulls. spins 11" of rear rubber w/o trouble.

i did make a few errors in my build, like i said the piston - valve clearance required a thicker copper gasket, was "surprised" by my mechanic with the yellow shroud cover...was expecting clear coated carbon fiber, was also expecting a bright colour on the fan...not just the polished fan i delived...but the build when 3x over budget.(and quote)..so i guess i should be happy money was saved..





i'm enjoying this thread, and i cannot wait to get my car back on the road...

[911 tweaks]

thanks Facey! Awesome set up and job!!
Question: In what ever set up we all figure out, I am guessing that twin plugging and an expensive aftermarket ignition system will be needed? Can't I use a Burn Bros. twin plug dizzy that is curved correctly w/1 or 2 coils and an MSD6 box and be all set??


Porschekid, thanks for your info. Can you provide you & your dads post so I can read it. Did you build a 3.3ss or a 3.5?? Any summarizing specs you can list here for this thread??

As far as additional performance specs I wish from the engine...I must say it is a work in progress as you all are way more experienced than me at building engines. However, I would think it is fairly easy, i.e. won't break the bank, to build an engine that has rwhp of 300 min. The goal is 350 rwhp = with 15% hp loss in the drivetrain means ~400+ @ flywheel.
This having been said, can a 915 withstand this hp? I dont know what torque this engne would develope since I dont know what cam, crank, cyl size, bore & stroke,...

Also, it was mentioned earlier what someones 300+hp set up would instantly redline when leaving in 1st gear.
Question: IF we build a 300+rwhp engine, and say I am at idle and stopped, then I floor it, will I be basically staying there cooking the bacon while everyone else passes me saying to them selves, "whats wrong with that car/guy?? OR can we make this engine hook-up and take off like a batt out of h^ll??
...maybe we should continue on this path of "reverse engineering" to best cut to the chase?
Thanks! Bob

[Drago]

Axle hop...lots off it.

[Facey]

a nicely set-up car won't have axle hop issues.

400hp is alot to get out of a 2 valve naturally asiprated engine. especially a streetable engine.

i have not met anyone who has met these goals.
though teo911 might be in this hp category.

hmmm, for ultimate hp there is no replacement for discplacement, so your looking at 3.8L+.

gonna have to have a knife edged crank, and the entire rotating assembly balanced to within a hair. looking at something like a ge80 (guessing here, i know you'll need a very serious cam).

however this build would break the bank. 400hp is not a normal target for a n/a 911 engine so the parts are more expensive.

320-350 is the peak of 'affordable' porsche n/a hp.


regarding the laying down the power.... these cars are great at that. such a huge rear weight bais over the driving wheels...its great. traction or not will depends at the starting point of first. are you letting the clutch out at ~3000rpm? then you should do very well, it'll be squirmy but fast... how if your at say 4000rpm...it will be a smoke show...or at least a smoky start.

good clutch, lsd, and big rear rubber are all required.

a 915 can handle it w/o excessive abuse. get all the wevo upgrades and it should be fine.

[Porschekid962]

Initial specs:
78 3.0 SC case, powdercoated.
100mm bore LN engineering cylinders
100mm JE pistons, 3 ring
Stock rods with ARP bolts
ARP headstuds
Stock crank
Stock bearings
Stock oil pump
78 sc heads machined to accept 100mm bore and twin plugs. No porting work was done.
DRCamshafts and racing springs with Ti retainers
Jenvey taper bore throttle bodies
Autronic SM4 engine management.

Compromises to be rectified at a later date include: 993 twin plug dizzy and two MSD 6al boxes will be replaced with either twin post coilpacks or individual coil on plug setup.

Replace SSi's with the original 993 heat exchanger setup that is laying on the garage floor once the muffler volume has been adjusted to acceptable.

Replace the heads with ported and twin plugged 3.2 litre heads, replace the cams with hotter ones, replace the crank with a 74.4mm stroke 3.2 crank to get to a 3.5 litre motor. Replace the rods and pistons with custom aftermarket units, hopefully CP/Pankl or Cosworth.

Then finish the design of my new induction system and slap it all back together and hope for over 350bhp.

While the engine was out we went ahead and replaced the 74 915 trans with the much later 915, sure it weighs more but the R&P ratio is better suited to this motor, the gears are longer, the helper spring makes living easier.


After a long time, it has begun! rebuild yay


thats the thread with the info and some pics.

[911 tweaks]

Facey: Seeing that your engine is putting out ~280rwhp, what is needed in your view to get it to your belief of 320-350rwhp for a n/a porsche engine?? Did you take into accout the rod length to your stroke? Is the 39mm Henry said the ideal/goal for porsche engines??

Porschekid: so the "initial specs" you list, are these what you did and if so, what rwhp does this make? What rwhp do you think the list of mods below the initial will make? Did you consider rod length to your stroke when setting up your engine?

Are Jenvey's or the like going to be needed to get the hp?? That set up is ~$5k, right? Why not the lgst pmo's (50's)? If dual plug, do you need engine mgt?? Can twin dizzy w/MSD suffice?
(trying to keep costs down and minimal or no custom parts)

Let me throw this out here: Does anyone know of such an engine I am trying to spec out that already exists? An engine by Chris Streit(sp)?? If we don't have to reinvent the wheel, I am all for that. Maybe someones' existing monster can be the starting point here for us. Maybe they can tell us the things they wish they did but cound'nt for what ever reasons??

Bob