Dollar per Modification HP

patkeefe · 06-29-2005, 03:17 PM

Hello, all:
After just perusing this thread, Dyno results I figure it is a good time to try and evaluate the cost of mods on a $/HP ratio. For example, I have a stock CIS 3.0 engine in my '78. I'd like to get up to the 210-225 RWHP range. What can I expect to pay for N/A modifications for this? I will back out the cost of the winter rebuild, which is going to get done regardless. Maybe I can get a rough estimate of what mods cost some of you who have done this? I am looking for cheap N/A HP, basically (which I believe is an oxymoron), as opposed to project x forced induction HP, which is cheap.

Thanks!
Pat

ChrisBennet · ChrisBennet's Garage

I can't think of any inexpensive horsepower for an SC but...SSI's really wake up an SC
-Chris

johnsjmc · 06-29-2005, 03:55 PM

If you are rebuilding anyway then regrinding the cams to the 964 grind will probably cost little extra. If purchasing pistons then a compression ratio increase is a good idea at little or no extra cost as well and will enhance the cams effect.

mattr_914 · 06-29-2005, 04:02 PM

I would urge you to remove your expectation of horsepower and do what modifications best suit your driving style. One example; S cams on an early engine will give you more peak hp but rob low end horsepower. This is good for a built up motor, but if you're looking for street driving and the motor isnt built for revs, you're not going to maximize your driving needs.

Randy Blaylock · 06-29-2005, 05:20 PM

Porsche 911 performance handbook. Spells it out pretty well. Take care Pat.

Dantilla · 06-29-2005, 05:37 PM

Shed pounds. Lots of pounds.

dd74 · 06-29-2005, 06:27 PM

Then shed more pounds. It's the most effective modification to these cars.

As for rebuilding, I'm increasingly of the mind that modifying these motors is a losing proposition. In many cases, they're already the best they can be.

Case in point: regrinding the cams will be...say...$700. What do they get you? About 10 hp. For $700, you can lose 100 pounds of steel and in return gain not just 10 horsepower, but better handling and braking.

johnsjmc · 06-29-2005, 06:50 PM

I think the engines in the 911 are pretty well optimized as is but my comments considered that IF you are regrinding a set of cams as part of a good rebuild you might as well go for one of the latest profiles for about the same money. Same goes for pistons and cylinders. I agree with the weight remarks as well.

Dantilla · 06-29-2005, 07:06 PM

My solution is a stock 3.2 in a 2200 lb 1973 body.

RoninLB · 06-29-2005, 07:16 PM

a good exhaust is a start.

Steve Marshall · 06-29-2005, 07:49 PM

Cams and SSI's are excellent suggestions.

I picked up 6 hp on my 2.7 CIS by removing the top half of the CIS box. But SC's have a bigger opening so it might be moot.

A lightened flywheel and light weight clutch are worth while and probably not a whole lot more than stock.

If your rebuild budget includes pistons you can probably buy high compression JE's or similar for the same or less than Mahles.

Jeff Alton · 06-29-2005, 08:46 PM

How much do you want to spend? Is this a one time event or do you want to make upgrades that will be compatible with future upgrades? Do you want only bolt ons, or are you willing to open the engine up?

Jeff

sammyg2 · 06-29-2005, 09:02 PM

N/A?
You're no fun.
Don't expect that much from SSIs, lots of folks here have reported less than stellar gains for the $$$.

You are very limited with the N/A 3.0, prolly the most effective $$ spent will be to install a 3.6

patkeefe · 06-29-2005, 09:11 PM

The driving style is mostly street. I will take it to DE's also, but no real racing for this car. So, I'm looking for power in the 2500 to 5000 range. This engine will not spend life at 6500 RPM. My little SC is fat at 2600 lb, and I don't see where I can get a lot of weight out of it without sacrificing some of the creature comforts like A/C, etc. Maybe I can get it down to 2400 with new bumpers, seat changes, other stuff that costs money. In the big picture, I figure any regrind cams are $600, P&C are $1500 minimum, probably lots more if I want to go the short stroke 3.2 route. I have a set of Webers which need some work, they were $450 as is, so that will end up at $1000. SSI is nice, but that becomes $3000 for exhaust. Cylinder head work is certainly a few dollars more. The big picture starts to look like a $12k to $15k rebuild. For what...50 HP?

Maybe I can go with a $5 k rebuild, and add a low boost turbo for another $3k. I need 915 work also, and figure a R&P change to the higher ratio gearset will also help out.

So, I'm actually trying to figure out if he numbers I have in my head are out of line with reality.

Pat

sammyg2 · 06-29-2005, 09:27 PM

there is absolutely no reason to modify your engine for a low boost turbo system, It is fine in stock configuration for up to 7 psi if you run it rich enough under boost and back off the timing a tad. you could go higher with an intercooler and supplimental fuel supply.

If the engine is bad and needs to be rebuilt, then do it. but don't take it apart just to modify it for a low boost turbo system.

The 996 twin turbo runs 9.5 to one compression ratio or something like that. Sure it's a more complex and modern system but this board is host to lots of people running stock pistons and turbos.

rdane · rdane's Garage

3.356 (3.4) liter (Mahle 98mm x 74.4)
Electromotive twin plug
'79 case and heads
Heads polished
CIS with new injectors
bored throttle body
20/21 web cam
boat tailed case
Carrera pressure fed chain tensioners,
Clewett wires
930 lower valve covers,
light flywheel,
half mooned cylinders
measured 9.8:1 compression
Mahle, Max Moritz 98 p&cs w/ sfl and ceramic tops
Ti retainers & HD springs
ARP head bolts
Pauter rods
new Sachs power clutch

A recent Dynojet tune after 7K miles, a change to mobile 1, and a cooler set of plugs.

223 rear wheel HP @ 6100rpm
214 rear wheel torque @ 4100

This engine is more fun as a street engine that anything up to a late model 3.6 varioram. Add a good set of carbs and a S cam and you have some fun....way past 223.

(easy to say having both) More low end usable torque on the 3.4.

RoninLB · 06-29-2005, 09:48 PM

Quote:

Originally posted by patkeefe

. So, I'm looking for power in the 2500 to 5000 range.

I have a set of Webers which need some work,

Maybe I can go with a $5 k rebuild,

your game seems to be mid rpm torque. Maybe set up the block for this and do the add-ons later? I went with low compression due to a fear of a continuation of the lousy street gas.

The webers will cost a few bucks to set up and plumb but the engine will then be ripe for cams with some overlap.

A good shopper like Superman is more efficent at spending your 5k than someone like me. I'm the worst in that dept. Personally I'd be concerned with building a reliable long lasting foundation now.

patkeefe · 06-29-2005, 10:02 PM

Ron:
I need enough HP to keep up with yours!
Pat

klaucke · 06-29-2005, 10:25 PM

T-bitz EFI may be easier (don't know from personal experience) to set up than other alternatives and emissions techs may not notice the upgrade. And it comes with a smoother running, quicker feeling engine(than CIS), that will allow you to run hotter cams, etc. Carbs are always a good alternative if you can circumvent emissions and don't care about mileage. Some reground cams, news pistons, and different induction/exhaust are worthwhile upgrades that can transform the motor. For longevity and power, there's no replacement for displacement (i.e. rdane's 3.4). Oh, and losing weight on the car never hurts.

island911 · 06-29-2005, 10:37 PM

with out a doubt; eram, and a cool collar.

bwahhahahha

SSi's aren't that great from a HP/$ stand point, but they do have other strong up-side. (glad I bought mine even though the dyno didn't bump that much)

For a 79, (and ~5k)I would say P&C's and cams, would be your best bet. Dont split the case, boat-tail, yadda yadda; just increase the displacement and the compression ratio. Those big runners will be happy to accomodate.