3.2 Short Stroke or 3.6 Conversion?

[WILSPEED]

Hay guys,

I'm thinking of doing a 3.6 conversion for my SC. I'm still looking for a 3.6 motor with decent leakdown numbers.

How much would it cost to get a 3.2 Short Stroke conversion with about 250 hp? In parts only and how about with labor together?

Any advice on such an upgrade instead of a 3.6 conversion? The car will be a track/weekend vehicle so aggressive cams/ exhaust/ carbs no problem.

I know 3.2 ss motors cost almost as much as a 3.6 but the mods and labor for the conversion can be $5000-7000 on top of the motor!

Any advice appreciated, Thanks.

[Dolphin911]

How much cost a rebuild on a 3.2 instead of a 3.6 ? This will help you to take make the right choice.

[longhornchris04]

Also consider that with a 3.6 conversion you have a 3.0 to sell.

Of course I'm partial to going to the 3.2SS, but that's because its my end goal, carbs look awesome, and I can do some of it incrementally... I've already taken care of the exhaust.

[WILSPEED]

How much are you guys spending for a 3.2 ss motor parts/ labor? Are you making comparable power to a 3.6 (250-270hp)?

[longhornchris04]

I make government pay (AF Captain)... so the 3.2 will probably be my promotion to Lt Colonel present . Next steps for me are an MSD unit, interior stuff, and chasing electrical demons.

From what I've seen in my research, a 3.2SS using 98mm P&Cs @ 9.5:1, single plug (usually MSD), '74 style exhaust (usually SSI), and a bit of tuning will get you in the 200 - 210 range. Adding 964 cams and some mild head work (port & polish) will bump up the power to the 230 range. For the most part, much of the labor in this is part of a rebuild anyway. If your P&Cs are Alusil then you have to replace them anyway.

The advantage to the 964 Cams is that they still play nice with CIS, have a streetable power curve in a 3.2, and run out of breath around the redline dictated by the mostly stock internals. If you go to carbs, you have a bit more freedom with the camshaft.

250RWHP is doable, but the costs start to spiral up. Specifically:

- going higher compression necessitates going to a twin-plug setup. There are multiple options, but none are cheap. You don't have to do this, but its one way to get a few more horses. Even with access to race fuel, its not a good idea to go high compression without twin plugs.
- going to higher revs. I'm not sure what the magic number is, but the stock rods & rod bolts aren't good for much beyond the original SC redline. You also have to worry about the valvetrain. Power being torque * rpm (divided by something based on horses) and agressive camshafts mean this is the best way to get power.
- too much torque and you risk grenading your 915... so you need to mod that as well. Of course this is true with the 3.6 conversion too. The bearing retainer plate and possibly differential plate to keep from warping the case and oil cooling to keep the internals in check. This can of course be limited by running a higher revving engine, but then you've got the previously mentioned issue.

As for total parts / labor cost... baseline would be whatever a full rebuild goes for these days (haven't looked recently) + parts cost. If you decided to twin-plug there's also the cost of head work. Ditto for regrinding your camshaft (if its possible).

Your best bet would be to search the engine rebuilding forum and/or post your question there. There are several professional & amateur engine builders who post there from time to time and are willing to give advice.

[Vin-barrett]

I am contemplating the same, build up my 3.0 or do the 3.6

Shortstroke 3.3 would be my plan with 100mm Nickies
, twin plugged 3.2 carrera heads
Electromotive ignition , PMO's with probably DC40 cams.

All that hardware really starts to add up and I believe will be more $$$ than what I can do a 3.6 for.

My 3.0 already has SSI's 964 cams and 9.8cr euro pistons. I kinda feel that financially this is about as far as I should go with it without spending silly money

And like chris mentioned I could sell this engine to offset some cost with a 3.6 swap.

The hotrodded SC engine is more appealing to me as I really dig the oldschool thing with carbs however, thinking with my budget I'm leaning towards the 3.6 for sure

[dfink]

Depends on what you are wanting. A 3.6 is a nice power package you will get the desired grunt you are seeking. But not much to show off. Open the deck and Yep there it is.
Or you can do the WOW motor. The WOW motor will stand out in a crowd, rev like crazy and free up a lot of room for working on it. Now for cost. The cost for the motor itself was not that bad.
Heads rebuilt and twin plugged with race springs. $1300 - $1500 (forget the titanium keepers unless you just want to tell everyone you have titanium keepers.)
Pistons I would go 10.5:1 very drivable yet that little extra umph. $1100
Bore cylinders can't remember exactly I think around $1000
Cams reground to streetable grind $250
Arp rod bolts and steel head studs $500
Nose bearing $200
Chains, cam gears and ramps $300
Gasket set $300
Rods rebuilt - $300
Rockers rebuilt $250
Stuff I forgot - sealants etc $500
Pretty stuff like powder coating $500
So basic engine say $6500 if you do all the work

Now the fun stuff
PMO throttle bodies with Electromotive TEC3r $8000
PLX-O2 sensor $250
Plug wires top and bottom $500
Headers $1200
New clutch $1200

Somewhere around $18000 if you do all the work will get you a very cool, very streetable, 275 RWHP flat 6. Probably another $500 - 600 to tune it. I would guess that is a $25,000 build if you pay to have it all done.

I don't know what to do for one in between. My stock 3.2 pulled 203 RWHP on a dynojet. You could just redo the cams in the 3.2 put on the headers get a chip and have a decent running car. Put the money saved in the suspension you will probably go faster that way.

[fred cook]

I am in the process of gathering parts for a 3.3SS (100mm pistons/liners) for my SC coupe. I bought a set of previously twin plugged 3.2 heads, a set of Mahle 10.3:1 100 mm pistons and am about to order the LN 100mm cylinders and XDI ignition. I already have SSI exhausts on the current 3.0 engine. I am still undecided on the cams, but will likely use either the CIS cams or a 964 spec regrind. I expect to have about $10-11k in parts to build this engine. Miscellaneous machine work should run about $500 or so. Throw in about $1500 for unforseen items and the total will be around $12-13k. Of course, this does not include my labor for the engine R&R, teardown or rebuild. On the plus side, I will wind up with some new tools and will have had a great adveture! It took me several months to find the right heads and I just happened to find a set of Mahle pistons at a very good price. The idea is to develop a plan of action, decide on the hardware you want to use and then try to seach out "deals" on parts that others are trying to sell. Good luck on your project!

[onboost]

Originally Posted by Vin-barrett

I am contemplating the same, build up my 3.0 or do the 3.6

All that hardware really starts to add up and I believe will be more $$$ than what I can do a 3.6 for.

And like chris mentioned I could sell this engine to offset some cost with a 3.6 swap.

however, thinking with my budget I'm leaning towards the 3.6 for sure

From what I;ve seen typically for on the 3.6 conversion, your looking at dropping minimum $12 to $14k depending of course on what you pay for the engine, what it needs/condition, and the accessories to make it plug and play.. this is also assuming most of the labor is yours.

If you're using a shop to do the interface and other odd-ball adaption work needed.. you can start bump'n that price up. Again, assuming the engine is good-to-go and needs nothing.

[Vin-barrett]

I do all my own work so labor is free...

Yes I agree true condition of the 3.6 engine is unknown and that is the caveat here.
I'm, thinking about 15k would pull it off.
Subtract the value of my current 3.0 and it makes the 3.6 look all the better.

[Bill Verburg]

There ain't no replacement for displacement

Given a $25K budget you can build a monster 3.6, your 915 won't live long though if you use it in anger

[DW SD]

I would go 3.6 as you get a dead nuts reliable package with many factory upgrades for performance - twin plugs, more displacement, etc. Yeah, it doesn't look or maybe sound as cool, but the area under the curve is probably significantly more than 3.2SS.

I'd go 3.6, but make absolutely sure you buy one that is a known quantity. I tried to buy a known quantity and had to have it rebuilt, which added $8k I wasn't anticipating. It is a great swap, but quite pricey. Muffler is another $500, throttle adaptor kit $200 unless you build your own, harness adaptor $250, clutch $600, adaptor flywheel $450.

Bear in mind, you need additional oil cooling ~ potentially $2k worth of coolers, lines, adaptors, fittings. The little things bite you in the A$$. There was a guy selling a whole engine and conversion kit for $12k or so at one time with all of the parts. That was likely a nice deal.

Selling my old 3.2 recouped $6500, which was a great help.

Doug

[ja78911sc]

Originally Posted by Bill Verburg

There ain't no replacement for displacement

Given a $25K budget you can build a monster 3.6, your 915 won't live long though if you use it in anger

Bill,

I feel this is the most overlooked aspect of a motor upgrade on a track car. I have a friend with a 3.6 conversion on a track dedicated car mated to a 915. He has broke gears on two different occasions.

That being said. What HP do you feel is the max on a track car with a 915? (DE only not racing). I don't feel this is off topic and actually a very important equation when considering a motor upgrade with a 915.

I am also considering a motor upgrade (track use) to mate with my 915. If I remember correctly the 3.2 euro's with a 915 had a tranny cooler. Rough HP I believe was in the 230 range. Maybe a 3.2 with 964 cams, headers, chip & a tranny cooler?

Thanks,
Jim

[Joeaksa]

How old are you? When I was a pup, I loved high revving engines with as much HP as possible.

The older I get the more I enjoy Torque... and it makes driving so much more pleasurable.

I have Bill's old engine and its a box stock 3.6, absolutely no changes other than exhaust and its got way more power and torque than I need. Was just out on the road yesterday and dusted a couple of American cars that felt that they were faster than I was.

[brads911sc]

You can do a 3.2 SS with top end for 8-10k if you do the work yourself.
You cant touch a properly done 3.6 for less than 20k when you factor in the oil cooling, conversion parts, beefing up the 915, etc... and thats without doing the top end on the 3.6.
You will get similar HP and Torque numbers especially if you have already have SSI's and Sport Muffler.
Youd be financially ahead cost wise just to buy a car with the 3.6 already in it if thats what you are after.
Not sure that extra 25 HP you might gain will really be worth the extra 10k you will spend.
To each his own I guess....

[Randy W]

It's not the HP, but the torque that makes a 3.6 (especially a Varioram) a faster motor than a 3.2 SS. They are a totally different experience. The 3.2 SS can be a snappier motor that can rev higher, it just doesn't have the torque of a 3.6. As noted, it can cost more to go the 3.6 route... if you do everything right.

[longhornchris04]

Originally Posted by ja78911sc

Bill,

I feel this is the most overlooked aspect of a motor upgrade on a track car. I have a friend with a 3.6 conversion on a track dedicated car mated to a 915. He has broke gears on two different occasions.

That being said. What HP do you feel is the max on a track car with a 915? (DE only not racing). I don't feel this is off topic and actually a very important equation when considering a motor upgrade with a 915.

I am also considering a motor upgrade (track use) to mate with my 915. If I remember correctly the 3.2 euro's with a 915 had a tranny cooler. Rough HP I believe was in the 230 range. Maybe a 3.2 with 964 cams, headers, chip & a tranny cooler?

Thanks,
Jim

Parroting what's been posted in the engine forum...

The 915 with proper mods (cooling, retainer plate, diff cover if magnesium) should handle 250Hp... but you are pushing it. Having a limited slip is also a good idea, as it will minimize having the transmission load and unload as the traction hits the limit.

Breaking gears is more a question of torque than horsepower. For the sake of example, an engine producing 250Hp at 7000rpm is less likely to break a gear than 250Hp at 5000rpm (numbers from the processes of rectal extraction, don't take literally). So the same 3.2SS with the same Hp as a 3.6 may not be as hard on the transmission. That 250Hp number may have been based on a high revving engine.

I've also read some stuff on people mating a 915 to a turboed VW Type-4 motor. Despite having the same power as a 3.0L, the larger ripple torque of the 4 cylinder had a bad habit of breaking stuff.

Regardless of how you make the power, cooling will be a major issue. If you are going much above 250 I'd consider options for beefier internals. And up goes the cost

[brads911sc]

So why wouldnt you just buy a car with the 3.6? It will have the G50 and cooling upgrades, will also have brake upgrades which we havent even discussed... everything you would need on a 3.0 or 3.2 car to turn into a proper 3.6... you can always remove weight cheaper than upgrading all these systems...
A 3.2 SS doesnt add to the cost of a rebuild. If I have to replace the P/C anyway, I am spending the same dollars.
That is not the case with a 3.6 upgrade.
Why would you do this? just a weight issue with the later cars?

Originally Posted by longhornchris04

Parroting what's been posted in the engine forum...

The 915 with proper mods (cooling, retainer plate, diff cover if magnesium) should handle 250Hp... but you are pushing it. Having a limited slip is also a good idea, as it will minimize having the transmission load and unload as the traction hits the limit.

Breaking gears is more a question of torque than horsepower. For the sake of example, an engine producing 250Hp at 7000rpm is less likely to break a gear than 250Hp at 5000rpm (numbers from the processes of rectal extraction, don't take literally). So the same 3.2SS with the same Hp as a 3.6 may not be as hard on the transmission. That 250Hp number may have been based on a high revving engine.

I've also read some stuff on people mating a 915 to a turboed VW Type-4 motor. Despite having the same power as a 3.0L, the larger ripple torque of the 4 cylinder had a bad habit of breaking stuff.

Regardless of how you make the power, cooling will be a major issue. If you are going much above 250 I'd consider options for beefier internals. And up goes the cost

[johnsjmc]

I agree with Bradsc above. Buy a 964 or 993 and put it on a serious diet. No AC new seats ,RS door panels etc can probably strip it to 2600 lb maybe less if you get rid of everything you can Thats less than a stock SC weighs and you get the 3.6, G50 bigger brakes etc..If you need a topend eventually then go for big valves,hotter cams and ARP rod bolts and look at 300 hp. I have done a 3.6 SC and now have a 993. I just sold a 1980 with 3.6 and lots of other upgrades for $18 and picked up a 95 993 for under 20K . The 993 needs the trans rebuilt as it grinds into 1st but the car has PSS9s,sways LSD and needs nothing else. I would not bother doing a 3.6 swap again as newer aircooled prices continue to drop. Also consider your stock unmolested older car will bring max money unmolested as people are seeking clean original ,not modded cars.

[Bill Verburg]

Originally Posted by brads911sc

So why wouldnt you just buy a car with the 3.6? It will have the G50 and cooling upgrades, will also have brake upgrades which we havent even discussed... everything you would need on a 3.0 or 3.2 car to turn into a proper 3.6... you can always remove weight cheaper than upgrading all these systems...
A 3.2 SS doesnt add to the cost of a rebuild. If I have to replace the P/C anyway, I am spending the same dollars.
That is not the case with a 3.6 upgrade.
Why would you do this? just a weight issue with the later cars?

That's what I did, I still had to pour thousands into it to make it into the track appliance that I wanted.

If you want a cheaper track car stay w/ the 911 chassis and stockish motor and go for light weight, you avoid a whole host of secondary issues that will need to be addressed w/ a 3.6 t/p track car.

If you want a street/occasional track car a stockish 3.6/915 will be fine. I ran into issues when I had a 3.8RS/915. The trans is a stock late('84) 915 w/ cooling. When it was stressed, especially in the lower gears, the side plate distorted. Much of that and the cwp teeth will start to splinter, probably the 1 -3 gears too. Wevo mods could probably rectify that but a late chassis is sooo much more capable that I decided that was the way to go, haven't looked back.

I'm very pleased w/ stockish 993/915 combo for street use in my '76, the torque is just so usable the car just burbles along making great noises

Randy is correct it's the torque that will cause issues not so much hp.