Let's design a 3.2 short stroke!
 

Alright, I haven't even driven my hi-po 2.4 yet and I already want...

More Power!!

So I'm completing a deal for a pile of 3.0 parts - case, crank, rods, heads, other misc. hard parts. Sounds like the perfect opportunity to make a 3.2l short stroker. I need to get some informed opinions (paging Dr. Weiner..) about the hottest compression and cam I can run, and still manage to idle and drive on the street, on pump gas. Yes, twin plugging is fine, I just have to sort out whether I will use distributorless ignition or 964 dual dist. setup. Intake and exhaust port size recommendations are appreciated too, though I imagine I need to decide on a cam first.

Target HP is 250-300.

What induction?

Tom

I was thinking MFI until I realized I'd be spending probably wayyy over $3k to get it the way I wanted it. It might make more sense to do some aftermarket induction/ignition system? If I can get programmable induction/ignition with twin plug capacity together for around $3k, works for me. As I want to run some fairly hot cams and have plenty of MFI parts lying around, I like the idea of using some bored MFI throttles so that I have a butterfly on each cylinder. I'm wide open for suggestions. Hit me!

You said the magic words: "Hit me!"

Going to Vegas would be a good start.

Seriously though: Clewett Engineering (I think that's their name) can set you up with a programmable TEC 3/3.2 combination induction for about $2,800.

I once priced pistons and cylinders for a short stroke 3.2, and they was about $4,000.

Cams? Hmmm...I don't know what might run well with programmable TEC 3/3.2 induction, but I chance to say 20/21, so you could get your cams reground to 20/21 spec by Webcam.

On ebay, I saw some 3.0 race heads, but they were like $8K. Maybe you can bore yours out or at least port match to the 3.2 induction/runners.

Or better yet, get some 3.2 heads. Those might work with a 3.0., and I've heard 3.2 heads are very good performance-wise.

I don't know, though. Maybe you should trade the 3.0 and some cash for a 3.2. A 3.2 with good exhaust and a chip can get about 240 hp. And reliably. The 3.0 with all the mods I described above might be a bit extreme for street driving, and REAL expensive.

YMMV...

Wow! What was the $4k piston/cylinder setup? Sounds like it must have been some Mahle rarity through Andial?

Is the TEC-3 setup inclusive of the manifold and timing trigger? Do I still need a distributor? Yeah, I've been living in MFI world for a LONG time...I've got some homework to do on EFI.

$8k for heads is out of the question, but I'm willing to spend a bit to port and contour a set of 3.0 heads.

I'd prefer not to just pick up a 3.2; I'm more interested in having a freshly rebuilt engine customized to my liking. Hopefully I can put something together for ~$10-12k above the purchase price of the 3.0 itself...otherwise I'll need to take that Vegas trip you mentioned. "Come on baby daddy needs a new pair of cams!"

I don't know if the manifold is included. This is the Clewett link...

http://www.clewett.com/

I know what you mean by "customized." I'm grappling with the same issues right now, though I might wait for a full teardown before I "tear in."

My wrench has a solution to boring the heads without taking them off the engine, which results in an engine drop. But it sounds like you'll be doing a complete tear down if you're going to do a short stroke.

About Clewett, as I recall, the TEC 3/3.2 can't handle really radical cams. It's nice for all around performance, and is worth about 15-20 hp increase -- though I'm not entirely sure about that figure.

You should call them about that.

Hi Dave:

Anyway you do this (correctly) its not going to be a low-buck project,...:)

You should stay at 9.8:1 or less for single-plug operation and 10.5:1 for twin-plug operation with pump gasolines. A set of 98mm high-compression Mahle P/C's (when they are available) runs around $ 3750. With the ever rising Euro, don't take that price as gospel. I would not use JE's in a street engine.

Early SC or Carrera heads are fine to begin with and a high quality flow job followed by a valve job is strongly recommended. They can be machined for the lower plugs at that time.

Cam choices are dependent on what you will do with the car and what induction system you use. Modified MFI, PMO's, or EFI such as DTA are just fine. Nothing is cheap here besides carbs (which make great power, btw).

I'd recommend a 3.6 dizzy or an RSR converted one with MSD's if you use MFI or carbs. Crank-fired units just don't do a good enough job of keeping the plugs clear in these applications; not enough juice,....:) If you use DTA, you can even use coil-on-plug ignition.

A short stroke 3.2, properly configured,.....can really rock!!!

Here's the 3.2 Short Stroke I'm building:

1977 Euro Carrera 3.0 Case
2.7 Crank & rods
3.3 Turbo heads ported (forget what they are ported to? 35/36? - Twin Plugged, of course
3.2 short stroke Mahle "RSR" pistons 10.5:1
Dual HPX ignition (Electromotive, with Clewetts crank fire wheels)
Weber 40s
Mod-S Cams

-Wayne

Wayne:

That looks like a great way to go.
What kind of gas milage do you expect from this engine and do you think it would be a good one for a daily driver? Carbs would be cost effective (initial cost, anyway) and powerful.

I've been considering two paths based on our previous correspondence and my conversations with Tom... 3.2 or 3.2 short stroke. Both would be a lot of fun, which do you think would be better for a daily driver? If I went short stroke, I'd do twin plugged, 10.5:1 and TEC3 management.

Thoughts?

JCM

Almost a silly question - this would be a power motor - not really good for cruising. The carbs would kill any good gas mileage. If you're looking for gas mileage, then stick with a stock engine. You can probably do much better with TEC-3, but then you're up to about $15K for the engine (mine is costing about $10K in parts alone)...

-Wayne

Silly questions are apparently my forte...
I know there will be a drop in milage with carbs, but I'd not seen what the quantitative difference would be. I'll do some research here.

Thanks,

Jason

From all I've seen, expect less than 15 mpg with your mods and carbs.

After stepping back from the issue and considering this thread, I'm now giving strong consideration to PMOs. I looked at some ideal setups for EFI and started getting into the $7-10k range!! Then I started realizing carbs will do everything I really need for much less.

Wayne, what is the "Mod S" cam you refer to? Any reason you didn't go with something hotter for this larger displacement motor?

Wayne,

How much is the dual HPX ignition?

Is this the most cost effective way of obtaining dual plug ignition?

Tinker

I was thinking of a budget motor like this as well.

78 sc long block (cause its what I have).
used webbers (~$1000)
S type cams (re ground on my cores) ($300)
JE 98 mm Ps (~$1000)
Bore and replate my Alucils (~$1000)
Miscellaneous machine work and gaskets ($1500)

I will stay 9.8 single plug and stock Dizzy initially, eventually I want to go Electromotive single plug.

I am curious why Steve says no JEs for the street? I have been thinking they were a great way to go, do I need to reevaluate?

Elombard, JEs make alot of noise while warming up. Some people are not fans of them.

This may have been true at one time with JE racing pistons but I don't think this is true any longer. I never noticed extra noise when I used them for a project.
-Chris

This may be true since I have not used them. I have heard that some piston manufacturers will offset the position of the wrist pin relative to the center of the bore the help with noise. Or redisign the piston to allow closer tolerance. If anybody knows please shed some light.

My motor originally had moderate compression 95mm JE's in within spec but slightly worn SC cylinders.

As a race engine (what it was before I bought it), the noise when cold was drowned out by the exhaust. As a street engine (as converted for me - a change in cams and exhaust, basically), it was pretty noisy. It never made it onto the street - I took the option of having new 98mm Mahles put in (no labour cost = no-brainer).

However, I must stress this is only my experience and was in relatively worn cylinders.

What I meant to imply that building a motor like this - gas mileage should not be top on your list - if you want good mileage, stick with the stock 3.2 + Motronic...

-Wayne

The Mod-S cams are an improvement on the 'S' cam profile - designed by Elgin. I was going to go with 'S' cams, but then I saw these on eBay, and I just had to have them.

A hotter cam would probably give more power, but I want to keep the engine's power band pretty uniform (less peaky). The 'S' cam on the 3.2 is a well-proven combination that gives plenty of low-end torque.

-Wayne

List price is about $1500, I think we sell it for less than that.

Cost effective? Probably about the same as the other methods, but you can control timing, and you never have to buy distributor caps again. Plus, the system has a good resale value on the market. I have an extra one used, if anyone is interested. I think I want $850 for it (it's an earlier model HPV system).

-Wayne

I don't think that Steve says this specifically, I think he said he would prefer Mahles to the JEs with everything else equal for street engines.

The JEs are a fine alternative, and can be very reliable too. Also, they are significantly less expensive when doing a rebuild.

-Wayne

Thanks for the advice... I've been hemming and hawing over which way to go, twin-plug short-stroke 3.2, or 3.2 with a SoK supercharger. I'm leaning towards the SoK 3.2, much better bang for the buck, and supposedly good milage too.

As an aside, I got both the 101 projects and the Engine Rebuild book in the mail yesterday, they're great. Nice job on the info, layout, and look.

JCM

Can't do this with 3.0L 95mm cylinders. The grove for the sealing ring makes it impossible. EBS can bore out 3.2L 95mm jugs, as they don't have the groove.

Tom

Thanks Tom I forgot about that. Better refigure my Budget.

Now when they bore out the 95's to 98 do the need to replate?

Yes.

I have a 3.0 SC twin plug engine with 10.2 comp., ported heads, RSR cams, 46mm Webers, and Electomotive XDI twin plug ignition, 1 5/8 headers with megaphones. Any idea of what kind of power increase I would see by just swapping to 10.5 comp. 98 mm pistons and cylinders to make it a 3.2 short stroke? Are the 98mm cylinders slip in or do the require the case spigots to be bored?

Jacko, how high do you rev this engine, and what kind of fuel are you running?

John, it is in a dedicated race car, and I am shifting at 7400 rpm. I am running 112 Sunoco leaded racing fuel.

I would increase the compression ratio up to 12-1 at least. with the type of fuel you are using you will have no problems and you will get a nice increase in torque and HP. I would also run the car on a chassis dyno with the combination you have now with the 112 fuel. I would also try some 100 or 104 octane. You should see a small increase in power with the lower octane fuel. With 10.2-1 and twin plugs the engine will be fine on 100 octane.

Yes, I want to run it on the dyno, but it hasn't been in the budget. I always worry about reliability when increasing compression ratio.