2.8 L Stroker conversion

[CW951]

Clark, this one's primarily for you.....or anyone out there running a 2.8L 944 conversion. I'm in the process of rebuilding my '89 turbo and have been considering a stroker conversion. Is that the route you went or is yours a big bore 2.8? I'm not looking for huge power figures, but a little more low end torque would be welcome....I'll bet it would do wonders for the turbo response too! Problem is, those 3.0L cranks are not easy to come by and I'd like to get some feedback from someone who has driven one before I waste a LOT of money.... Any thoughts??
P.S. - We all miss the Garage!!.......Charlie

[fletch944t]

Hi Charlie,

I did a lot of other modifications when I built the 2.8L engine. I also did a big valve head, Mass Air, and bumped the boost up to about 19 psi. So, I can't tell you exactly how much difference the 2.8L alone will make. Before all the modifications, I was running the 2.5L engine with a K27/8, Chips, and running the boost at about 14-15 psi. I can tell you that the difference between that engine and the 2.8L engine is absolutely phenomenal. The first time I drove the car at full boost, the only words I was capable of uttering were "holy sh%&, I need bigger brakes". I'll be installing the Big Reds next week. In fact, the car actually develops too much torque for the factory clutch because it occasionally slips when the car hits full boost. So, I'll also be installing a different compound clutch in the near future.

Anyway, it is a ton of money to spend on a car. But, to an adrenalin junkie like myself it's been worth every penny. So much so that I currently have a brand new 968 block sitting in my basement waiting for me to get the bucks to build a 3.2L engine. BTW, there are still two new 968 blocks available if anyone is interested ($1550 plus shipping). Sorry, couldn't resist the plug.

The availability of 3.0L cranks tends to run in cycles. When I was looking for mine, it took me six months to find one at a reasonable price ($1100). However, a couple of months ago, I could have bought 5 or 6 at the same time, all at a fairly reasonable price.

Nowdays, there are many more options with regards to building a 2.8L than there were five or six years ago when I first started accumulating parts to do mine. So, the cost has come down significantly but, it still ain't cheap. Also realize that you don't have to do everything at once. I bought bits and pieces to put together the 2.8L for almost 2 years. I'll likely have to do the same with the 3.2L engine.

If you'd like more details (parts manufacturers, who to buy from, etc.), email me with your questions and I'd be happy to answer them. (fletch944t@hotmail.com) We can even discuss stategies for buying parts to build the engine.

Regards,
Clark

[CW951]

Clark, thanks for the wealth of info! I'm sure you'll be hearing from me....Charlie

[Blackfoot]

any thoughts about the 2.8l huntley completes?

http://www.huntleyracing.com/whole_engines.htm

[CW951]

Blackfoot, I have considered the Huntley 2.8 engines but they are big bore engines using sleeved blocks and I wasn't sure they would give me the low end torque I've heard the stroker does. The price looks pretty good though - drop it in and go! I've heard some horror stories about the longevity of the sleeved motors, but then too much boost will kill anything!! I'm sure Huntley has those motors pretty well sorted out....they're still under consideration for sure. Thanks for the reply........CW

[very~worn~944]

Hey guys...i might be rebuilding the bottom end of a 951 soon...and i thought about a 2.8 stroker kit. Is it a crank and rods from a later 944? What all do you need to have it run...and what is the cheapest way to go about it? How much difference will I FEEL with just 2.8 liters, and how about if i convert it and spend about 1500 on performance mods? How much power are we talkin? you mensioned 968 blocks...what good are they? Thanks

[fletch944t]

This is going to be a very long post because I'll try to answer as many of the previous questions as possible.

First, with regards to the Huntley complete engines. Since, I do all my own work, I've never considered buying a complete engine. However, if you're not into that, or don't have the resources to do-it-yourself, one of the Huntley engines is certainly an option. You can email me privately for personal opinions about dealing with different performance parts vendors. I've dealt with most of them over the years, with a few exceptions.

Now, with regards to building a big bore engine, there are so many options, I didn't really want to get deep into it. However, there seems to be some interest.

First, to build a big bore engine, you can bore, or you can stroke, or you can do both. With the 2.5L block, many have taken the route of boring rather than stroking because it's somewhat cheaper as it saves the purchase of a 3.0L crank ($1100-1500 used, $3000 new). It also saves because the increased stroke requires the sides of the main bearing saddles to be machined (to use the factory rods-cost about $400) or a set of aftermarket rods with shorter rod bolt shoulders must be purchased (around $900). In addition, because of the increased stroke, you now have to worry about the pistons traveling too high in the cylinders and contacting the head/valves. So, you have to purchase a set of pistons with a higher wrist pin location so that the piston height is the same at TDC (typically about $1250 for pistons to be used with the stock cylinder walls). However, with overbored cylinders you're going to buy new pistons anyway.

Now with regards to boring a 2.5L block. When you significantly overbore the 2.5L block, it must be sleeved. That's because when you significantly overbore the cylinders the cylinder walls get very thin. And since they are aluminum alloy, you need a cast iron sleeve to provide the support needed to keep the cylinders from floating at the the top. You see the 2.5L block cylinders are free standing which means they are not supported at the top. As opposed to the 3.0L block where the tops of the cylinders are acutally webbed together for support. The 3.0L block also has more thickness in the cylinder wall area which makes them a better candidate for boring. Typically, sleeve thickness run about 1mm. So, (assuming you don't change the stroke) if you bore the cylinder to 106mm and sleeve, you end up with 104mm bore which gives you a 2.68L engine (normally referred to as a 2.7L). If you bore to 108mm and sleeve, you end up with a 106mm bore which gives you a 2.785L (or 2.8L). And if you bore to 109mm and sleeve, you end up with a 2.838L engine. Boring to 109mm and sleeving is about the physical limit that you can go with 2.5L block. Personally, I'm not a huge fan of significantly overboring the 2.5L block. Significantly overbored blocks are more prone to the cylinders moving around which ultimately makes them more prone to head gasket failures. However, once again it is a cheaper alternative.

It is not uncommon to see blocks which have be overbored enough to sleeve back to the original bore. So, why do this? Because the stock cylinder bores are a silicon impregnated aluminum alloy, they require pistons that are specially coated (typically with iron) and special rings. Early on, the only source of the specially coated stroker pistons (with the higher wrist pin locations) was Mahle. And they could only be obtained through Andial (around $1250). However, you can now get other aftermarket pistons with special rings and send them out to be coated (ultimately still about the same price). By boring and sleeving back to the stock bore, there are a number of sources for aftermarket pistons that can be used without special coating or special rings (JE, Cunningham, others). However, they're still going to run you somewhere in the $700-900 range. So, the bottom line is that bore and sleeving back to same bore or using the specially coated pistons is about the same price.

Finally, if you want to go all out, you can bore and stroke to get 3.0L + displacements. For example, if you bore and sleeve a 2.5L block to 104mm and use a crank from a 3.0L engine, you end up with 2.983L (or a 3.0L engine). If you're going to go bigger than 3.0L in displacement, I highly recommend using a 3.0L S2 or 968 block as a starting point. It will be much more reliable in the long run.

So to summarize what you'll need for different big bore engines:

1) Overbored engine - bored and sleeved block, custom overbore pistons, and depending on size of overbore a special head gasket.

2) Stroker engine - 3.0L crankshaft from S2 or 968, block main bearing saddle machining or aftermarket connecting rods, custom pistons with higher wrist pin locations (again specially coated with special rings with alloy cylinder walls, non-coated with sleeved block).

Hope this helps.

Regards,
Clark Fletcher

[Blackfoot]

thanks for the boring & stroker information, most interesting. clark, what's the realistic $ figure you have in your head for doing a complete 3.2l from your 3.0l block?

[fletch944t]

Hi Blackfoot,

I usually try not to figure up how much it's going to cost me to do something. I'm afraid it will scare me and I'll start cutting corners. Anyway, I ran some quick numbers just for grins. I'm figuring I can do it (since I do all my own work) for around $15000. That's for a 3.2L engine figuring the price of the block, boring and sleeving the block, crank, pistons, rods, 16V head and necessary head work, custom intake manifold and exhaust headers, ball bearing turbo, oil pan, gasket, seals, and bearings. And, I actually threw in about a 20% margin for unexpected costs. Now, that doesn't include engine management. But, I already have an Electromotive TEC 3 that I'm in the process of installing on the 2.8L engine. If you add in a stand alone engine management system figure an additional $2500 - 3000.

Truth be told, dollar for dollar, a 2.8L engine is a much better value. You can approach the 500+ hp threshold with a properly built and setup 2.8L. However, the higher you get way up in horsepower, the dollar cost for every horsepower rises exponentially. Heck I can do an extremely nice 2.8L setup from the ground up for a little more than half the cost of the 3.2L engine.

So, the bottom line is this. My plan is to continue developing the 2.8L engine until I feel like it's no longer worth the effort to get more horsepower. If I get to the 500+ HP (at the wheels) threshold with the 2.8L, I may abandon the 3.2L project altogether. I'll just have to wait and see what happens.


Regards,
Clark

[jakell]

Great post Clark!

PS: I miss the Garage, it really helped in my early 951 days.

JAKE

[fletch944t]

Patience Grasshopper.

The Garage will be back soon. And, I guarantee it will be worth the wait.

Regards,
Clark

[Blackfoot]

yup, i knew it must be a lot, but wasn't expecting the $15k! sounds like the 2.8l gives the best value. how about doing the 3.0l, would that save significant $ or would it also be in the $15k range?

[XJOSHX]

besides the stronger clutch what other mods do you have to do to the car to make it handle 500bhp at the wheels?

[fletch944t]

Hi XJOSHX,

The condition of the engine itself has to be sound. In other words, you should start with an engine that has been freshened up (i.e. rod bearings, main bearings, head rebuild). But, you don't try to squeeze 500 HP out of the engine right off the bat (IMHO). Break it in gradually and then slowly build it up to whatever horsepower you're shooting for over several thousand miles.

A lot of folks will tell you that the 944 Turbo transaxle can't take that kind of horsepower. Well, since I've never made 500 HP, I can't confirm or deny that to be true. However, I've spoken to one person (let's face it, there's not a lot of people making that much HP) who has built several cars well above the 500 HP threshold that the transaxles have done just fine.

Now, I am swapping to a 968 six speed transaxle which is generally a little beefier than the 944 Turbo transaxle. However, I'm not doing so because I feel it necessary. I'm doing it just because I want to.

The big thing with the 944 transaxles (all of them) is that you can't be dumping a huge amount of torque on them suddenly. For example, revving the engine and dropping the clutch during a drag race. Try that too many times and the transaxle will start spitting teeth at you.

It's also a good idea to make sure that everything in the suspension is in good working order. And, as I stated before, I realized with the 2.8L at 19 psi boost that I was going to need bigger brakes.

Regards,
Clark

[fletch944t]

Hi Blackfoot,

Sorry it took so long to get back to you. I tried to post a reply the other day and the board wouldn't let me for some reason.

There's really not a huge difference between doing a 3.0L and doing a 3.2L. With the 3.0L you can use the stock bore but, then you have to buy the specially coated pistons. With the 3.2L, you're going to bore and sleeve the block. However, you get some of that cost back by being able to use a cheaper set of pistons. In the end, the difference between a 3.0L and 3.2L is probably going to be less than $500.

Regards,
Clark

[porschepatron]

All very intersting stuff, I too have been juggling a rebuild for the past several months, almost a year now. Originally I had sent my short block out to Garrity but things went sour and he has now rertired from the biz. When I recieved my block back it had been bored to 102mm and I had never collected on the pistons. So here I was stuck with an grossly oversized block (still retaining the alusil bore mind you) and no pistons. I tried several aftermarket shops and even went so far as to contact Mahle (Mahle motorsports) to fit a piston to my red headed step child motor. Still no luck, they would not custom make pistons for my project. I really did not want to sleeve and I was running out of options. So one day I was flipping through Excellence and came across an add for U.S. Chrome, a company in WI which specializes in nicom plating (nickel carbide) cylinders etc. So I explored the option and to make a long story short I have decided to put whatever faith I have left in these guys to get me on the road. It's actually a pretty neat process, and I would be able to run a forged piston instead of a hypereutectic NI TIN plated piston. Another benifit is the process enbles them to take a cylinder back down to spec 100mm in our cases. I had thought about going back to 100mm but I think I gonna stick with my 102mm bore as I do feel there is plenty of meat left on the cylinder. So in the end I'll end up with a 2.6 with billet rods, forged JE pistons, and nicom cylinders. Just thought I'd enlighten you guys as I myself had never heard of this but Im sure glad I found them because I think this may be a better alternative to the sleeve, just my opinion though.

Thanks a bunch
Brian Hanlon

[CW951]

Very interesting...let us know how it all works out. We could all use another option or two for saving those otherwise dead blocks. Let's just hope it doesn't go the way of the early BMW V-8's

[fletch944t]

Hi Brian,

The nickel carbide plating sounds like a great alternative. Please keep us posted as to how it turns out, cost, etc. I'd be very interested in doing that myself when and if I proceed with the 3.2L project.

Regards,
Clark

[Blackfoot]

since this is a really interesting subject, how about some updates?

charlie--what's the status of your rebuild? break down & go with the huntley 2.8?

clark--how "developed" is your 2.8 now? enough power, or do you suspect you'll want to undertake the 3.2? change your clutch disk yet? bigger brakes in? 6-spd?

brian--did you go with u.s. chrome nicom plating alternative?

[fletch944t]

Well, you asked for an update. So, here it comes. Be warned this is a long post.

The 2.8L has way more power than I'll ever need. Of course, with me, too much power is never enough. I suspect I'll play with the 2.8L until I wring as much power out of it as I possibly can before I move on to something else. The plan right now is to do a 3.4 liter with the 968 block I have. Whether it will be a 16V remains to be seen.

I haven't bought the new clutch yet. The finances just won't allow it till after the first of the year. Reason being that I also plan to purchase an aluminum flywheel at the same time. I have purchased a set of new 968 drive shafts for the 6 speed. I also have purchased an Electronic Ratio Adapter for speedometer signal development. I plan to use an ABS sensor on the front wheel to provide input to the ERA. The nice thing about that is that it allows me to set up the speedometer prior to installing the 6 speed so I can get all the bugs worked out. I'll simply use plug connectors to swap back and forth between the normal speedometer pickup off of the trans and the new pickup off the front wheel until I get everything dialed in. I'm still trying to locate a used 968 shift linkage so that I don't have to buy it new from Porsche.

I've installed the Big Reds but, I'm going to end up having to pull the hubs back off. As it turns out, my M030 hubs aren't really M030 hubs after all. The only way to tell is by casting number. The problem is that the standard ABS hubs aren't as deep as the M030 hubs. Consequently, without using spacers the rotors rub the caliper frame. So, I'm in the process of trying to located a different set of hubs. Also, my fender clearance wasn't what I thought it was in the rear and ended up shredding a brand new S03. So, I have to roll the fenders in the rear.

While I'm waiting on the stuff to do the clutch, I'll be starting on the TEC 3 install. I've fabricated the mounting bracket for the TPS. This last weekend I welded a socket onto a spare coolant pipe (head-to-radiator) for the coolant temperature sensor. I didn't want to drill and tap the block at the stock sensor location in case I decide to sell the 2.8L engine down the road. This weekend I'll weld the spacer onto the PS pulley and fabricate a mounting bracket for the coil pack.

Almost forget, I've also installed an 0-100 psi fuel pressure gauge in a dual A-pillar pod (along with a boost gauge). The pressure sensor threads right into the instrument gauge tap on an Aeromotive or Weldon FPR. It worked out very nicely. If I get time, I'll post some pictures of my new fuel system setup this weekend. I fabricated a new fuel rail from extruded aluminum fuel rail stock. You may find them interesting.

Sorry about the length of the post.

Regards,
Clark