Stroke, bore, and motor integrity questions

Dubstep Shep

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Since I committed to the DOB R-Spec, I've been looking for ways to improve on my current motor. A lot of specifics are up in the air as this project is a ways off, but I'm trying to do some research and ask questions now so I can start to form an idea of the final goal and cost.

Concern #1 is going to be strength. Without filling the block, this is gonna be tough. My goal is to max out the 3.4L Whipple on e85 with a higher compression ratio. Best guess is 1200-1400hp. Why? Top speed and mile drag race. For road race I'm going to be running a much lower boost setting. I want to stick with an aluminum block for weight savings on the road race track, and I also don't like how the iron Boss setups have fewer main bolts. I feel like with enough tricks and $$$ it should be doable. I'm also looking into putting larger head studs in and O-ringing the block to keep the heads on.

Concern #2 is performance. Coatings, displacement, etc. Basically maximizing the amount of power I can get through changes in the motor.

I'm for sure doing a dry sump system with a billet oil pan, a DSS mains brace, a full front thust bearing with a billet plate where the oil pump used to go, and a rear main seal billet plate. Also thinking about cryo treatment and WPC treatment for everything. I'm also modding the cooling system so both banks run at the same temp.

I'm looking into wet sleeving the block with Darton MID sleeves, which opens up some unique possibilities. The MID sleeves apparently increase the overall strength of the block, while also increasing bore and cooling capacity. Their bore specs are 92-95mm. Of course, these are Dartons claims and I'm still looking into them. For the time being, I'm assuming they're correct and looking at my further options.

So with that I can easily run a larger bore and unshroud the valves. Not sure on the exact bore needed to accomplish that, but I would like to run at least that large. If Darton comes back and tells me I can max out the 95mm bore, then I may go that route.

The other question I have is stroke. I would love to do a 3.800" stroker, but I have some concerns about the integrity of that. I've been reading some engine books lately, and some people have concerns about the strokers. Chief among them is the stability of the piston in the bore at higher RPMs since with a stroker it comes further out of the bore at the bottom. Again, I would love to have more displacement, but not at the expense of integrity. Any experience here?

Minimum displacement with stock stroke length and the MID sleeves at 92 mm comes out to 292 cubic inches, a fair improvement. 95mm with stock stroke is 311 cubes. To me anything 5.0 or bigger is a big step up, especially if the sleeves improve cooling and strength while they're at it.

Maximum displacement with the 95mm bore and a 3.8 stroke is 334 cubes. Idk if that's been done on an aluminum block. Could be sketchy.

What're everyone's thoughts? Obviously there are big performance gains from unshrouding the valves, but once you're there is there really anything to be had from further boring and stroking?
 

eighty6gt

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Go with a GT500 powertrain. (I only say this because you don't want to use a boss block,) also call FRPP and see what their thoughts are on the boss blocks durability vs. main bolts. They have an outstanding technical department.

You'll have $200,000 into this car?!
 

blownGTvert

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What's the cost for the Darton sleeves? Largest bore possible would be my choice. And the stroker to get 334 cubes is enticing. If the rod angle isn't crazy I wouldnt be scared of the stroker.
 
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Dubstep Shep

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What's the cost for the Darton sleeves? Largest bore possible would be my choice. And the stroker to get 334 cubes is enticing. If the rod angle isn't crazy I wouldnt be scared of the stroker.

Expensive from what I can tell. Sleeves are like $1,400 I think, plus installation, which I would be letting Darton handle. I have no idea how much installation will run.

Yea, having a 334 cubic inch motor would REALLY bring out that 3.4L whipple. Plus having a 3v that big with that much power would be AWESOME.
 

eighty6gt

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Local guy twin turbo'd his GT500 to do the top speed thing. With the blower. I don't know how much he breaks the 1000 mark by...

edit: he turned his engine inside out in the fall, ordered whatever is likely to be the most expensive MMR GT500 short block available. It's back together now.
 
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Dubstep Shep

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Local guy twin turbo'd his GT500 to do the top speed thing. With the blower. I don't know how much he breaks the 1000 mark by...

The primary purpose of the car is road race. For that purpose, a PD is the best option for a power adder. The R-Spec has the best cooling capacity of any PD kit I've seen. That was my reasoning.

If DOB wants to make me a custom R-Spec for a GT500 motor, well, that would be a different story hehehe.
 

blownGTvert

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Expensive from what I can tell. Sleeves are like $1,400 I think, plus installation, which I would be letting Darton handle. I have no idea how much installation will run.

Yea, having a 334 cubic inch motor would REALLY bring out that 3.4L whipple. Plus having a 3v that big with that much power would be AWESOME.

If cubes were my goal the new FRPP 5.3 short block would be on the list. Your going to have some $$$ to get the same displacement using the Darton sleeves.
 

Dubstep Shep

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If cubes were my goal the new FRPP 5.3 short block would be on the list. Your going to have some $$$ to get the same displacement using the Darton sleeves.

The one that uses the boss iron block?

Like I said, I'm not a fan of those blocks. Fewer main bolts and they're iron. I'd rather have the weight savings and additional mains.

The $$$ isn't really that big of a deal at this stage. I'm well past that point.
 

95ragtop

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Jpc has boss blocks with 2 additional mains at each point with billet caps to make it a true 4 bolt, but that 80lbs over the nose is a big hit when road racing. I've heard of the darton sleeve setup and know it's expensive and if you go with it I can't wait to hear it.
 

rcm90

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What kind of rpm's are you looking to turn? That's going to play a major factor in durability and what crank I would use.

A dry or wet sleeved 05-up block will handle the power.
 

Dubstep Shep

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What kind of rpm's are you looking to turn? That's going to play a major factor in durability and what crank I would use.

A dry or wet sleeved 05-up block will handle the power.
Depends.

If I stay with stock stroke, probably 7000 or more.

If I go longer stroke, probably do lower, maybe 6750 or 6500.

The longer stroke and lower rpms mean I could pully the blower down and have a wider sweet spot. Gearing I can do whatever with, maybe run something smaller than 3.55s.
Can you use a 2.9L there?
You mean whipple size? I've always heard the 3.4L is vastly superior to the 2.9
 

eighty6gt

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On what track are you planning on road racing a car with 1400 hp? How long have you been racing? Usually when you have that much balls you are driving something that weighs more like 1800 pounds and gets much of its grip from aero. Makes a $200,000 Mustang GT seem like a bargain.

Wonder how much HP that guy who rebuilt the whole car with heat exchangers in the rear is making. I think that thing melts tires and brakes somewhere...
 
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W3bb3r04

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I dont think a 2.9 or a 3.4 will get you to your HP goal unless you are spraying a ton too. I know the guys with the 5.8s in GT500s are using the 4.5 whipple and KBs to make 1400 whp. That is with a bit more CI and a lot bigger of a blower. I think youd be better with a bigger blower and less boost for heat if you are set on those power goals.
 

Weou09

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The real question is are you prepared to tear it down often? Doing things like you are talking about requires constant maintenance. Honestly how efficient is a s197 at either of your races? Wouldn't it be cheaper, and better, to build two dedicated cars?
 

Dubstep Shep

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On what track are you planning on road racing a car with 1400 hp? How long have you been racing? Usually when you have that much balls you are driving something that weighs more like 1800 pounds and gets much of its grip from aero. Makes a $200,000 Mustang GT seem like a bargain.

Wonder how much HP that guy who rebuilt the whole car with heat exchangers in the rear is making. I think that thing melts tires and brakes somewhere...

I'm going to dial it back to 600 or 800 for road racing.

Eventually I want to build something in the 2000lb, 1000hp range for road racing, but for now this is what I have.

And you mean Jacen at DOB? He has dual heat exchangers and runs a R-Spec kit doing road race.

I dont think a 2.9 or a 3.4 will get you to your HP goal unless you are spraying a ton too. I know the guys with the 5.8s in GT500s are using the 4.5 whipple and KBs to make 1400 whp. That is with a bit more CI and a lot bigger of a blower. I think youd be better with a bigger blower and less boost for heat if you are set on those power goals.

Like I said, it's not a definite goal. If I reach the end of the 3.4L and want to go bigger, I'll reassess then. With high compression, e85, and a larger bore breaking 1200 should be possible though.

http://www.6speedonline.com/forums/automobiles-sale/265883-2009-rossion-q1-modded.html

Here's something that I'd rather whore out for regular track duty - maybe a more ratty example. Noble M400. Then just get a rocket car/?? for the top speed stuff.

Hahahahaha rocket car. I'll pass on that.

Really what I want to do eventually is build a Factory Five GTM and get it up to about 1000hp. That's the 2000lb, 1000hp car I mentioned above.

The real question is are you prepared to tear it down often? Doing things like you are talking about requires constant maintenance. Honestly how efficient is a s197 at either of your races? Wouldn't it be cheaper, and better, to build two dedicated cars?

I'll probably be tearing it down once a season anyways. This is, after all, a race car.

The biggest point of this build was to have a car that could compete in multiple areas. A jack of all trades. While I've only mentioned road race and top speed, I'll likely be doing drift, drag, autocross, etc in this car.

Also, I just like having a mustang. Short of a Ford GT or the aforementioned GTM, this is the car I like the most.
 

psfracer

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I will confirm with you the following, even though a completely different motor the principal is the same.


With my motor setup, we determined the 4.5 stroke was the maximum just for that reason, as we felt with the 4.75 stroke the piston skirt just came out too far, which would put excessive wear on the piston skirt.

Also, piston speed becomes a factor which you can not ignore, based on your expected rpm range. In my case 4.600 bore X 4.500 stroke = 598 cid with a maximum expected rpm of 8200 but peak power probably 7600 or so. Don't forget your rod/stroke ratio can affect the cam specs you may want to go with.
 

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