I wanna de-stroke a 3.8

[mike49]

Wow.. great car man, sounds mean too!

Couldnt give us some more info about the twin throttle bodies could you? ive been wanting to make something up like that for ages... so any info would be much appreaciated... sorry for going off topic

 

[Dr Goggles]

hot metal pump

A twin TB set up with added plenum like that ain't gonna fit under a bonnet but you could build a sidewinder. That one in the pic is built with 6mm Al plate, I just chopped off the top off the standard manifold added about 65mm height on either side and leant it out a bit, made a plate that covered the old entry point on the end and then welded it all up with a flat lid on it , cut two holes in the top and then conned our fix it man into making a linkage that worked. We didn't bother with sequential linkages figuring we really only need WOT so it didn't matter that they both opened at once...it probably messes with the MAP a bit but it's fine when it gets going. I chopped of the stepper bypass and welded that up on one of the throttle bodies, I used a mig with pure argon, 1mm wire and about 180amps, I use a little hand held sand blaster to clean things up before welding . when you look down through the throttle bodies you can see the valves, as you probably figured we don't run air cleaners, we do about 10mins hard running between seasons/rebuilds so reliability/ longevity isn't really an issue..

I haven't looked that closely at what's offered for under bonnet but if you divided the plenum you could send them in from either side and put a partition in so the path didn't turn too steeply......

It's a lot of work to make it all happen nicely for a road car, getting the intake ducting sorted, making the throttle cables work...personally I'd have a really good look at the commercially available ones before I embarked on a job like this.....

 

[mike49]

cheers for that man, much appreaciated
fitting under the bonnet isnt an issue.. wouldnt mind some filters out the bonnet... but yeahh ill have a look around firstly before i attempt anything.

 

[Dr Goggles]

de-stroke!

Hi The Yanks made 3.0 liter version of the Buick V6 as detailed below.

"A small 3.0 L (181 in³) version of the Buick V6 was produced for GM's 1980s front-wheel drive cars. Introduced in 1982, it was a lower deck version of the 3.8 designed for transverse application in the new GM A platform cars such as the Buick Century and Oldsmobile Cutlass Ciera. It shared the same bore size as its larger sibling, but featured a smaller stroke of 2.66 in (67.56 mm).

I spoke to Crankshaft-rebuilders today and sho-nuff those 3 litres cranks will do the job so I looked and I found a "refurbished" 181 crank, under $100 in LA. We'll get it shipped.But we won't be doing that refit for a few years yet.

I did buy a manual series 1 yesterday which I'll pull the crank from, our motor has an auto crank in it and we've been using an adapter for the flywheel .

We'll get it tuftrided and cleaned up, get it trued and get the whole lot balanced.

I've bought some adjustable stainless LS-1roller rockers, we're getting the solid profile Wade 1644a and we're still deciding whether we're gonna make inserts for the hydraulic lifters ar whther we're gonna buy some solid LS-1's...


on we go

more salt shots here...... Speed Week

 

[na3point8]

what needs to be done to fit the ls1 rockers mate? how big is the solid stick? is the bottom end gonna survive these mods?

 

[Dr Goggles]

Bump sticks and bottoms

what needs to be done to fit the ls1 rockers mate? how big is the solid stick? is the bottom end gonna survive these mods?

The LS-1's need to be separated and have special pedestals made.We've been told the bottom end will hack it, the solid cam is a 1644, my nets slow at the mo' so I won't chase up the spec sheet on it . "Been told " is , admittedly, different to "done it heaps of times" however.We aren't making stupid amounts of horsepower, if all the stars align we might be lucky and get close to 300hp. What we are after is a motor that is making all or most of it's power at really high revs, that's how we go fast. As I mentioned above , in landspeed racing......

"He who fires his spark-plugs the most times, wins"

If we have more than 250hp and our motor can rev to 7500rpm we will be in the vicinity of 225mph or 360km/h, a sedan would need over 800hp to do that(based on production cars I know that have run over 210mph and what they have dynoed at), and would have severe traction issues.

That 250+hp isn't going to break the crank, but 7500rpm might cause some problems....we only do about 60 kilometres between rebuilds so our reliability issues are more concentrated on "holding together" than lasting years.........

 

[Dr Goggles]

OK, I'm back....been buying parts and been flat out on some other projects. Got a new five layer fire suit from the States...I'll be able to sit in a flaming car for about 40 seconds now, better than the 15 that the old suit would have allowed ..not that I'm hoping I'll ever need to test it.

Our 3 litre crank is on the way from Ohio so we might even get started on building that motor this year using the hydraulic valve train that is coming out of the motor we ran at the lake this year.

I'm hoping to get out to see Steve at Mace this week so he can help me with the pedestals and rockers for the new stage three heads. He's been very helpful so far...

I'm speaking to Wades this week and ordering the new cam, and also pulling down the motor so we can send a piston and rod with the new manual crank,clutch pressure plate and billet flywheel to get balanced.

On another front I've just finished writing an article for this years Street Machine Hot Rod Annual.

 

[VT-565]

Interesting reading, this thread.

Good you got your crank issues sorted, what are the big end journal sizes on the 3 litre crank?
I was going to suggest an offset-ground 3.8 crank and get a set of custom rods made up.

Question, with the lower piston speeds, will you get a drop in intake and exhaust gas velocity?
Maybe a stock port size would suit better then?

 

[Dr Goggles]

Question, with the lower piston speeds, will you get a drop in intake and exhaust gas velocity
At this stage I can't give you a definitive answer on that, the piston will travel a shorter distance for each turn of the crank, thus it will travel slower for the same rpm.....I'm not going to make claims that I can't support but I believe that there is sense in the explanation that was given to me by a guy called Jack Dolan who has a long history in landspeed racing in the States. He built the motors for Don Vescoes record setting Kawasaki streamliner. As he put it "people are always trying to get more out of motors , bigger ports, bigger valves, longer strokes for more torque, I figured I could turn that on it's head". He went on to make the point that people are always trying to bend the rules not interpret them. "Everybody wants heads that will flow massive figures.....well why not put reasonable heads on a little motor ...and run in a class that it fits in?"....
That's what we're figuring......we've got some decent heads, they might run like crap at lower revs but at the point when the 3.8 starts to run out of puff, the 3.0 will be trying to pull about 22per cent less air through the ports. That, and the lower stresses ( and losses)on the piston/rod/pin assembly we hope will make for a motor that will rev toward 8 grand and still be making power .....and not coming apart.We'll be up against a Supra motor in that class run by some guys who said we'd never go fast with the V6, we're going fast now but it'd be nice to destroke it to F class , and see what we can do...

what are the big end journal sizes on the 3 litre crank?

I'll get back to you on that, from memory we aren't in for any surprises....but I'll fill you in soon, the crank should be here within days.......

 

[delcowizzid]

weight match all the rods and pistons and match them before heading off to the balancer sometimes the rods can vary pretty bad in these things upto 8 grams difference or more thats a lot.you can overbalance the engine for high rpm work. Buick Turbo V6 Engine Build Overview - GM High-Tech Performance Magazine never mind its for the turbo buicks it has lots of pointers like the oil mods and rod bolts etc