My First Post - 408+T56 Idea

Hi Everyone,

This my first post on here, though I've been lurking awhile.

I have just resurrected my '89 Super Coupe 5-speed after a six year hiatus. Worst thing was cleaning up the mice mess. But at any rate, I have the car running again and not too badly at that. Car has 155,000 miles on it, and I've owned it since 1994; I bought it as the second owner and it was still under warranty.

Ok, the thing has been a bear to work on ever since I got it. Changing plugs is one of the most horrific jobs I've ever done to a car.

I have been thinking of doing a V8 conversion. I have read through a bunch of threads on here. XR7 Dave has offered some great commentary.

Anyway, here is my idea:
Remove the V6 mill and M5.
Replace it with a Windsor stroker engine. I was originally thinking a 427 built on a Dart block with AFR 205 heads. This would be backed by a Tremec T-56 Magnum transmission. I have since read that a 408 is a very common build and you can do that with a stock block (late 60's block with heavier walls) and it will hold up OK. But at any rate, I was thinking somewhere around a 408 or 427. By removing the blower, and intercooler, and already having an iron block with aluminum headed engine, I think an iron block aluminum headed V8 would come out about the same weight as the original engine+blower system, so it shouldn't mess up the handling. I'm still working out the details, but I think the Dart block at 427 cubes, all forged reciprocating assembly, AFR 205 heads, Victor Junior intake, and the appropriate induction system.

I would prefer fuel injection, but the Edelbrock stand alone kit was in the $3300 range and that's getting up there. I'm not sure how to make the EEC IV for a six cylinder work with an 8. So, a properly tuned Holley 750 might do for now. Actually, I have a new one in the box right now...

Problems I see: How strong is the 8.8 IRS setup? My buddy says he's seen the half shafts just disentigrate when you start pumping real power through them. I see you can get a girdle to beef up the stiffness of the diff itself. What about the stub shafts?

I don't plan on doing any crazy mods to the body work, so really about a 245 would be the widest tire I could fit on it. Being traction limited, wouldn't that help save the half shafts?

I'd be going from 210hp and 325 ft-lbs to 500 and 500. If I took it easy in 1st and didn't really start getting on it until 2nd or 3rd, wouldn't that really help out?

Just the same, I don't want to have to worry about it breaking. So, after the engine/trans swap, what would I need to look at as far as keeping the rest of the car together?

I really like the way this car handles. Right before I parked it, I installed a Tokiko performance handling kit for it that works with the ride control. Where it was soft and firm before, now it's firm and harsh. We also used some different alignment settings that dialed out some of the understeer. The car handles great. And as much as I love big blocks, I don't want the weight messing up the handling.

So anyway, I'm strongly considering a big inch Windsor (I don't want a 5.0....). It looks totally doable to me. But I don't know how weak the rest of it is.

Another route might just be a nicely built 351 that is still a 351, if the rest of the driveline can't take 408 or more without $10K worth of add ons. But if a girdle and stout half shafts would suffice, I'd really like to do a 427 small block.

Can you guys help me?

Thank you,
Jim
'89 SC 5-speed

Jim,

First of all, if you are going to do a Windsor, don't stop short of the 408/427 idea. At 500/500 you are just approaching the level of a well built 3.8, and a 351 just won't measure up without forced induction to help it out - well that is unless you want a high rpm screamer, but then again the Windsor isn't a great high rpm foundation, so we are back to the big inch version.

Believe me, the drivetrain isn't an issue. We as a group have run these cars with more or less stock driveline's into the 700hp range and 9 sec territory. With street tires I wouldn't worry about it at all.

And finally, on the fuel injection, by all means stay with the Ford EEC, all you need to do is swap in the electronics from a 5.0 Tbird or 94/5 5.0 Mustang.

This is an ambitious project if you go ahead with it. Don't think for a minute it's all going to be plug and play, but if you are up for the challenge it's completely doable.

David

David,

Thank you for the reply. Maybe I'm all wet here and should look at hot rodding the stock engine. I didn't think you could get power like that out of that mill. I'd read a lot of posts and it looked like you could put $10K into the 3.8 and maybe make 375hp with it. Which, at 100hp/litre, is pretty impressive. But, that's a lot of money to only get 375hp. Maybe I was wrong?

I thought the SC's block was a stouter piece with higher nickel content than the more plebian 3.8's. As well, I thought that the reciprocating assembly in them was forged. I thought it was a first class piece of equipment...just too small. (though Kenny Dutweiler did wonders with little Buick 3.8's.....)

And, I never understood why they "only" made 210hp (or 225 or whichever depending upon the year) when it's a 232 cubic inch. For every 14.7psi of boost, you essentially add another engine's worth of cubic inches, so a 3.8 at 15psi should be like a normally aspirated 7.6....which is like a 465 or so. So even though mine never made more than 12psi, I guess I never understood why they were only rated at 210hp instead of around 400hp or so. I know the torque was decent at 325 ft-lbs or so. But still, any decent modern V8 (like an LS2 for example) can beat it in both torque and horsepower and do it in a much more simple manner.

But all that being said, how do you get 400hp out of the 3.8? I would think you'd start with new headers to free up the exhaust, then go to an under drive pulley on the blower to speed it up. Port and polish the heads, bigger valves, O-ring the heads so you don't blow head gaskets, then a better air filter, bigger mass air flow sensor, then larger injectors with higher volume fuel pump, probably an after market chip to modify the computer settings....am I close? Is there that much untapped potential in these engines?

It may be heresy to admit this on this board, but I have always been a Mopar guy, with the exception of this SC. I just read where Car Craft took a Mopar Performance 426 Hemi crate engine and dyno tested it. Chrysler always rated those engines at 425hp, and I always heard that was under rated. Car Craft said this one was rated at 465hp. Well, they changed the cam and the intake manifold and went to a big Race Demon carb, and they made 588hp with it on pump gas. So (A) Mopar was playing Poker Face and (B) the Hemi has a ton of untapped potential that's not hard to get. Are these 3.8's the same way?

I just thought that a big inch Windsor would be a much simpler solution. And like you pointed out in an old thread, it sure would sound better If I went with the Dart block, I could use a 4.125" bore and the 4.17" stroke crank (same as used to make a 427...but it's not over square with the Dart's thicker walls and bigger bore) and you wind up with like a 443 or so. I believe you can build a 468 or something like that with the Dart block.

My biggest worry with this switch out was destroying the drivetrain from the tailshaft back. But if you guys are pumping that much power through these cars and they're holding up, then that puts new light on things. I was about to give up on the idea entirely as it was starting to domino out of control.

408 is about it with a factory block. My Ford Guru buddy says he's seen them split the block though to where only the oil pan and intake manifold held the engine together. The Dart is pricey, but not that outrageous; $2200 will get you one and you'll pay $500 for an old one and clean it up. But at least with the Dart block, you could throw the laughing gas to it and probably not split it.

Anyway, I'm really wondering now....if I built the 3.8 up to 400 or 450hp, what would it take? And then, would the M5 survive behind it?

I drove the car to work for ten years at about 90 miles a day; it's all high way miles. And I've run Mobil 1 in it since I got it, which was at 40,000 miles or so. It runs pretty well right now. It's been a good car and I really like it. First car I bought out of college, so it's got some sentimental attachment. So I am interested in what can be done with the original motor.

But that being said, I really like the idea of a big block displacement in a small block package.

Thanks for any help and guidance you'd be willing to share.

Jim

You might want to think about where the hp numbers are coming from. Most of the numbers you see posted on this site is hp at the wheels, not crank hp like the majority of other motors are referred to. It was something Dave pointed out to me the other day.

Taking in drivetrain losses and how much hp it takes to drive the blower etc, you could easily see these motors making 500+ internally.

We need to compare apples to apples here .

Fraser

I have not been talking rwhp numbers here, but neither has Jim, as a 427 Windsor isn't going to put 500hp to the ground. That would take 650hp at the motor and that wouldn't be streetable.

These motors make 300rwhp easily which is to say 375hp at the flywheel. All that takes is a mild cam, a little head work, and bolt on upgrades (and no, not headers). This can be done and maintain full stock drivability.

To make 350rwhp (400-425hp at the motor) requires a little more effort and should include some forged pistons and better rods for safety sake. I've made a lot more than that on stock rods and pistons, but I wouldn't call it 100% reliable. At this power level you are starting to have something with slightly more racy manners. And you'll spend a lot more on bolt ons too.

To make 400-450rwhp (500-550hp at the motor) takes you to pretty much the limit on these cars. You run into issues with pump gas and the amount of boost required, as well as require a better blower than your typical M90. In a sense this is your $10K+ powertrain. To take the SC to this level requires a personal need to have a faster V6 than your buddies' V8 because it isn't the most practical path into the 500hp area.

The problem in comparing this motor to anything new is the fact that these motors only make about 70% VE. The LS motors make more like 95% VE, and some of the new motors (like the new 5.0 Coyote motor) make over 100% VE. Our motors take about 5psi boost just to make 100% VE.

So that's that.

If you want to go V8, I'd look at the new Boss 351 blocks. We have a Boss 302 block in the shop right now and it is a really nice piece while being less expensive than a Dart. Plus its actually Ford!

I'd put a set of fully ported 205's (with CNC they'd end up more like 225cc's) and a good solid roller cam. MMMMMM yummy.

But the V6 will kill the 427 on fuel mileage (I got 24mpg with mine while making around 500hp), and the blower was great for scaring people.

there's a guy on tccoa that has a 408 turbo 5spd build going on, he originally had a 92 lx that he did a 351w and 5spd swap in, he bought another block and built that engine, then half way through he decided he wanted the ARC and TEVES systems, so he bought and stripped a 90 supercoupe, the car is completely bare I mean naked bare butt nude, it actually leaves tomorrow to get walnut shell blasted and primed, I've been following the guy's build so closely I feel almost as though the two of us are one

there is no way that car won't be running in the low 9s easily just as long as the STOCK m5r2 and STOCK IRS holds up, he will be testing the limits, he has thoughts of running in the 8s with his other mn12 friends that live local to him, only time will tell, I can't wait till it's done

there is no way that car won't be running in the low 9s easily just as long as the STOCK m5r2 and STOCK IRS holds up

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I don't think you'll be able to launch it hard enough to run those numbers without breaking the stock IRS or the transmission, but I'd love to see you try.

David

I don't plan on doing any crazy mods to the body work, so really about a 245 would be the widest tire I could fit on it. Being traction limited, wouldn't that help save the half shafts?

Click to expand...

Jim,

You can easily fit a 275 wide rear tire without doing body work, and with the right wheel a 285 is possible. Welcome and good luck with your project.

David

PS: Dart block is very heavy and not required if all you want is 500 or 600 HP.

Guys,

Thank you for the excellent replies. I truly appreciate it. I think I have definitely tapped into the right body of knowledge here. You guys sound very professional; no shade trees here at all.

I'm an engineer myself. Degree was in aerospace and got my P.E. in mechanical. So I'm pretty good with airflow and I like engines. I'm the engine go to guy for all my EAA buddies. I think this kind of stuff is fun.

Dave, you've really got me questioning my whole project now. The car runs good with the stock power. If i could turn up the wick to say, 425hp, like you mentioned, even if it is a little edgier, that would be plenty to hold me over for now. Even at 375hp (all figures off the motor), that wouldn't be bad. With so many miles on it, the car probably needs to have the heads redone and new bearings, so I'd be tearing it down anyway. A set of rods and pistons wouldn't be that bad. The crank is already a forged piece, isn't it? Even if it's cast, I would think that since it's only got three throws instead of four, it should be stiffer than an equivalent V8 crank anyway.

Let's say I wanted to do a 425hp SC V6. What rods and pistons would you recommend? Would you keep the original compression ratio? Should i O-ring the heads? I've been fortunate to not have ever blown a head gasket, but I've not modified the engine at all. Do I need bigger valves? What cam would you recommend? Are the stock injectors and fuel pump up to the task? Will the EECIV just adapt to this or would I need to get a "chip" to trick it?

A lot of questions I know. And the answers are probably on this board somewhere, but I really did read through a ton of threads looking at this kind of stuff, so I apologize in advance if I'm reinventing the wheel. I just didn't think it possible to get that kind of power out of these engines. This does put things in a different light.

So I guess I'm down to two ideas here: (!) Just hop up the OEM mill and run the M5 or (2) Do a wild V8.

I was thinking that (2) was the way to go, but now I'm starting to really wonder if I shouldn't just hop up the V6. 400hp would do me nicely.

Thanks for your help!

Jim

The stock crank is forged so that is plenty strong. For 400hp I recommend H-beam rods and forged pistons. We use 351W rods and custom pistons from Wiseco at our shop. Normally we keep compression in the 8.5-9.0 range so that the motor remains pump gas friendly. We do not O-ring, we just use MLS gaskets and ARP head studs. O-ring is ok but we find it is not necessary.

The heads we treat to larger valves and some porting work and then a custom cam to match. Roller rocker and all the other necessary parts are readily available as well.

The stock fuel system is only good to about 300hp so that will all have to be upgraded - fuel pump, injectors, MAF, and chip. With the chip we don't trick the EEC, we have the ability to remap it completely so we are able to tune just about anything to run nicely. For example, most guys here are running 60lb injectors with 100% stock drivability.

To get to 400hp, expect to spend at least $6000 if you do some of the work yourself and maybe score a few good used part deals. If you aren't careful you can spend $10K, but for that price you could pretty much send me the car and pick it up later ready to drive home, so that should give you an idea of what is possible and what is practical.

Jim... If your serious about making that kind of power Dave is the man that can get you there. He knows these engines inside and out, this is what he does.

The first step is taking the initial plunge, now that you know what you need to do, start ordering the components to get you there.

I've had nothing but good dealings with Dave, I even call him from time to time with technical problems which says a lot considering the speed shop I'm with has been business since 1958.

2nd, Dave is the man! His real name at birth should have Been "Super Bird" lol

Dave,

I must agree with the other gentlemen; you certainly seem to know your stuff! Before I posted, your's were the posts I liked to read. Very informative, very knowledgable, very thorough.

Beyond that, when you started talking about volumetric efficiency, I knew you knew what was going on. Very few rodders I talk to know about that. That's engineer speak I guess these engines are so low in VE is because of all the twists and turns to finally get to the cylinders? Whereas an LS engine is a much straighter shot? Wouldn't a Windsor with a good set of heads and good intake manifold be right up there with the LS?

$6K is more than I want to spend on the stock engine, let alone $10K. For the 375hp build that you said was very easy to get, what would I be looking at there? You'd mentioned that the bolt ons really go up for the 425hp motor. I'm assuming that might be a place of some significant savings as pistons and rods really don't cost that much.

I agree with you on the fuel mileage thing. The fact that you're getting 500hp and 24mpg is pretty darn impressive! Boost is a wonderful thing; power when you need it, small motor when you don't I saw a guy who put a built Duramax into a Chevelle. He could make 700hp and got 36mpg on the highway. That was a really neat car. But, he had $110K in it, so a bit rich for my blood.

I respect the heck out of you guys that are pulling huge horsepower out of these 3.8's. I guess another idea I had toyed with was ditching the blower and going with a turbocharger setup. I see others on here have done it already. Truth is though, it's hard to argue the reliability of these Eaton blowers. My car has over 155,000 on it and it's still going fine. You can hear a little thrashiness from the blower bearings if you put a screwdriver against it and to your ear, but it's not bad yet.

I guess that would lead me to another question. I know the official word is you unbolt it, send it to Magnuson along with a bunch of money and he sends you a reman one. But really, isn't the only thing in them to wear out the bearings? Couldn't you just go to a bearing supply house and get new bearings? The rotors should never actually make contact, right? So there should be no wear there? In other words, couldn't I overhaul the blower myself if I had new bearings and a press?

I like the idea of overhauling the engine, maybe bore it .030 over if needed and going to forged rods and pistons, a cam change, some head work, an overhauled blower, and then the bigger fuel/induction as needed. I would think that could be done for maybe $3K or so. And if that would get me up to over 300hp or so, that wouldn't be too bad.

But beyond that, I think I'd rather just do a whole new engine.

Do you think the AFR 225's would be too big? I thought they would for a street car, but with a 445 engine would they still be too much? And a solid roller cam...aren't those the type where you have to adjust the valves every couple months or so? Would a big hydraulic roller be OK?

I'm kind of rambling here, but you guys have given me more info in fewer posts than I thought I'd ever receive. Kind of making me rethink some things here. But anyway, I appreciate it all.

Dave, I'm only one state over. Maybe someday I could visit you at your shop.

thanks!

Jim

By all means, come check us out. We have meets up here from time to time - in fact our annual summer picnic is the July 11th weekend. It's in Newcastle, PA, but I'm going to be tuning the next day up here in Ohio. Check the events section for the Ohio Valley SuperCoupe Picnic post.

For a street car I'd probably back off the 225's. The 205's with CNC porting will be nearly as big and will be more efficient with better velocity.

I like solid roller cams. Big lift, big duration, mild street manners, what's not to like? With modern technology (ie. good springs, stout valvetrain components and shaft rocker arms), adjustment isn't an issue. Our circle track guys run all season without adjusting (against our advice being that they see 7000+ rpm for extended periods of time) and we've never seen any valvetrain issues with those motors. If you want to run 9500rpm, then you have pay a little more attention - well and a lot more for valvetrain components in general.

Hydraulic rollers are ok for 6000rpm and below, but above that they just suck. You can't use enough valve spring pressure to control movement and the added weight of the HR lifter just makes for bad juju. Pretty much anyone who runs much above 6500rpm with even the best HR stuff is bouncing the valves all over creation and beating the snot out of everything. In fact that is one very good reason why people with solid roller cams had to do so much adjusting in the past - they were over running their valve springs and beating the snot out of everything. Well that and stud mount rockers just plain suck. I will never do a roller cam without shaft rockers.

To keep your 3.8 build on budget, I would not rebuild the motor unless it is hammered out. New bearings, gaskets, and a coat of paint. Voila. Seriously. We had a great running 200K mile motor making about 550hp on stock pistons until we detonated it and broke a rod. No sealing issues, no blowby problems, original rings. The new motor never did make as much power as the old one did. One thing I've learned about forced induction motors is that a good ring seal is not as critical as on an NA motor. As long as you aren't blowing oil out the dipstick, it's all good.

To do any high performance fuel injected motor you'll have to do injectors and fuel pump upgrades. Well, you have to do that on a carbed motor too, but people seem to look at that differently. We routinely have $800-1200 in a good carb for a large cubic inch motor, so having that tied up in injectors, MAF and chip really shouldn't seem too out of line. But the point is that you will spend more money supporting HP than you will making HP. Making power is easy. Heads/cam/blower. Done, that's about it. But then to support that power you have to do intercooler, exhaust, fuel system, bolt ons, etc. It just all adds up.

So my point is that I would spend minimal money on the motor itself. Just freshen up a little so it's ready to run and not leak all over the floor. Then spend your money on the heads/cam/blower. The supporting stuff you have to buy regardless, even if you do a V8, so while you do have to pay the bill, you really can't add that into the cost of making power, its just something you have to do.

If you come to our picnic you'll meet Dan. He has a sharp 90 SC that he has spent about $3000, if that on (he's the cheapest bugger I know, lol!) and it makes about 375hp all day long. He's run 13.2's on street tires numerous times with it. It would take a couple more thousand to get it solidly into the 12's, but he's happy with it and his pocket book at this point so he lets it be. He and I worked together on that car making sure that everything we did was going to net gains, and if it wasn't going to, then we didn't do it, no matter how cool it seemed. Doing stuff like that takes some discipline. It's very easy to get carried away as I'm sure you know.

Oh, and rebuilding the blowers - yes we do it all the time. The only bearings that are problematic are the ones that bind the rotors to the gearbox. Those are impinged into the case and will not come out without breaking away material. And then there is the whole issue of re-timing the rotors. If you get them off by the smallest amount they will still spin fine, but will drag under load causing extreme heat and high parasitic loss. And that is assuming you can even get them back together reliably. So we generally don't rebuild the rotor packs. Fortunately the Pontiac GTP uses a similar (but not the same) M90 blower so we have been pirating the rotors out of junked Pontiacs for some years. But rotor packs are the biggest issue with rebuilding these blowers.

Porting the blower and then subsequently overdriving it is the key to making power with these things. We generally either port the blower (if it is a 94 case) or get a new case from Magnum Powers to put on the back of the blower. This makes a huge difference in performance.

Eh, it's only money!