moving engine rearward: performance gains?

[Guest Anonymous]

Hey all. I bought a finished ZS project from a guy. He did a REALLY REALLY nice job on it and the whole thing is beautiful. I bought the JTR book just to see what went into it and noticed that he mounted the engine about 3.5 inches further forward than the JTR mod. The JTR book says the placement makes a big difference.

 

So my question is, how much of a difference would 3.5 inches of engine placement make, and do you think it'd be worth all the trouble of cutting the driveline, cutting the exhaust, making new mounts, moving the fuel pump to the back, pulling the motor, tweaking the trans crossmemeber jamming everything back in there? I'm not going to autocross this but the JTR book makes a big deal out of engine placement.

 

Anyone?

 

Oh yeah, the car:

 

Tyler's 78 280Z V8

[Guest Anonymous]

etothen,

 

It sounds like he mounted it in the scarab position, which is mention in the JTR book. This was the first conversion, and the mounts are still available through MSA, and I beleive hooker sells them, or did?? Most people now use the JTR method, as it does have quite a few advantages, mostly in handling, actually, it seems to me they are all in handling. If you are not going to Auto-X the car, I wouldn't redo the conversion. Looking at the pictures it does look as it has been done beautifuly, and unless you really want handling performance on the street anyway, I would leave it, besides, more weight on the front wheels means it will burn out and drift much easier, 2 of my favorite things to do

 

Just my $.02

Kris

[DavyZ]

Absolutely gorgeous car! I don't even want to know what you paid for the car, but I can tell you that you own one sweet ride.

 

To answer your question you have to answer this question:

 

Do you like the way the car handles presently? If so, don't change it, you'll be cutting up a very nice finished job, not modifying an existing project car. Perhaps after some time has passed and you think you want a little more out of the car, like more hp and handling, wider ties, and so on, then do the mods, otherwise keep it the way it is--remember, it is finished very nicely right now.

 

That said, all things being equal, I would opt to modify a Scarab-type of engine mount (which this is) to the JTR version. However, with a car as nice and as finished as this one is, drive it around and see if you like it. If so, do not touch it. Also, if you can drive someone else's JTR Z to compare, definitely do so. You may (or may not) be surprised. Food for thought.

 

Davy

[Guest Anonymous]

I actually bought the car off eBay. When I called the builder he said had had over $13K into it and I believe him. I stayed up till 3am to bid at the last second and got it for $6,600. Had it shipped from OK to WA.

 

Anyway, before I bought it he showed me some pictures and I could tell it wasn't the JTR conversion cause the hoodlatch was unchanged and the engine was a few inches further forward. I asked him if it was a Scarab conversion and he said he'd never heard of that: He made the motor mounts himself. and actually, comparing a Scarab mod to a JTR mod, this mounting seems to be somewhere in the middle somewhere. I think the Scarab is even further forward than this... about seven inches further forward than the JTR mod.

 

OK so based on this input, I think I'm gonna just leave the motor where it's at right now. Thanks for the help.

[jeromio]

No, that is definately a Scarab style conversion. The difference is about 3 - 3.5 inches front to back and 1 to 2 inches high.

 

A few months ago we had a VERY long and very informative discussion of the Scarab vs. the JTR. One key take home (for me anyway) was that you shouldn't necessarily take Mike Knell (the JTR guy) and his book as the end all on the subject. He rally isn't fair to it. I think the only truly undisputed point is that you must do the JTR style in order to use a T5 or T56 manual trans. You should search for that thread and read thru it.

 

Just to echo what everyone else already said - Nice car. Chrome! Very polished looking.

[pparaska]

There are a bunch of threads here that talk about this issue, the largest thread on this topic (and any) is:

http://www.hybridz.org//ubb/ultimatebb.php?ubb=get_topic&f=1&t=001259

 

I'd agree that if you like the way it handles, leave it. If you think it's nose heavy, relocate the battery to the rear if that hasn't been done (didn't look at the pics yet), use AL heads, radiator, water pump, etc. (not sure what you have now).

 

After that, I can say that the difference in the Polar Moment of Inertia based on some quick calcs I did showed a 20% decrease for the JTR position over the Scarab. That's the PMOI of the engine alone, relative to the CG of the car. The PMOI is a measure of the resistance to change of the yaw attitude (turning) of a body. But this can be overridden by tire traction, etc., to some degree.

 

If your engine is between the two positions, I doubt it'd be worth the trouble of moving it, but who knows, you'd have to change it by only moving the engine and making no other changes to really know the answer.

 

Congrats on a nice ride!

[Mikelly]

I'd also talk to some who have changed their configurations from the Scarab to the JTR and see what their initial feeling was after the conversion. Dan Porter, owner of this site was one of the guys who swapped from Scarab to JTR. Bottom line is, ultimately it is your choice. From an engineering stand point it does make sense to lower the position of the weight in the car, and move it further back to the firewall. Of course, if you are happy with the car, change out a few things that Pete mentioned above and see how much it changes the cars feel.

 

Mike Kelly

[fl327]

another scarab, quite a vanglorious automobile replete with chrome and a wonderfully stock appearance. i run a muncie four speed behind the scarab positioned car, and have had to do some mods to the console to get it to stop banging my knuckles in third and reverse, but the mods i did to the shifter and the trans tunnel are much easier than shifting the motor three inches back in order to obtain the clearance. i believe that a t5 or t56 would actually fit a lot better than the muncie, the muncie is shorter than both of these trans, another couple inches or so gained from the five and six speed gearboxes would put the shifter closer to stock, and would be nice to have some overdrive. i dont notice any ill handling effects from the scarab, and am an avid scarab fan. my car has the carb legal sticker obtained because the car had been converted before the z car had obtained smog exemption, another reason i wont change it, its a scarab scarab! i'm very happy with my car with the way it handles and drives, granted i dont autocross it at all. i figure, the hard part has already been done, making any tranny fit is just a matter of creativity, and you can make it handle better with suspension and putting the car on a diet, the suspension you would do to either conversion, and by diet i mean you can reduce the weight of the car, or you can build it up with more power and torque to bring hp to lb up. scarab.

[Guest dankinzle]

I've been through both of the positions, and I can definitely say there's advantages to each--especially if yours is already in the scarab position. Although I feel that the JTR position that I have now is better than the scarab, there wasn't really anything wrong with the scarab position either. If your car runs well and you're happy with it, I say just leave it there. If you wanna scrouge the extra ounce of performance, go ahead and switch. That's what I did .

[Mikelly]

Well and here is another point FOR keeping the Scarab... If it is an original factory done conversion, you would be insane to do the JTR and depreciate its value... REGARDLESS of any percieved or proven performance benefit.

 

Did I just say that???

 

Mike Kelly

[fl327]

ah, i feel real good now.

[BLKMGK]

What trans does the car have in it now? I suspect an auto although a non-overdrive 4 speed is a possibility. If it's got an overdrive auto in it you're golden

 

The T5 and T56 come up through the shifter hole perfectly in th eJTR position. If the motor were moved forward with either of these transmissions I suspect that you would quickly find yourself banging the heater controls with your knuckles. An overdrive trans is pretty desireable for these cars since the rear gears tend to be a bit short as are the tires. What sort of RPMs are you seeing on the highway? Looks like it's got A/C too - sweet!

 

IMHO, drive it like it is, get used to the car. After awhile you'll KNOW what you do and don't like. In fact some things will drive you nuts - fix THOSE things first. If it revs too high, overdrive is in order. If it's an auto you can probably do this and leave the engine where it is (700R4 perhaps). If it's a stick then consider a T56 or T5 - considering the absolute STEAL you got the car for I'd go T56 and treat yourself ;D If it doesn't rev too high but handles worse than you'd like then move the battery and consider some other weight saving ideas. Move the engine as a last resort. Yeah, the JTR position is "better" IMO but getting there from where you're at is a PITA and the car is looking pretty finished right abut now. If it's not broken don't monkey with it too much!

 

Enjoy the car - you got a very good deal. The previous owner's $13K figure is probably not far from the mark. Don't muck with it strictly because another way might have been subjectively "better". If you like the way it drives then leave it alone.

 

Looks very nice BTW - setup a nice WEB page with smaller pics and details please

[fl327]

i think the five and six speeds would fit nice and pretty close to stock place, i have a four speed manual and it doesnt hit. but hey that car is really nice, dont mess around with unless you really cant stand it.

[Guest Anonymous]

The tranny in it is actually the one crappy thing about the car - and the first thing I'm changing. It's got what's called a 200 Metric, which is basically a crappy version of the th350. It gets mushy once it heats up in spite of my massive tran cooler with good air flow, shifts poorly and generaly sucks.

 

I've got a thread going in the drivetrain forum about the tranny. Next month I'm putting a TCI Streetfighter 700r4 in there. I figured that would be a good time to move the engine so I made this thread. However, I think I'll leave the engine positioned where it's at right now. It would make a slight performance difference but it'd be a huge PITA.

 

I'm working on a page with better pics and better documentation. Once I get it documented I'll post the URL to a new thread so everyone can get a taste.

 

I have lots of plans for this car, but I refuse to make a "future mods" page because 90% of the time those things never come to fruition. I'll post as I mod.

 

Thanks for all the good replies.

[pparaska]

FL327, I have heard that the use of an internal rail shifter type trans like the T5 or T56 (or Tremec 5spd) will in fact require the use of the setback engine location, aka JTR position. Otherwise, with the Scarab/John's Cars kit location, the shifter of the T5 and T56 will be quite forward and most likely require relocation of the fuse box, cutting out of the shifter hole in the tunnel and console, and of course, a bent back shift handle and possible the deletion of the radio in the stock location.

 

While those mods may be called "creativity", I'd think that if one wants to use one of these internal rail shifter trannies, and they're starting from scratch, they'd do well to consider the setback/JTR position.

 

Does your shifter on your Muncie bolt directly to the trans, or does it require a bracket to space it back and longer shifter rods?

[fl327]

no bracket or spacer for the shifter, all stock,stock rods, it comes out of the fusebox, which i have relocated previously in order to run a blade style fuses and rewired everything. before it wasnt a issue with the fuse box right near the shifter. i have modified the trans tunnel to clear the shift rods, i suspect that the shifter will come out at least one inch farther towards the back of the car with a five or six speed, making it easier to mount it, without taking the radio out of stock position, or the console either, im not running the center trans tunnel console, ive opted for the hemi cuda style where its all carpet and the shifter has a simple boot and plate, right now i have absolutely no problems with the setup, you just have to put some brain power to the situation, and make it happen, none of these parts are supposed to be in the car you know, i believe it will work ok, i would suggest jtr to people because its readily available and includes everything from mounts to the radiator. great kit. but i dont like mike knells blasting the scarab to make his kit sound better, not to say its not a great kit. i think the internal rail trans will require mods to work in a scarab setup, but what trans doesnt require mods to work in a z?