Installing a V8 will automatically unbalance the car and tilt the world on its axis

While talking to a friend at an event this weekend I mentioned we’re toying with the idea of installing a 5.0 Ford into the Datsun. My reason being I have my Formula 500 (it’s an 87 Novakar) which is vintage legal but can’t be used at track days (open wheeler) whereas the Datsun would make a fine track day hooligan car. Also I’ve now race the 1200 for 30 years and it may be time for something different.

My buddies reply was a V8 total unbalance the car!!! Note he’s running a BMW E30 which has a motor that weighs more than a SBF. Naturally a modern twin cam turbo motor was suggested.

Here is the rub the fully dressed motor and tranny in my car weighs 239lbs (motor 185 + trans 54lbs) so regardless of what I install it’s going to quote unquote unbalance the car.

So some food for thought; a 5.0 ford with aluminum heads & manifold and T5 tranny are 500lbs, the usual go to for Nissan swaps is an SR20DET, motor &trans weigh 493lbs.  For comparison a Miata motor and trans weigh around 435-450lbs (so I’m told).

So any motor swap is going to add 200-250lbs to the car, the car itself is 1625lbs so even with the V8 lump we’re still talking a 1900lb car. Any conversion in my car will involve firewall and tunnel surgery so the motor could be pushed back a few inches.

I guess what I found amusing / intriguing is the fact that people don’t seem to be aware how heavy modern twin cam 4 cylinder engines are.

Tom

PS: Before anyone suggests a Hayabusa motor; it would be a whole lot of fabrication work for at best a  35-40 horsepower gain.

The same conversations happen with 944 folks when V8 swaps are bandied about.  Even though the 944 engine is mostly aluminum, its still weighs 365lbs, the turbo is even worse with the added plumbing, etc.  So the weight gain is negligible over a SBF or an LSx after you move the battery to the rear (where it should be anyway), etc.

The Miata, RX-7 and other similarly common V8 swap sportscar targets also have the same conversations.

People seem to think that less is less and more is more without getting some legit information on whether that is actually true.

I'll paraphrase Carroll Smith, because he lives on my desk at the office and I appreciate his writing style:

Saying that will unbalance the car is a gross oversimplification of an inherently complex system.

That being said, stating that a V8 will unbalance the car might be fair if you assume all other factors are held constant (I don't know how the car's set up).

Because they failed physics 101, most people are not aware that the extra weight does not all fall on the front axle. As such the thought is that the front axle is going to carry a few hundred extra lbs and become an under-steering monster.

The reality is that the extra weight will be distributed between the front and rear tires in a distribution pretty close to the factory F/R weight distribution, give or take a bit for fore-aft engine location.

As to "unbalancing" the car, there is some merit in that statement in that  the suspension did receive a lot of attention  at the factory  from some smart people with fancy tools that factored in weight at each corner. Spring and shock ratios should change to accommodate extra weight and any weight transfer. Few of us are really up to the task of doing that calculus/development. Oversprung and over-damped is the default amateur  recourse.  Of course once you start messing with springs and dampers, you also mess with weight transfer and braking, so that might factor into the "Unbalanced" column.

In the end it don't matter: If you get what you want at the cost of what you don't need, you win.

Pete

In reply to Tom1200 : Sorry to throw cold water but you’ll need to add a little more weight. 

Exhaust, is going to be twice the weight, plus the cooling system will be heavier, it will take more coolant to cool more power. Fuel will get heavier because it will take more fuel to make more power. 

There are things you can do to maybe minimize the effects of that.  Cast Iron hubs can be made from aluminum. Perhaps iron or steel suspension links can be replaced with tubular components. Solid sway bars replaced with tubular.   A full sized starter can be replaced with a gear reduction starter. 

 Steel fenders, hood, trunk lid,  doors, can be the pattern for carbon fiber replacements.  Interior bracing can be attacked with a hole saw and dimpling dies. The metal removed will help and the dimple die will put much of the strength back in.  

Obviously glass will be replaced by polycarbonate.  A heavy battery can be replaced by a much lighter battery and a plug in Jack for initial starting 

To quote WEEN,

"just do what you want to, and it'll be OK"

I stuffed an all aluminum dohc v8 where an iron 4 slapper was. Added a minor 35lbs to the nose. Relocated the battery. Felt better than before. 

Moving the battery to the trunk will help that weight distribution.  You'll also be upgrading the entire driveline so heavier driveshaft and rear diff will help move some weight back.  Frenchy is right about the radiator, the one in my Ford powered monster Miata was HUGE and thus held a lot of coolant.  

But all that aside, with a good running V8 up front, your car won't instantly turn into an understeering pig.  It might lose a skosh of nimbleness but it will eat up corners just as well as before and shorten the straights far better.

frenchyd said:

In reply to Tom1200 : Sorry to throw cold water but you’ll need to add a little more weight. 

Exhaust, is going to be twice the weight, plus the cooling system will be heavier, it will take more coolant to cool more power. Fuel will get heavier because it will take more fuel to make more power. 

 

 

the exhaust will run the length of the car and probably do not much more then just add weight vs. disrupt the f/r balance. Fuel is also usually near the rear axle so if anything adding a larger tank would help offset the balance of adding a v8 out front. The cooling system is really the only other addition that will put the majority of it's weight in front of the front axle and really a larger aluminum radiator plus a extra gallon or 2 of coolant over the factory stuff will only add a handful of pounds.

all things to be considered but nothing really notable that is going to create a nose heavy, uncontrolable car

In reply to edizzle89 :

The exhaust system by itself is not a lot but 8 cylinders  is twice as much as 4 plus likely a bigger diameter set of pipes.  

And it’s not a couple of gallons of coolant at about 7 pounds a gallon it’s also the bigger radiator.  10-15 gallons of fuel instead of 4-5? Again not a whole lot of weight. Plus I gave you all those ways to shed weight.  

But more power equals more speed then the added. Weight along with the greater velocity into the corner? Will the brakes be up to it?  If not Wilwood sells nice light aluminum ones that should do the trick.   Is the rear end up to dealing with the added power? What options are there in case?  

Then comes the unknowns.  Greater speed, more weight, harder braking, are the stock spindles  capable of dealing with  everything? I honestly don’t know and I’m not trying to talk you out of anything.  

Just a question thrown out for consideration.  

frenchyd said:

In reply to Tom1200 : Sorry to throw cold water but you’ll need to add a little more weight. 

Exhaust, is going to be twice the weight, plus the cooling system will be heavier, it will take more coolant to cool more power. Fuel will get heavier because it will take more fuel to make more power. 

There are things you can do to maybe minimize the effects of that.  Cast Iron hubs can be made from aluminum. Perhaps iron or steel suspension links can be replaced with tubular components. Solid sway bars replaced with tubular.   A full sized starter can be replaced with a gear reduction starter. 

 Steel fenders, hood, trunk lid,  doors, can be the pattern for carbon fiber replacements.  Interior bracing can be attacked with a hole saw and dimpling dies. The metal removed will help and the dimple die will put much of the strength back in.  

Obviously glass will be replaced by polycarbonate.  A heavy battery can be replaced by a much lighter battery and a plug in Jack for initial starting 

 

I would not overstate hte cooling system. If the 1200's stock radiator is brass, a lightweight aluminum one is going to weight substatially less. The stock fiat 124 Radiator weights a ton compared to a similar sized modern radiator

This was a sort of generalization thread but just for the record;

The larger radiator and extra coolant will add 28lbs, I still have the battery mounted in the standard position (right front) and yes moving the 24lb battery would offset this. The car has a small aluminum radiator and any motor swap would necessitate a larger radiator.

The larger fuel cell and added fuel will will add 21lbs; any motor swap I do will require a larger cell so regardless of an SR20 or SBF this will need to be done.

The rear end in the car now is capable of handling 285ft lb (the plan was to run a near stock V8). I don't wish to cut the rear fenders so it will still be on 13" wheels and that will further insure the rear end. (Before you howl V8 Capris ran 13' wheels)

The car uses 280ZX coilover struts which, complete with brakes, weigh 47lbs each. There stupid heavy for a small Datsun 4 cylinder car but up to the task (the 280ZX motor is slightly heavier than the V8.

At 1622lbs my car is a bit of pig for a Datsun 1200 because the bodywork is all steel and I've got things like an overbuilt  cage, 280ZX front suspension and a station wagon axle in it.  

I have 58lbs of weight reduction that can be carried out (fiberglass hood, Lexan rear window, LifPo battery etc) that would offset some of the weight. 

frenchyd said:

Fuel will get heavier because it will take more fuel to make more power. 

What?

Gas is going to stay 6 pounds per gallon or so no matter what engine it's going into, and installing a bigger engine doesn't make the fuel tank bigger.

Okay, honest edit because clearly I missed the part about the fuel cell. But that was a pretty odd way to phrase it.

About the radiator - take the engine into consideration. I know that an old Miata BP does not cool anywhere near as well as an LS does, so the radiator does not need to be any larger. No gain in weight on the cooling system there when you're comparing a turbo Miata to an LS Miata.  In fact, you don't need to do as much to keep the LS cool. I can't speak about the old SBF, though. It's of a different generation. If you're comparing a turbo four, you also have the (significant) mass of the turbo and the intercooler to add. A 1999 Miata with an LS3 weighs pretty much the same as the 2005 factory turbo Miata.

The braking will not be any harder with the V8, assuming it will be at the limits of the tires in all cases. However, it will go on for longer.

Whatever you do don’t tell your buddy my iron block aluminum head v8 240z is 50/50 f/r weighted with me in it.  I wouldn’t want you to ruin his day.  

If you're going faster, you don't need as much radiator since you have more airflow through it...

That was kind of a weird thing to discover when I added a bunch of power to the RX-7... it started running cooler, because there was more airflow, and the straights got a lot shorter.

My classic Mini cools better at full throttle too. But that's okay, because it gets to spend a lot of time there.

Patrick said:

Whatever you do don’t tell your buddy my iron block aluminum head v8 240z is 50/50 f/r weighted with me in it.  I wouldn’t want you to ruin his day.  

I've wrangled L24 parts.  That GenIII in your car probably weighs less.

IIRC the bare engine was over 500lb.  Add manifolds and accessories and it's way more than a quarter of the weight of the whole car!

There is an aluminum radiator in the car now; due to its small size it only weighs 11lbs. The 3 core brass one it replaced weighed 15lbs. There is no way it will handle a V8, it's something like 18" wide by 22" tall.  Now if I buy a second one the two combined might do it.

The front brakes aren't an issue as a 280ZX weighs something like 3200lbs, the rear brakes are 240Z alloy drums so there is no issue there either.

The drive shaft will be negligible as the 1200 has a 90" wheelbase; it's likely to be all of 4' long if that.

A heavier engine will make the car handle worse.   How much?  I dunno.

If you want a v8, then put in a v8, no need to 'justify' it to anyone here.

I'm not really looking to justify it, I was genuinely surprised by the automatic assumption that this will turn the car into an ill handling truck.

As for my replies I'm simply sharing what I've learned from my preliminary research. I'm a purchasing analyst so looking at various options is SOP from me. I've got spreadsheets for everything (I need to get out more)

Define handling worse; lower cornering speed? transient handling? Both? As a blanket statement the heavier engine making it handle worse is something I wouldn't necessarily agree with. A 240Z is thought of as an excellent handling car for its era. The Z has a motor that weighs as much as a small block but would we argue that a 1200 is a much better handling car.  I'm not trying to be a pedant but having a car that can turn in at a greater speed (1200 by virtue of its lightweight) doesn't necessarily make it a better handling car. 

Spreadsheets for everything,  I just go ahead and weld everything instead.  ;)

I can't add much, other than I often think about the opposite: taking a heavy car with a heavy engine/transmission--say a Lincoln Mark V with a 460--and replacing its powerplant with something significantly lighter, say a 3.5 Ecoboost.

In reply to Tom1200 :

Frankly I’d love to see you do it and have a lot of fun with it.  Please don’t listen to the neigh sayers. There will be plenty!  But I’m sure  Shelby heard a lot of the same comments when he stuffed a SBF into that little AC.  

It sounds like you’ve considered most of my points, and frankly I don’t think you’re far off.  I do hope you realize that now you’ll be put with the big engine class rather than the little engine class.   Those big boys will greatly outweigh you, have one tire bigger than all 4 of yours, and you’ll very much be a David against a whole bunch of giants.  

Besides the weight of the SBF  might come down from your 500# number a bit.  I know the old small block Chevy  had  some aftermarket aluminum block variants, and the sprint car boys all used an 18 pound crankshaft rather than the heavier stock one.

There are titanium connecting rods available  tapered wrist pins  and other tricks to make the engine lighter.   

How much of that is available for the SBF ?  I don’t know. 

Then there is the transmission

production 5 speed transmissions  all have 5th gear as an overdrive.  You don’t need that on a race track. Not with a relatively mild engine.  

In  a light car  like yours 4 speeds will be just fine. And save you weight.  Not to mention some cost.  

Now,  as to total weight.   Steel fenders and hood can easily be made out of carbon fiber at only a slight premium in cost over fiberglass.  In order to tell the whole truth I have to ask if you tend to do your own work or have things done for you?  

 I’ll assume for purposes of this discussion  you do your own work.   There are three steps to making a fiberglass or carbon fiber part.  

1 is the pattern. You use a steel part for that and coat it with slippery stuff so the pattern  comes out of the mold you make  around it.  

2 the mold, it’s just the shape of  future part in reverse.  Made as cheaply  and quickly as possible. 

3 the finish part.  It can be a hand layup of Matt, fiberglass cloth, or carbon fiber cloth. 

Matt is cheaper, think of it as a thick wool blanket. But it uses more resin in order to get it all wet.  

Fiberglass cloth is stronger and lighter

carbon fiber is just like fiberglass cloth only black but even stronger and lighter still.  

Let’s say Matt will cost $6 for the material to make a part 

cloth will cost $9 

carbon fiber will cost  $14 

the resin needed is the same, well slightly less for the carbon fiber. 

The labor is 5 min for a chopper gun. 

20 minutes  to do a cloth hand lay up. 

20 minutes to do a carbon fiber hand lay up 

Will said:

frenchyd said:

Fuel will get heavier because it will take more fuel to make more power. 

What?

Gas is going to stay 6 pounds per gallon or so no matter what engine it's going into, and installing a bigger engine doesn't make the fuel tank bigger.

Okay, honest edit because clearly I missed the part about the fuel cell. But that was a pretty odd way to phrase it.

You are correct. To make my statement proper I should have said the “total” weight of fuel will get heavier.  I original wrote going from 4-5 gallons a race to 10-15 gallons per race.   But erased it  for the sake of brevity. I hadn't really commented on the weight of a bigger fuel cell.