V8 front suspension

[speedbug78]

Thanks for the welcom jhayden!

Nothing quite like the sound of a U20 as it approaches 7K redline and an indicated 100 mph on the clock, but neither is the feel of accelerating UP hills as effortlessly as DOWN!

I agree high RPM engines sound super cool. I will say the acceleration is amazing in this car. I've never owned a street car that was this quick before, it seems to accelerate just as quickly in 4th as in 1st. One of my goals building the car was to keep it slower than 11.50. I hope I succeeded.

[Pjackb]

Thanks for all the help guys!

I did make it to the scales tonight. I weigh 1250 on the fronts and 1000 on the backs, 2250 total. That is with 3/4 tank of gas and no one in it. Not sure how that compares, but at least I have a number to work with.

At 2250 you’re about 250lbs over stock weight which is 1985lbs
I can’t find it right now but Alvin G. Did get his car on a similar scale and I believe he was at 2050 but I don’t remember if he was in the car but believe he was. (He has an SR20)

Spriso has done several SR20 cars that are at 1950lbs but more importantly they usually drop about 50lbs from the front increasing balance and he puts bigger brakes

If you start with the premise that the premier handling characteristic of the car is mild to heavy under steering you can understand why adding 100-150+ pounds to the front will screw handling and braking.

I don’t think there’s any bias against your swap and that’s not what’s being commented on but rather that you added weight to a front heavy car therefore you have limited solutions,

Best of luck

[speedbug78]

Thanks for the numbers to compare against. Do these cars typically have even front/back numbers?

[jhayden]

SR(L)311-(U)

Vehicle gross weight: 2249lb

Distribution of Vehicle weight w/o load: 1135lb F, 800lb R
With load: 1246lb F, 1003lb R

Chassis weight: 1113lb, (771 F and 342 R)

Height of Gravity Center: 18.503in

Source: U20 Engine and 5-speed trans for Datsun Sports 2000, Nissan Motor Co., Ltd, Tokyo

Jon

[Alvin]

At 2250 you’re about 250lbs over stock weight which is 1985lbs
I can’t find it right now but Alvin G. Did get his car on a similar scale and I believe he was at 2050 but I don’t remember if he was in the car but believe he was. (He has an SR20)

Spriso has done several SR20 cars that are at 1950lbs but more importantly they usually drop about 50lbs from the front increasing balance and he puts bigger brakes

Mine was 2120lbs with the U20, 2040lbs with the SR20, both without me in it.


Spriso's "Bob":

Dave Joliff's S13-powered '66 was 1950lbs



Most stock-powered street cars are in the 2100lb range:
from Ted, white '69 SPL car was 2120, red '66 SPL was 2160, blue '64 1500 was 2100:

[Alvin]

At 2250 you’re about 250lbs over stock weight which is 1985lbs
I can’t find it right now but Alvin G. Did get his car on a similar scale and I believe he was at 2050 but I don’t remember if he was in the car but believe he was. (He has an SR20)

Spriso has done several SR20 cars that are at 1950lbs but more importantly they usually drop about 50lbs from the front increasing balance and he puts bigger brakes

Mine was 2120lbs with the U20, 2040lbs with the SR20, both without me in it.


Spriso's "Bob":

Dave Joliff's S13-powered '66 was 1950lbs



Most stock-powered street cars are in the 2100lb range:
from Ted, white '69 SPL car was 2120, red '66 SPL was 2160, blue '64 1500 was 2100:

[JT68]

The 1600 (which the suspension was designed for, not the U) weighed 1984-2025lbs in full factory trim depending on the year- source Nissan FSM.

GROSS weight includes 243lbs of passengers and stuff, so lets avoid apples&oranges measurement technology. My guess is Nissan knew fairly precisely what the car weighed when they shipped them.

"The gross vehicle weight rating (GVWR), or gross vehicle mass (GVM) is the MAXIMUM operating weight/mass of a vehicle as specified by the manufacturer including the vehicle's chassis, body, engine, engine fluids, fuel, accessories, driver,passengers and cargo but excluding that of any trailers." So GVWR isn't what was weighed - plus the 302 car also looks to be a "work in progress" so likely isn't at it's final vehicle weight either.

The SRL added about 25-75 pounds over the 1600 depending on what you read. Cars that are over this mark clearly have accessories added to them.

Anyway you slice it, the iron block V8 is overweight in the front which is why most folks avoid that swap- that and the fact that the exhausts exits right at the frame rails and the steering which creates some creative "opportunities".

I've driven many swapped cars, the V8's handled the worst hands down-sure they were fast in a straight line. Just like an Chevy S10 with a V8.

1600,U20, SR20 and rotary were the best certainly in handling. Not really a big surprise. I have not yet driven a CA18-T- probably pretty decent.

Perhaps we can agree that fortunately at least its doesn't have an AT with a giant torque converter, iron heads and a 9" rear--it would easily be overweight by 350-400+lbs. More aluminum up front is certainly a good idea WRT to handling, kinda obvious really.

[theunz]

Since speedbug78 said in his first post that he doesn't road race and that the car is being built as a street/strip car, and the fact that he has installed a V-8, it's pretty certain that he is mainly interested in drag racing and doesn't particularly put much emphasis on cornering ability. Under those parameters a complete (read expensive, more than he quoted) front suspension and steering system rebuild should give him a reasonably safe and satisfactory ride. Not my cup of tea, but that's why ice cream comes in many flavors.

[FergO2k]

Yes, close friend of Eric who owned the 302 V8 powered roadster, that has now gone to Oz.
I have a complete spreadsheet, but it is on work computer. (Shhhh)
It had Ford 8.8 rear end.
From memory, 240 lbs heavier total, but surprisingly that was 100 lbs on front, 140 in rear.
The spreadsheet breaks down the differences between my U-20 stocker and Eric’s (roll bar, gas level, battery location, etc)
That car had no front end changes, other than several u-joints and pillow blocks in the steering shaft to get around the headers.
Pedal box was a challenge. I always thought Eric was a talented, “in touch” driver who chose to drive without shoes, but it turns out that he couldn’t drive with shoes cause of lack of room! (But he is very talented)
Gobs of torque made keeping up with him in the twistiesVERY challenging.
More info to follow.
Edit:
Oh, we got f/r weights by going to the trucking scale and putting the cars half way on, so no corner weighting numbers.
And consider this, in terms of weight increase, Eric weighs in at 175 and (at the time) I was more like 225. (All scale weights were done with car empty)
So it seems like lots of the V8 engine weight increase was offset by the “eat less cheeseburgers “ factor!

[JT68]

Since speedbug78 said in his first post that he doesn't road race and that the car is being built as a street/strip car, and the fact that he has installed a V-8, it's pretty certain that he is mainly interested in drag racing and doesn't particularly put much emphasis on cornering ability.

Agree! With that consideration, he might want to focus on the REAR suspension and add a locking rear, otherwise rear traction and wheel hop will be a limiting factor. Boiling the tires isn't really helpful.

Otherwise, considering the weight results, Mike was spot on.. several bags of concrete in the trunk will even things out.

To further illustrate I have no distain towards a 302, If I was going to do a V8 swap, I WOULD want one that handled well, so yes, way less weight up front, AL engine, integrated tubular chassis and probably an IRS type diff. Spmething like a little Cobra or Ariel Atom with a roadster body for vintage aesthetics.

Another way to think about the "weight problem" and effect of cheeseburgers is that with no passengers, this particular swap already exceeds the GVWR intended by the Nissan engineers by a healthy margin- and that's an unfinished car, with no Driver, passengers or cargo:-O To each their own.

[speedbug78]

Jhayden, thank you for the numbers, esp. the cog height. I would like to find out where that ends up on my car.

Over all it looks like I am 100-150 lbs over a "normal" SRL, and 250 over GVWR when I typically drive it.

I should be able to drop weight pretty easily if I choose to. That's why I ask the questions now, before the car is "done". I have to be careful not to drop too much or I'll end up too fast for the racing I'd like to do (nhra quick reference). Going faster than 11.50 adds much more renewable safety equipment than I'd like.

JT - I'd prefer not use to concrete on my car, it doesn't serve any useful purpose, but I do hear you. You've suggested it several times. If I want to add weight to the back I'll add the 9" rear out in the shop (un-sprung weight I know, but it shouldn't be too bad with aluminum parts and disk brakes).

Ideas to reduce weight off the top:
Remove all the sound deadening that the PO put in the car (thick tar stuff)
Chromoly cross member and rack/pinion steering. This is pretty easy to do as I still have to finish this area of my car.
The Wilwood front brake conversion. Again its an area of the car that I already need to address.
Racing seats. Kirkly aluminum seats are very very light.
Choromoly Roll Bar - Again, pretty easy to do and I need to work on it to meet the rules.
As mentioned above, aluminum block. I planned to replace this short block before I even started, so this is still a good option. Not sure I'll choose it, but it's still on the table.

And just to be clear, other than the concrete, I pretty much agree with JT. If I want to road race this car it would be wise to do a frame-off with a new tube chassis that better positions the drivetrain, reduces weight, and sets everything up properly. I don't have the capacity to go that deep on this project right now, and also feel that this car is close to "happy" for me.

Also to clarify the weight data we're talking about the difference of 25 gallons of fuel (~150lbs). JT - any idea what the tank level was on those cars who's weight you posted? I could be much heavier if they all had empty tanks. <-- Edit: Ooops I think I got this backward. I had 3/4 tank, so I could be some heavier if they all had full tanks.

Any other constructive ideas to improve what I've got?

[spl310]

Get the front end rebuilt and see how you like it.

[speedbug78]

spl310 - that's definitely step 1, and for me projects are 1 step at a time

Another thought would be re-building my exhaust in SS. I made it all out of 16ga+ mild steel. Not super excited about this as it's a lot of work, but an option, and it would turn out nicer the 2nd time.

[JT68]

Yep, if you add front brakes, stay light. Wilwood’s are nice. Z32 calipers (AL) are fine but the rotors are fairly heavy.

Remove ANY weight you can from the front- and move it to the trunk.

Higher spring rate up front. The stock springs are definitely over matched. Much better shocks. I have a set that is calibrated for DP 860 lb/in springs or use Koni on medium/hard rebound.

To clarify, that was Mike’s suggestion on adding weight to the rear for balance and traction- I just passed it on. It is valid though.

I really do think you will want weight in the back and positive/LS/locker or you’ll boil the tires. I’m sure you still can..

[speedbug78]

JT - agreed. I was hoping to start another separate topic on the rear suspension after getting the front sorted. Right now I'm mainly concerned with street manners and any racing will likely be 1-2 years away. I saw some references to trying coil overs, and I have used the QA-1 adjustables on other projects. There are many spring rates available for them. Would it make sense to convert in this case, or do you feel that the DP springs you reference will be adequate?