V8 car weight [Archive] - MX-5 Miata Forum (2024)

Dr. Jekyll

9th August 2002, 23:19

I weighed my car today and found total weight to be 2864 lbs with almost 59% on the front. Based on what I have read, this seems somewhat heavy. Has anyone else weighed their car and what were the results? Also, I've experienced occasional wheel hop. Does anyone have a solution for that problem? One last question has to do with protecting the lower portion of the radiator. Since it hangs so low, I'm concerned with road debris damaging the radiator. Has anyone attempted to fabricate some type of brace or shield to protect the radiator?

Cal

Steveamnmn

10th August 2002, 10:26

Are you sure that the scale was accurate? Most of these cars have come in from 2450 - 2600 lb. Also, have seen 53-55% on front. 59%...Wow!

The B-50 Sportsman block is supposed to be 10 lb. more than the standard roller block. Add 5 lb. if you have a stud girdle. Heaviest aftermarket manifold is maybe +10-15 lb. If you have iron heads they're ~40 lb. heavier than the aluminum on most of these cars. A/C adds ~45-50, power steering a few pounds, maybe 20? Heavy aftermarket wheels can add 40 lb., but only half of that's on the front axle.

I'm so curious to know where the extra weight is coming from, if the scale is accurate. My friend's 66 mustang with V8 and automatic is lighter than that. Don't see how that's possible...doesn't compute in my wee little brain!

Please tell us more about your combo.

Steve A.

MX-5.0

10th August 2002, 13:53

My car has aluminum heads, large Permacool radiator, Baer Claw brakes (rotor heavier than Wilwoods) substanitally more chassis reinforcement than a "real" Monster Miata (the only V8 Miata I've seen directly to compare it to). Larger and seemingly haeavier guage rails than Martins kit and a different style (may be lighter or heavier?) rear member with aluminum 8.8 rear and heavy axles. Exensive welding.

Weighs in at 2627.
Stock it was 2252.
Conversion gain of 375 lbs.

I dont know the split as I used a Truck Stop Scale! I'll be on pads soon.

Chris92

10th August 2002, 21:00

JohnB./CRUZ-MSL

10th August 2002, 21:42

..........even with the 60 poound blower...2565. It also has ford a/cond. leather...power windows..man/steering.

.........I haven't done much as far a chassis bracing. Mine is pretty close to the advertised 52/48% weight bias.

......."Wheel hop" was in the picture, until I increased the rear shock travel( raised the back end one half inch)...and softened the rear koni's to the softest setting.It is better now...and the New Perilli's seem to have gottn rid of the rest.

JohnB

JohnB./CRUZ-MSL

10th August 2002, 22:12

Cal..

I changed the radiator mounts. Insted of using what came in the kit...I added (welded) studs to the top of the radiator, that go through the header. Also welded different brackets to the sides of the radiator, and the frame. ( angle iron ) they too are studed...so the entire radiator slides down and out, when all four nuts are removed. It gave me some additional clearance, as the kit brackets were below the radiator...three quarters of an inch.

In addition...I added the factory "R" pkg. front air dam. it covers the lower porion...and gives no real protection, other than the sound of it hitting something first...UGHHHHH !

JohnB

MV8,Mstr ASE/A&P/FCC

11th August 2002, 08:32

Rich Wilkman

11th August 2002, 13:15

A gallon of fuel is roughly 8 pounds. The mnemonic for water is "A pint's a pound the world around" and for estimation, gas can use the same rule. There are 2 pints in a quart and 4 quarts in a gallon so there are 8 pints in a gallon or roughly 8 pounds/gallon.

There is a lot of fluid weight in a car; esp. if you've got the bigger radiator and overflow, larger clutch/brake fluid tanks, more oil in a dry-sump, that silly tank of windshield washer fluid and the full bladder of the driver. Let's not forget the driver, too; the best performance mod many of us could do for our cars would be to lose 30 pounds ourselves! :)

Usually cars are weighed with 1/2 or 1/4 of a tank with the driver sitting in it if you are looking for total weight. For front/rear bias you don't need the driver in the car (doesn't hurt, doesn't help). To know if it's "too much", though, you'd really need to have weighed the car you started with.

-Rich

Dan&Zoomy

11th August 2002, 13:32

Rich Wilkman

11th August 2002, 15:01

You're right. Checking the "Pocket Ref", Gasoline has a SG (specific gravity) of .74 so it actually comes out to a hair under pounds per gallon (figured relative to pure water with an SG of 1.00).

-Rich

JohnB./CRUZ-MSL

11th August 2002, 15:40

....ok, here in sunny Pennsylvania, at the Local lumber yard....it weighs...2574 pounds. It shows three quarters of a tank of Sunocco 94 octane. Has the slightly heavy Compomotive rims...and slightly lighter Perilli P-7000's.

The set up is a 306/alum head's, Kb blower, man steering, ford AC, Ford T-5 tranny,ford rear center, wilwood fronts, Miata 10.75 rears...pretty much what monster motorsports advertised in there weight specs....so if you are at 2800 pounds...check the scale...something sounds wrong with that "picture".

Chris92

11th August 2002, 17:23

But did u fill your frame rails, struts, and tires with helium yet?

just dont do the spare tire or you will have oversteer in rain/snow conditions...

:rolleyes:

Dr. Jekyll

11th August 2002, 21:02

I suspect that the scales were off. When I weighed the car(1990), it was with 3/4 full tank and no driver. I'm using a stock 90 5.0 engine with Ford air and manual steering. Everything is from Martin's kit so I can't imagine how the car could be so much heaver than others.

I weighed it at a local speed shop that specializes in building drag cars. He used individual mechanical scales on each wheel with frames that placed the scales approx. 2 feet out from the tires. The shop owner said the readings had to be multiplied by 4 to get the correct weight. He read the scale weights so I didn't see the actual scale readings. The whole system seemed suspicious, but he claimed that his scale weights were never off by more than 5% from scales used at drag meets.

I'll weigh the car somewhere else. I was also a little concerned when he told me that he had never heard of a Miata!

Steveamnmn

11th August 2002, 21:54

A 5% error on 2500 lb. is 125 lb. That's not very precision as a target, and sounds like the procedure left lots of room for error.

I'm bettin' you'll be pleased when you re-weigh it on an accurate scale.

Shall we have a "guess the weight" sweepstakes?

My prediction is 2575 lb.

Steve A.

Rich Wilkman

12th August 2002, 00:46

Cal:

That sounds like an "okay" race weigh-in to me; I'd trust it more than a truck scale calibrated to weigh vehicles with six or seven tonnes loaded, myself. Being 2' out from the car on a frame isn't going to throw things off if the unit is calibrated for that (and you can do the math to reverse it if you really had to. He probably built the frame to let him handle many different types of cars and still be able to read it without crawling around on his knees. It ain't a NASCAR weigh in! The whole "multiply by 4" bit doesn't make sense unless he was just weighing one corner of the car. If he's doing that and picks the "heavy" side up front it could be close. If he had scales at each corner (the best way to weigh in), then it's just a case of adding.

Race scales are easy to calibrate; just like any other smaller scale. Probably use a 50kg solid slug for each corner scale as each corner is probably rated for 800 pounds or so.

Me, I'm gonna vote that the car is heavier than you think, lighter than the weight you just got and that you can find a scale that gives you the numbers you want. Kind of the way we weigh ourselves when we're on a diet. :)

A really good performance alignment shop should also be able to give you an accurate 4 corner weigh-in. Probably cost $50 and an hour or so of your time. 4 corner is what you use when you have to properly balance (weight wise) a car for a track and need to know where to strap the lead weights.

One place to pick up 40# easy, though, is in tires (don't get me started on wheels). I know that there was a wide range of weights on the rubber keeping all other dimensions equal.

-Rich

[ 12. August 2002, 12:30: Message edited by: Rich Wilkman ]

Tim Thompson

12th August 2002, 09:17

MX-5.0

12th August 2002, 21:05

Originally posted by Rich Wilkman:
Cal:

I'd trust it more than a truck scale calibrated to weigh vehicles with six or seven tonnes loaded, myself.
-RichThat wasnt aimed at me, was it?!? The stock measurements were taken at the track so I trust them. The indiviual 5.0 parts weighed in about 350-400 lbs over stock so the figures seem fairly accurate. BUT I do agree that it wasnt the best way to do it which is why I am getting to the pads soon!

Rich Wilkman

13th August 2002, 00:01

Not aimed at anyone, really. The original was in reply to Cal thinking the way the shop did the weighing was wrong.

Truck scales are quite accurate and most are certified by whoever manages weights and measures for your state. They are really good at weighing tractors and trailers, et. al. and can often be less predictible outside the weight range of the tractor. Heck, some of them won't even register something less than a ton or more! Those scales have to be good enough to detect if the load that was last weighed in is still there or if more or less than the right amount was offloaded at the last stop.

The same types of scales, regulated the same way, can often be found at the local dump and they do much better on passenger cars and trucks. It's often easier to pull into the truck scales on a light day and convince the local Highway Patrol to let you weigh your car than it is is to drive your Miata to the dump and risk, well, dump things happening to it.

-Rich

Originally posted by MX-5.0:
Originally posted by Rich Wilkman:
Cal:

I'd trust it more than a truck scale calibrated to weigh vehicles with six or seven tonnes loaded, myself.
-RichThat wasnt aimed at me, was it?!? The stock measurements were taken at the track so I trust them. The indiviual 5.0 parts weighed in about 350-400 lbs over stock so the figures seem fairly accurate. BUT I do agree that it wasnt the best way to do it which is why I am getting to the pads soon!

Miata4321

13th August 2002, 11:43

Chris92

13th August 2002, 13:39

what do you have for heads and accessories?

BTW i will weigh mine soon at the town dump... i'll post that here

Originally posted by Miata4321:
Weighted mine at the local grain elevator with full tank and me 200 pounds 2750 total, front 1480 and rear 1260 = 2740......back out me and the gas, drops it to about 2480-2490 range

Miata4321

15th August 2002, 07:33

Dr. Jekyll

16th August 2002, 14:37

Ok. Finally got a chance to re-weigh my car at a local business truck scale. Total weight was 2540 lbs with 1380 on the front end and 1160 on the rear. I don't know how accurate the axle weights are since I just weighed the front and rear wheels separately by rolling half the car off the scale.

Cal

JohnB./CRUZ-MSL

16th August 2002, 20:17

Steveamnmn

17th August 2002, 09:43

Originally posted by Cal Clayton:
Ok. Total weight was 2540 lbs with 1380 on the front end and 1160 on the rear. I don't know how accurate the axle weights are since I just weighed the front and rear wheels separately by rolling half the car off the scale.

CalIf you weighed the whole car first, and then the axles separately, I'd say the readings are dead-on because the two axle weights add up to exactly the total weight.

the-dragonfly

18th August 2002, 11:07

Hey guys, I am a bit scared, all of this power and no one is weighing in at the dragstrip. I weigh my car everyweek, with its tiny 4cylinder (2130 lbs this week).

grain silos, town dump, lumberyard, truck stop I was impressed with the effort, but wonder how many of the V-8's out there get drag strip duty.

Rich Wilkman

18th August 2002, 14:48

I guess it's just the science background, but the fact that the two came out to match makes me question the numbers. Imagine the odds of getting the exact correct balance point to the edge of the scale for the front, and then for the rear on a car where you had no idea where the center point (weight wise) was. Now imagine the odds of doing it the first time! It's always fun to give students a pile of things to weigh and to see the variations they get; it's why you measure a few times instead of just once. Still, I'd bet he's within 25# or so of the car weight (depending on the granularity and accuracy of the scale), and that's good enough for this type of work.

The weight did come out closer to what y'all expected, though. I'm assuming that the driver wasn't in the car the first time as the delta is far more than you could explain with fluids, etc. The delta would fit a "weigh the heavy corner and multiply by 4" model.

-Rich

Originally posted by Steveamnmn:
Originally posted by Cal Clayton:
Ok. Total weight was 2540 lbs with 1380 on the front end and 1160 on the rear. I don't know how accurate the axle weights are since I just weighed the front and rear wheels separately by rolling half the car off the scale.

CalIf you weighed the whole car first, and then the axles separately, I'd say the readings are dead-on because the two axle weights add up to exactly the total weight.

Dr. Jekyll

18th August 2002, 22:56

Rich has a good point. The actual rear weight was 20 lbs more, but I adjusted it downward since the two weights exceeded the total. I'm no mathematician, so it will have to do until I weigh each wheel.

Cal

jjville

20th August 2002, 00:55

Nobody touched the wheel-hop so I'll take a stab. Even with a live-axle car you will get wheel hop from an improperly setup suspension for drag racing. Having adjustable shocks will enable you to 'tune' out some of it, but the independent suspension is more ideal for handling than quarter-mile runs. Putting the V8 into the Miata is an awesome combination for track duty (course) though.

Of course you might want to also try some stickier tires as I assume you are using some type of all-weather radial.

As far as the radiator, I ran over a BIG, HUGE, MONTROUS, ORANGE, CONE (well maybe it wasn't that big :p ) and toasted my radiator & a/c condensor so even stock the underside is pretty weak.

[ 20. August 2002, 00:58: Message edited by: jjville ]