BlackRocket

Anyone out there know the weight balance on the early C3s; (68-71 Big Block cars). Are they close to 50:50 or more like 60:40???

Thanks!

tfi racing

The last time I weighed my 74 small block on my race scales,it was close to 50/50,about 49% rear weight from what I recall,I should have kept the sheet.The big block won't make a huge difference in the distribution,remember almost all that engine weight is behind the front axle centerline.

bvanpelt

As I recall, the BB adds about 400 lbs. This weight increase is almost entirely on the front wheels. I think it goes from 50:50 to about 60:40.

Everyone says the SB's handle better...

yel76low

Well... no. There isn't going to be that much of a difference.

So lets say the SB car is 3300 lbs, and has 50/50 distribution (I'm not claiming this is true, just using it as an example). That's 1650 front and 1650 rear. If a BB weighs 400lbs more (which I don't think is true, 400 lbs is a lot) and we put all of that weight on the front wheels (which again is not true, because the engine is primarily behind the front wheels - as a result some of that weight will go to the rear wheels) we are at 2050 and 1650 front and rear.

That's 55/45, and this is worst case. So there isn't too much of a difference between BB and SB in weight distribution.

DRIVESHAFT

I dont know about total car weight, but a big block only weighs about 100 lbs more than a small block.

zwede

Early C3's with big-blocks are 50.5/49.5 to 52/48 depending on options. The 50.5/49.5 is for aluminum heads/no AC.

Big-block adds ~100lbs, not 400.

BTW, base small-blocks are actually reversed, 49/51, i.e. heavier in the back than front.

tfi racing

Slow day in the shop,lets whip out the scales!
74 L48 vert,1/2 tank fuel,sidepipes,weld wheels,no spare/carrier,no AC



No driver / 210lb dumb *** driver
LF 891 RF 837 / LF 953 RF 841
LR 810 RR 825 / LR 900 RR 881
Left% 50.6 / Left% 51.9
Rear% 48.6 / Rear% 49.8
Total 3362 / Total 3574

Add 50lbs to engine
915 863 / 977 866
812 823 / 901 881
50.6 / 51.8
48 / 49.2
3574 / 3624

Add 100lbs to engine
936 880 / 995 885
813 832 / 904 888
50.6 / 51.7
47.6 / 48.8
3463 / 3673

Add 150lbs to engine
954 900 / 1013 906
821 837 / 910 893
50.6 / 51.7
47.2 / 48.5
3514 / 3723

I'm reluctant to add another 50 lbs on top of the valve covers and air cleaner,you should be able to see the trend.I think a BBC weighs 80# more than a SBC,dont forget to factor in AC and a bigger rad.I'll leave the car on the scales for a few hours,if you want to see something else.

roscobbc

I have just put-in new 489 with Ally heads, Ally water pump (and at this rate probably an Ally rad) in to my manual low spec. non a/c '68 coupe - so this should now be similar in weight and distribution to similarly equipped small block?

69427

tfi,

Sweet setup with the scales. As much as I hate to spend money, I may have to spring for a set like that in the future.

BlackRocket

AWESOME TFI!!!!

I know that a big block doesn't weigh that much more than a small block...maybe 150 lbs at most. Looks like they are pretty even considering that they are front engine cars built almost 40 years ago!!!


TFI, what class of car do you race? Looks nice also!

Guru_4_hire

I think I was reading a car and driver review of the 1973 vette and it came out to be 53/47.

tfi racing

The keys to the almost 50/50 balance are that the driver almost sits on the rear axle and the engine is behind the front axle centerline.A Chevelle for example is probably lucky to make 40% rear weight,next time you look at a bare frame this will all be more apparent.

This race car is a super late model,I run it in the ARCA West series in Western Canada and the Pacific Northwest with more grief than success...It is your basic fiberglass skin, tube frame straight rail,2900lb,540 horse stock car on 10" Hoosier slicks.It gets around a 3/8 mile oval in about 18 seconds,these things are rockets and are a rush to drive when it all goes your way!
Here's how it scales out,full of fuel w/driver as a comparison:
LF 770 RF 706
LR 939 LR 560
LS 1709 57.5%(max allowed 58%)
Rear 1499 50.4%
Crossweight (wedge)1644 55.3%
Total 2976(must weigh over 2900 at end of race)
It pushed like a dump truck at these numbers!

zwede

Keep in mind that the 73-up has the cast iron crash barrier/vacuum tank up front that the earlier cars didn't have.

sxr6

You would also see quite a diff if fuel tank was full compared to empty!

I'm not sure how much a BB weighs over a SB but it'll about bust a gut trying to carefully sit a BB head on the motor in the car

Steve439

Here are the extra weights from GM:

l36 427/390 ________+215
l68 427/400 ________+151
l71 427/435 ________+149

I saved it from a thread by magicv8, I think.

bvanpelt

I will graciously admit that I was wrong. Don't tell my wife!

yel76low

TFI... that's fantastic!

So the 74 that you have pictured is reasonably stock? (Expect for what you have listed?)

Any guess how much weight you saved removing the spare/carrier?

tfi racing

Its about as stock as they get,and about as slow as they get.I would guess the spare tire and carrier weigh 40 to 50 lbs,I just never put it on,I think it looks better without it since there are no mufflers back there to fill the sides.

69427

The weight difference between the L36 (iron heads) and the L71 (Aluminum heads, I assume) looks correct. The L68 number, IIRC, should be close, or heavier due to more carburetion weight, than the L36. Did the L68 have any major differences compared to the L36 that I'm unaware of?

wfo76

The L36 number cannot be right since all 3 of these engines used an aluminum intake.






L71 also used iron heads. The L68 is an L36 with 3 carbs instead of a q-jet so weight difference should be negligible.



Yep, your engine probably weighs within a few pounds of what an all-iron original small block would weigh.