b to c head swap = weight GAIN?????? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 8 Old 05-21-2011, 11:41 AM Thread Starter
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b to c head swap = weight GAIN??????

weird situation, need some ideas,
did a b-to-c head swap, and car now seems heavier

road race car with full maximum motorsports suspension,
with the stock b heads, and (ironically) a mark VIII block,
car handling was pretty close to neutral

total weight with me (240#) IN , was 3216, with 1/4 tank of gas
left front= 866..........right front= 897--------------front=1,763......front %=54.8%
left rear= 742...........right rear= 711----------------rear=1,453.......rear %=45.2%
left corner= 1,577.....right corner=1,639



the swap consisted of an aviator long block with c-heads
aviators have aluminum 4.6 blocks, so that shouldn't change anything,
b heads vs c heads would SEEMINGLY weigh about the same,
total weight with
OUT me was 3,026, with 1/3 tank of gas

additionally we have now dropped the strut tower brace (12.2 #)
we added ~2 quarts of oil capacity with the pan (?2#)
new canton RR oil pan (?#)
(consider these last things three things a wash)

left front= right front= front %=
left front= 849..........right front= 850--------------front=1,699......front %=56.15%
left rear= 663...........right rear= 663----------------rear=1,326.......rear %=43.85%
left corner= 1,512.....right corner=1,513

car has a yucky new push/understeer, which it has never had before, since installing the suspension,


no suspension items were changed other than :
a) removal of the strut tower brace (shouldn't cause an understeer), (and DOES lighten the front just a hair)
b) removal of k member brace to accommodate Canton pan (don't know that this would cause an understeer, or not).

there seems to be a definite weight gain,
and front weight will cause weight gain.

both weighings were done on longacre scales
different sets,
both were zeroed prior to use.

the difference between 1/3 and 1/4 tank of gas probably wouldn't be more than 10#, and being in the rear, certainly wouldn't cause an understeer.

thoughts???
WTF???????


Last edited by docstang; 05-21-2011 at 11:44 AM.
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post #2 of 8 Old 05-21-2011, 12:39 PM
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The weight gain could be if the Aviator had an "NVH block" and a forged crank.. that would add a good 25-30 lbs versus a Teksid/Mark VIII cast crank.

Could you have an alignment change or even more worn tires or something to cause your understeer? Could you simply be going faster? Sounds dumb but I had that problem earlier this year.. thought I had a handling issue, found out I was running about 10 MPH faster on most autocross courses due to seat time and improved transitioning.. lol.

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post #3 of 8 Old 05-21-2011, 12:58 PM Thread Starter
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Quote:
Originally Posted by SVTCobra347 View Post
The weight gain could be if the Aviator had an "NVH block" and a forged crank.. that would add a good 25-30 lbs versus a Teksid/Mark VIII cast crank.
so I am guessing an NVH block has extra material on it to give a quieter ride, etc?
Would make sense, and help partially explain a net 50# gain

I had heard from one source a cast crank would be LIGHTER
Another said it would be heavier
Tie breaker????
Any source on verifiable numbers???

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Originally Posted by SVTCobra347 View Post
Could you have an alignment change or even more worn tires or something to cause your understeer? Could you simply be going faster? Sounds dumb but I had that problem earlier this year.. thought I had a handling issue, found out I was running about 10 MPH faster on most autocross courses due to seat time and improved transitioning.. lol.
Definitely faster
Enjoying the power
No suspension changes
New tires
Refunding breaking points due to the speed
But this is s push ON TOP OF THAT

Thanks

Doc
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post #4 of 8 Old 05-21-2011, 01:50 PM
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Quote:
Originally Posted by SVTCobra347 View Post
The weight gain could be if the Aviator had an "NVH block" and a forged crank.. that would add a good 25-30 lbs versus a Teksid/Mark VIII cast crank.
The avaitors use a WAP aluminum block and a 6 bolt cast crank. A 4.6 cast iron block would add about 80lbs and the forged crank would add 12.

I would check the block to make sure it was a stock avaitor block and not one that was replaced, say under warranty or by someone that had no clue.

It's an 05 engien correct?

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post #5 of 8 Old 05-21-2011, 02:08 PM Thread Starter
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Yup
An '05 aviator for the donor swap

Though the aviator COULD HAVE had an iron transplant prior to going to salvage
Just like my cobra had a mark VIII TRANSPLNT BEFORE COMING TO ME, via ebay

Heading to the warehouse with a magnet this afternoon
I am correct in thinking that it'll stuck to an iron block but not an aluminum one right?
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post #6 of 8 Old 05-21-2011, 02:46 PM
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Yeah, and an iron block will be black or rust colored, where an aluminum block will be a natural dull silver color. Also the aluminum will show ribbing on the outside.
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post #7 of 8 Old 05-21-2011, 07:28 PM
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1.35% more weight on the front is definitely going to cause more understeer.

With your previous cornerweights, the car is going to oversteer more in right turns and understeer more in left turns due to the unequal diagonal weights. If the track you drive on is run clockwise, then your impression of the handling will be more to the oversteer direction since the track has four more 90 degree right hand turns in this direction.

Given the same geometry, a forged crank will always be heavier than a cast crank. Forging results in a higher material density, so therefore more weight.

Double check your alignment to make sure nothing changed.

Removing the STB reduces the torsional stiffness of the chassis. Whether the chassis twists during cornering or the suspension compresses and extends at each end of the car, the results are the same. The relative torsional stiffness at each end of the car determines the percentage of weight transfer that occurs at each end. The end of the car that receives more of the weight transfer, has less total grip. I would try putting the STB back on.

My guess is that all of these factors are contributing a small amount each to the change in handling balance.

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post #8 of 8 Old 05-21-2011, 09:10 PM Thread Starter
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Quote:
Originally Posted by Jack Hidley View Post
1.35% more weight on the front is definitely going to cause more understeer.
still trying to chase that down

How consistent (or INconsistent) are various sets of longacre scales?

If it is the block, for whatever reason, I am stuck.
It's in, running, and I hope to not have NEED of a new block for a while

So now the search is to diet the front end even more
Consider it's road race application, and the MM k-member (and soon to be the NEW k-member brace) . . .
A) What are your thoughts on a scaled down Cro-moly bumper, and getting rid of those low-speed-impact bumper piston things?
B) what are your thoughts on a light weight radiator support, like I know some drag racers use?? (I do have a new flui-dyne radiator)


Quote:
Originally Posted by Jack Hidley View Post
With your previous cornerweights, the car is going to oversteer more in right turns and understeer more in left turns due to the unequal diagonal weights. If the track you drive on is run clockwise, then your impression of the handling will be more to the oversteer direction since the track has four more 90 degree right hand turns in this direction.
interestingly, the worst understeer was noted in two right handers.

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Originally Posted by Jack Hidley View Post
Given the same geometry, a forged crank will always be heavier than a cast crank. Forging results in a higher material density, so therefore more weight.
makes sense, I'll take this reasoning for a tie-breaker
na_svt said the cast crank was lighter. Which would work to my advantage <7,000 rpm
Thx

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Originally Posted by Jack Hidley View Post
Double check your alignment to make sure nothing changed.
will do
Rear sway is set on a mid-position
I guess tightening it would help counteract some of the understeer??

Quote:
Originally Posted by Jack Hidley View Post
Removing the STB reduces the torsional stiffness of the chassis. Whether the chassis twists during cornering or the suspension compresses and extends at each end of the car, the results are the same. The relative torsional stiffness at each end of the car determines the percentage of weight transfer that occurs at each end. The end of the car that receives more of the weight transfer, has less total grip. I would try putting the STB back on.
gonna order a new k-member brave to fit the new canton pan and order a new stb to fit the new intake MONDAY.

Quote:
Originally Posted by Jack Hidley View Post
My guess is that all of these factors are contributing a small amount each to the change in handling balance.
Thanks for the above (and upcoming) responses.
I didn't realize just how well balanced it was with your maximum grip box
Until this.
Thanks
Doc
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