Fox / SN95 SBF engine setback [Archive]

tulowd

11-06-2014, 10:04 AM

Hey All:

As some of you know, my '87 vert continues along its way towards pretending to be a road race / well handling "sports/muscle" car. While this is an unlikely goal to ever be met, one of the motivations is to continue improving the metrics of the car from what Ford originally did. Seam welded chassis, full frame, 8 pt roll bar, coil overs, Koni double adj sport shocks, full poly/delrin/spherical suspension mounting arrangement, Torsen diff, Cobra brakes, relocated battery.....all the usual small stuff has been done.

Weight reduction efforts will also continue, once the interior and sound system are done; PSP ported alum Victor Jr heads will shave app 50 lbs off the nose in the spring.

Maximum Motorsport Tubular k member and front control arms are in the future as well; which brings us to the point of this thread:

Planning on moving the engine back 1" as allowed by the K member design. It appears only the driveshaft length and collector to catalytic converter pipes will need to be shortened by 1". The trans cross member looks like it will work, clearance between scattershield and firewall looks ok; have BBK 1.75 long tubes going on with the new heads, along with another MM long clutch cable and heat shield.

Has anyone done this, and what comments and insight can you give me? Interested in the improved weight distribution and resulting steering effort reduction and increased front tire bite/ reduced understeer. Will eventually increase the wheelbase by 1.5", as well as widen the front track with Cobra length control arms. I'm of the mind every little bit helps.

Have at er - all comments and thoughts appreciated.

http://i1245.photobucket.com/albums/gg582/tulowd/87%20Vert%20TU%20LOWD2/IMG_6767_zps2f31c499.jpg

http://i1245.photobucket.com/albums/gg582/tulowd/87%20Vert%20TU%20LOWD2/IMG_6291_zpsbfa086ef.jpg

http://i1245.photobucket.com/albums/gg582/tulowd/87%20Vert%20TU%20LOWD2/Kookscollectorsinstalled.jpg

11-06-2014, 09:11 PM

My $1.98. Not sure the end justfies the means. The MM K member and additional wheel base option does work. Before I went to the hassle of moving the engine back, would pop for an SLA and 10" front rims and call it a day.

tulowd

11-07-2014, 09:53 AM

part of my longer plan is to do 10" front wheels after the wheelbase extension and track widening.
I'm thinking moving engine back is not that expensive; maybe a couple of hundred bucks.
SLA would likely work even better with less mass on the nose as well - after the lottery win.

Question is: has someone done an engine setback in a Fox and what does the car feel like after - any discernible difference and any real minuses?

2DXTRM

11-09-2014, 08:23 PM

Why the BBK 1 3/4 over the Kooks??

Some things to consider with the engine setback. Taking the bell housing out can be a pain in the arse. Front sump of the oil pan may hit the rack (depending on what brand oil pan you have). Shortening the driveshaft, possibility of headers hitting the firewall etc.

TurboFox

11-09-2014, 08:54 PM

My engine is set back basically against the firewall. I am going to have a real blast trying to get the bellhousing bolts out to remove engine. Will likely have to pull it all at once

Ponyryd

11-09-2014, 09:10 PM

For trans removal it would be as easy as dropping the k-member a few inches to get to the bellhousing-nothing to worry about IMO. I've never done it but my main areas of concern would be the oil pan contacting the rack and clearance between the header tubes and steering shaft-1" will probably mean you need one custom bent tube at the very least. 1" may be just enough that you can get away without modding the driveshaft, would need a test fit and good hard run to know for sure.

tulowd

11-10-2014, 09:39 AM

Thx guys. The oil pan and trans cross member will work as is. Not concerned about the bellhousing removal - trans can come out as is, to get at clutch motor comes out.

Headers not sure until they go on, steering shaft was lengthened and moved to accommodate the Kooks which still needed a custom #8 tube. Swapping to BBK to make more torque, gain some ground clearance and clean up the slip on leaks. Kooks will be for sale in spring; they are 1-7/8 ceramic plated with ported head adaptor plates. Would be ideal for a 351 based 408 or 427 stroker methinks.

Concerned about the gains - some of the more techy forum posters are saying 1" setback makes less difference in weight bias than relocating battery. I get the moment of inertia on a 40 lb battery 10" in front of the wheel base, but a motor/trans rear shift by 1" should equal more than removing 27 lbs off the front wheels. That is equivalent to swapping one cyl head from iron to alum. or losing efi and a/c system.

Any engineering types on here feel like using their pocket protector and slide rule to figure out the potential weight bias improvement ?
Looks like the complete motor with alum heads, front serpentine/alt, headers, carb, fluids, flywheel, clutch and scattershield should weigh 500 lbs; trans is app 75 lbs. Current scale weights incl me (175 lbs fully dressed) in drivers seat, full fuel tank and 110 lbs of ballast in trunk. 52.6% F 47.4% R

With 50 lbs ballast (=stereo install), and new cyl heads (-50 lbs) it looks like it will be app: 52.7%F 47.3%R at 3640 ttl weight.
K member and A arms will knock another 35 lbs off the front. Lightweight wheels will save another 40 lbs, equally distributed.
Looking for alum rear bumper crash bar from 79 Pace car.

Engine relocation should turn that into......WHAT? Bueller......Bueller, are you on it? lol

http://i1245.photobucket.com/albums/gg582/tulowd/87%20Vert%20TU%20LOWD2/IMG_5204_zps6550e66e.jpg

RedSN

11-10-2014, 10:37 AM

Any engineering types on here feel like using their pocket protector and slide rule to figure out the potential weight bias improvement ?
Missing some information for that calc: what is the wheel base, and what is the current location of the center of mass of the engine/transmission?

Assuming a wheelbase of 100 1/2", and locating the engine/trans at say 9" behind the front wheels?
Moving a 575 lbs mass 1" closer to the rear will result in:

-6 lbs off the front
+6 lbs added to the rear.

....so the techy forum guys are right.

jibbijib

11-10-2014, 10:39 AM

What about moving the k member forward an inch? Youd have to change your fenders and bumper extensions to 90 plus, but you'd gain caster which apparently helps these things turn better.

Has it been done before? Is it maybe too complicated? All I can think of is youd have to re-box your front frame rails, punch new holes for the k member mounts, adjust the motor mount position and change your oil pan. Unless you have a dry sump, which would be ideal anyway.

Thoughts?

tulowd

11-10-2014, 11:47 AM

tulowd

11-10-2014, 11:51 AM

Missing some information for that calc: what is the wheel base, and what is the current location of the center of mass of the engine/transmission?

Assuming a wheelbase of 100 1/2", and locating the engine/trans at say 9" behind the front wheels?
Moving a 575 lbs mass 1" closer to the rear will result in:

-6 lbs off the front
+6 lbs added to the rear.

....so the techy forum guys are right.

Not sure about the behind CL spec - assume it is somewhere arrears of the engine mounts ? How much of a diff does that make if say the current engine/trans CG is say 14" behind compared to your calc? A nice mulitcoloured graph along with a youtube type video explanation would be awesome, lol

RedSN

11-10-2014, 12:12 PM

LOL, about the same.
Problem is it's only 1" setback on a 100" wheelbase. That's 1%.

http://www.roymech.co.uk/images/bm.gif

Your wheel loads (Ra and Rb) are a ratio of the mass location and the overall wheelbase (L)

W=575lbs
L=100"
a=14"
b=86"

Add 1" to 'a' to get your new reaction values and compare with the originals.

tulowd

11-10-2014, 01:00 PM

jibbijib

11-10-2014, 08:01 PM

Will eventually be extending the wheelbase by 1.5" forward via MM k member + forward offset control arms. Never heard of moving k member forward - lots of extra work like steering shaft challenge as well.

I've never heard of moving the k-member either. Just made it up. Maybe that's what the MM piece achieves so you retain factory mounting position...

I'm no math surgeon, and have no idea what I'm doing most of the time. So take my suggestions lightly lol

tulowd

11-11-2014, 08:53 AM

Just emailed Jack at MM; let's see what he comes back with. :mechanic:

11-11-2014, 09:02 AM

Looks like your largest gains are gonna come from the new cyl heads followed by wt reduction and improved geometry of MM K member n bits. Now if you wanna cut the firewall n dash out and really put the engine where it belongs, gains your looking for will follow.

tulowd

11-13-2014, 04:55 PM

From Jack Hiddley at Maximum Motorsports:

1) Moving the engine/tranmsission back 1" changes the weight distribution 0.2% on your car. I've used your cars mass of 3,741lbs and assumed that the engine/trans weighs 600lbs. The formula that you linked isn't the correct one. The correct math can be found at the link below in chapter 2.

http://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/media/faa-h-8083-1a.pdf

Conversely moving the wheels forward 0.75" will shift the front weight distribution 0.39% towards the rear. Moving the front wheels forward has more affect on the weight change and has other benefits.

With the MM k-member and either FCA, you will be able to get a little bit more camber. With the MM k-member and nonoffset FCAs, you will be able to get several more degrees of caster and a little bit more camber.

The MM k-member adds Ackermann steering when used with the nonoffset FCAs. When used with the reverse offset FCAs it removes Ackermann. In either case, the k-member raises the FCA pivots so this raises the roll center height back up which is good on a car that is lowered so much.

11-13-2014, 05:03 PM

pretty much what Don said??

tulowd

11-14-2014, 09:52 AM

sort of but its a different number and calculation based on centre of gravity as the basis; not the direct weight on the wheels. Aircraft calculations are done via wheel weights but the differentials are calculated using moment arms and mass.

Seems to mean the engine setback alone is worth a lot more than a 27 lb shift according to this calculation : 0.2% weight bias change is pretty significant, actually, 0.39% change with 0.75" wheelbase is a big deal.

This means the whole enchilada of alum heads, 1" engine setback and 1.5" wheelbase extension will yield something close to a 1% shift, if not more. Along with 1.5" front track increase, way bigger front tires and wheels, and the higher potential caster and camber settings, the final improvements should be pretty significant.

11-14-2014, 09:55 AM

An SLA with 10" wheels n 275's up front would make it a monster.

tulowd

11-14-2014, 10:10 AM

An SLA with 10" wheels n 275's up front would make it a monster.

Grrrrrrrrrrr lol

Spoke to MM about their SLA plans:

S197 version is in development/track usage now - app 1 yr until on market
SN95/Fox SLA may follow depending how much carryover they can use from above and the integration with their existing K members and feeling about return on investment.

Reading between the lines, I would expect a S550 SLA to be made available shortly after the S197. (my intuition, they said nothing and I didn't ask).

Having said that; lots of fast cars use strut suspensions - M3's Porsche 911/Cayman etc.

The $9000 USD price tag for a Griggs Fox SLA road race setup is enough to make me dream of an all alum 427 engine set back 15 "

http://www.griggsracing.com/article_info.php?articles_id=8

http://www.griggsracing.com/index.php?cPath=10&osCsid=ed0fb4028ee555733908c5ad6a49273f

RedSN

11-14-2014, 10:28 AM

sort of but its a different number and calculation based on centre of gravity as the basis; not the direct weight on the wheels. Aircraft calculations are done via wheel weights but the differentials are calculated using moment arms and mass.

Moving the engine/tranmsission back 1" changes the weight distribution 0.2% on your car. I've used your cars mass of 3,741lbs and assumed that the engine/trans weighs 600lbs. The formula that you linked isn't the correct one. The correct math can be found at the link below in chapter 2.
A 0.2% weight distribution change on a 3,741 lb car = 7.5 lbs

I was off by 1.5 lbs :dejection:
....assuming Jack didn't round up his results

tulowd

11-14-2014, 10:49 AM

A 0.2% weight distribution change on a 3,741 lb car = 7.5 lbs

I was off by 1.5 lbs :dejection:
....assuming Jack didn't round up his results

I want to watch you two argue engineering calculations about my overweight, underperforming, underpowered old shitbox! :dump:

I thought a weight distribution change is different than a distribution percentage change. I was wrong. :)

Current
3741# TTL
1011+957 = 1968# Front = 52.6%
910+863 = 1773# Rear = 47.4%

Change by 0.2%
F52.4%/ R47.6%
F = 1960# (less 8#)
R = 1781# (plus 8#)

Hmmm - ok - good to know 2 smarter guys than me agree on this.
1) Now what happens when I lose 50# off the front/top of the engine, knock 50# off the rear (no ballast) stock engine location.
2) Then move the engine back while saving 30 lbs with the k member, same wheelbase
3) Then extend wheelbase and widen front track by 1.5" respectively, ttl weight remains the same.
4) Lastly knock off 40 lbs for lighter wheels

Have at er !

PS: This also magnifies any small changes that can be made like losing anything in front of or behind the wheelbase in order to reduce the polar moment(s) of inertia. Need that alum rear crash bar!!

RedSN

11-14-2014, 11:05 AM

Now what happens when I ....
http://rs919.pbsrc.com/albums/ad37/thebloodofkonstantin/reaction%20gifs/tumblr_mdg72sKsdL1qef2y7.gif~c200

too many variables, not enough information.
my initial calc was based on some assumptions and using a simple beam reaction formula to illustrate the effect of moving a 600 lb iron slug back 1"

HyperGT

11-14-2014, 11:46 AM

Grrrrrrrrrrr lol

Spoke to MM about their SLA plans:

S197 version is in development/track usage now - app 1 yr until on market
SN95/Fox SLA may follow depending how much carryover they can use from above and the integration with their existing K members and feeling about return on investment.

Reading between the lines, I would expect a S550 SLA to be made available shortly after the S197. (my intuition, they said nothing and I didn't ask).

Having said that; lots of fast cars use strut suspensions - M3's Porsche 911/Cayman etc.

The $9000 USD price tag for a Griggs Fox SLA road race setup is enough to make me dream of an all alum 427 engine set back 15 "

http://www.griggsracing.com/article_info.php?articles_id=8

http://www.griggsracing.com/index.php?cPath=10&osCsid=ed0fb4028ee555733908c5ad6a49273f

I would just do the heads and Kmember personally. Until you get to a point where you are wanting that last 10th or three of lap times its is not worth it. Unless of course you just want to have a unique car and fun project, then go at it.
Not sure what 911 has struts, 1999 forward at least was coilover design (over a strut if that is what you mean) but they were not separate strut and spring suspensions thats for sure.

tulowd

11-14-2014, 11:47 AM

http://rs919.pbsrc.com/albums/ad37/thebloodofkonstantin/reaction%20gifs/tumblr_mdg72sKsdL1qef2y7.gif~c200

too many variables, not enough information.
my initial calc was based on some assumptions and using a simple beam reaction formula to illustrate the effect of moving a 600 lb iron slug back 1"

lol...what else do you need to know mon ami?

110 lbs of ballast were in the trunk, this will be reduced by 50 lbs to 50 lbs of audio equipment only

new cyl heads will knock 50 lbs off front of engine/trans assembly; lets say 550 lb ttl mass for engine, flywheel clutch, scattershield and trans

new k member and arms will knock off 30 lbs from existing front weight

this will keep ya busy in between thinking/planning about your garage; lol

I just hung a pair of 16" high bay 84W compact fluorescent fixtures in my car shelter - looks like the entrance to hell at night from the street now :)

HyperGT

11-14-2014, 11:53 AM

tulowd

11-14-2014, 01:33 PM

Dont forget bigger tires and rims will add back alot of weight to the front. I just put speedline 17 inch with 275/245 on my car and the difference was huge compared to my 225/16 setup. I mean I can really feel the weight, car feels sluggish. Rotating mass is 3-4x that of regular static weight.

current setup is 50 lbs / corner with 255/40/17 on 17x9 Cobra R's
10.5's with 275/40 adds app 2 lbs per corner to 52 lbs

switching to Enkei 10" wide wheels will reduce weight by 9 lbs per corner back down to app 43 lbs per corner with 275/285 tires

1BAD92LX

11-14-2014, 05:28 PM

I agree with HyperGT. But I know your not a person to settle.
I've done the MM k member and it feels so much stiffer. I went with reverse offset arms to not have to mess with fender clearance. Delrin bushings also.
I can't wait to put aluminum cylinder heads on and cut off some more weight. Just which ones is the question now.

tulowd

11-18-2014, 10:32 AM

From Jack Hiddley at Maximum Motorsports:

1) Moving the engine/tranmsission back 1" changes the weight distribution 0.2% on your car. I've used your cars mass of 3,741lbs and assumed that the engine/trans weighs 600lbs. The formula that you linked isn't the correct one. The correct math can be found at the link below in chapter 2.

http://www.faa.gov/regulations_polic...-h-8083-1a.pdf

Conversely moving the wheels forward 0.75" will shift the front weight distribution 0.39% towards the rear. Moving the front wheels forward has more affect on the weight change and has other benefits.

With the MM k-member and either FCA, you will be able to get a little bit more camber. With the MM k-member and nonoffset FCAs, you will be able to get several more degrees of caster and a little bit more camber.

The MM k-member adds Ackermann steering when used with the nonoffset FCAs. When used with the reverse offset FCAs it removes Ackermann. In either case, the k-member raises the FCA pivots so this raises the roll center height back up which is good on a car that is lowered so much.

RedSN

11-18-2014, 10:46 AM

^^^re-posting that from 18 for emphasis?

tulowd

10-21-2015, 10:52 AM

ADD or OCD most likely. Thinking about this still/again lol

10-21-2015, 06:35 PM

Paul's making big jam, not a good place for one of those shafts.

tulowd

10-22-2015, 08:18 AM

Paul's making big jam, not a good place for one of those shafts.

why thank you, a two sided compliment so early in the morning :)

toofast306

10-22-2015, 10:56 AM

Paul's making big jam, not a good place for one of those shafts.

Any recorded failures? I ran one without issue, putting down 485 lbs ft. Eventually the Cobra clutch failed, then the trak-lok failed, then the Centreforce DF clutch failed, but the shaft was intact. This was launching on MT ET Streets.
I'm currently running another Aerostar AL shaft in a more gentle application.

10-22-2015, 04:45 PM

Thought was they are getting long in the tooth age wise.

tulowd

08-04-2016, 07:02 AM

So engine has been set back 1"; front wheels have moved forward 1.5"; looks like track width will be increased by 2" both front and rear.

Custom 3" steel driveshaft with Spicer U joints made up by Dwight at Driveline out in Whitby.

Aluminum has a fatigue life that can be a concern. Road car, 4.10 gears, 20 yr mileage; plus high speed track days makes ya think.
My old Ford Racing driveshaft was worn out at the output end u joint attachment point....it couldn't be shortened / rebuilt.
19 lbs vs 14 lbs, but much stronger and brand new/balanced.