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64Chevelle
10-11-2009, 04:12 AM
Hi,

I'm trying to set my engine back and down as much as possible.

What is the recommended minimum distance between the oil pan and k-member? Poly motor mounts

Min. space between transmission and trans tunnel? Poly trans mount also.

Anything else I need to consider? Any recommendations and/or best practises?

Don't want to regret doing this in the future :)

Thanks in advance for any help and useful info!

novaderrik
10-11-2009, 12:14 PM
you don't need much room for theo il pan- 1/4" shouldbe fine. just don't plan on taking the oil pan off in the car.
at the firewall, ideally you'd want enough room to get the bellhousing bolts out, but depending on how easy you like things to be, you could jsut take the motor/trans out as a unit instead of just dropping the trans, or cut access holes in the firewall with a hole saw to bet to each bellhousing bolt and make some sort of covers for each hole. there is also distributor clearance to think about- but the firewall could be pounded out of the way or a notch welded in for clearance.
once you've got the motor down and back, then you need to think about header fitment and collectors scraping on the ground, as well as driveline angles unless you also drop the trans crossmember the same amount as the engine.

The WidowMaker
10-11-2009, 01:52 PM
some people still cant wrap their heads around it, but i moved mine up and back. i didnt have crap for header or bell housing clearance and it was keeping the car from being dropped even further. with a lot of work, i was able to drop the car another 1.5". the motor still sits the same height off the ground, but the entire car is dropped around it.

so, before doing so, make sure you have custom headers and a bellhousing that doesnt sit like my mcleod.

Tim

David Pozzi
10-12-2009, 06:03 PM
If you do some calculations, you will find moving an engine a couple of inches isn't worth the effort if reducing front wheel weight is your goal. If you move it 8 to 10 inches, then it might be of benefit.
It's far better to move something heavy like a battery from up front to the trunk, it would be equal to moving the engine back 10"!

The WidowMaker
10-12-2009, 07:13 PM
read this thread to understand where pozzi is coming from. it saved me a lot of work when i was going to build a new firewall and move the motor even further back.

http://www.chevelles.com/forums/showthread.php?t=186119&highlight=moving+engine+back+battery

64Chevelle
10-13-2009, 12:19 AM
Hi all,

a lot of interesting reading here. I will post pictures later today of my progress so far. You all have a lot of valid points to consider and have changed my mind a little about my priorities...

Jim Nilsen
10-14-2009, 10:25 AM
If you do some calculations, you will find moving an engine a couple of inches isn't worth the effort if reducing front wheel weight is your goal. If you move it 8 to 10 inches, then it might be of benefit.
It's far better to move something heavy like a battery from up front to the trunk, it would be equal to moving the engine back 10"!

When I moved my battery to the trunk, I got one that weighed 1/2 as much so I moved my engine back 6" to make up the loss/gain,LOL


It is going to be interesting to feel the difference when I get my car on the road and compare it to what it used to be like. With so many other mods to the suspension it may be hard to tell. 6" and down 2" is hopefully do something of a benefit but I know that 21lb. battery is going to do just as much to help.


The biggest deal with going back is the hood hinges. You will be wanting them out of your way everytime you are under the hood. I switched my hood to open the other way because of it.



It's also a lot of work. Like starting over kind of work. Everything changes something else and the amount of things that change when the engine goes back are endless. I found it easier to go back than to try and change the mounting of the engine in the front frame section I used.

Goodluck

jfaria78
10-15-2009, 11:05 AM
If you do some calculations, you will find moving an engine a couple of inches isn't worth the effort if reducing front wheel weight is your goal. If you move it 8 to 10 inches, then it might be of benefit.
It's far better to move something heavy like a battery from up front to the trunk, it would be equal to moving the engine back 10"!

I agree with David. Mostly becuase I have worked on lots of drag cars with motors moved back a few inches and they were a complete pain in the ass to work on. One thing to mention, I have not seen this done too often to a car that uses the stock firewall, you can, but it may take a lot of work.

I have moved a motor back in a 65 chevelle 8 inches and that was a lot easier than I thought it would be, but then again it was a full on racecar.

James

Rhino
10-15-2009, 12:04 PM
What about lowering the engine within the car vs raising the engine and lowering the car. I'm on the border with this decision.
I don't necessarily want a crazy low ride height because of exhaust/engine clearance. I wouldn't mind a slightly lower ride height if I could keep the exhaust off the ground.

Would I be correct in the assumption that as long as the engine stays the same relative to the ground, you're effectively lowering the CG? Obviously unsprung weight stays at the same height as the car is lowered so we're only talking about lowering the body shell/ interior.

Norm Peterson
10-15-2009, 02:53 PM
Yes. If nothing moves up relative to the ground and anything at all moves down, the CG has to drop.

Taller or shorter tires will affect the CG height.


Norm

pdq67
11-27-2009, 06:22 PM
Us 1st Gen car guys can move our engines back against the firewall so tight using stock parts that our dizzies give us fits!

Better yet is to put the battery in the trunk over the pass side tire.

pdq67

PhillipM
12-07-2009, 11:02 AM
read this thread to understand where pozzi is coming from. it saved me a lot of work when i was going to build a new firewall and move the motor even further back.

http://www.chevelles.com/forums/showthread.php?t=186119&highlight=moving+engine+back+battery

That was a lot of help... Thanks for the link.:smoke:

monteboy84
01-06-2010, 06:00 AM
Moving it downward will give more of a "feel" difference than moving it back 2-3 inches or whatever you have in mind. With our 69 Corvette SCCA car, the motor is as low and back as we could get it without hacking the firewall, and it's a major PITA to do anything on. Bellhousing bolts, front pulley, you name it, it sucks to work on. Stock location or a little bit lower won't lose you much in performance, but will save your knuckles lots of injury :)

-matt

Jim Nilsen
01-14-2010, 03:54 PM
It's not apples to apples but it is interesting to note that my car and Bad Penny weigh almost the same amount overall, I may be 75 to 100 lb less but that has to be seen on the same set of scales to be certain.. The F/R weight is 52/48 on both cars at this time. My engine weighs 125 lb more from what most say is the difference between an LS and standard SBC. My engine is back 6 in. and both cars have the battery in the rear. The front body weight of the cars should be close since Steve has the carbon fiber stuff and I have a lightweight fiberglass hood and other lighter pieces to help.

It makes me wonder what it would be like if I had my engine in the stock location? Did moving my engine back 6 in. gain the same F/R weight as taking off 125 lb. ? If I went with an LS would it make it 50/50? It definately would take 125 lb. off of the car by changing the engine but does it change the F/R that much?

I can say this. Compared to the way my other 67 handled , you can definately tell that the front end is way more responsive to shift changes left to right but that may be attributed to the Vette suspension.

I can hardly wait for the Motorstate to get here so it can be compared with the same scales.

-DA
01-22-2010, 03:39 AM
Beyond just front/rear weight distribution, what about the benefits of reducing the yaw moment of inertia value by moving the engine back?

As the P.A.T. goes, the crucial factor is how far the mass is from the center of rotation (I total = I + M*d^2). Looking at a first gen F-body with 52/48 front/rear weight distribution, moving a 500lb engine 5" back, from 40" to only 35" forward of the vehicle CG, is comparable to totally removing a 50lb battery from the the engine compartment or trunk (~65" from CG either direction). And, ironically, you could actually increase the moment of inertia value if you placed the battery too far back in the trunk. :hand:

So, with the engine moved I know the car would theoretically be easier to turn but how much could you "feel" it on a 3500 lb vehicle? Other than engine placement and suspension components there aren't many big ways to reduce a cars moment of inertia as everything basically has a fixed location. This is where chevy engineers took out two birds with one stone when they rear-mounted the tranny and brought the engine back further...

But the question still stands, would it be worth the headache to move the engine?

-Dave

68Formula
01-22-2010, 08:33 PM
Here's how Steve finally managed a perfect 50/50 weight distribution on Bad Penny. (Hope it's been long enough that we can joke about it :-) )

https://static1.pt-content.com/images/pt/2010/01/0804phr_17_zrear_quarter_panel-1.jpg

HILROD
01-23-2010, 10:18 AM
One thing I haven't seen discussed here is the lever type action an engine can have from being rather far forward. Example, an S10 V8 conversion might only gain 300 total pounds. When checking the weight before and after you might find a 400lb front gain and a 100lb rear loss. This is when leaving the trans in it's stock location as is normally done with these trucks.

-DA
01-24-2010, 06:05 PM
To lose 100lbs off the rear in that manner, say 100" wheelbase, you'd have to add 1000lbs @ 10" forward of the front wheel contact patch, 500lbs @ 20", or 333 @ 30"... that seems a little impractical for a v8 swap unless the front wheels start out under the tranny. Good point though as any weight placed beyond the wheelbase certainly pulls weight off the other end of the car.

BillyShope
03-09-2010, 05:45 AM
Here's a spreadsheet which allows you to see the effect on wheel loads when components are moved:

http://www.racetec.cc/shope/tim.43.htm

64Chevelle
03-10-2010, 01:18 AM
Here's a spreadsheet which allows you to see the effect on wheel loads when components are moved:

http://www.racetec.cc/shope/tim.43.htm

Thanks, very interesting to play around with. This is approximate values of what I've added up so far from the baseline 58% front weight ratio:

- Moving engine/tranny back (700lbs -> 3") (-0.7%).
- Moving battery to trunk (-2%)
- Light front bumper (-1%) adds tiny amount to CGH
- Remove A/C compressor (-1%) adds tiny amount to CGH
- Lee steering box, ATS spindles, SPC arms, new alu radiator, lighter wheels + tires front (about the same weight out back) (-1% estimate), also adds a bit to CGH, but not much ~0.05"

Which adds up to an increase in CGH of ~0.2" and a front weight ratio of 52.3%. Still a way to go to reach 50/50. A carbon fiber hood would probably be one of the relatively simplest and best solutions.