Questions about mounting engine and transaxle.

[BigB98]

Ok, so I have an RCR MKIV, and I have the engine dangling in the bay waiting on me to make a decision to mount the thing. Build thread here: http://www.gt40s.com/forum/gt40-build-logs/24438-bigb-s-rcr-mkiv.html

Before I mount the engine (Shelby FE) and 930 transaxle, what all should I consider? Things I think I should be considering and questions:

• How far foward should I go? What seems right will put the pulley past the firewall an inch or two, but I can modify with relative ease. Should I be trying to make it as far forward as possible? If not why not?
• How deep into the pocket should it be? I could potentially go another half inch or a full inch, but either way, I would need to make some sort of skid plate to protect the pan...or modify the pan.
• Obviously need to make sure the engine and transaxle is square in the pocket, but are there any other considerations I should make?

Thanks for your input.

 

[Jac Mac]

First I would check out your starter clearance- looks like you could have an issue there. Then let your halfshafts dictate the fwd/rwd placement, up to an inch fwd/rwd of in line with rear hubs should be tolerable- vertical height is the one that affects plunge distance and this will probably have to be as low as possible to minimise this plus ensure that front of motor is higher than rear to prevent airlocks in cooling jackets. Remember most if not all FE were dry sumped in GT40 applications so a special pan may be reqd for wet sump.

The Chev SB water pumps can be adapted with spacers to an FE, this would possibly allow the use of some of the more efficient and shorter competition type SBC pumps if your stuck for room & dont want an electric system. Also check out Russ Nobles 'Kiwi Scratchbuilt' thread for a neat pump shortening job.

If you really get stuck for ground clearance & cannot accomodate the FE oil pump in the lowered pan you can fit an external belt driven single stage pump-essentially a single pressure stage from a dry sump setup- and fit the toothed belt crank drive sprocket between the damper & front cover. Just finishing up a FE with this setup for a local guy doing an 'Eleanor' clone at moment.( Only had 1.25" between Rack & Block so std pump was definitely a no no!)

 

[BigB98]

Thank you for the input Jac Mac. I'll need to do some research on plung distance, as I am not familiar with the term. I think the water pump will be ok with a little firewall adjustment.

I'll look into the dry sump setup. I see Aviaid has a setup, so maybe they'll take my pan back and apply it to the cost. That said, do you know what the cost is for the complete setup. They conveniently don't advertise that part....I think that means expensive!

 

[Jac Mac]

'Plunge' is the distance the halfshafts or axles change in effective length when the rear suspension moves up or down, if mounted at the correct height and if half shafts are of the correct length this can be held to a very small amount. Not as critical in CV units as it was in the sliding spline type shafts of older cars, it still pays to keep it to a minimum to reduce heat buildup, especially when used in a high load or race type environment. quite simple to check if you remove a coil over unit and simply raise/lower the rear upright and observe the amount wherever it occurs ( CV or sliding spline if fitted ). If you have large amount you could risk damage to the CV from it bottoming out or trying to extend past the circlip length.

Most dry sump setups are $$$, but payback in increased HP & reliabilty is worth it in the long run- the first spun bearing from an inadequate wet sump system will cost more to fix than the dry sump system would have taken to fit. Even the external setup I mentioned is more than halfway to fitting the dry sump system, so why not go the whole way. I picked up a mint Peterson tank /heater element/lines on ebay last year for around US$50.00, doesnt need to be expensive if you shop around.

 

[Iain]

The "Winow" for the drive shaft angle if you are using CVs is, I belive, 7deg. ie 7 up & 7 down from its normal position.

I would be interested in hearing opinions on the payback drived from moving the engine / transaxle assembly as far foreward as possible in the chassis. I drove a true mid engined race car a couple of weeks ago and could not believe how nice it felt. Having said that I was coming off a fairly low base with my existing ride. We moved our assembly as far foreward as possible and have been paying the price ever since !

Iain

Iain