Couper

Yea but my tree is pretty strong. Any idea where info could be found on what mods were done to the suspension to handle the factory 390?

Norm Peterson

Front coil spring information should be available in the Moog spring catalog. There's a vehicle lookup to part number, and a table with dimension and rate information for many of the part numbers (but I don't think all of them). The dimension and rate table is also available on the 'net as a spreadsheet, but without any application cross-reference.

Car Life published a table with many mechanical specs from the 1968 US domestic cars that I think has some sta-bar diameter information. Might have some spring rate data too (it's been a while since I last looked at it for this sort of information).


Most current setup thinking is considerably different from early/mid 60's OE, partly because of advances in tire technology and partly because it is assumed that power assisted steering is an integral part of the arrangement (read: you don't have to compromise caster down just to make steering physical effort reasonable). So, caster that's much more positive, camber that's statically a little negative rather than slightly positive, maybe even front steer vs rear steer (and the associated change in compliance steer effects) and more. You're still "crutching" a less than optimum weight distribution, but it's a fairly effective crutch.


Norm

2+2GT

Higher-rate coil springs, and a thicker sway bar. Stuff you'd want to do anyway.

67mustang302

It comes down to how much handling you want. Remember than Shelby preferred the small blocks in the cars they road raced that were front engine. The reason there aren't a lot of "My 390 car handles like crap" threads is that most small block Mustangs weren't given a beefier suspension package, whereas the 390 GT option was considered a performance option so it was given a comparable suspension package. It resulted in a car that dealt with it's weight disadvantages better than other Mustangs(typically).

The fact remains that no matter how much you alter the suspension, the more imbalanced the weight is, the more you're fighting physics. Weight balance actually has a pretty huge impact on handling/braking performance. There's a reason that most sports cars try to get really close to 50/50, and why cars like the GT40(old and new) and Ferraris, Lambos etc run mid engine configurations.

Sure, you can get a Big Block Mustang to handle decent, but it's never going to handle the as well as one with a Small Block and a comparable suspension package.

Also consider that in a road racing type situation, power has a much smaller impact than people realize. A 50-100hp advantage in similar cars can easily get trounced by a slightly lighter car with better balance. Most of the time you're at part throttle, so the vast majority of the time you can't even use all your power. The idea is that you use your suspension and weight balance 100% of the time, but your full engine power less than 50% of the time. On windy tracks you may only spend 20% or less of a lap actually at WOT.

Couper

[QUOTE=67mustang302;7509760]It comes down to how much handling you want. Sure, you can get a Big Block Mustang to handle decent, but it's never going to handle the as well as one with a Small Block and a comparable suspension package.QUOTE]


I'm talking about a weekend toy, straight line fun only, I just think its funny that whenever anyone brings up this topic, most, if not all of the posts are: driving an ark, handling like ***, nose heavy,etc...but I never see the same posts directed towards the guys with the stock 390's.

67mustang302

I've never actually seen a stock 390 Mustang myself. Worth keeping 390 perhaps because it was that way stock, but I'd never want a BB for a street car.

As far as straight line fun, the reality is that for as fast as most people want to go, it can be done in a 302 block. Granted though, it's easier to get power out of a BB just because of the cubes and better heads stock. I have seen a few people that have put BB's in cars because they weren't concerned about handling that much, and end up being somewhat disappointed because it handled worse than they thought it would. Most people just don't like driving a car for fun that feels like you have to force it to make a turn.

And keep in mind, that at the same HP levels in a straight line, the small block wins every time, and twice on Sunday. Less weight up front helps with load transfer on launch. The Porsche 911's run as much as 60% REAR weight, 40% front....they have a crapton of gear and launch like mad; typically running faster ET's than you'd expect for the power levels. More weight up front also makes the car stop worse too. Some people don't think it's fun to drive a car with a lot of power that feels like it won't stop.

It's just things to consider. I've seen quite a few people over the years get into BB setups where it wasn't needed, and end up disliking it. If you're trying to build over 600hp n/a in something that you could consider streetable, then yeah the BB is a good foundation. But otherwise you're better off in every regard with a SBF, except if you have/can acquire and build the BB for cheaper and are strapped for cash.

My point is there are a lot of factors to consider in any build. Handling, braking, launch traction, fitment, cost etc etc etc. On ad infinitum. It's not as simple as "stick a big block in it and go faster."