Between block and lightweight internals maybe 100 lbs. Compared to an Iron 351 based motor 200 lbs and also a bunch of that lost from up on high.Sean, I'm no expert on this one....but what I've heard discussed around here is that while the aluminum is lighter, to achieve reasonable rigidity there has to be a fair bit of extra webbing. The extra webbing v. the iron block adds weight, so the delta in weight savings is modest for an aluminum block of good/decent rigidity. Maybe 60-80 lbs? That's certainly something but it's not a couple hundred pounds difference. Just my $.02.
The difference is the same as running a half of load of fuel instead of filling them both up. On track running the drivers side tank dry and removing the passengers seat does make a little bit, and I emphasise LITTLE, bit of diference in that the car just feels a little bit lighter on the brakes and corners just a bit more responsive. Lap times really don't change much but it seams like the car is easier to drive at near the limmit.
60 pounds is enough to effect performance AT THE LIMMIT, but unless the car is driven that way then you will never feel it. What's a second worth per lap? If you aren't racing, nothing. The car will still be a blast to drive at the track and faster than you will ever be able to drive it on the street. Any serious oversteer can be tuned out and should be anyway. If I can make my GTD push then anything can be done with suspension tuning.
Save the money and buy a second set of wheels and tires would be my recomendation. R6 Hooizes will get you at least 4-5 seconds a lap over street tires and THAT"S a difference you can feel!
Of cource we all are on difference budgets. If the money isn't the issue (god bless you) then an all aluminum engine IS cool. Kinda like webbers, they look really cool but they really don't make the car much faster.
My interpetation from what you are saying is the aluminum block weight loss wont matter and could be counterporductive without the proper setup. As the setup with a iron 302 is well established its the easier route.Weight is the enemy in car racing, dead weight has to be carried, accelerated & stopped.... dont believe me, chuck a 20kg sack of whatever over your shoulder and run up an 100 meter hill, walk back down and do the same thing without the 20kg, provided you dont die or injure yourself from the first attempt you will find the second run is faster... the simple answer is most folk are too lazy or lack the drive/knowledge etc to optimise the car to the lighter weight, there never has been the perfect car, probably never will be, too many variables..weight & brakes do not necessarily go hand in hand, other factors like aero downforce & anti-dive geometryplay a huge part, problem is then that in the case of aero you might have good brakes at higher speeds,& crap at slow speeds, antidive might help at slow speeds, but impose issues in roll center height & tire contact etc, its about finding balance...
Are you saying loose the weight elsewhere, where it can do more good, ie unsprung weight.Jac, I can't dispute you other than to say that open track day running isn't racing. Real race cars always have a weight minimum in the rules and running a 2060 pound car in a class that has a minimum weight limit of 2000 pounds will be a huge disadvantage. Hell just look at FF lap times and you can see that weight is the factor that makes them so damn fast. It sure isn't power, brakes or downforce. It would be a hell of a self built GT40 that gets around most tracks that fast. 1.26 at laguna for a FF
Mazda Laguna Seca - Trackpedia
check out everything else
Laguna Seca lap records - FastestLaps.com
But an open track car can be run at 95% (usually should be) and be more fun than a barrel of monkeys. All things being equal 60 pounds low in the engine room won't make enough of a difference for most people driving a 2500 pound car in a open track session. The fun factor to cost ratio just doesn't justify some expensive things like alum blocks, at least for me.
I think I would be looking for really light wheels for the slicks to spend the extra money on instead.
Wrong, your ideal setup should always be for what you have got, ie: if your car is 20kg lighter due to an alloy block then the perfect setup should require lighter spring /bar rates & softer shock settings, if you run lighter wheels, more of the same.. in other words thinking light but strong right from the start will be best...but if your from Howards 95% category it probably does not matterMy interpetation from what you are saying is the aluminum block weight loss wont matter and could be counterporductive without the proper setup. As the setup with a iron 302 is well established its the easier route.
There are magnesium versions of the BRM wheels available, when you lift one the difference is VERY noticeable. The cost difference is also very noticeable.Are you saying loose the weight elsewhere, where it can do more good, ie unsprung weight.
I have heard the Gt40 auminum wheels are heavy, is there a source for really light wheels.