Aluminium or iron block?

[lorito13]

Hi everybody,

I'm trying to buy the right engine for my Superformance Cobra.
I'd like to put in an aluminium block cause the weight, but somebody told me that this kind of block moves too much and needs a lot of maintenance.

Is it true? Can you help me?

Thanks everybody.

[bobcowan]

Not true. It will require no more maint than an iron block. It will last as long. You'll save about 80#. You'll spend an extra $2,500 or so. Unless you're racing and every 1/2 second counts, you will notice absolutly no differance between the two engines.

[Ron61]

I agree with Bob mostly except for one minor thing. It seemed to me that when I went over my engines the aluminum block one had more bolts that would back off just a little. But I would check all the bolts and torque them on both engines any time I ran them hard and if I was just driving them, I really never noticed much difference in the upkeep. I always got under the car and on top of it and checked all bolts and hose clamps and everything after driving anyway, so they never went for any period of time without being checked. I now only have the iron blocks and they are great for what little driving I do.

Ron

[ENTDOC]

I think you will notice the difference between the two, not in straight line performance, but in handling.

[Fordzilla]

I've had both & I agree with all 3 posts above me. The lighter weight of aluminum does help a little in handling & a little in straight line performance, but unless you are racing, it is irrelevant. Yes, bolts will loosen slightly for some reason with aluminum, and it never seems to stop (They constantly loosen). I run only iron now & am a firm believer in a good seasoned cast iron block.
Just my 2 cents.
Regards,

[edwhite7]

You will notice the difference in the corners and you will need to pay attention to hardware. I have lost engine mount bolts and header bolts before I learned to check everything any time I look at it. I have an early torsion bar suspension and I had to reset the torsion bars after changing to the aluminum block and heads. I have a Shelby block with Dove heads and intake. I have had no problems with the Shelby block and would use it again if I needed another one. I can't say the same for the other stuff.

[patrickt]

... if you have to pass an emissions test. Many states will set your emissions based on the year of the block. Oh, and savvy inspectors are not fooled by an aluminum block with "period correct" codes on them.

[lorito13]

I know only Shelby and RDI making aluminium blocks, wich is the best? Somebody knows somone else better?

[philminotti]

The aluminum FE reproductions are Shelby, Pond, and Genesis.

I suggest you use the "search" function of this forum. You will find a wealth of information about all three.

phil

[RICK LAKE]

lorito13 A little more info would help on your question. You can't compare apples to oranges. Most Cars and lite truck you buy now have either a complete aluminium motor or top half with an iron block. I am not a fan of the mix block because of different expansion rates and time of the rate. I have 2 Shelby motors, CSX#58 & CSX#428. I have been running 58 for 9 years. Racing 98% of the time. Started as a 452 and is now a 482. For the money and time you spend trying to find a good 427 or 428 block, have it sonic tested, pressure tested, bored, plate honed, cam bearings, enlarged or cleaned out oil gallerys, you are at the price of a new iron block from Ponds or Genises. Sorry I forget which makes them. You have no worries about if your old block has a rot hole in a water jacket that was not picked up from pressure testing and after 20-30 heat cycles it cracks a hole. This has happened to guys on this forum. My motor weight is 495 lbs complete without fluids. This is the weight of a small block. Except for money issues or building the perfect orginial cobra why you would not go with a aluminium motor. 200lbs off the nose of the car, 150 if it's a small block. Aluminium grows more than Iron. When you match iron to aluminium over a lot of heat cycles, head gaskets and intake gaskets and seals will seep and leak a little when cooling down. The expansion rate works both ways, from hot to cold and back. Yes bolts do loosen up or time. This is part of smart maintainance of the car. If you drive normal, let your motor heatup on it's own, I have seen less problems. Most people get in the car and 10 seconds are out on the road just like their personal car going to work. This is not good over the long haul. For the amount of PLEASURE you will get from the car, a 1 day of maintainance is little to ask. I do this when putting the car away for the winter, oil fog the motor, back off the rocker arm shaft assemblies, fill with a new filter and fresh oil, build oil pressure in the motor, empty the fuel rails, drain the gas and add new with stablizer, make sure the coolant is 50/50 and topped off, moisture bags go into the exhaust pipes and are seal with tape. set tire pressure and jack car off the ground and level. In the spring drop the oil pan, check all studs and bolts on bottom end, new gaskets, and repeat the same for the top with checking torque on head bolts, intake bolts, rockershaft bolts, perlube and start motor, OUTSIDE the GARAGE.. You are ready for the new driving season. I have found problems with my aluminium motor. Shelby has helicoils in all the fastener holes and some have pulled loose or backed out. I have replaced all the heilcoils with TIME-Serts. IMO they are alot better and are stronger than helicoils. At this time the car is still being run, so my major check before winter is not started yet. IMO the new stuff is better engineered than the 40+ old stuff except of the high nickel blocks ( if you can find one that is not .060" over or sleeved.) FE motor are thined walled but there is a test for checking them on this. IMO save the weight and go aluminium, it gives the car better balance for driving and racing. Rick L.

[undy]

Originally Posted by patrickt

... if you have to pass an emissions test. Many states will set your emissions based on the year of the block. Oh, and savvy inspectors are not fooled by an aluminum block with "period correct" codes on them.

Except in our state, Virginia. 2007 legislation made it so any replica must comply with emission standards of the year that the said replica represents.

[MaSnaka]

I was reading an article about rear ends built specifically for racing by having weight reductions to the outer case. They mentioned a 6 lb. reduction in weight was equal to gaining 1 horsepower. If in fact that is correct...a 200 lb weight difference is a win win. Better handleing and less power reguired. Just something else to complicate things.

John

[vector1]

depends where the wt. is lost the effect it will have.

assuming a constant starting speed for a set distance for comparison

losing 15 lbs. of dead wt. on the car would net .20 speed change = 2.14hp

losing 15 lbs. rotating wt. axle speed is worth .60 speed change = 6.42 hp

losing 15 lbs. rotating at engine speed is worth 3.00 speed change =32.10 hp

so reducing rotational inertia on driveline has 15 times benefit of just reducing wt. of car assuming 13 inch dia. disc mounting to crankshaft flange. components rotating at axle speed are 3 times as effective as non-rotating components.

from chassis engineering by herb adams pg. 109