Aluminium v Iron Block

Taking weight saving out of the equation, is there any performance advantages of using an aluminium block v iron block? I am running Comp Eliminator in Australia (similar to NHRA Comp but index system a bit different and different classes but same style of racing) and currently running Aluminium block but the weight break is 4.45 lb/ci where if I were to run a water jacketed iron block the weight break is 4.1 lb/ci.
The combo is 10.2 Rodeck block with 4.5 bore and 3.92 stroke, 18 degree big chief heads with Littlefield 14/71 HH retro with a powerglide in a dragster, car has to weigh 2216 with this combo to suit the class, would be able to drop 175 pounds out of the car if I went to an iron block. My thinking is going to a good iron block I wouldn’t see any loss in horsepower but can take 175 pounds out of the car or can go the rule submission route to get the weight break changed

 

Are you able to drop 175 lbs. out of the car if you add an iron block? I’m thinking it was about 125 lb difference or so between engines going from the iron 9.8 to the aluminum 10.2. I like the iron block because I feel it has better cylinder wall stability at a larger bore than it’s aluminum sleeved counterpart, especially if it’s cast aluminum. I haven’t run a max effort iron block deal, so I cannot speak to their long term durability. Maybe someone else can chime in, I know they have issues cracking from the head bolt holes with the 4.600 bore stuff. If you make the switch to the iron block I’d be looking to go 4.560 bore minimum.

 

yeah I’ve had to add 200 pounds to the car to make weight so getting rid of it again would be no issue, If I go to an iron block I will keep it at 4.5 bore and 10.2 deck just so I can use everything else off the engine

 

So you’re only going to end up 75 lbs lighter? Depending on how the weight distribution changes it might not be worth much et at all. I had a similar setup in a 2000 lb 242” hardtail and I could go faster with 50 lbs in the nose because i could 60’ better with more power in at the hit.

 

Some time ago I was quoted a 50hp loss for aluminum block in an 800hp NA SmallBlock application. Have not verified it myself.

 

Shouldn’t be an issue with leaving the start line, I put a lot of weight in the front already and still struggling to get enough wheel speed, went from 34.5/17 down to 34.5/15 and that’s helped. A few years ago went .96 to the sixty with tyres that were well north of 60 runs

 

I’ve heard similar from people I have spoken to as well, I’ve read it’s due to better ring seal due to iron block being more rigid.

 

ya, that’s my point. You’re going to add weight to the back of the car with an iron block and then take the weight off the front to try to get down to weight. That could easily turn a car that can go .960 into one that will rattle All the dzus’s out going 1.04

 

Sorry was reading that the wrong way around, you’re spot on. I have put in a rule change proposal as I would prefer not to have to replace the block and add weight to the rear, I done some more digging in the rule book and found that the equivalent class for a funny car doesn’t have a different weight break for cast aluminium or cast iron block so was a pretty easy decision to submit a rule proposal