Ar aluminium block Question..

Hi Guys,

Haven't been on here for quite a while! I'm now "retired" from drag racing but have got involved in a land speed project  

Looking at putting together a motor based around an 11.2 deck AR aluminium block. could be as big as 665ci but the car owner is looking at slapping a couple of turbos on it.....Question is, how much power can this block safely handle?  I have seen the Roberts design blocks being used upwards of 3000hp but I'm not sure on the (older?) AR block. were they designed for blown alky applications, as I've been told the big casting on the side of the block was for a blower idler??

Thanks,

Brain.

Tom Roberts also designed the block that you have--he was the in-house pattern maker for Arias-Root.

Over 3000 hp, I'd recommend some billet steel main caps. I see no reason why the A/R aluminum cylinder block couldn't support that much power as they were supporting more power than that over 20 years ago in Top Fuel drag racing. That said, I would also take the rotating assembly's 5-inch stroke into account (keep rpms down) and would think you need the strongest crankshaft available. Further, you should also take into consideration the duration of each pass of the vehicle (land speed racing). Based on our experiences, my guess is that with a twin turbo 665 you will have to detune, detune, detune in order to get your car's tires to hook up with that big powerful engine. Billy added 1000 pounds of ballast over the rear wheels of his car and he still had to remove a down nozzle from each cylinder before the car would hook with just a feather's touch on the throttle.

The features on the front of the block that you describe are for an optional accessory gear-drive system, usually set up for a mag drive or something like that (not a blower drive). It requires a special front cover and parts that total about $1500 last time I checked.

Paul

X2 what Paul said. I really don't see the need for the 5" stroke crankshaft. I would go with a much shorter stroke in order to reduce piston speed.
Charlie

Thanks for that guys...

We used to run an 11.2 deck with 4.5 stroke & 7.5 rods in the '34 in my avatar. Would that be a suitable starting point? Seemed a much nicer package than a 4.5 stroke in a 10.3 block with the pistons staying in the bores @ BDC. Might need to run a slightly shorter rod to allow a dished piston/space to move the ring pack down. As for RPMs my gut feeling is to try to keep below 7000, maybe even 6500 to keep a happy, reliable, valve train. This did start out as an N/A project, hence the original 665ci plans, but you know how these things get out of control...   


Brain.

This is the same block that I'm using in my twin turbo build.

Brain (Martin?),

I understand how the pistons look at BDC in the 385 Series crankcase with the big strokes, but there really is nothing to concern yourself with.  I really don't want to get involved in telling you how to build your engine, and since you already have the 11.2" block I suppose you could stick with that and your 4.5 stroke/7.5 rod combo...frankly I'd rather see you do that combo than a bigger engine.  You already have plenty of piston material for putting the rings pretty much wherever you want, and they won't protrude much at BDC with that 7.5 con rod and +0.900" tall deck. Keeping rpm's down below 7000 is a very good idea, assuming you will be doing the long-course racing I am thinking you will be.  It's really hard to make suggestions without knowing the actual racing format, engine rules, etc. Using your pre-existing engine parts might be cost effective; if money is not an issue then I might start with a standard deck height block and even less stroke (depending on the rules).

Even with your existing parts at 598 cubic inches I still think you're going to make more than enough power and chasing traction; land speed racing is the opposite of drag racing in so many respects.

Here's an example: I don't think it has run in recent years, but the Ford-powered streamliner below took home fastest car award in a couple of past events at Bonneville. It is claimed to also be the world's fastest Ford, at 337+ mph.



The above car ran a 10.3" deck A/R aluminum block (basically the standard deck version of the block you have), and has just 482 cubes displacement (4.625" bore x 3.59" stroke), TFS A460 heads, and ran 60% nitromethane.  The team was having tune-up issues (melting pistons) and I used to speak to the driver once in awhile when he was seeking advice about this. My point is that several miles (or kilos) is a long way to go under load and with forced induction such as turbos (or nitro, etc), and that--while not the automatic answer--even with this smallish engine the car still won fastest car at more than one event.

I am not familar with the venues in the UK, where are you gong to run the car? Also, what kind of car will it be, which class, top speed goal, engine rules, etc?

brain@fbracing wrote:Hi Guys,

Haven't been on here for quite a while! I'm now "retired" from drag racing but have got involved in a land speed project  

Looking at putting together a motor based around an 11.2 deck AR aluminium block. could be as big as 665ci but the car owner is looking at slapping a couple of turbos on it.....Question is, how much power can this block safely handle?  I have seen the Roberts design blocks being used upwards of 3000hp but I'm not sure on the (older?) AR block. were they designed for blown alky applications, as I've been told the big casting on the side of the block was for a blower idler??

Thanks,

Brain.

Hi Brian,

We have 4 of these blocks here on our tractor and they can handle a lot. Only had some issues with cracked aluminum main caps. We replaced the 2,3 and 4 for steel main caps. External oil pump and magdrive on the front work great

Don't know if you want to run water but these blocks are solid and have no water jackets.