Although I already have custom pistons and steel rods for my 482 race motor, I am wanting to use a set of alloy rods. From what I have read, the minimum piston to head clearance should be about 0.060". The pistons I have are set up for 0.001" deck height. Could I use these pistons with the aluminium rods and gain the piston to head clearance with a 0.060" thick head gasket? With this much clearance, the motor will still be 13 to 1 compression, would a set of Cometic gaskets be okay with that compression? Thanks.

personally don't see the need for a aluminium rod unless you plan on spinning your motor past 8000 RPM. Compensating for rod stretch with a thicker head gasket will likely work, but also seems counter productive. The Cometic is fine for that and more compression.

More info on the rest of the motor and intened usage will get plenty of suggestions. Since you all ready have the parts, why not run them ??

A set of CNC ported Blue Thunder High Riser heads, forged 4.25" stroke crank from Barry R., Diamond custom pistons that will give 13.5 to 1 comp with a 0.040" head gasket, T&D rockers, tunnel wedge intake with a pair of modified 660 centre squirters, a solid roller cam yet to be determined ( will pick that once I have the heads flowed), all wrapped up in a Pond aluminium block. This is going into a Thunderbolt clone race car, backed by a Jerico 4 speed and a 4.86 geared 4 link rear end.

From the computer dyno programs I have used, it shows hp may peak around the 7000-7300rpm mark. I don't plan on reving past 8000rpm, but will probably go through the traps at about 7500rpm. I may end up using the steel rods I already have. However, if I was to use aluminium rods, I would rather build the motor that way now, save on having it re- balanced in the future. But if I have to gain piston to head clearance with a new set of pistons, then I will just use the parts I have already got, to get the car going and competing.

That would be a simpler way to increase the piston to deck clearance.

I'm with Dale though, a set of 9500 RPM rods probably won't make a difference in a 7500 RPM motor. Sure you can argue that it will rev a bit quicker but lowering the compression it would also have less power. Seems like it would be a wash.



1912 Model T Ford touring Salmon (ugh!)
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1967 Cougar GT 390 Cardinal Red / Black
1968 Cougar GTE 427 Augusta Green / Saddle
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One thing to consider, rebalancing to use steel rods after balancing to aluminum rods might involve lots of mallory metal which can get expensive, RWJ

and a 4 gear as well. Too Cool! At that RPM, I'd still stick with the steel rod, but Royce had the right idea about moving the pin height to get your deck clearance if you do decide on Aluminum.

You could also run into pan rail or other clearance issues with the bigger aluminum rod and that stroke, but I'm sure others here have run that setup, so my advice is worth little. Post some pictures !!

stick with your steel rods. Unless your spinning that engine to the moon the aluminum rods will offer only a little benefit in lower reciprating weight.

Dave Walters
427 Galaxie Registry
Website
http://home.ptd.net/~pwalters

I worked with Jack Roush /Wayne Gapp and their other three emploees, at what was known as Gapp&Roush...(actually, 1972, when the Muscle Parts program closing put me out of work !!) I helped Jack sell engines and parts, anyway, Jack sold/leased lots of Pro-Stock engines, all with BME rods,, his answer was....TWO FACTS OF ENGINE LIFE....a steel rod will spin a brg./bust the rod/come thru the block...and this will happen in millisrconds....an aluminum rod will get hot/expand the bearing end / and at the most will tap the head.... since a good race program include head removal and inspection, the contact was always visible, and deck height was monitered....you dont have that luxury with a steel rod....JMHO JOHN V

I have the same set up but went with the 4.28 bore on the pond block, single 4 manifold though. I at first was going to use aluminum rods, but decided not to since I was not going over 8200 RPM, the difference in HP will not show up on the dyno but I have been told it will accelerate faster. My question is why you would keep the rpm's down so low and go with the high riser head? They flow almost 405 and at your CI would have a RPM choke point of almost 8800 RPM. My computer says with 14.5 comp and those heads at 482 CI it should produce 925 HP at 8600 RPM. If you are spinning it only to low 7000 'S, it is not an optiminzed combination. May be better off with BT medium risers and keep the velocity higher to produce a better average HP number. Some might say otherwise, but on this build of mine that just started I did 3 months of research before I made my decisions. Back to the original question, I talked to BME a few weeks ago, they shelf stock rods that are .020 under sized, any thing else they need a few weeks to make but will do it for the same price.

Hey there todd i guess that might be you coz of the toddzc login, in case its not i wont go on anymore

from Perth.

Mate its greames brother from windsor engineering, greame had mentioned your new project in passing sometime ago, it sounds awsome, how far have you got with it, any pics to post.

Wayne

G'day Wayne,
Car is in the chassis shop at the moment, having the cage and fittings installed. Have most of the motor parts, but won't start building until the body is finished. I will do a full build up of the car before it goes for final paint. When final paint goes on, the engine will be built. It's slow going as work and family commitments are taking priority, but would like to run the car at the Nostalgia meet in 2010.

You can order the rod .010 to .020 short or you can use a thicker head gasket. I like to have about a total of .040 quench area so Im would order the rod about .020 shorter which is pretty common on the aluminum rods. GRP which we handle would be glad to do us some that way for you. Good luck, Keith Craft

As for my 7500 rpm limit, at this stage I am purely going on a guess of what my heads and intake will flow. The intake needs to be ported, but if I can get both intake and heads to support over 400cfm flow, then I will choose a cam that will use the flow. If the potential hp will peak near or over 8000rpm, then I will use aluminium rods.



Sounds like the undersized rods might be the way to go. When it comes time to order, I will be in touch with you Keith.



How much would a set of 6.7" (or 6.680") aluminium rods expand with an oil temp of around 200F? As I mentioned above, my pistons have a deck clearance height of 0.001" with a 6.7" rod. So if I use a 0.020" undersize aluminium rod with a 0.039" head gasket, once the engine is warm, will I have close to 0.040" quench height?