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Old 12-31-2012, 10:26 AM
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demolition derby engine

i am in the process of designing the perfect demolition derby engine for the sole purpose of demolition derby. so im not trying to build for tons of horsepower or torque. i have an idea in mind, just wanted to run it past you hot rodder and engine builders to get your input. the number one enemy in a derby engine is heat, so that is what im trying to eliminate. im starting with an 010 small block chevy 350. it will be bored .030, and the crank i will be using is a lightweight 3'' stroke crank. i will be using lightweight 6" rods with 350 type keith black flat top hypereutectic pistons. with the 350 type pistons that will keep the pistons down in the cylinder by about .18" which will lower my compression. i will be running dart iron eagle heads, but unsure to go with the 49cc heads or with like a 62cc. i want to get my compression around 5.5-6:1, and will i get more rpms from using an old school mechanical flat tappet similar used in the original 302, or a full roller with roller rockers? im looking for low compression, low heat, high rpm. i will get my torque from the gear ratio of 5.13:1. i want my motor to spin fast and be able to run without water if i should lose my radiator. any input would be greatly appreciated.

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Old 12-31-2012, 10:44 AM
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In a derby car revs are your worst enemy, revs create more heat. Derby cars need TORQUE, not horsepower. Second I would not run a 350 chevy, especially one that's still good. 350's we used to trip over at the junk yard. Now they're getting harder to find. I also would not use any performance pieces of any kind in a derby engine as they are subject to get ruined.
The derby engine of choice for us was a dead stock 305 with a 2 barrel.
If your 010 block is a 4 bolt block, roundy round racers will give you quite a nice sum for just the raw block alone. The 010 is their perferred block and they're getting hard to find.
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Old 12-31-2012, 10:56 AM
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it is a 4 bolt main 010 block. no stock stuff for me. im competeing in high dollar derbies, not county fair junk yard wars.
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Old 12-31-2012, 11:13 AM
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I would build a very loose 355/366 all with cheapo rebuilder parts,lots of ring gap.
posi/welded diff with a set of gears.
not sure what the rules are for cooling,if you know what I mean?
Im a big fan of Smokey Yunick when it comes to reading the rule book.
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Old 12-31-2012, 11:21 AM
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no rules on engine, can run whatever you want, only rule for cooling is that radiator must stay in stock location, ill be running 5.13:1 gears, full spool, slider driveshaft, th375 tranny, tranny cooler, engine protector, aluminum radiator, dual electric fans, it will be a 15,000$ derby car. just want input on heads and cam selection. my mind is already made up on the internals of the shortblock. it would be quite scary to hear a 5,000 lb car screaming across the track at you at 9000+ rpm....yea its going in a mint rust free 1976 olds 98
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Old 12-31-2012, 11:34 AM
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7,500 rpm is the limit with out spending a lot of money. I would use a premium cast iron head (dart). I would like to see (as tech would say)the verbage about the cooling system,lol. Again,think of Smokey Yunick and his fuel lines for roundie round cars.

Camshaft I would use with 5.13 and 305 cube destroked engine,,,something like this
111313-06S NA 279 279 247 247 .585 .585 106 102 .022 .022 1,2,5
3000-7200 Small Base Circle, fair idle, Street performance mild Oval Track use.
note the low ICL
This would only be if you were spending the money,,,lol..
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Old 12-31-2012, 12:11 PM
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yea i plan on spending the money, thats why im going with lightweight components. my crank is 1000$ alone. i will use dart iron eagle heads, but unsure to go with the 49CC combustion chamber since my pistons will be .18" from the top of the cylinder, or go with something around 62 or 64 cc. i want to be around 5-6:1 compression ratio.
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Old 12-31-2012, 12:33 PM
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If you really plan on turning 9k,you will need rocker shafts,titanium/ssss valves,carillo rods,callies crank,


9,ooo RPM puts you at 60MPH in low gear
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Old 12-31-2012, 12:37 PM
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what about ignition system? im assuming hei wont keep up with 9000rpm.
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Old 12-31-2012, 12:50 PM
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you will need the best digital crank fired MSD or better
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Old 12-31-2012, 09:44 PM
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demo derby

I hate to say this but you don't belong on this Hotrodders forum. Hotrodders preserve old cars, not destroy them like you guys do. I've seen some beautiful old cars destroyed by you guys, namely Imperials. Go back to your derby forums!
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Old 12-31-2012, 10:29 PM
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HMMMM does the rule book say you can only have one radiator? Or that "the" radiator must remain in the stock location and that you can only use that one to cool your engine lol. You could always put another one inside the car hehehe. Just joking around with you. We used to race a few different classes of local dirt track and I'm all about "rule book interpretation". We got an aluminum intake past the tech for a whole season by painting it and shaking metal shavings from the local brake lathe on each wet coat for 3-4 coats so the magnet would stick during tech time (rule book said "no all aluminum intakes, we will test with a magnet" key word being "ALL" aluminum). They never caught it til they pulled it one night lol. Kinda like "no gun drilled axles" didn't say we couldnt cross drill them. lol Good luck with the car and the crashing. Happy new year
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Old 12-31-2012, 11:41 PM
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High dollar derby cars...didn't know such a thing existed!

Not sure why you would need a high revving small block as anyone whose been around derby's knows it's big blocks and weight that wins those contests...concrete filled fenders and frame rails seemed to be the hot ticket back in the old days.

Anyways back to this issue, what you want is a sealed cooling system with high capacity that vents steam as a cooling method. No radiator is used just a large heat exchanger like a snowmobile uses under the foot boards, no coolant just water mixed with as much salt as it can dissolve...raises boiling point.

Traction always limited in these races so I doubt a high revving hotrod engine is going to net you anything, what is a good thing is installing narrower axles and offset wheels to make the wheelbase as narrow as possible to protect the tires with polyurethane foam sealant in the tires to keep them as inflated as possible and prevent losing a tire off the rim.

None of these mods are a secret, they are old school derby mods...the engine is the least important part of the package...and a screaming SBC coming at you isn't scaring anyone on the track.

A big block Imperial with 8000pds of concrete in the bumpers and frame rails and traction from a fully inflated set of tires however...thats something to fear.
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