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Discussion Starter #1
Ok guys I need some help with my next race truck motor build. I don't drag race like most of you do. I run 150ft side by side mud drags. Now with that said I'm needing to build a motor that will make 800hp and pull 15 inch of vacuum.

So here are the rules for the class I'm running.
500 cubic inches limit
cast heads
single carb.
no nitrous or anything like that
motor must pull 15 inches of vacuum
must be factory chevy block

That's where I stand with the motor part of the rules. The rest of the rules are more about the truck and tires.

Now I'm stuck between a 421/427 sbc or 496 bbc. I am new to building gas motors. always played with diesels still I started racing mud trucks. So I'm here asking for some help.
 

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First post, you better go the the newb thread and introduce yourself before some of the guys crucify you for this.
 

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Definitely go to a 496cid engine. will be much easier to reach your goal of 800HP. Also playing in the mud you will need a lot of torque. When you say cast head are you restricted to Iron or you can use Aluminium heads?
 

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i would think cast would be iron heads?? if so i hope your class will let you use a set of after market iron heads ? the engines i built for some class.s will let you use a after market head . could be built with a stock iron head like a 990 but alot less time and money to buy a iron head with a better ex port
 

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Discussion Starter #7
Iron heads is the only thing we can run. I can run a aftermarket head. But I would like to keep it close to stock looking as I can. Some places are a little picky about the head stuff. I was thinking a big block was the way to go. What size heads would I need to run to get the hp I'm looking for.
 

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Wheel speed is king. Big bore short stroke would be the combo. Are you allowed a GM "Bowtie block" or only passenger car blocks? Bowtie is a "factory block"
Used to use Merlin iron heads on 572 pump gas marine engines and make 770 HP.
If no Bowtie then you will be stuck with 4.250 stroke to get the 500 inches in a tall deck truck block, if you can even find them anymore.
 

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yes wheel speed is king i done a few but the 496 is as big as he going to go with a stock mark 4 block and has a limit at 500 CID so really no need to go to a 4.3/8 crank done many of them but that puts him over 510. like you said he is stuck with the small bore at 4.310 to 4.320 if he could go bow tie GM then the 4.600 bore 3.760 crank with the old RHS 360 iron heads would be what i would build . if he has the money . old 10.200 truck blocks are not to hard to find. just did one to 540 but that block will not offer any more bore size then a mark 4 9.800 deck Gm stock block less you fine a rare thick wall 10.200 truck /marine. way before bow tie
 

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Discussion Starter #10
I may be able to get away with a GM Bowtie block. I'm going to make a few calls around tonight and make sure. I have a 72 545 block from a 72 Chevy c20 truck. It's already been bored .30 over to build a 496. And it was free. Kinda saves me some money. But I have around 6,500 just for parts. And maybe 4,000$ more for other things. I built my 415 last year and its still holding up. So I was hopping I can build this one to save me some money on that end.

My biggest thing is heads. I still don't where to start with them. We only have a few shops where I
from. But they can't understand what I'm trying to do. All of them tell me to just go 632 and be done. More or less they just want to build me a motor for around 15,000 and say here hope it works.
 

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I may be able to get away with a GM Bowtie block. I'm going to make a few calls around tonight and make sure. I have a 72 545 block from a 72 Chevy c20 truck. It's already been bored .30 over to build a 496. And it was free. Kinda saves me some money. But I have around 6,500 just for parts. And maybe 4,000$ more for other things. I built my 415 last year and its still holding up. So I was hopping I can build this one to save me some money on that end.

My biggest thing is heads. I still don't where to start with them. We only have a few shops where I
from. But they can't understand what I'm trying to do. All of them tell me to just go 632 and be done. More or less they just want to build me a motor for around 15,000 and say here hope it works.
well you need to find out if using a dart or world or RHS iron head is going to be fine if so then that.s the way i would go your builder may want one or another brand to work with .i built engines like this for racing like what you do. i know how i would build it . but i am not going to post every thing on hear :) i have a machine shop were i build mostly BBC and a dealer for many parts and direct on many part.s . i know i could build you a engine for your budget
 

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I would use a Bowtie Block,Merlin iron 345's,14-1 compression or higher,custom ground cam spec'd by Uratchko or someone like him and a 1400+cfm dom on a single carb topped Pro-Ram.
 

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Discussion Starter #13
I can not use a Bowtie block. so it looks like I'm stuck with my 72 block. I can use a aftermarket head. But I'm going to have to sand the names off them.
 

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Well then you are stuck with the 4.250 stroke combination. It will work but not quite as well as the aforementioned 3.750 deal. Same heads though, or comparable. Scribe the chambers to the bore you are going to use, put in a 2.325 intake valve, at least 14 compression, and set up the valve train to turn at least 76-7800.
You should go for steel caps on at least the 3 center mains, and if the rules allow a dry sump also.
Check with champion racing heads in Florida, they used to do a lot of iron head stuff for boats and they may have some old stock of heads.
The Boggs RFD Heads, guy on here does some truck stuff, he may have something that could work also.
 

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Discussion Starter #15
Thanks for the help everyone. I will post pics in a month to show what I have came up with. Mine prob won't be as clean and nice looking as y'all's. it's hard to keep one clean when playing in the mud.
 
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