302 block

94greenmile · Feb 18, 2008

I am interested in building a supercharged 2 bolt 302 with forged internals but was considering if the block would handle 450 rwhp. I am not going to be revving past 5900 and it will not be a track car but a daily driver with some power. I am leary about the block lasting. give me your opinions.

BlownFiveLiter · Feb 18, 2008

Aftermarket blocks start getting pretty pricey with the initial purchase price and machine work, but I'd feel safest going that route when pushing what many feel is the limit of the stock block. You can sometimes get lucky finding a good used A4 or R302 block that will put less of a dent in your budget. FWIW, the cast crank in the stock block will usually outlast the block in terms of durability, or ability to handle power.

PJC Racing · Feb 18, 2008

HP is not what kills stock blocks, RPM does. With the RPM you intend to spin, a stock block and a well balanced rotating assembly will be fine.

BlownFiveLiter · Feb 18, 2008

I disagree PJC, and in a big way. Power splits the block in half along the mains. Take a twig and bend it until it breaks. Now take a 2x4 and do the same. Can't do it? Not surprising. Sure they're not metal, but it's the same principle. The thin casting simply can not handle the power.

PJC Racing · Feb 18, 2008

There are plenty of +500 hp stock block engines out there that run without any problem, when the rotating assembly has been correctly balanced, the block machine work has been done with attention to detail, and the rpm range remains under 7K. Is 450 hp in stock block smart? Not necessarily. Is 450 hp a problem? No. 95% of the time when a factory block fails it is due to cap walk at high rpm or the machining was done incorrectly.

Edit: Now I just saw he is talking rear wheel horsepower, this would make over 500 at the bell. I say spending the cash on a aftermarket block would be smart.

But, I will still say that with proper machining, assembly, and 5900 rpm max. the block will hold together until he misses a shift.

BlownFiveLiter · Feb 18, 2008

Again, I still have to disagree. Cap walk isn't what breaks stock blocks. It may, or may not be a contributing factor, but the problem still lies in the thin casting of the block itself. If it were strictly a cap walk issue, a main girdle would essentially solve that problem with the added support they provide. The best a girdle will do is hold the halves together after you eclipse the max power level of the block, so you can hopefully salvage your rotating assembly, when you pony up the money for a good block. You can machine a stock block as much as you want, it still doesn't add material to the main webbing like is done in the aftermarket. A perfectly balanced rotating assembly with perfectly aligned mains is not going to make the block stronger.

blksn955.o · Feb 18, 2008

IMHO 450-500 hp you have a very small margin of error. People have made that power and had the block last a while. I do not think anyone can expect said motor to last 100k either.

Both the posters above are correct if you think about it. To get those power numbers with a stock 302 block you will be reving higher than the stock peak point. Add boost and lower the rpm and your still moving the stress to the pistion/rings/rods/ect...that all ends up putting more stress on the crank and mains...just as a faster rotating mass puts loads on those things so does more load at a lower rpm. Your talking about a load period and generally X hp of load is the breaking point that has been found...that X is around 5 hundo.

I know of local guys who had 420-ish rwhp boosted cars with stock longblocks and a gt40 intake and a good tune. Block was good and they ran 13-15lbs IIRC. It can be done but I would at least say start saving for when it wears out and do not be shocked if it ever does.

blksn955.o · Feb 18, 2008

putting a forged crank in a stock block is a waste if you ask me. Like said above the block will gen. fail before the crank. Although I have heard of superchargers putting stress on the crank snout causing a break at the #1 main due to the belt putting stress on that area.

Save the money on the forged crank for a better block.

PJC Racing · Feb 18, 2008

StangGT1995 said:
Again, I still have to disagree. Cap walk isn't what breaks stock blocks. It may, or may not be a contributing factor, but the problem still lies in the thin casting of the block itself. If it were strictly a cap walk issue, a main girdle would essentially solve that problem with the added support they provide. The best a girdle will do is hold the halves together after you eclipse the max power level of the block, so you can hopefully salvage your rotating assembly, when you pony up the money for a good block. You can machine a stock block as much as you want, it still doesn't add material to the main webbing like is done in the aftermarket. A perfectly balanced rotating assembly with perfectly aligned mains is not going to make the block stronger.

True, a main girdle will only hold it together when it fails. And true, balancing will not make the block strong (I never implied that). And if it were me I would be going aftermaket on the block for longevity.

But, IMO the stock block can and will handle this power level at this rpm. I agree to disagree

BlownFiveLiter · Feb 19, 2008

I'm not saying it won't handle it, but it's really pushing the limits. I don't want to start a pissing match any more than you do though, so I agree to disagree as well.

Jackie Chan · Feb 19, 2008

ive seen too many with that power level NOT fail. The ones that have failed have already been beat to hell or people were doing stupid crap

keep the revs down, put a nice topend on a stock s/b, tune it right and it will be fine for the most part with less than 450rwhp

94greenmile · Feb 19, 2008

Now the delimna begins. I am considering the aftermarket boss 302 block but if i go that route I will supercharge and stroke it to a 331. I am undecided about the block lasting because some have lasted and others have not. I appreciate the replies. decisions ! decisions! decisions!

96stangRC · Feb 19, 2008

Hard to really answer whether or not it will hold up. Some people have had them hold up for a long time and others aren't so lucky. The block may be able to handle 450rwhp, but as others said, theres very little margain for error. All it would take to split that block is some detonation or a severe over-rev. If you do plan to do this with a stock block, keep rpm's under 6,000, timing low, get a good fuel system (not 24lb injectors and an FMU), and a meth injection if it isn't intercooled. Meth injection is great because not only does it allow you to run slightly more overall timing (don't overdue it tho), it can also save you from detonating if you ever get a bad tank of gas.

PJC Racing · Feb 19, 2008

If your you are going to stroke it, don't stop at 331. There is no reason not to go 347 stroke.

Zero_chance · Feb 20, 2008

If you plan on dumping some serious power into it, Id still consider the block the weak point. Im all for doing things smart and cheap, but at those levels, Id be worried anytime I got on it. But I can see why a lot of people dont want to dump over a grand into a block because that takes money away from other things. It is good insurance though. Ill never have to worry about things like this because I can guarantee Ill never pay a huge sum of cash for a bare block. Then again I dont have plans for that much power so....

302 block

94greenmile

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BlownFiveLiter

have car, will race....wait, it doesn't run

PJC Racing

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BlownFiveLiter

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have car, will race....wait, it doesn't run

blksn955.o

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Jackie Chan

I didn't read this.

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