What is it about modding a stock block that gives out?

[StreetDreamsGT]

I was sitting trying to decide wether to try and supercharge my car or wait to save up and beef up the block, then I realized, I didn't know what exactly I had to worry about. I've heard people talk about splitting their blocks and all but i've also heard people talk about needing to have a block with good internals. I figure the internals are most likely to give out before the block, but I wanna know exactly what I should worry about when I supercharge my car. I don't have the money to go replacing things once I toss on the sc so what exactly would I have to look forward to if worst came to worse and the sc plus h/c/i was too much for it? Should I save up for a rebuild kit before I go and sink money into aftermarket mods?

 

[85_SS_302_Coupe]

One of the biggest causes is the mains giving out since they're only 2 bolt mains. Doesnt matter if you've got the best internals in the world, if the block can't hold them while they're doing their thing, it'll give out. That's why the performance blocks you see like the Dart blocks and Ford's R302 block have 4 bolt mains. When you're talking about making big HP, the block is THE most important part of any performance engine's ability to make and withstand high HP.

 

[willys1]

How many miles on it?If its a 92 or earlier throw some boost on it(super-charge)The block will be fine.10 pounds of boost should give you a chubby Youll need a bigger fuel pump,injectors,maf,TB,adjustable F.P.R.up grade your ign. system and getting a dyno tune would be a good choice!!THEN,,sub frame connectors,DR's,U & L controll arms.What kind of tranny?Mite wanna beef up your rear,because 10 pounds of boost is gonna give you some nice HP

 

[Daggar]

What he said, I'll add to just a little. Newer trick dual turbo (and the like) systems aside... If you take a stock 302 block and build with good components including beefing up the bottom end with half inch bolts or girdle or both and intend to run it on the street on nothing other than pump gas then I think you'll find that in most cases the stock blocks are adequate. When you start talking about ridiculous boost pressures and outrageous compression ratios and HP output topping more than 500 Hp then you're pretty much waving bye bye to streetability anyhow. That's not to say that there aren't streetable engines out there worth more than 500 FWHP but they're way out of range of your typical shade tree mechanic and the cost of those components can easily get to the point where you're spending lots of dough on just a relatively small amount of gain. Back in the real world... 500 FWHP is more than I've seen ANY Stang able to effeciently put down to the pavement. Concentrate instead on bringing the rest of the car up the point where it can well handle the Hp it's putting out (I.E. suspension, body strengthening etc.) and you'll see a much better return in performance than you will with a thousand Hp on a stock chasis.

 

[StreetDreamsGT]

One of the biggest causes is the mains giving out since they're only 2 bolt mains. Doesnt matter if you've got the best internals in the world, if the block can't hold them while they're doing their thing, it'll give out. That's why the performance blocks you see like the Dart blocks and Ford's R302 block have 4 bolt mains. When you're talking about making big HP, the block is THE most important part of any performance engine's ability to make and withstand high HP.

I'm only planning on tossing on 9 psi of boost and maybe cobra, ported of course, or better intake possibly porting the stock heads(gt 40s or so if i can find a good price) and a good cam to have it all work good (only doin the h/c/i so the blower could be put to good use) I wouldn't think that'd give me too many ponies to split the block, would it?

How many miles on it?If its a 92 or earlier throw some boost on it(super-charge)The block will be fine.10 pounds of boost should give you a chubby Youll need a bigger fuel pump,injectors,maf,TB,adjustable F.P.R.up grade your ign. system and getting a dyno tune would be a good choice!!THEN,,sub frame connectors,DR's,U & L controll arms.What kind of tranny?Mite wanna beef up your rear,because 10 pounds of boost is gonna give you some nice HP.

124,000 and it's a 90. I'm just worried about starting to sink money into the engine to have it come back and bite me. I'm not planning on beating too hard on the car it's my daily driver.

 

[5spd GT]

124,000 and it's a 90. I'm just worried about starting to sink money into the engine to have it come back and bite me. I'm not planning on beating too hard on the car it's my daily driver.

I would rebuild the engine (a compression check will help you know if you really need one or not)...but alls it takes is a crankshaft to start walking or the equivalent and its over...

You can get rebuild kit with everything for the bottom-end (besides the crankshaft - you can have that undercut .010) from Summit Racing...the forged piston kit is around $400 and the hyper-kit is $280 or so...hypers can take a pretty good hit of boost (its all in the tune)...they aren't as bad as perceived...but you have forged anyways...so replace it with forged though they don't seal as tight as hypers...due to heat tolerances...

If that is only daily driver that can be somewhat dangerous...I'm nervous with my h/c/i setup...and with a blower I'd be "freakin" out...

Good Luck

 

[StreetDreamsGT]

Concentrate instead on bringing the rest of the car up the point where it can well handle the Hp it's putting out (I.E. suspension, body strengthening etc.) and you'll see a much better return in performance than you will with a thousand Hp on a stock chasis.

Precisely the reason I wanted to just supercharge it, I figure toss on a small sc to get a little boost, port the heads, maybe a new intake, a nice cam, TB, and be done with the major power mods. Take care of all the other systems, fuel, tranny, suspension, etc.

You can get rebuild kit with everything for the bottom-end (besides the crankshaft - you can have that undercut .010) from Summit Racing...the forged piston kit is around $400 and the hyper-kit is $280 or so...hypers can take a pretty good hit of boost (its all in the tune)...they aren't as bad as perceived...but you have forged anyways...so replace it with forged though they don't seal as tight as hypers...due to heat tolerances...

If that is only daily driver that can be somewhat dangerous...I'm nervous with my h/c/i setup...and with a blower I'd be "freakin" out...

If i'm tossin on boost shouldn't I just go with the hyper kit then? Or are the forged ones guarenteed to withstand it better?

 

[Copperstang87]

Definetly forged pistons over hyper especially if u wanna run boost.

 

[68stangman]

Most that I've talked to say if you run boost, your bottom end should be forged.

 

[Rick 91GT]

The weakest part on the stock block and assembly is the 5/16" rod bolts, they will break long before the crank, or stock block.

Having the 2 bolt mains isn't the main reason it is weak, 4 bolt mains on that block would would help with crank walk which could lead to a block failure. The main webbing is very thin, along with the entire block casting this is why they split up the middle.

I'm with Dagger if your only planning on 500HP or less (which it seams you are) then you will be fine with a stock block, just make sure the rest of the parts are up to par and you would live a long life.

Running a crank support of some sort (they are different depending on what blower you go with) will help take the pressure that a blower puts on the snout of the crank, especially when you start cranking down the belt tension like you are not supposed to do but everyone with a serpetine belt does to help with belt slippage.

If you are planning on boost a forged piston is much more forgiving if the tune gets greedy, the hypers would work but they do not take abuse. You can get stock replacement size rod from SCAT that comes with ARP fasteners for a little more then it would cost you to have the stock rods resized and bolt added, and the SCAT cast rod is a nice piece. I've built a few motors using the Summit kit and it isn't that bad if you want a basic rebuild with nothing special.

 

[TT91]

Most that I've talked to say if you run boost, your bottom end should be forged.

Stock internals will hold more power then the stock block when it comes to boost, forged or not. A ****ty tune will destroy your investment, forged or not. The stock blocks being to crack atthe main webbing where the crank sits and goes upwards to the lifter valley.A main girdle does not but keep the crank held together, or somewhat held together when the block blows. SEE BELOW

 

[StreetDreamsGT]

so anybody got suggestions as to which rebuild kit I should get?

Rick, you seem to know a lot about blocks, what all would you suggest I do before boosting it?

 

[TT91]

youll be fine with 9-10pis and keeping its under 470ish rwhp. The stock internals will hold that for quite sometime. If you want to upgrade your stock internals then ur wasting your time unless u plan on upgrading the block along with it, or sometime down the road. Of course with boost your going to need all the supporting features, like more fuel, better airflow, ect ect. Simply slapping a SC on a stock application with net you 350hp if your happy with that. Some preventative maintenance would be to do a compression test on your cylinders, inspect all your seals, make sure its in a good overall working condition before adding hp.

 

[StreetDreamsGT]

Yea I kno I've gotta worry about fuel and all the other stuff. Getting mild h/c/i combo wouldn't push me too far past the 350 right? maybe 400? say ported cobra ported stock heads and a cam to wrap it all up?

 

[5spd GT]

Yea I kno I've gotta worry about fuel and all the other stuff. Getting mild h/c/i combo wouldn't push me too far past the 350 right? maybe 400? say ported cobra ported stock heads and a cam to wrap it all up?

A mild h/c/i setup (by itself) will give you about 325-330bhp (280rwhp)...and when you put on a supercharger you'll be looking at 400+rwhp...of course all depending on what kind of boost you run...

Go forged for sure...I was just stating that the hypers aren't as bad as people say...

 

[CManT1914]

I've been asking about supercharging lately too, and this is what I've come up with. Basically, on a stock motor, as long as it is in good condition, can EASILY handle 6 lbs of boost. Most people run 9 with no problems. There's even a few that run 12 lbs with no problems yet. But the most important thing about supercharging is the tune! It doesn't matter how much boost you're running, if you don't get it tuned, and I mean good, it's gonna crap out on you. Also, you need to make sure you're getting enough fuel to go with all that air. For example, you'll need to upgrade your fuel pump and injectors, also the MAF, throttle body, and maybe the ignition, although the stock ignition is pretty good. That's what I've learned lately about supercharging. Hope this helps some.

BTW: If you're looking for prices, check superchargersonline.com, they have the CHEAPEST prices I have EVER seen!

 

[tjm73]

One of the biggest causes is the mains giving out since they're only 2 bolt mains. .......

This is not correct. Not entirely anyway. The 2 bolt mains isn't the problem. There are 2 bolt main blocks that take A LOT of power.

A stock 302 roller cam block has an design that saves weight by reducing the amount and compostion of material in the main journals. They are thinner in cross section compared to older designed blocks. The blocks also have less nickel in their chemical composition. These are the 2 biggest reasons the blocks are considered "weak" from a design stand point.

The reason high performance blocks have 4 bolt mains is to better control "crank walk" which is an action that leads to cracking and spliting of blocks which is what happens when a 302 production block splits. The 2 bolt mains aren't up to the task of controlling the crank because their isn't enough material where it needs to be to stay together.

So it's not the 2 bolt mains that are the sole problem. Block material and construction are also major factors in block strength.

If you research aftermarket and FRPP blocks you will see they are heavier than stock. The extra weight is more nickel in the forging process and more "meat" in the mains. Then they add 4 bolt main caps to capitalize on the improvements.

450-600 rwhp is the common area that production blocks start cracking and spliting. Power adders add tremendous stresses to the engine so the threshold is lower with them. Sustained high RPM is also a block killer, but the quality of the engine build up has a significant impact on the blocks longevity. A long article could be written on this topic, but those are some of the basics.

 

[85_SS_302_Coupe]

This is not correct. Not entirely anyway. The 2 bolt mains isn't the problem. There are 2 bolt main blocks that take A LOT of power.

A stock 302 roller cam block has an design that saves weight by reducing the amount and compostion of material in the main journals. They are thinner in cross section compared to older designed blocks. The blocks also have less nickel in their chemical composition. These are the 2 biggest reasons the blocks are considered "weak" from a design stand point.

The reason high performance blocks have 4 bolt mains is to better control "crank walk" which is an action that leads to cracking and spliting of blocks which is what happens when a 302 production block splits. The 2 bolt mains aren't up to the task of controlling the crank because their isn't enough material where it needs to be to stay together.

So it's not the 2 bolt mains that are the sole problem. Block material and construction are also major factors in block strength.

If you research aftermarket and FRPP blocks you will see they are heavier than stock. The extra weight is more nickel in the forging process and more "meat" in the mains. Then they add 4 bolt main caps to capitalize on the improvements.

450-600 rwhp is the common area that production blocks start cracking and spliting. Power adders add tremendous stresses to the engine so the threshold is lower with them. Sustained high RPM is also a block killer, but the quality of the engine build up has a significant impact on the blocks longevity. A long article could be written on this topic, but those are some of the basics.

Yea as soon as Rick 91GT pasted i started thinking about main webbings and the stock rods. Can't be right all the time

 

[StreetDreamsGT]

Just got the new MM&FF mag in 2day got a nice big article on superchargers, gonna be readin up on this.

 

[Daggar]

Just got the new MM&FF mag in 2day got a nice big article on superchargers, gonna be readin up on this.

As you're reading that article, keep in mind that the Kenne Bell is not a Roots supercharger (they kind of elude to that but don't say it directly). It's a twin screw and is much more efficient than your typical roots/Eaton type super chargers.