4.1 guru build

[bmurany]

would greatly like to know if a 291 casting would hold up in a daily driver under 25lb of boost max. it would be bullit cap ,girdle,and block hard filled to the bottom of the soft plugs and forged bottom end. i have two block that are good.using pte 76.

 

[49-blues]

i would think so, im also going to build one., 3 front center caps, forged crank, good rods and forged pistons.

 

[johnplogii]

I thought those blocks were weaker than 109's? What heads? What cam? Boost is really only a measurement of the air that DOESN'T make it into the engine. I would not attempt it unless you are really on your game. A 252+ inch motor with good heads & properly selected cam with a 4276 at 25psi could easily make 1000+ horsepower. When it comes apart & you lose your steel crank, rod(s), piston(s) and possibly damage more you'll wish you would have started with a better block.

John

 

[bmurany]

build

doing all in threads. gn-1,stroker,400 turbo transbrake too. 22-25lb boost not all the time though.

 

[Dynalow00]

4.1 + 25psi

I'll let you know in a few months..:biggrin::biggrin::biggrin::biggrin: -Steve

 

[No Tie]

I have been beating my 4.1 for 3yrs at 22lbs.w/alc.on the street.Cheap build w/hypers
studds.stock crank&rods,ported heads,61 turbo. rjc fm ,60 inj. If it blows I WOULD build
another.

 

[Eticket]

I have been beating my 4.1 for 3yrs at 22lbs.w/alc.on the street.Cheap build w/hypers
studds.stock crank&rods,ported heads,61 turbo. rjc fm ,60 inj. If it blows I WOULD build
another.

He's going to be using a 76 turbo, not a 61 turbo. There's 300hp difference between the two at 25psi.

We're talking about a mid-high 9 sec car at those boost levels. Big waste of time if you ask me. Take it down to a 67 turbo and you'll probably be ok.

 

[boostingbuick]

I was making close to 600 rwhp with mine. Ran 130 in the quarter. Plus I have spoke with lots of builders who can't say the blocks are weaker. I have not seen an issue with them other than the crack I have in the deck from the head bolt to water jacket. Was there when I bought the block, and is still there. Never caused a leak or any other issue. I will not go back to a 3.8 unless I have no choice.

 

[DoWork]

I have been beating my 4.1 for 3yrs at 22lbs.w/alc.on the street.Cheap build w/hypers
studds.stock crank&rods,ported heads,61 turbo. rjc fm ,60 inj. If it blows I WOULD build
another.

What size turbo? what size pistons? you have captivated me....

 

[BOOSTBROTHER]

What size turbo? what size pistons? you have captivated me....

x2

 

[SHADOWII]

I say ....

go for it! It will prove the durability of the block, especially tested against the 76. The hardblock should help stabilize the the block, especially combined w/the caps and girdle. Just keep an eye on the operating temp. when using the h/blk. There has been some talk of the h/b separating and can cause a problem in the rad. damage the w/pump.etc. Might create a metal screen, brass, ss, etc. shaped like a top-hat w/a narrow brim to fit into the rad. hose neck and reach to the front side of the rad. so it can be inserted w/o interferring w/ the water flow and pulled out for inspection and cleaning at intervals.

 

[87GN_70GS]

I would consider a lifter valley girdle since the lv is open and not closed off like the 3.8

 

[bmurany]

thanks for all your help so far

As far as block hard, I have run it in SBC for several seasons before. I don't get my motor hot though. Lifter girdle might be much. I will be epoxying and screening the valley. 22psi is every once in awhile more like 17 psi. It makes you think with machine work and parts, it might be cheaper to do a stage 2........