Hi.

is there any safe limit when boosting a 0.30 bore 350 Gm block? It have been procharged at 10-12psi without problems but i´m hoping to see 20-25psi with twin turbo! hopefully it will be allright!
9.0:1 CR twin Holset HX50.

Anyone tried high boost before?

/Svante.

 

What main caps do you have?

 

Just look at Marty's setup..it speaks for itself

https://www.theturboforums.com/smf/index.php?topic=61219.0

 

Svante,

It not about boost, it is about hp.
An early 010 SBC, with a short fill and 3 steel center caps.
With the above you are good for about 900 ish HP.
Main Cap walk will be the thing to watch for.

 

Well it produced about 900 at the flywheel with the blower@38degrees timing with E85. I still use the standard mains. The goal is to reach 1200hp with twin Holset HX50. I will just try if the mains are holding up, when the plan is to build on a Dart block next year, and i don´t want to tear it down just to machine for new main caps on a old block!

/Svante.

 

I was gonna suggest the same thing look at Matry's build up he has over 77 pages of his antics.

 

Twin HX50's on a 350. Id think there would be a little lag there.

What do you spin this thing to.

where do you want boost to come on at , etc..
Id think 1 modified S400 would do the trick better.

 

Although you have more cubic inches than I do, I have quite a bit of lag already with one HX50 on a 318. To cut down the lag, I put a plate between the exhaust flange to block off half of the turbine housing (is twin scroll). If you run twin HX50's, I think you'll have too much lag. Why not use just 1? I had it on a 360 at first and it spooled to 15 psi by about 3500 rpm and then I let go (I didn't have it wastegated at that time). It would easily have spooled higher. I think a HX50 is capable of around 950 HP.

 

I ran a 87 one peace rear seal 2 bolt mail 350 with the
stock cast crank @ 20psi for about 3 years.

9.90's @ 3850 lb's on pump spraying washer fluid.

 

Nice times! Them blocks are better than people think. And WE are out to prove it!

 

each motor is different .. all depends on how well it was built and the tune.. and there is only one way to find out .. and thats to just turn it up a lil at a time.

 

I honestly can't recall ever seeing a factory GM smallblock failing due to high horsepower. I am sure it happens but I have never seen it. The main caps usually walk before the block goes.

 

Sure they never fail.....
Try harder!
Please notice the easy access cam bearings.


#ad

 

Oh shit...

So now I have seen a sbc fail. Damn thing ripped the mains right out!

Dude, how did that happen??

 

Well, you can find stock block SBC's of all types any weekend running 9's all over the county
in cars from 4000lbs-2500lbs.

Dirt track motors take way more abuse than dragrace motors of the same power level
and the thousands of these makeing 700+ HP every weekend.

 

failure to the gm blocks is due to detonation, bad tuning, etc., wrong crank clearances, bad mech workmanship....wrong turbo selection, etc..etc. put tall diff gears in, keep rpm down... under round 7000
i had twin t3/t04E's 57trim ,on 355 sbc, scat 4340 3.48 crank, eagle h beams speed pro pistons,je pins , 1000+ hp and 1000 ft/lb , injected meth
now updated to twin gtk's , 32.5 psi, run extra 6 mph over 1/4 mile
run it little fatter on a/f ,more boost, make more torque, cooler egt's, faster she go's...
355 sbc , stock 882 chev heads, 1.5ex 1.94 in, flat tappet cam, .5 total lift, locked 26 deg timing
7.4 @ 184

 

GM blocks are tough.

 

400 blocks are definitely weaker since the bigger bore undermines the main webbing more than a 4 inch bore does. Its so weird how people claim the main caps walk and stock blocks will show weird main bearing wear patterns but i took a 2 bolt unprepped pile of crap and am close to 1000 hp with no block failures yet. I have inspected the bearings recently and it all checked out ok except the main caps had fretted the block a slight amount from some pinging on pump gas and crappy stock main bolts only torqued 75 ft.lbs.
I wanna see pix of a 4 inch bore early block thats broke to hell since thats a whole different deal than a 4.125 bore block or even a 80's thin wall cast 4 inch bore block IMO.

 

here... stock block getting a flogging..
run them little fatter on a/f ratio, and you'll be surprised how long they last

update///
stock block goes 7.2 @ 190 mph...

 

Go For it! I am. I am running even the stock cam in my motor....Gonna see what it does before any upgrades....


If it aint broke.....trying to fix it may not make any more power but it sure will cost ya alot of money for sure. I would rather try to make power and break it than spend alot of money and then worry about all that money and not end up making any more power....If my motor pops the only thing that sucks is the labor of pulling and replacing it....

Hey I spent alot of time degreasing my engine....I dont want to have to do another one real soon.....


I have iron 882 heads as well. I am going to keep upgrading parts as I go but I never intend to replace the crank or block untill it gives me a reason too. I have built some expensive engines in the past and never used them to their potential....Its about time to see if there was a reason to ever build a expensive engine....(406 Pontiac with aluminum heads etc.) And prior small blocks with steel cranks and good rods & pistons etc....


My next upgrade for my engine is the Main girdle kit with studs in the bottom end better rods and pistons and a better cam. then I might try to find a better casting head less prone to cracking than the 882's