hey what would be maximum psi for a stock tpi 305 with the cast bottom end? Im looking into SC's for the future so I dont have to modify my engine. Any ideas? 9-12psi

 

from expirence i wouldn't go above 6 psi

 

6 psi thats like 40hp. Yeah umm, not worth the money.

12-15psi would be, from an intercooled procharger. Assuming a sledgehammer crank, h-beams, dished pistons and fastburn heads on a 383 stroker with 350 mains. How much. I'm looking towards the future I might be getting a real old Chevy

 

go away troll

 

hey i am allowed to ask, im getting a project so I keep my hands out of my baby. My 350 engine turned out to be a 305. So I am rebuilding it and making it run till I can afford a real engine.

Project= Chevy 2dr.

 

Oh and nightrider I dont troll these boards, I troll 3G0, a place that deserves it

 

Anyone whose can give a educated guess would be appreciated.
Just a psi range, I really dont know much about forced induction. I would like to learn. But its also slightly harder to learn than engines and transmissions. You really cant get learner's permit parts for free...

 

i dun like you enough

 

Some reading:

https://www.thirdgen.org/techbb2/sho...hreadid=217973

We put 12-13 psi into the stock 350 TPI for most of the summer. Fredrik has a very heavy right foot so it was many hard miles. We had no mechanical problems with the engine att all.

This was with Ethanol fuel ( E85 ).

We would have gone higher but the spark power was not strong enough so it would start to miss.

As long as you keep RPM down and keep the engine from spark knock it will survive a lot of boost.

 

There's so many variables, there is no universal answer. What might work on one well kept high mile SBC might blow up someone elses second hand abused high mile SBC. When you start changing the internals (as in it goes from a stock LB9 to a built 383) then again you change a bunch of variables.

Here's the way I see it: Its going to be a compromise between what you deem safe and what the motor likes. Most likely you will have to find the answer when the setup is already built. Look into methods people use to supress detonation (example, timing retard per psi boost, intercooling, higher octane fuel, injection of some sort). You'll need to try different setups and really pay attention to your sensors, most importantly the knock sensor and second the air/fuel (my opinion anyway). This is how you would find what the motor likes. Then you gotta take into account what you deem safe, which basically means how long do you want the engine to last (or how long do you think it will last). If its built with the right stuff (foarged internals, o-ring'd, etc) then yeah you can push it, but if its stock then you might be asking for trouble. Compromise between the two and you have your answer.

I picked 6psi for my Z28 because the L98 is a stock bottom end and I dont want to be rebuilding it anytime soon (50K on boost still going). I know the motor can take more boost but since I dont want to chance it I run low psi. If you had an intercooled setup and you know the motor is strong (or its a weekend toy you can afford to break) I dont see 12 psi being unreasonable.

 

i agree with that, i just assumed it would be a daily driver, cause thats what i do with my cars. I know when i'm ready with a built engine that i can just swap in after, i will just run like 25psi with methonal injection and a big fmic on my 305 until it goes boom.....but it doesn't quite sound like thats what you want to do..... so play it safe with 6psi or take a chance and go higher, its your car.....

 

As I already stated I am going to be getting my hands on a classic Chevy. This would be a daily driver. I have an old LG4 sitting in my garage(bare block). It has all the parts so I might just make it a running motor. I plan to use this car for my later years in college. It will be running Jamaica Queens so I wont be dropping much into it. Cheap motor, Junkyard tranny, some glass and thats about it. My Iroc has 37K on it, still a showroom car. So I was looking for what is safe for her. I dont want to take anything off the motor just add boltons I can remove. Thanks for the help.

 

MY friend runs a 16psi turbo on his stock 302 block in his mustang, he has little performance mods except the turbo and methanol injection, it seems to do pretty good, it dynoed at 500 RWHP. Of course, i've heard ppl say the ford 302 blocks are better than chevy 305 blocks.

Question: Are the blocks the same for the 305 motors? meaning, is my 305 block that I got from an 85 Z28 the same as a 305 motor from a truck?

 

Small block chevy’s are significantly stronger then 5.0 ford blocks. The crank and rods on the 305 are probably stronger also. Pistons depends on the year, early mustang HO 5.0’s got forged pistons, and late ones got hypereutectic (I think that there was a year or 2 of cast ones in the middle, and most of the 5.0’s got cast pistons when used in other vehicles), both of which are stronger then the cast ones used in most stock SBC’s.

16psi… I’m not sure I believe that…, not on a stock engine. Most 5.0 blocks and cranks get questionable around 500hp at the crank (the block has been lightened enough and the crank is not so rigid and the combination results in crank flex and eventually they split lengthwise down the block). Otherwise, the issue with running 16psi on either engine, the 5.0 or the 305 would be detonation control. Even with methanol/water I’d expect something has been changed to help control detonation, at the very least, larger chamber/aluminum heads.

 

No, he runs 16spi, oh, i forgot that he put in new 7.2:1 pistons. Everything else is stock, heads, cam. The intake is an after market one to allow more air flow from the turbo. He lifted his heads a few times so he had to get some ARP head bolts.

Intercooler, Methanol Injection, 7.2:1 pistons, huge *** turbo.

 

I bet that 302 has a main griddle too. Almost any ford 302 I've seen that makes some decent power has a main griddle. Thats like the only thing that hold a 302 together. Chevy small block are stronger than ford small blocks. 302's have less head bolts, so they have head lifting issues.

 

7.2:1 pistons… that’s something like a 25cc dish…

That makes things TOTALLY different and nowhere near the “stock engine” that this question is asking about.

And it’s still living on borrowed time putting out those kinds of power numbers.

 

Been there, done that (on an unmentionable brand of car, but it had a V8 ).

You can safely easily use 6 psi, you can go 8-9 if you keep a keen ear out for detonation. And don't worry, even a 6 psi setup will plant you in the seat....OK I'll mention this-I had a 6 psi Powerdyne on a '90 5.0. Car was stone stock except supercharger. The supercharger knocked right at a full second off my ET in the 1/4. 6 psi is typically worth around 75-80 hp. I use the rule of thumb of 12-15 hp per psi boost, assuming there is nothing nearby that really heats the air up.

Hope that helps! Now, can you help me with my post? https://www.thirdgen.org/techbb2/sho...hreadid=314196

 

That totaly depends on what your boosting. 1 lb of boost in a weed wacker engine is not going to give you an additional 12-15hp. If you want to quantify it per pound of boost I think 6-7% of your NA hp per pound would be a slightly conservative estimate. By the way Mcdamit, that works out to be a lot more then 40hp from 6psi on your stock 305...ever heard of a pressure ratio??

 

LOL true. I'm just taking into account the average V8 between 300-400 cu. in.

 

6 lbs of boost is way more than 40 hp, more like 80. ProCharger claims 100 hp off of 8 lb boost.

 

I run a 410sbc fully forged whit a procharger F1

I think its more of 30hp / psi !
But the engine itself play a big part...

Putting a blower on a 305 is just a waste of time... Get a 350 at less, they have plenty 350 outhere..

 

Boost doesn't make horsepower, airflow does.

6psi this, 6psi that. Give me a break.

The better question is: how much cylinder pressure, and thermal expansion can a stock 305 take. And noone here can answer that question with any sort of reliability.

-- Joe

 

"We put 12-13 psi into the stock 350 TPI for most of the summer. Fredrik has a very heavy right foot so it was many hard miles. We had no mechanical problems with the engine att all.

This was with Ethanol fuel ( E85 ).""


So...what did you change in the fuel system to allow the use of E85? That is a commodity in great quantity here in MN and is pretty cheap.

Did you change the o-rings in the fuel system? What about intake gaskets or fueling changes to the prom?

Thanks...

 

I wouldn't consider anything but a 350. And when she blows there will be more cubes in store

 

We had already installed larger injectors and a tuned the chip for that. We only changed the injector constant in the chip when converting to E85. When we increased boost the stock fuel pump maxed out so that was the next thing to change.

We did not change o-rings or any gaskets. When we later installed new fuel pumps (two Bosch) and had to buy new fuel hoses we used ethanol safe ones.

 

Thanks for replying Joby...

I read the other thread and I must say that the project is really cool...

I also read the tuning for E85 and was curious because from what I understood from what I had read, the amount of alcohol in E85 requires different o-rings and gaskets in the fuel system...I had read an article from a magazine a while ago where a guy converted a carbed GTO to run E-85 and it was stressed that the alcohol would eat the o-rings or gaskets over time.

Is this not the case for FI vehicles?

I would love to give it a try and see what happens but I am concerned about the longevity of the fuel system...

Thanks!

 

Yes, he is correct.

Another friend of mine works at a place that make and sell hydraulic hoses. We looked in their data books.

A 'standard' fuel hose had 5 for fuel and 3 for Ethanol on a 5 grade scale.
The hose will age quicker, but you probably won't notice anything for a few years. Same with o-rings on the injectors.

It is no need to replace everything right away to test ethanol. If you convert, try it for a while, and decide that you like it, Then you can replace the hoses and get other o-rings.