How much power?

[Chris]

The other thing you have to be wary of is engine builder and dyno operator adjustments on dyno testing. The term "corrected horsepower" can sometimes tell the whole story. RMBuilder (Bob Madara) has done some writing before on this topic. I have seen myself some correction factors that pushed the numbers on a dyno test far beyond reality. Sometimes it's due to an engine builder pushing his own numbers upward to make things look better, sometimes it's a dyno operator looking to make a customer feel better about their dyno session and the cost.

In addition, a max number on a dyno sheet doesn't come close to telling the whole story. Boats need big, fat midrange torque curves. Lots and lots of times, guys with lower horsepower engines win races. Simply because they're out-accelerating the guys with the big numbers.

[phragle]

SMP you can never have enough

[Tomas Wallin]

The other thing you have to be wary of is engine builder and dyno operator adjustments on dyno testing. The term "corrected horsepower" can sometimes tell the whole story. RMBuilder (Bob Madara) has done some writing before on this topic. I have seen myself some correction factors that pushed the numbers on a dyno test far beyond reality. Sometimes it's due to an engine builder pushing his own numbers upward to make things look better, sometimes it's a dyno operator looking to make a customer feel better about their dyno session and the cost.

In addition, a max number on a dyno sheet doesn't come close to telling the whole story. Boats need big, fat midrange torque curves. Lots and lots of times, guys with lower horsepower engines win races. Simply because they're out-accelerating the guys with the big numbers.

Yes of course! the dyno that I dynoed on is supposed to be one of the more accurate ones around, but you never know I suppose. That's why I posted the dyno sheets.

I wouldn't mind having a few more foot-pounds either, it's not the HP I'm after really - just the ability to go faster

[Chris]

It's actually not the dyno, it's the operator. The "correction factors" are an area that sometimes are fudged. Raw data is "adjusted" for external conditions- air density, etc.

On your engines, I can't help but believe that a set of good aluminum heads would give you more on top and fatten up the middle nicely. Blowers compensate for alot of sins with heads, but there are limits.

[Chris]

This is an excellent tool for analyzing different head attributes.

http://users.erols.com/srweiss/tablehdc.htm#BBChevy

The things to look for beyond port CC's are-

-How well do they flow at partial lift?

-How does the relationship between volume and flow velocity look?

-What is the intake/exhaust ratio?

On a blower, you need more exhaust flow relative to intake flow. Forced induction increases charge density- a port will flow the same at atmospheric pressure as it will at atm+ so you get more fuel/air regardless of flow characteristics. So, you need higher exhaust flow. The blower won't have any effect on gases exiting from the engine.

Take a look at the AFR 315CNC head- relative to flow vs. velocity and int/exh ratios. This head works amazingly well on a motor like yours- looking at its capabilities on this chart relative to others is a good clue as to why.

[Tomas Wallin]

It's actually not the dyno, it's the operator. The "correction factors" are an area that sometimes are fudged. Raw data is "adjusted" for external conditions- air density, etc.

On your engines, I can't help but believe that a set of good aluminum heads would give you more on top and fatten up the middle nicely. Blowers compensate for alot of sins with heads, but there are limits.

That's what I meant

Alu heads would definately make things alot easier, but in my case it's all about optimizing what I've already got.

[Mrhorsepower1]

900 hp on Iron heads?

Frank I have built 468's SC with GM heads ported that make 850 HP and a 540 Merlin headed package that makes 975 HP.

[Mrhorsepower1]

Thge head bolt is in the way on the exhaust- there's just not enough material to open them up enough to flow the kind of flows you'd need to make those sort of numbers. The exhaust ports are raised on all the aluminum heads- to lessen the effect of that hard bend on flow.

And the iron head doesn't have near the thermal efficiency- which leads to detonation. That should be worth 75+ hp.

My guess is Dean was referencing how much HP the bottom end would handle.

Yes Chris , I was answering Thomas's question. How much power would the rotating kit would handle safely.

[AGITATOR]

yes on pump gas 93 with torco lead accelrator booster one qt for 15 gallons and i ran it to death and it ran great

[Chris]

What kind of $$ to make a set of 088's breathe?

[Mrhorsepower1]

What kind of $$ to make a set of 088's breathe?

The situation you run into now a day Chris, is by the time you perform all the machine work, porting , and component pricing for a bit more money you can buy a set of Dart Pro 1 or equal cylinder heads and bolt on more power. The 468 I was referencing to was built 20 years ago before all these nice parts were available.

[Chris]

That's what I figured. Good benchwork by a pro that knows what he's doing is expensive.

[Geronimo36]

Frank I have built 468's SC with GM heads ported that make 850 HP and a 540 Merlin headed package that makes 975 HP.

Thanks Dean. Is that on 91-93 Octane?

[Geronimo36]

yes on pump gas 93 with torco lead accelrator booster one qt for 15 gallons and i ran it to death and it ran great

What was the final octane after the torco?

I'm not trying to poke holes, I'm just saying on pump gas with such small cubes I'd think it would be hard to make 900 hp reliably on pump gas (91-93 octane). I could be completely wrong, so don't mind me! I just think that if it were easy, everyone would be doing it.

[PatriYacht]

Depends on your definition of reliable. Smitty aka Arcticfriends found that leakdown after 150 hrs was pretty poor at that boost level. Set up and tune has to be correct also. We're lucky that we have all of that water to use for cooling. Just use a restricter instead of a thermostat and jet rich enough to keep the piston tops and oil from overheating.

[PatriYacht]

A member here, Ben Perfected is making 800 hp with a 502 naturally asperated single carb. I think he built them to the old B class rules. It does take a few more rpm though.

[MikeyFIN]

Here's what the heads in question look like. They are also lightely port matched to the intake and exhaust.

The chambers is close to 120cc, that's about 2 more than the original 118.

They vary all the way up to 122cc, depends a lot on the deck thickness and that´s one of the reasons we call GM original heads for Grusian Motors heads.
The key in heads are Velocity not necessarily top flow even with a boosted engine.
If I vere you I´d got with the Dart Big Iron heads ...the have a raised exhaust port and that´s the Achilles heel on them original heads.
I´ve done a few boat motors with those heads and Nowadays replace every 990 or 088 head with these if it´s a seawater cooled boat.

http://www.dartheads.com/products/he...gle-heads.html

It´s your choice to go with either 308/345cc heads.. I´d opt for 345´s in your case.

[Tomas Wallin]

They vary all the way up to 122cc, depends a lot on the deck thickness and that´s one of the reasons we call GM original heads for Grusian Motors heads.
The key in heads are Velocity not necessarily top flow even with a boosted engine.
If I vere you I´d got with the Dart Big Iron heads ...the have a raised exhaust port and that´s the Achilles heel on them original heads.
I´ve done a few boat motors with those heads and Nowadays replace every 990 or 088 head with these if it´s a seawater cooled boat.

http://www.dartheads.com/products/he...gle-heads.html

It´s your choice to go with either 308/345cc heads.. I´d opt for 345´s in your case.

Yo Mikey

The chambers on these heads are just about 120cc.

I'm not going to replace the heads, if I would there would be no problem in using aluminum ones since the water over here is more or less brackish.

I'm just trying to optimize the engine as it is, and the first step will be to optimize the boost and carbs.

[MikeyFIN]

I'm just trying to optimize the engine as it is, and the first step will be to optimize the boost and carbs.

the first step IMO would be pocket porting and optimizing the exhaust ports...

[Tomas Wallin]

Yes but then the first step would be to deassemble the engine... And that's not happening! It's not interesting - the interesting part is how much it's possible to get from what I've got today - ONLY with tuning.