HP Per ci

[headcase]

Hi

I was wondering about fuel consumption and other factors after looking at different engine ci - power possibilities.

Eg:

2 identical cars, both at 650hp.

Car 1: 428ci (stroked 351 small block) = 1.5 hp per ci.
Car 2: 360ci ---------------------------- = 1.8 hp per ci.

Which of the 2 will be a more efficient engine in terms of street cruising and which would be more efficient under wide open throttle (racing)?

Which would have better acceleration (flatter torque curve)?

[skatinjay27]

You cant know with just the displacement and power numbers... Need more info ie: compression,cam profile...

[MattO]

There's too many factors to make a judgement based on that. There's just so much that goes into it. Yes, hp/ci can be a measurement of efficiency, but again, alot goes into that. I remember a bunch of Honda S2000 fanboys saying that, at the time, the motors in those cars made more hp/ci than any other n/a motor produced at the time. Problem: You didn't really make any power until the VERY top end of the RPM range. Down low, the cars were pigs by comparison. Same deal with the rotary cars I've driven (Mazda RX7/8).

[headcase]

So there is many ways to get a 351 at 650 hp with different cams etc and still produce same power even though the bits were all different?
:confused18:

Hmmm.

[Steve Chryssos]

The 351 (C or W) is not known as the world's most efficient engine. As such, 1.8 to 2 HP per cube usually requires a lot of race-only design elements including high compression, and aggressive cam and revs.
You might be happier with goals in the 1.2 to 1.3 HP/cube range with a carb and 1.4 with EFI.

DISCLAIMER: I'm talkin' real horsepower, not internet horsepower.

[DTM Racing]

DISCLAIMER: I'm talkin' real horsepower, not internet horsepower.


Wait you mean I can't take my engine builder's word for it? But he SAID my 225cid Slant Six should be good for 650HP with this 3/4 cam!

I love taking cars to the Dyno. Complete heartbreaker for some folks. A customer of mine swore up and down that there was no way my Road RUnner only made 400rwhp, since my car was way faster than his "600hp" 383 Stroker 350. We spent the day tuning his car on the dyno...256rwhp.

[Matt@BOS]

I can't imagine that 360 engine would be any fun to drive on the street.

[IMPALA MAN]

George,
Building / specing an engine is no different than a car. To a degree, the limits are endless. The question you ask is like asking which car would be better for setting a land speed record, a Charger or a Gremlin. The answer is.... Whichever one you choose. Keep this in mind. The Speed Demon that set the record for the highest horsepower for a piston engine was a 4 cylinder. Why, because it was built for it. How would it run on the street? Probably not too good.
The answer to your question lies in the answer to what you want. A Flathead Ford can be built to provide you whatever you want. Yes including a land speed record.
Step 1. Figure out what you want to do with the car.
Step 2. Go to a reputable engine builder and ask him for his suggestion.
Step 3. Ask a few owners that have that type of engine.
Step 4. Get it built.

If you continue to ask on the forum, you are more than likely to end up with way too many reccomendations than you can digest. Personally, I like 383 stroker (GM) engines. They are the best all around for what I like to do. If I was building a 32 Ford, I would use a Flathead V8. Why because it looks cool and I know it can make the power if I need it to. A Buick Skylark, a Nailhead. Etc, etc. I hope this helps.

[headcase]

Thanks for the feedback.

I know I want 10.5:1 compression. We have 98 Octane fuel here at every pump. May as well get the compression up. I know it will produce more efficiency.

My car is basically a street car but I want it to hammer through the RPM's. If light goes green, I want those 600 HP ferrari's behind not in front. THose cars hit 0-60 in 3.0 seconds.

I know Torque is good there, but My purpose to car is to make it handle so it can keep up to those cars on a track to in corners. So I wondered what is the happy middle here.

Im happy with how ferraris drive on the road, no drama with them, but the RPMS fly up when they start to kick the power. I can see a big cube (small or big block) leaving them dead right there. How would more cubes effect a cars road course speed though and why would it be bad (if at all) when it has more to get out of the corners... or is that the actual problem as the car would spin out.

[Flash68]

Hi

I was wondering about fuel consumption and other factors after looking at different engine ci - power possibilities.

Eg:

2 identical cars, both at 650hp.

Car 1: 428ci (stroked 351 small block) = 1.5 hp per ci.
Car 2: 360ci ---------------------------- = 1.8 hp per ci.

Which of the 2 will be a more efficient engine in terms of street cruising and which would be more efficient under wide open throttle (racing)?

Which would have better acceleration (flatter torque curve)?

George,

The 428 would clearly be better at that 650 hp level for street cruising and longevity vs the 360. As others have mentioned, the 360 would also need tons of rpm at the sacrifice of low and mid range power to hit that number.

The acceleration and flatter torque curve questions cannot be answered with the lack of info provided.

my 540 bbc makes 1.5 hp per c.i. single four barrel, big hyd roller, 10.7 comp, trick full cnc heads.... i think the motor made 100 more hp from the full cnc port job...

Yep, 1.5 hp/cube can be easily done these days with good parts and stuff that is not too radical or on the edge.

[Steve Chryssos]

Thanks for the feedback.

I know I want 10.5:1 compression. We have 98 Octane fuel here at every pump. May as well get the compression up. I know it will produce more efficiency.

My car is basically a street car but I want it to hammer through the RPM's. If light goes green, I want those 600 HP ferrari's behind not in front. THose cars hit 0-60 in 3.0 seconds.

I know Torque is good there, but My purpose to car is to make it handle so it can keep up to those cars on a track to in corners. So I wondered what is the happy middle here.

Im happy with how ferraris drive on the road, no drama with them, but the RPMS fly up when they start to kick the power. I can see a big cube (small or big block) leaving them dead right there. How would more cubes effect a cars road course speed though and why would it be bad (if at all) when it has more to get out of the corners... or is that the actual problem as the car would spin out.

EFI or carbureted? What is your budget for cylinder heads? A set of Kaase heads, for example, will excise all of the Windsor platforms shortcomings (which re mostly related to chamber design and valve spacing). The best part of the Windsor platform is its symmetrical ports. (as opposed to siamesed ports like a Gen 1 small block)

Can you spring for coated everything? pistons, bearings, etc? The right combination will get you to 1.4 HP per cube, EFI. Then it's simply a matter of having enough cubes. 347 x 1.4 = 486 HP Aw....

Cubes:
http://www.dartheads.com/products/iron-eagle-ford-sportsman-block.html

[headcase]

Looking at EFI for reliability.

Everyone mentions the Windsor blocks. What about Clevelands?

[hp2]

Horsepower is like that hot looking, busty gal in a bikini that we can't help but look at when she walks by. Torque is the fair looking girl with a nice smile and a good sense of humor that we take home to meet the parents.

Torque is where its happening. More torque at lower levels will make a car more enjoyable on the street. Torque production is also a better measure of efficiency than horsepower, IMO.

It also is fair to say that more cubic inches will always produce more torque or horsepower than less cubic inches. It also will produce that power at lower rpm levels with less effort. However, it also will require more fuel to feed those cubic inches. You can improve the efficiency of the larger displacement by squeezing the charge tighter or introducing better atomization of the charge so it burns the fuel more completely (thus needing less fuel for the same power). This is where the engine build gets tricky because there are multiple factors involved that can help or hurt you and it is never as simple as saying I want X compression producing Y power. It becomes a balancing act of compromises. Also keep in mind that 600 horses from 500 inches requires a whole different level of components than 600 horses from 360 cubic inches because of the rpm levels involved. That can become a huge factor in the cost to achieve the repsective power levels.

Additionally, when looking at the weight you're carrying and how it relates to the handling, with your mustang, you will have a greater range of spring options that can be used to offset the additional weight you would carry with a big block over the small block. You may wear out tires faster, but, that may actually equalize the overall wear of the fronts as they carry more weight to match the burnouts you'll produce with the rears as a result of massive torque under your foot.

One issue of concern with a mustang is that they do not fit big blocks very well. Sure, some were put there by the factory, but their sheer size means service can become more of an issue than an equivilent small block. Ford engine bays, and mustangs in particular, are unfortunatly small. In this regard, your 351 small block stroked to 427 would be an easy answer.

If you don't track the car regularly, I wouldn't get too hung up on racer based perfomance. Race cars are very tempermental, require lots of upkeep, and regular maintanance and need to be inspected regularly (remember the bikini girl above). A street car with lots of torque is more fun to drive within a moderate rpm range and it won't require as much meticulous maintanence procedures as often.

Enjoy what you have for a while before jumping into big future plans. You may be surprised by what your mustang has to offer you. Once you get to the point that you are bored with its power levels, then see where you want to go with it.