What goodies do I need to build a Fast slant 6
You said
Hi All
I’m wanting to build a fast cranky slant 225 6cyl !! Something between a drag, race engine but able to drive on the road.
I want it to have a lumpy cam and whatever else is needed to make some big HP numbers I’d like to get 300rwhp + .
I’m not a mechanic and don’t know what works to get that type of HP so I’d really appreciate it if those who have built these before, and have got these types of results!, if they could Please elaborate on what they did to there engines in detail so I can build something similar.
I have friends that are mechanics so hoping I can get the block, head and other engine bits and pieces and give it to them to put it together for me.
I’d really appreciate any help and you time letting me know.
Thanks
Hi Hyper
Thanks for the information, I wasn’t sure if people on this forum just want people to get straight to the point but yes I should’ve given a bit more info to get a better reply.
I know this is a bit last know but I’ve got an ap6 I basically just wanted an old school car that I could still afford and have a hot engine that really cranked out some fun power!, I’m 50yo and never had something cranky so to say and yes I could’ve got a V8 and something newer that would certainly have more power but I really wanted an old school car.
I’d seen some 245 and 265 engine’s really crack hard without spending a fortune so for 6k and thought that the 225 might be similar but I’ve obviously been mistaken lol, so perhaps I might have to look at the turbo side of things but guessing that won’t be very cheap either.
Anyway thanks for your time and help it’s greatly appreciated.
Cheers
Hi 12many
Yes I hear you 15k is a lot for a 6 that has basically no technology advancements just all old school, and yes I’d thought about a V8 but I have a V8 engineered into my Toyota 4Runner so just wanted to go with a six cylinder with a real lumpy cam setup I had hoped it wasn’t much stuffing around to put a 265 in it as they can make a heap of power pretty cheaply but I’ve had a few tell me that it’s also a bit of stuffing around!, and at 50yo I’m past the stuffing around stage in life been there and done the and the body’s just to broken and tired so was hoping now that the 225 was able to make some reasonable power gains but just didn’t realise How expensive they are to make power.
I’m open to suggestions still at this stage as it’s just sitting there and hence why I’m on here trying to figure out how to go about it.
Cheers
Okay;
So, by now, you have a better understanding of a project like this. A lot of the replys are in response to your initial post, which laid out a goal of 300RWHP.
While this might be possible, big Horsepower is a function of big rpm. Cuz that is the math and the physics of it; and that is what I want to talk about;
The formula for horsepower is
(Torque x rpm)/5250 = horsepower.
If your engine can only make 225 ftpounds, then; at 4000, it will make 171 hp; at 5000 then 214hp; at 6000 then 257hp; at 7000 then 300hp; at 8000 then 343hp. You can see how that works, right.
But to get those numbers, you have to build that engine in such a way as to move the power away from a lower rpm to that higher rpm, thus giving up low-rpm power. And the engine still has to do two things;
1) it has to survive the trip, and
2) it has to actually move the required amount of air thru the engine.
That said;
anytime you sacrifice low rpm power in a streeter, with no other changes, it is usually a bad thing.
So what causes the low-rpm power loss?
Well the first thing to go, as you begin moving the power curve, is low-rpm pressure. Pressure makes heat, and heat is power, so it just goes away. Which is fine in a drag-racer, cuz you just increase the stall, so the engine does not need to operate in that zone. But driving around on the street with a 3500 or 4000 stall TC, is not gonna be your favorite thing to do for very long.
So, then, you gotta get the pressure back up, to where it becomes fun again. But after you do that, now, with the power-peak not coming around until 6000rpm, you come to find out that the 2.7x gears you are running, put the power in first gear, at 6000rpm= 57 mph, or so; and the march to the peak doesn't even start until 42mph.That is where it might start. That is horrible for a streeter, because something like 98% of your driving will be well below that speed/rpm. So those 2.7s gotta go, and now you are faced with the probability of giving up hiway cruising, to bring that power down into a usable roadspeed range.
So then, now you are looking at installing "race-gears" to go along with your "Race-Convertor" and your "race engine". And you have to start doing "Race-car" maintenance.
So lets go back to the Normally Aspirated 300RWHP. . All the power formulas and such, work off crank hp so; allowing for powertrain losses, this will be more like 300/.85= 353 crank hp. To make 353hp,
with any engine, requires a specific minimum amount of fuel thruput of, .5 pounds of fuel per hp per hour so; .5 x350=175 pounds per hour; which at 6pounds per gallon is 29 USg per hour; so your fuel system has to deliver that.
But more importantly is thruputting the air that goes with that. To thruput at the rate of 175 pounds of fuel per hour will require 12.5 times as much air by weight, so 2188pounds of air per hour. At STP, that comes to 2188 /.081= about 27,000 cubic feet of air, or about 34 bedroomfulls. Ok then, 27000/60minutes=450cfm. But this is at 100% efficiency and at STP which is Standard Temperature and Pressure, which in this case ,IIRC is 68*F and 1.0 atmosphere.
Ok so; any engine, to make 350 hp, will need to combust fuel at a rate of 175 pounds per hour, with 450cfm of air, at STP and 100% efficiency
Now the crusher;
225 cubes is just 0.1302 cubic feet. At 100% efficiency and 5500 rpm, that comes to 358 cubic feet. Accounting for the slanty design, you might get 80/85% out of it; so this 358 might be closer to 295cfm.
Good luck building a NA 225 to go from 295@82%, to the required 450cfm @100%, which is an increase of~53%...... See what I mean? That's gonna get expensive real fast!
at 100%Efficiency;
A 225 can make 450cfm at 6912
A 318 can make 450cfm at 4852
A 360 can make 450cfm at 4320
A 408 can make 450cfm at 3812
A 440 can make 450cfm at 3535
The lower you bring the number, the funner the engine will be, on the street.
the 360 at 85% Efficiency can make 450 at 5080; that's a pretty streetable cam.This engine practically falls together at 350 Crank hp.
Check my math.
1 cubic foot is 12x12x12 inches= 1728cubic inches.
In a 4-stroke engine, each cylinder inhales on every other revolution. So for purposes of calculation, you must halve the cubic inches. So, the formula is
(cubic inches/2, divided by 1728) times rpm =cfm @100% Efficiency and STP.
For a given horsepower at 100%E, take the calculated cfm and rearrange the formula like so;
Known cfm divided by {(cid/2)/1728}=rpm; example for 350 hp;
450 divided by {(225/2)/1728}=rpm=6912 @100E@STP
100%Efficiency means the engine is able at some point in the rpm band, able to inhale a quantity of air equal to it's size.
Typically,from factory to hot streeter,at WOT, the numbers range from 70% to 100% or occasionally 105% in a really hot streeter. The Slanty, because of it's design architecture, is gonna be on the low end of the scale, whereas pushrodV8s will come in closer to 85 to maaaaybe95% . Few streeters are built to the high end of the scale; mostly because...... the powerbands are rising ever higher, and eventually, the combos become decidedly un-streetfriendly........... Not to mention, expensive.
Ok so now, you have a better idea of why we are so "down", on your thread.
Had you asked about a 200crank hp streeter, the numbers present as doable.And the combo is much less expensive.
Had you asked about 300crank hp with a turbo; that's a nice streeter.Particularly with a slanty, because of the breathing restriction they suffer in the head as normally aspirated. But; a cranky-sounding slanty and supercharging are not very good bedfellows.
Had you taken streetability out of the equation, AND not mentioned horsepower at all; well then
cranky it up.
Just remember to leave room in the budget for the rest of the combo; like Stall, gears and support systems, like cooling, ignition, exhaust, and fuel; not to forget suspension,steering,brakes, and tires.
You can still build a fun streetcar, with far less than 300RWHP
Speaking about tires; lol, all this talk about 300RWHP is meaningless if it all goes up in tirespin. Unless, of course, tirespin is what you are after.... In which case, there are far cheaper, easier, and less complicated, ways to achieve that.
And finally, as you go up in elevation, the smaller your engine is, and the crankier it is, the sooner it will begin to wheeze due to loss of oxygen. And that is where supercharging will level the playing field.
As always; I'm just trying to help, and
Happy HotRodding.
