i saw a board showing flow numbers for the F20C honda S2000 head and also a cobra dohc 4.6 rated at 248 ish cfm, the f20 head showing 311 cfm, both at 500 lift, how well would a 300 run with stock cam values, then with cams rated for a good street rod and finally the 232/232 cam mentioned for my 300hp goal build?
F20C copycat 300
- Thread starter Tbone3366
- Start date
This might be overly simplistic, but maybe it helps… you need a certain amount of air flow to hit a certain rpm.
So, imagine you need to fill up a 5 gallon bucket with a garden hose. If one hose is 1/2” diameter and the other is 3/4”, you will need to shut the valve off sooner using the 3/4” hose.
A better flowing head is kind of the same. It will require less time and distance for the valve to be open to get the same amount of rpm as a lesser flowing head. But! As Pmuller9 already stated, it’s not that simple. Flow numbers are not the only thing that matters when selecting a head.
So, imagine you need to fill up a 5 gallon bucket with a garden hose. If one hose is 1/2” diameter and the other is 3/4”, you will need to shut the valve off sooner using the 3/4” hose.
A better flowing head is kind of the same. It will require less time and distance for the valve to be open to get the same amount of rpm as a lesser flowing head. But! As Pmuller9 already stated, it’s not that simple. Flow numbers are not the only thing that matters when selecting a head.
aussie7mains
Famous Member
Not quite sure what your on about here, the flow figures given has almost no relevance to a 300ci truck six, those engines are all modern engines unlike the Ford 300 which is ancient by comparison. If your aiming for 300 honest BHP, then you will need (superflow empirical data here) 300/6 50bhp per pot, and 50x4 cfm @ 28 inches test pressure, 200cfm. I doubt you will get that on a stock head, reworked with bigger valves and careful port work, maybe. The key is low restriction to flow (high cfm numbers) so anything you can do to help here is good. Spend your money on breathing. When you have good breathing you can use less cam duration to achieve your goal. Long duration high overlap cams have their drawbacks, (rough idle terrible fuel consumption) for street use you should aim for minimum duration that will get the rpm you want. In the case of the 300, its not going to be a big rever, so work to its advantage, low rpm torque, I would not use a cam over 220 degrees for a manual trans and even less for an auto. Aussiespeed have good 4 barrel manifold. The cast iron EFI exhausts look fairly good, headers would be slightly better, you will need a minimum of a single 2.5 exhaust and low restriction muffler. IMO this will give about 220 honest BHP which is pretty good for this engine (would be rated around 270). High compression isnt needed for this, if you have somewhere around 9:1 your good to go. Best advice, dont go overboard.
not what im getting at, im going with the whole, if honda design an F20C head for the 300, dohc with vtec punching 311 cfm and what the possibility of the 300 would be, the honda is 1997 cc pushing 237hp, the 300 being 4914cc, what could the 300 do if the honda is making about 118hp per litre, i know the larger chamber will change how efficient the 300 would be, im only trying to get an idea what it possibly could make, if the 300 made 1:1 hp with the f20 it should make in the realm of 580ish hp based on the numbers
Keep in mind that HP is an RPM based number. The total work is a formula of HP and TQ @ a given rpm. The 1:1 engine power comparisons above would be valid only at the same RPM.
aussie7mains
Famous Member
Ok, I see your discussion point, decreasing inlet restriction raises the VE and therefore the BMEP, your proportioning is overly simplistic in that the Honda is a small 4 pot that can be made to rev to a great height, the 300 is very unlikely to do that. However a better example might be the DOHC 4valve falcon barra engine, its 4 litres (240ci) and gives 195Kw (260bhp to din) in stock form whilst running unleaded and emissioned, that is an example of what can be done with careful design. This engine is a bulletproof thing that will go 500000km fairly easily. The 300 was never designed for this use. So your 300 could, if given a 4valve dohc head achieve considerably better VE and BMEP, but would not approach the level of BHP that the small 4 pot could, as stated the BHP is a calculated number only based on Torque and RPM (2Pi NT in metric), more RPM more power, the torque is the only thing actually measured on a dyno. So in conclusion the 300 could probably make something around 325bhp if airflow was similar to the barra. People like frenchtown have made more, but not as a streetable unit. AND there are tonnes of much easier ways of getting the power, Coyote for instance!
This is why I didn't answer the original question in detail.
The Honda F20C engine made 237 hp at 8300 rpm.
If you are looking at a 1:1 power ratio with respect to engine displacement, the 300 six would also need to make peak power at a very high rpm.
In order to do that the 300 would need a head the flows a lot more than 311 cfm and a very big camshaft profile.
If you want to consider what a 300 six would produce power wise with a head the flows 311 cfm, that is a totally different story and is separate from a power to displacement ratio of a smaller displacement engine.
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im just trying to shoot for roughly the stock ish range of idle to 5k + or - 600 rpm is all, pmullers answer was enough for me to accept that theres no number that would be good to go with since theres so many factors,
for the 1:1 i was being very optimistic with a ported head and 7000 to 7500 revving engine, atleast this comes from my readings from other builds
for the 1:1 i was being very optimistic with a ported head and 7000 to 7500 revving engine, atleast this comes from my readings from other builds
There are several builds here that make power from 1000 to 5000 rpm.
They used a ported head with one of the 4 cams listed below that have around 220 degree .050" duration.
The compression ratios were from 9.0 to 9.5
Crower 284HDP (19205) .509”/.517” 220/222 284/290 110deg
Howards 280996-10 .501”/.501” 221/221 275/275 110deg
Schneider 140H (13912) .496”/.496” 222/222 280/280 110deg
Erson E270321 (Hi-Flow AH) .504"/.504" 220/220 284/284 110deg
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by chance do you know the length of the atlas 4200 cams? ive seen the engine a handful of times and looks similar in size but not sure, if a custom head was made those cams could possibly be used
The bore spacing for the 4200 is only 4.055" and the cylinder bores are 3.66"
The cams along with the head would be way too short for the 300 six engine that has a 4.48" bore spacing.
was curious on it, thank you, thoughts on taking 2 cams, grinding off one set of lobes ie exhaust lobes to leave 6 intake lobes to run a single cam with a wishbone roller rocker to run 2 intake valves and vice versa, ford 300 cams not the vortec
In order to run a wishbone rocker arm, the cam lobes must be centered over the cylinder bore.
The lobes on a 300 camshaft are offset just over an inch from the center of the cylinder bore.
i imagined they would have to be offset position wise, if you were designing it would you prefer belt or chain? obviously keep it non interference
If you want to have a hybrid head that has 300 cfm of flow, use sections from an LS3 head that has rectangular intake ports.
Do not waste time using any of the LS cathedral port heads.
If it is a stock head, have it ported after it is completed.
We were looking at using an inexpensive aftermarket head that flowed 320 cfm right out of box.
Do not waste time using any of the LS cathedral port heads.
If it is a stock head, have it ported after it is completed.
We were looking at using an inexpensive aftermarket head that flowed 320 cfm right out of box.
Belt is more efficient.