Big cam small head vs small cam big head

[dezza]

Found this one for you
30340513

416A3
3000 - 6800
.630"/.637"
247/256
276/286
106/100
.018"/.018"
High performance street, mild strip, oval track or jet boat cam. Needs 3000-3500 RPM stall converter, headers, 10:1+ com- pression and 3.90+ gearing. Rough idle.
Page 114
http://www.lunatipower.com/PDF/Lunati-Catalog-2012.pdf
Use the big head and 3000 stall

[dezza]

Mostly street driving. I live in a relatively rural area so I'd like to take it out on some country roads and enjoy it. I was thinking peak power around 6000 and max rpm 6500. 2" head pipe. 2500lbs. 4 speed. 3.54 rear. Dual plane intake.

That cam I quoted would not be a good street cam
110 and more lsa would be better

[dfree383]

Barry R just introduced a new cylinder head casting thats right up your ally for a street build.

http://www.survivalmotorsports.com/

Get ahold of him.... he's wrote the book on FE's

[Joel Dubose]

I would use a head that flows well with a smaller runner section of the port. The a smaller duration cam and a fuel injection. With the fuel inj you could get a bit more carried away with flow as well as size because your not using the flow to create a signal to the carb to pull fuel. Also if you use an electronic FI , It will help with the overall tune up from different days, weather, part throttle, w/o throttle etc. Have fun and make it fast ... Good luck .

[289nate]

Just because a lobe has less .050 duration does not mean it's smaller. It very well could have more lobe area through greater lift. That properly combined with a well designed larger cylinder head can make for a very fun street/strip car with a very broad power band. Plus run well at the track.

[289nate]

Here is a link to some info on the heads from Barry that Defree referred to.

http://www.hardcore50.com/vbulletin/sho ... post468516

[My427stang]

I'd go in between the two recomendations on both cam and heads. Something like a 320-325 cfm intake cylinder head and a 246-248 intake duration cam. And drop the static compression to around 10.5:1. A half point of compression might lose only 6-9 hp, but you'd never have to worry about detonation under "weird conditions". The above recommendation is a generalization and dependent on specifics, but that said, I think it would be THE sweet spot.

JMO,

paulie

This is pretty solid advice for a street FE. Although it's certainly not a budget head that will get to 325.

I will also add, there really is no BIG head for an FE. Its not like a 460 or 351C where you can choose a head that is too big. (I wish they did have something as a stroker guy)

Even the original high risers and TPs are streetable and most modern heads have evolved from the med riser which is really a raised port not a larger port.

So IMHO, get as much head as your budget allows using a med riser port, then cam to match the rpm range you want. I don't like the idea of trying to go big cam to make up for a weak head.

Barry's new heads look very promising, even more with a little rubbing. As do a few of the other supplier's Pro-port variations

When choosing the cam, with a light car, you can get a bit more aggressive, some even like to kill the low end a little with the cam, but IMO don't put the peak above where you'll use it, even if its only every so often. If you have traction problems, lift a little.

[blykins]

"I've narrowed my build to one of two engine builders. I'm looking to have built a Ford FE 427. 4.250 bore 3.78 stroke. Single Holley. For a cobra kit. In discussing heads builder A wants to go with a Medium Riser ported to flow 360 cfm intake 260 cfm exhaust. Cam is 240/244 @ .050 with 110 LCA. Builder B suggested a head that flows 300 cfm intake and 220 e haunt. Suggested a cam of 252/260 @.050 with 110 LCA. Both suggested an 11:1 static compression. Which is the better approach?"

Flow is not everything. Velocity is key. I'm curious as to which head is claimed to flow 360cfm? I don't know of any readily available head that does that unless it's a worked Blue Thunder head and they need some specialized parts to complete the rest of the package.

A 300 cfm FE head is going to make some decent horsepower and shouldn't break the bank, as it's easily attainable with some mild work on an Edelbrock head without opening up the volume considerably.

A 252° @ .050" with 427 cubic inches is going to be a pretty revvy engine. With out of the box Edelbrocks, a 248° solid roller on a 428 will peak at 6500 with a Tunnel Wedge intake. You're going to be at least there if not higher with more head and more cam. A high peak tends to leave the bottom end lacking and unless you're working with a 3.70-4.10 rear gear, I think you'd be unhappy with that combo.

I would build the engine with some ported Edelbrocks (300-320 cfm) and cam the engine to have a great powerband where you will be driving the most. As My427stang said, there's no use of putting the peak way up high if you're never there. A 236-240° @ .050" camshaft (preferrably a hydraulic roller if your block is drilled for it) will give you a 5500-6000 peak and will not make for a fussy engine down low.

I've been down this road before in my own Cobra. It had a TKO 500 with 3.70 gears. First engine was a 425W that dyno'd at 485hp @ 5400 with 500 lb-ft of torque to back it up. It was a really fun engine and I should have left good enough alone, but I had to build an FE for it, so I ditched the Windsor and built a 428. That 428 was the one with the out of the box Edelbrocks (with a nice valve job and clean up), a T/W, and a 248/254 solid roller. It made 533hp @ 6500, but had only 470 lb-ft of torque @ 5400. It was peaky and fussy.

FWIW, the 428 was 11:1 compression. If you have access to good gas and the combination is well thought out, it's do-able, especially in a light car with some gear behind it.

[plovett]

The theoretical cylinder head I had in mind was a fully ported Edelbrock (not Pro Port) with big valves for the 427 bore. Something like Barry's CNC Edelbrocks. His new FE cylinder head ought to be even better, but it's so new that I don't know if there are any fully ported/big valve flow numbers.

IMO, a cobra should be a fairly gnarly beast with a rough idle and high rpm shifts. I would hate to see it tamed too much. I don't think anybody is suggesting that. I'm just saying where I'm coming from.

paulie

[289nate]

Aren't we talking about 400 + cubic inches here? How much low end torque do you guys think he needs in a 2,500 lbs Cobra with what I assume will be a manual transmission? Do you really think a decent port that only moves 325'ish cfm is going to hurt low end torque? I doubt the intake going on this build will have short runners. How bad do you plan to screw up the valve events and/or carburetor to have to worry about velocity with a decent 325 cfm head on a combo like this?

My weekend and drag strip toy '65 Mustang fastback runs a .060 over 289 (4.060 x 2.87) I put together with mildly ported Canfield 195 heads that went 297 cfm before the valve job, a Parker Funnel Web intake that has a bunch of taper removed to port match it to the heads (you'll know what I mean if you've ever held one and looked down the port) which went 320+cfm on each port, a 950 Holley HP based carburetor, dual 3" exhaust with no H nor X pipe, and only 10:1 compression for 91 octane pump gas. The intake lobe on the tight lash solid roller cam is only 225 at .050. It does have .650" lift though with the 1.7 rockers so lobe area isn't small. Exhaust lobe is 244 at .050 with less lift believe it or not. Peak torque was 5,300 rpm and peak HP was 6,900 to 7,000 rpm on the engine dyno. Nice split between the two which indicates a broad rpm range which was also evident by the little motor making 274 lbs/ft at 2,800 rpm which was the lowest we pulled it down to.

So what isn't street friendly about this combo? What is lacking about the throttle response and low end torque when I stab it to half throttle (full throttle gets the rpm high and too loud for a neighborhood) breaking the tires loose easily in first and second at the end of the following video? This weighs around 3,000 lbs with me in it. The video was taken before driving it to the track which is about an hour to 45 minutes each way.

http://www.youtube.com/watch?v=cUqM4DPg ... re=related

A couple weeks ago it ran a new best in the 1/4 of 11.12 at 122.4 MPH at Famoso shifting at 7,500 rpm with only a 1.535 60 ft. The next pass it picked up about one MPH in the 1/8 shifting at 7,800 rpm. Unfortunately a rocker backed off and the back half stank or it would have gone 123+.

So why the heck are you guys concerned with low rpm power and velocity with a 400" cube engine and a 325 cfm head? I just don't get it.

[blykins]

I wouldn't worry about the port velocity with this application as much as the cam specs. But, that 360 cfm head is probably going to need some rpms to take advantage of it.

I do tons of motors for Cobra replica owners. Most of them like to cruise and head downtown as much as they like to open them up. An engine that's peaky, hard to tune, fussy, etc., usually is not asked for. It is 2500 lbs, and it doesn't take much to get it moving.....but that's even more reason for some guys to have an engine that is friendlier on the street. 400hp in these things will MOVE.

[My427stang]

So why the heck are you guys concerned with low rpm power and velocity with a 400" cube engine and a 325 cfm head? I just don't get it.

I am not concerned with it at all, for FEs and their available heads, I say go for the best airflow you can, then pick a cam within the usable range.

Unfortunately, aside from some one-off race stuff, there arent a lot of real big flowing FE heads, but on the bright side for the street applications and smaller displacements, there also aren't any huge CSA or large volume heads either, so if you have flow, you probably have a very clean port, not a very large port.

What I don't like is someone "kills" low end with a Cobra by overcamming, then shifts at 5700, why bother living with a gumpy cam? Just push on the go pedal less, or regear, if the tires spin down low.

I

[blykins]

Nate, do you have a 3.08 rear gear in that Mustang?

[Timm]

The car's only weighs 2500, get the best head you can with really good valve springs, then go with a smaller cam, should make good power and be really fun to drive, if you don't like the way it runs cams are cheap and you already have the heads to support a lot more HP from a simple cam change.

[289nate]

Nate, do you have a 3.08 rear gear in that Mustang?

Of course not and neither does this guy. I also don't have 427 cubic inches and my car doesn't weight 2,500 lbs. I can start from second gear and still have too much torque for the street tires if that's what you're wondering.

Any sensible person will use the rear gear that will get them through the traps at the rpm your powerband and mph dictates when you care about getting you money and time's worth out of your combo at the drag strip. Doesn't matter if you have a twin turbo stroked big block or a naturally aspirated 289. Thus I run a 4.56 rear gear. Cool part is I just shift into overdrive and cruise the freeway and streets like I have a 2.90 rear gear.

Some people will say this type of build will see less than 3,500 rpm the vast majority of the time. But the vast majority of that low rpm operation is at less than 30% throttle. However, at full throttle, the majority of the time will be spent at higher rpm and the shift will not be needed before the engine starts laying over. From a stop, or a very slow roll, you are onto the mid rpm range very quickly. Out of first gear and anyone will down shift if they're serious about accelerating quickly. Even true for a desiel. Thus no time spent at low rpm.