Big cam small head vs small cam big head

[289nate]

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

I agree.

This thing is going to have a dual plane to boot. Low rpm power is not going to be an issue in this application. Getting it to make power out to a reasonable enough rpm to make some numbers that are worthy of not having to exaggerate about at cruise ins and car shows will be.

[289nate]

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.

And you already have heads to take it to the next level. We all end up wanting to go faster.

[blykins]

"Of course not...."


Exactly....

Most Cobra guys run 3.08 and 3.31 gears, behind TKO 500 and 600 transmissions. They're not set up for high rpm screamers, and cruising around at 1800 rpm while the engine is bucking like a bronco becomes pretty old very quickly. Some guys start out wanting 7000 rpm engines, aluminum flywheels, and button clutches, all because they sound cool. They change very quickly to smaller cams, steel flywheels, and traditional style clutches. It happens all the time.

But you are correct, you can get away with more in a 2500 lb car. However, remember, that a lot of Cobra owners just get out their checkbooks and write checks. They are not builders. They are not engine builders. They are not tuners.

I agree with the others....stay with a "normal" FE style cylinder head, like a ported Edelbrock, and keep the cam on the mild side.

[289nate]

Blykins, I think it's pretty unfair to throw this guy right into the more money than sense poser Cobra owner category. I personally would jump all over a 360 cfm head for a 427 Fe build destined for a 2,500 lbs car with a 3.54 gear and four speed. Id think this engine was going to end up in a Galaxy cruiser the way some are talking in this thread.

By the way, I can cruise around all day at 1,500 rpm in 5th gear with this vastly smaller engine in a 300'ish lbs heavier car. Don't need to down shift to accelerate away from there nor does it buck and jerk. The larger, higher flowing, and efficient cylinder head and intake are a big part of what allow this combo to have good manners while still making power out to am rpm where it will run decent.

[blykins]

How many 360 cfm 427 FEs have you built?

Do you even know of a head that flows that much for an FE?

I'm sorry, but I can't agree with you on any of your points.

As for the OP, there was no bad intent, and I didn't mention him specifically. You know that. However, he is having an engine built by someone else and is asking for advice, so that's my advice based on building FEs for a living, building engines for Cobra replicas, and having owned one.

[JDR Performance]

I've got a couple of friends that have had those cars. One had a 427 FE motor and one had a 347 small block. The 427 was almost impossible to hook up even from a roll and with good tires. It would spin in any gear and from a punch at 50 mph or so. The 347 car was fast and fun to drive. I'm not too sure that a lot of front end weight and tons of power is the ticket in those cars based on what I've seen but maybe people get it to work.

[PackardV8]

I've got a couple of friends that have had those cars. One had a 427 FE motor and one had a 347 small block. The 427 was almost impossible to hook up even from a roll and with good tires. It would spin in any gear and from a punch at 50 mph or so. The 347 car was fast and fun to drive. I'm not too sure that a lot of front end weight and tons of power is the ticket in those cars based on what I've seen but maybe people get it to work.

X2, John. Couple of years back a customer was building a replica Cobra. We priced him in round numbers $5K for a 347" SBF and $15K for a bad cam "genuine-side-oiler-488" FE" from an out of town specialist. He naturally went for the FE. First time he took it to an autocross, he got humiliated by another replica with a box stock Mustang 5.0. Same thing on the strip. He never mastered easing off the line and into the throttle. He'd get left by the better drivers in the SBFs most of the time. After a few near death experiences when it would bog and then roar, he just drove it to shows on Sunday mornings and parked it. Plus the FE was like riding in a toaster oven. His wife made one fifty-mile trip on a summer day and said never again. She caught a ride home in a sedan. Your results may vary.

jack vines

[289nate]

How many 360 cfm 427 FEs have you built?

Do you even know of a head that flows that much for an FE?

I'm sorry, but I can't agree with you on any of your points.

As for the OP, there was no bad intent, and I didn't mention him specifically. You know that. However, he is having an engine built by someone else and is asking for advice, so that's my advice based on building FEs for a living, building engines for Cobra replicas, and having owned one.

I assumed the builder he talked to was going to use a worked over Blue Thunder head. Getting over 350 cfm shouldn't be impossible with that casting. Apparently it's also in the budget as the original poster is seriously considering it.

I didn't know we were talking about actually building an FE. I was under the impression we are talking about the characteristics of an engine with two types of heads and cams. I'm pretty sure an FE will plug into Stan's programs like any other.

If it makes you feel better I have not built an FE. Doubt I ever will either since I only have interest in building and my own personal stuff and do not like that particular big block.

What I have done is build an engine , and car for that matter, which doesn't have the negatives down low that you mention should be expected with an engine that wants to shift well over 7,000 rpm at the drag strip though it is only 4.060" x 2.87" and in a car that goes down the street right around 3,000 lbs. That first hand experience, tested by myself on the street, dyno, and track, is what I offered up for discussion.

Some very smart people were there to point me in the right direction and keep me from building the typical AFR 165 and dual plane Air Gap intake 289 combo that so many told me would be good enough and be the limit of what I should use and expect any street manners or low end power with. I'm very thankful to those people that kept me from building such a thing as I would have been selling myself short.

No sweat off my back if you can't agree with what I know first hand and have done. It sure won't affect how my car drives. At the end of the day I'll talk about what works for me and you can feel free to talk about what works for you.

[blykins]

No problem. Different strokes for different folks.

Going off of my customer base and the various emails/calls I get about taming an engine down after its been treated as a "7000 rpm street engine", it's a common change that people want to make. I'm not alone in this way of thinking, there are many other builders in this thread that have shared the same feelings. A 2500 lb car does not magically transform an engine into a 5.0 Coyote with VVT...

I would like to see how your mustang would behave with a 3.08-3.54 gear. You keep using your application as a comparison, but there is not a comparison to be made there.

[blocker]

How many 360 cfm 427 FEs have you built?

Do you even know of a head that flows that much for an FE?

I'm sorry, but I can't agree with you on any of your points.

As for the OP, there was no bad intent, and I didn't mention him specifically. You know that. However, he is having an engine built by someone else and is asking for advice, so that's my advice based on building FEs for a living, building engines for Cobra replicas, and having owned one.

I assumed the builder he talked to was going to use a worked over Blue Thunder head. Getting over 350 cfm shouldn't be impossible with that casting. Apparently it's also in the budget as the original poster is seriously considering it.

I didn't know we were talking about actually building an FE. I was under the impression we are talking about the characteristics of an engine with two types of heads and cams. I'm pretty sure an FE will plug into Stan's programs like any other.

If it makes you feel better I have not built an FE. Doubt I ever will either since I only have interest in building and my own personal stuff and do not like that particular big block.

What I have done is build an engine , and car for that matter, which doesn't have the negatives down low that you mention should be expected with an engine that wants to shift well over 7,000 rpm at the drag strip though it is only 4.060" x 2.87" and in a car that goes down the street right around 3,000 lbs. That first hand experience, tested by myself on the street, dyno, and track, is what I offered up for discussion.

Some very smart people were there to point me in the right direction and keep me from building the typical AFR 165 and dual plane Air Gap intake 289 combo that so many told me would be good enough and be the limit of what I should use and expect any street manners or low end power with. I'm very thankful to those people that kept me from building such a thing as I would have been selling myself short.

No sweat off my back if you can't agree with what I know first hand and have done. It sure won't affect how my car drives. At the end of the day I'll talk about what works for me and you can feel free to talk about what works for you.

What rear end gears do you run? Low end power is easily fixed with low gears in a street car and can mask plenty of problems..

[plovett]

I run a 252/260 @ .050 cam in a 428 FE in a car maybe 900-1000 lbs heavier than the 2500 lb cobra. It doesn't buck or shudder or or do anything horrible. I drive it to work. I can cruise around town at 2000 rpm in 3rd gear. It's a C6 with 4.11 gears, rather than a 4 speed with 3.54 gears, but I doubt the extra gearing makes up for 1000 lbs. If my car were 1000 lbs lighter I'd likely run even more cam and rpm.

Every time I buy a part for my car, I later wish I had bought a "bigger one" whether it be cam, gears, stall converter, heads, you name it. I've spent way too much money replacing mild parts with more radical ones. I had a 3.00 gear, then had a 3.25 gear put in, then a 3.75 gear, then a 4.11. Stall speed went from stock to 2800 to 3600. Now I wish I had about 4500 stall. Max RPM's went from maybe 5500 to 6200 to 6700 to 7000+ now. I now have a 2x4 bbl single plane Tunnel Wedge intake with two 750 Holleys (not installed yet) to replace my tame 1x4 bbl dual plane with a Holley 850. Sigh.....

An FE powered cobra is a car begging for a "serious engine" in my opinion. But that's just my opinion. It's up to the owner if he want's something tame to cruise around in or if he wants something more in the spirit of the original 427 Cobra. I'm guessing 90% of cobra kit car owners want something tame and easy to control. And don't forget "tame" is a relative thing. So, I can see both points of view. If I had Cobra kit car I'd be in the 10% group.

paulie

[JDR Performance]

It's off topic but I should clarify what I was talking about. The BBF car had ported heads, solid roller, and the owner told me that the motor had been built by someone in TN or KY that specialized in them. I was told that it was around 700 hp on the dyno but never saw a sheet. This was 12-13 years ago so I don't remember all the details. I had just done the carb for him and the motor was just put in so no idea what could have been done with the suspension. He had good tires on it, same as the SBF car. Summer weather. The BBF car was like driving on pavement after snow flurries, you could spin at will even on the highway and it seemed to "push" bad if you tried to corner quickly. It was still fun and sounded great. The SBF car handled well, didn't sound as good, but would stick and accelerate and in my opinion would beat the big block car in any type of race. Again, it may have been something that could have been fixed with good suspension work but it wasn't really even usable like it was. You could actually go faster with the other car and not feel like you were on ice.

[blykins]

I run a 252/260 @ .050 cam in a 428 FE in a car maybe 900-1000 lbs heavier than the 2500 lb cobra. It doesn't buck or shudder or or do anything horrible. I drive it to work. I can cruise around town at 2000 rpm in 3rd gear. It's a C6 with 4.11 gears, rather than a 4 speed with 3.54 gears, but I doubt the extra gearing makes up for 1000 lbs. If my car were 1000 lbs lighter I'd likely run even more cam and rpm.

Every time I buy a part for my car, I later wish I had bought a "bigger one" whether it be cam, gears, stall converter, heads, you name it. I've spent way too much money replacing mild parts with more radical ones. I had a 3.00 gear, then had a 3.25 gear put in, then a 3.75 gear, then a 4.11. Stall speed went from stock to 2800 to 3600. Now I wish I had about 4500 stall. Max RPM's went from maybe 5500 to 6200 to 6700 to 7000+ now. I now have a 2x4 bbl single plane Tunnel Wedge intake with two 750 Holleys (not installed yet) to replace my tame 1x4 bbl dual plane with a Holley 850. Sigh.....

An FE powered cobra is a car begging for a "serious engine" in my opinion. But that's just my opinion. It's up to the owner if he want's something tame to cruise around in or if he wants something more in the spirit of the original 427 Cobra. I'm guessing 90% of cobra kit car owners want something tame and easy to control. And don't forget "tame" is a relative thing. So, I can see both points of view. If I had Cobra kit car I'd be in the 10% group.

paulie

A converter makes up for a lot when it's not locked up...

Y'all need to hop on over to club cobra sometime and read the threads about guys wanting a milder engine.

I'll be honest, I like the peakier engines too, but they don't belong in cars with 3.08 and 3.31 gears that spend 99% of their time at 2000 rpm. It's just not a good match, especially for guys who are not familiar with high horsepower carb engines.

[289nate]

Blykins, I think I'm just waaaaay out of touch with the average Cobra customer. Throw me into the same category as plovett. If I make more power, I will find a way to make it work or die trying. LOL. I'll be happy to listen to any pointers you have if I ever decide to put an FE together.

[blykins]

It's certainly not limited to just FE's....

One guy over there bought an all aluminum 427SBF from Ford Racing. Ended up having an issue with a solid roller lifter, but wasn't happy about how the engine behaved off-idle and at cruise rpm. He talked to me about rebuilding it, but ended up getting FRPP to pretty much warranty it...and he had them swap it to a mild hydraulic roller. Loves the car now.

I will say this...all of my cars that I've built for myself have deep rear gears and the engines are a little "happier." So I join you and Paulie in your wants and desires. However, I would say the majority of guys don't understand the implications of a mismatched combination of a high strung engine and low 3's rearend gear.

At what port volume do you end up with 360cfm on an FE head? A 205cc head that flows 360cfm is going to be a lot more fun than a 260cc head that flows 360cfm. You take a cylinder head with big flow, low velocity, a long duration camshaft, a dual carb intake with some fussy carburetors, and a 3.31-3.54 gear, and you'll have a guy who will hate the car in not much time... I understand that that the OP doesn't have a dual carb intake, but I'm just trying to make the point that anyone who is buying an engine needs to be made aware of the total combination and what the results will be.