Reply to "COBRA JET: Unleashing The Performance Capabilities Of 351 Cleveland Engines With Open Chamber 4V Heads (Q Code)"

quote:
Originally posted by PanteraDoug:
Personally, I would use 10:1 static compression ratio as the maximum. I wouldn't worry too much about whether you have 9.5 or 10.

The point is, you want to run higher then the 8.0:1 in the stock open head engines.

That's my opinion on a rebuild.


As far as a camshaft, YOU need to determine what the definition of a "street engine" is. "We" have all sorts of race and former race engines being run on street registered and street driven cars.

The old definition of "street driven" on cars like Panteras, if not all current vehicles has changed significantly since the '60s and '70s.

Few are going to use any of these cars as "everyday transportation".

In that old definition where you need to worry about being in city type traffic of bumper to bumper then I agree with GP's limit of camshaft timing.

Even that is on the "racy side" but in this limited use existance of just taking the car to a car convention, a high speed on the track event or even a "cars and coffee" thing down near the beach, limiting the cam timing is much less of a concern.

For one thing at least with a Pantera, you don't need to worry about the operation of an automatic transmission being effected by the camshaft timing.


To select a mechanical lifter camshaft is sentencing yourself to a "race car" type maintenance of almost daily readjustment of the valve train.

There definitely cars running them out there but those are really falling into the definition of a "Pro-street" car.

If those types of maintenance issues don't concern you and you just want the maximum amount of hp that you can get, then yes, go for it.


Hydraulic roller lifter cams have become more dependable and there is a greater variety of "off the shelf grinds" for you to select right now.

They are going to give you closer to a maximum hp then a flat tappet cam but the amount you gain is always going to be debatable.

Aftermarket kit components in the past or should I say initially left a lot to be desired on a dependability consideration but there are a lot of them running around the streets now with much less issue.

The main consideration is going to be the initial cost vs. a convention flat tappet cam.


I personally like solid lifter/flat tappet cams. I know how to deal with them better then the other alternatives and find that they are a better compromise as far as approaching maximum hp in a street driven car with high dependability.


I would however recommend a hydraulic lifter flat tappet cam for a true street car.

Then you could just jump into the thing, drive it anywhere and not worry about weather changes, finding racing gas along the road, and even let your daughter drive the car down to the "hamburger stand" without too much worry of being able to drive the car without a nervous break down.

By far the single most significant factor in determining the character of the car is the camshaft that you select.

Although I agree with George on the recommended timing, I'd say that you can go hotter on the cam then 236 @ 50.

What you really want to do is to limit the overlap timing on the cam to under ABOUT 70 degrees and you want a valve lift that is going to let these heads work which is going to be over .550 to as much as .625.

These 4v heads were designed to work at around .600 lift.


The more that you ask others, the more that you are going to find that the camshaft selected and LIKED is a very personal thing.

You actually would be better off "interviewing each CAR", experiencing how they sounded and their idle manners before you selected something.

How you are going to do that, I have no idea, but good luck on that one.


I’m not wedded to any particular static ratio so for me, I think I can live happily with ~9.5 How I can achieve it with flat tops and some milling of the head and deck or domes, I’ll keep working on figuring out, but it looks that using flat tops instead of Ross pop ups may save roughly enough to cover a hydraulic roller setup.

I very much appreciate what you are saying about Street.
When looking at Street for me, I am thinking probably roughly similar to you, that it won’t need lash adjustments at the weekend, won’t have a super rough idle, won’t be temperamentally unreliable if used to as a daily driver for a few days whilst my BMW is undergoing repairs or whatever, but it will have the capability to unleash some serious torque and HP, and maybe enjoyably compete in vintage style racing events, hill climbs and the likes, and still remain a reasonably mannered cruiser for the occasional long journey into the Scottish highlands or across Europe.

I’m not building the car as a daily driver, and again apologies gents that it’s a Mustang rather than a Pantera, much more a weekend fun car, something to be driven though rather than simply looked at.

With this I also don’t need to be worried about the auto trans, as i’m going to mate it up to a Dave Kee rebuilt RUG-JA big block toploader.

With the wise words of you and George in my mind Doug, I’m leaning very heavily towards the hydraulic roller setup and I’m going to take a more serious look at what sort of compromises and financial travails that entails during the next couple of weeks.

As for interviewing the cars to understand the cam selection, well it might have to wait until next year now, but I’ll find a way, might make for a fun vacation.
(I was also considering picking up a couple of OEM style cams from Rock auto or summit to get a feel for the changes in power bands and idle, going hydraulic might make that an expensive proposition though I suppose.)
×
×
×
×