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Hi all. I'm a bit of a novice with motors, but here goes (please be patient with my questions):

I have a 533 CID BBF with Edelbrock 460 RPM heads, demon rs 975 carb, hi po rods, crank, etc.

On a recent chassis dyno run, I could not get the motor to make any power after 5000 rpm. It stayed at a repsectable 500 hp, but would not climb (like it should) to 6000+ rpm. Instead the power curve turned into a flat, wavy line.

I think there is some problem in the valvetrain causing float or bind. Some specs. Hyd flat Cam is 236i/246e @.050 lift is .584i/.611e. Springs are 120/330#. It has 1.8 ratio roller rockers

Assuming carb, ignition, exhaust are all ok, please consider theseQuestions:

Is valve bind/float causing this issue?
Are the heads too small for the motor? Porting?
Is the cam adequate?
Is this too much lift for a hyd flat cam? i.e will this destroy the cam? (FYI, the cam self destructed once already)
Should I switch to a more radical hyd roller cam, in the hopes that it will provide more power and not fail?

Anyone that is interested, i can email you the dyno sheet.

Thanks,
CC





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Walt Barnes
(no login)
4.33.181.188 desktop dyno says
No score for this post November 9 2001, 1:29 PM

First, I'm assuming you are NOT using the Edelebrock springs that they sell for those heads. Those springs are specified as good only to .600 lift at the valve.

Second, I'm assimung the cam specs you gave are already adjusted for 1.8 rockers

FWIW, I put your combo into desktop dyno and it said 500 HP at 5,000, flat to 500 HP at 5,500, dropping to 480 HP at 6,000 RPM. About what you got in RL, right?

If you port the Edelbrock heads you will move the peak to 550 HP from 5,500 RPM flat to 6,000 RPM.

Ported Aluminum CJ heads show they will do about the same with your current cam. (Don't even think of using the Aluminum CJs without porting.)

If you go with a street roller like Comp Cams XR280R (with 1.7 rockers) with ported Edelbrock heads (your really need the porting to take advantage of the big cams) your HP will peak at 620 HP at 5,500 and be above 6000 HP from 5,000 to 6,000.

Want more? Don't care about the street? The Comp Cams XR292R will move the peak to 630 HP from 5,500 to 6,000 and torque is still above 600 ft/lbs from 3,000 to 5,500 RPM.

Do yourself a favor. Get desktop dyno for cam selection.

Walt






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Chris C
(no login)
168.73.245.57 533ci
No score for this post November 9 2001, 2:52 PM

Interesting problem you have there. First, the Edelbrocks are kind of unknown because they are so new, but they should make power over 5000rpm even on the 533. You definitely have enough carb. You didn't mention intake, what are you running? Now, that cam is mild for a 460, it is on the small side for a 533. That said, I really can't say if it would make power after 5000. That is a lot of lift for the duration, I don't know that I've seen a flat tappet that aggressive before. I'd expect your motor to make right at 525-550hp with the current combo. What are you running for headers?

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Brad
(no login)
216.106.37.32 533" dyno
No score for this post November 9 2001, 8:15 PM

Will it still rev to 6000, or does it stop at 5000? valve float often seems like the engine is hitting a rev limiter. when the valves float, most times it will not rev any higher than the rpm they begin to float. If on the other hand it made 500 rwhp @5000, and still made 500 @ 6000, then something is limiting it other than valve float. You have enough carb. The cam seems a bit small for 533 inches. It will probably have a peak rpm of about 5000. Edelbrock lists those heads as flowing 326/207 cfm @.700". I guess these numbers are out of the box? comparable to a set of aluminum CJ's. Porting could bring them easily to 340/225 cfm. If you want more power at a higher peak, try a bigger cam. I have heard good things about the comp street roller cams. Is this a street driven engine? you didnt mention if this was a automatic or a stick, but the assumed loss's are 23%, and 18% respectivly. so 600-650 at the flywheel isnt bad. And having all that power at only 5000 is easy on parts.

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mcs
(no login)
216.224.166.173 You're showing 120lbs. on the seat for your valve springs...
No score for this post November 9 2001, 9:20 PM

better check your cam specs again, that might be on the light side. If it is, that could be part of your problem.

You didn't say whether you were running a single or dual plane manifold. That can make a BIG difference. Single plane manifolds will run circles around the dual plane.

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Bob M
(no login)
63.26.4.87 spring pressure and intake...
No score for this post November 10 2001, 9:02 PM

Too much spring pressure will NOT cause a high-rpm problem (too little will), and a single plane intake will not necessarily "run circles" around a good dual-plane intake like the Stealth.

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mcs
(no login)
216.224.143.172 Please re-read my post again slower about the spring pressure...
No score for this post November 10 2001, 10:16 PM

I not trying to argue with you, but I know of no dual-plane intake manifold in general, that will horse-power, or allow more rpm than a good single plane intake manifold.

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Bob M
(no login)
63.26.4.240 Sorry... \=^)
No score for this post November 10 2001, 11:02 PM

My mistake...Thought I read Tight instead of light.

I Don't agree with your blanket statement about single verses dual-plane intakes though. A Stealth will perform better than a single-plane Streetmaster or Torqer and in some applications would be a better choice than the Victor. The Stealth or Performer RPM would not quit working untill higher than the RPM range specified in the initial post.

Bob

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mcs
(no login)
216.224.143.172 No problem Bob...I'm generalizing about the single vs. dual plane...
No score for this post November 10 2001, 11:19 PM

intakes. I did some testing with Desktop Dyno, and the single plane manifolds all showed quite a difference. Like 30-40 horse-power more, and the rpm shot up. I'm not doubting you though.

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Chuck C.
(no login)
216.140.239.157 More Info
No score for this post November 12 2001, 6:37 PM

Thanks for your help.
Below is more info that was requested:

- 460 Torker II intake (single plane)
- The edelbrock springs are good to .700 lift I think
- Header are very non restrictive side pipe assemblies.

I have the dyno sheet in e-mail format if anyone would like to see it...

I think I have a couple of issues...
1) the lift is too much for a hydraulic flat tappet.
2) the cam is too small for a 533 CID motor
3) the heads do not flow good enough for a 533 motor.
4) springs may be a little on the light side.


Solution:

Put in big hyd. roller cam (rump rump), along with new springs. While I'm at it, send the heads out for porting.

Please let me know your thoughts on:
What would be the best cam to use for hi-po street use on pump gas (10.25:1 compression)?

Is it easy to put a hyd. roller on a 460? I thought that it takes all kinds of goofy retainers, etc.?

Will my pushrods work with a new roller cam? If not, how do I figure out what length I need.

Thanks
CC



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Brad
(no login)
216.106.37.192 interested in dyno sheet
No score for this post November 12 2001, 7:34 PM

could you send me a copy of the dyno run? have some answers/thoughts, just need to confirm with the dyno printout.

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Bob M
(no login)
63.25.252.133 Thought on the side-pipes...
No score for this post November 12 2001, 8:51 PM

Most Cobra kit-car side-pipe assemblies are much more restrictive than you would think. Ford Power Parts found that they were a major power choke on the dyno. Slip the mufflers off or out, and make another run to see.

Bob

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Walt Barnes
(no login)
4.33.181.188 sounds good
No score for this post November 12 2001, 11:41 PM

A big hydro roller (or a mechanical would be even better) will actually have more duration at .050 but less advertised, so it will idle better. Yes I think you need it.

The roller or hydro roller is a bolt in.

You will need different pushrods. To be sure you will have to measure them. It is a slight hassle.

Those heads will come alive with a good porting job. It is money well spent.

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Steve
(no login)
209.140.200.191 Need way more cam
No score for this post November 13 2001, 12:39 PM

You need more cam. When you pick one out, go one size bigger after that. My advice. 535 will always have a ton of torque.

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Ken
(no login)
165.154.190.12 Some thoughts
No score for this post December 14 2001, 10:07 AM

Been there. You do not mention what intake but doesn't matter. My 521 had the same problem. You could put a brick on the gas pedal and walk away from it and it wouldn't rev over 6200 under load.
The problem is two fold. A motor this big just will not run decent without a tunnelram in my experience. And 1200 cfm is just gettin close for air.
We switched from a 950 and weiand stealth and immediately could rev to 7200 and one would think there was two motors under the hood.
Back to back comparrisons on a second motor (460 c.i.) that wouldn't rev (portosonic and 1150) switched to a weiand tunnel and 1150 and instant 6800 and power.
We just tried a Victor and 1150 and it seems to work well to 7000, and if you look at the runners length and plenum size, it really is a tunnel ram disguised as a singleplane.
 
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