Too much cam? Please help diagnose

[mrmustangman357]

Here is my setup:
351W
9.8:1 compression
retrofit hydraulic roller cam.
Specs identical on intake and exhaust: .530 lift, 230 dur @ .050, 110 centerline. That is all I know for the cam
trick flow twisted wedge heads (not the CNC ported ones) i think 170cc
Edelbrock performer RPM air gap manifold with 750 cfm carb
C4 with 2300 stall converter
8" with 2.73s (still looking to upgrade that)

I originally thought I had an intake gasket leak, because it would pull very little vacuum. I swapped the gasket and it seems to pull 14 inches of vacuum at idle, but in gear it pulls around 5-7 inches! That is with an idle speed around 650-700 rpm. The distributor is properly adjusted to 36 degrees total, but the manifold vacuum reading was taken without the vacuum advance connected, which is right now connected to ported vacuum source (I was also doing the ign. timing at the time). I know i no longer have the intake manifold leak. What can I do to get more low speed/ idle manners to this setup? Can I try advancing the cam? or do I need to turn up the idle speed and if so how far can I go? Perhaps I am overlooking something. I do have power brakes with a vacuum reservoir so I would like to be able to use them How radical is that cam? personal experiences would really help.

Problem is, everywhere I look, i can only get information about vacuum for STOCK motors. With high performance, I should expect it to be lower, but I'm hoping I can improve the number from 5-7? I saw Rhoads lifters, but for $300 for a roller lifter set, I think I can spend that cash elsewhere.

Thanks in advance for any help,
BWill

 

[RUSTYNUT]

There is an outfit that makes a hydro- boost master cylinder that runs using the power steering pump. Old school are vacuum cans,electric vacuum pumps. I'm also planning to much cam for daily driving and am leaning toward the hydroboost or just keeping manual brakes. Check out Summit for prices on this stuff.

 

[iapexl8r]

the car will be much eaiser to drive when you get some gears. high gear ratio large cam no good. do the brakes run out of vacuum now???? chris

 

[bnickel]

well the idle speed should probably be a littl higher, but you didn't say if that idle speed was in gear or in neutral, i'm assuming in neutral, if so you should probably bump it up to around 850 or so, that will help some. the cam isn't all that radical but it does have a fairly narrow LCA, a wider LCA would give better idle characteristics. the higher gearset is probably hurting you a little as well, you probably need more like a 3.50-.370 gear as well.

 

[ratio411]

That cam is on the large side for street manners, but not overly large.

You say you have the vacuum resevior?
That should be fine to provide extra vac to your booster.

IMO your idle is too low.
Vacuum in N is about right at 14...
It will drop in gear, but not as bad with a decent idle speed.

Those gears need to go fast!
With those gears, I bet you don't even fully utilize the converter much.
The heat caused by the low rpms will do your converter in, if not your whole tranny.
You need gears that will keep you at or above converter rpm most of the time.
You converter is a little on the mild side for that cam, but it won't matter if the gears burn it up.

The way your setup is now, you probably don't make power until around 2500 rpm.
Your intake starts at 1500, so you have 1000 rpm of that wasted.

I was in that situation once and the car performed much better and had much better throttle response with a mild single plane (Torker 289).
If you can pick up a cheap used Torker 351w, you might just try it out.
If you don't like it, you can always resell it.

I took my T289 off looking for more low end and tryed a Perf. RPM.
It sucked really bad. Felt like it made the engine very lazy.
The cam was 228/235 @.050"... didn't come in until 2800 rpm.
Right where a single plane shines and a dual plane begins to be a detriment.
Don't get me wrong, the car still made power to 6000 or so, but just when the cam was coming on like a lion, the intake was getting lazy.
I put the T289 back on and it felt great again.
The cam was too big for a dual plane... and that was a 302.
A 351 will have even more use for a mild single plane IMO.

Just some thoughts.

 

[D.Hearne]

I used a similar cam in my 331 and it's idle and street manners are fine. Mine's a Z303 with 1.7 rockers. (.587 lift [email protected] duration, 112*LSA) Do as Ratio411 said and idle it up. My 331's power comes on a 1500 with a high rise dual plane 3x2. Yours should as well. It's backed by a mild stall C-4 and it takes nothing to break the tires loose, a slight powerbrake and it'll lightem up.

 

[mrmustangman357]

lol that's how it is right now! i'll idle up and im off to the strip! yay!

 

[mikethebike]

That cam is on the large side for street manners, but not overly large.

You say you have the vacuum resevior?
That should be fine to provide extra vac to your booster.

IMO your idle is too low.
Vacuum in N is about right at 14...
It will drop in gear, but not as bad with a decent idle speed.

Those gears need to go fast!
With those gears, I bet you don't even fully utilize the converter much.
The heat caused by the low rpms will do your converter in, if not your whole tranny.
You need gears that will keep you at or above converter rpm most of the time.
You converter is a little on the mild side for that cam, but it won't matter if the gears burn it up.

The way your setup is now, you probably don't make power until around 2500 rpm.
Your intake starts at 1500, so you have 1000 rpm of that wasted.

I was in that situation once and the car performed much better and had much better throttle response with a mild single plane (Torker 289).
If you can pick up a cheap used Torker 351w, you might just try it out.
If you don't like it, you can always resell it.

I took my T289 off looking for more low end and tryed a Perf. RPM.
It sucked really bad. Felt like it made the engine very lazy.
The cam was 228/235 @.050"... didn't come in until 2800 rpm.
Right where a single plane shines and a dual plane begins to be a detriment.
Don't get me wrong, the car still made power to 6000 or so, but just when the cam was coming on like a lion, the intake was getting lazy.
I put the T289 back on and it felt great again.
The cam was too big for a dual plane... and that was a 302.
A 351 will have even more use for a mild single plane IMO.

Just some thoughts.

One more case in support of matched components.

 

[D.Hearne]

One more case in support of matched components.

My 331's cam, converter and intake combo aren't "matched" components, but they do work well together. Just because some company catalog says one thing about a component, doesn't mean it won't work with some that supposedly don't. That's what Hotrodding is all about, experimenting with different combos. Some work, some don't. Why limit yourself to what some tech guy says you need?

 

[brianj5600]

My cam is 229 at .050 and .544 lift and 112 lsa. I have a Torker II and the cam is set with 111* ICL. The motor only has 8.8:1 compression. It idles fine at 650 and looses less than 50 rpm's in gear. The motor is set up for a turbo and I am surprised it runs as good as it does N/A. My TC is a 3200 which helps a ton with idle as well as acceleration. It has gone some 8.20's with 3.08 gears in the hot, humid weather in TN. I think with some more tuning it will go some 7.80's once it cools off. I think that some tuning and a looser TC will do wonders for your car.

MM357, what is your initial timing set at? More initial timing will usually help vacuum in gear and throttle response. I think 36* total may be a little much with those heads too.

Check your carb to see how much of your transfer slots are showing with the way it is set at idle. You have to remove the carb and look under the butterflies. There is a slot that is exposed more and more as the primaries are opened. They should look square with the butterflies closed. I set my primary idle with the carb on the bench. Once on the car I use the secondaries to set idle speed with the car running. It is a bit of a pain, but it can be done.

 

[ratio411]

My cam is 229 at .050 and .544 lift and 112 lsa. I have a Torker II and the cam is set with 111* ICL. The motor only has 8.8:1 compression. It idles fine at 650 and looses less than 50 rpm's in gear.

The 3200 converter and 112 LSA are surely big help.
Is this cam flat tappet?
The roller is going to have much more aggressive ramps.

Not to minimize your post... I think you are definately right about the TC.

I still cringe thinking about that cam turning 2.79 gears!

 

[brianj5600]

It is a flat tappet. One of the claims to fame for a HR is less seat to seat time for the same .050" duration, which should mean better idle/torque. My motor has a full point less CR and shorter intake runners. I am also guessing his ICL is closer to 107*. All this should add up to a smoother idle and more torque.

 

[mrmustangman357]

She ran 13.4 at 107 mph! 60 ft was around 2.4, of course due to the rear axle.
Initial timing is around 14 with the vacuum line disconnected. I connect the vacuum line to ported vacuum, but it does have a slight vacuum from this port, so maybe my butterflies are starting to come off the idle circuit. I'll look into it as I get the car running better.

Don't get me wrong, I am all for "matched combos" but when you run out of cash and have enough to spend on one component, I choose to spend it right. better to have quality stuff and one bad component (axle) that can easily be swapped out than spend half on every component then everything is half-assed. Wouldn't you agree?

Regarding the carb, I'll mess with the mixture screws a little bit more in search of vacuum. Would it be beneficial to do it in gear as opposed to being in park?

 

[brianj5600]

Good MPH, but the 60'....Was it spinning? Open diff? Double pumper or vacuum 750? What were you 1/8 et and mph?

 

[jerry S]

You have a roller cam and pull 14 inches at idle. My flat tappet cam (bigger than yours)

Lift: INT 538, EXH 534
DURATION AT .50 DEGREES: INT 236, EXH 242

pulled 9 inches at idle, which made the power brakes very scary when stopping at a light, but when under load, never pulled less than 20 something inches. I think something is not right given that you have a roller cam. I don't think you should be pulling that low vac while under load.

 

[mrmustangman357]

Good MPH, but the 60'....Was it spinning? Open diff? Double pumper or vacuum 750? What were you 1/8 et and mph?

the 60 ft was because of the pegleg rear axle. I had to walk it off the line, but then by the 60 ft she really took off. my 1/8 mile was 8.89 at 86.3 mph, with the quarter mile at 13.42 at 107.3 mph. Carburetor is a vacuum secondary 750

 

[mrmustangman357]

I checked it today and at idle in park, I was able to get 18 inches out of it at 1000 rpm. when it goes into gear, it goes down to about 700 rpm. The wideband is showing higher than 15:1 at idle, but at cruise it jumps off the scale to lean quite a bit but sits around 12:1-12.5:1. Shouldn't it be around 13.5-14 at cruise? At WOT, it sits around 12.5:1 which is a lil rich for what I want but oh well. I'm eventually hoping for 110 mph in the traps before my axle swap, so some more tuning is definitely needed.

 

[mrmustangman357]

here it is uncapped:
http://www.youtube.com/watch?v=h1j2pkY8CoY