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Discussion Starter #1
I need some serious tech help here guys.
I just swapped cams in my Incon TT 331 Cobra. The results were HIGHLY dissapointing. I swapped out the Stock GT cam I got from Ed C. for a little fast-ramped custom I speced out.

Stock GT cam (Cam Dr. specs):
278/278 @.004
210/210 @.050
115LSA, 114ICL (Per Ed)

New cam (I call it 'weak-nuts'):
Comp lobe #3326, single pattern
267/267 @.006
217/217 @.050
113LSA, 119ICL

Setup:
8.9 to 1 331
GT40 Iron heads, stock valves, exhaust bowl work, 130lb (seat) dual springs, stock pushrods, 1.7 'cobra' RR's.
Ported Cobra intake
VRS catted X-pipe
Dynomax race-bullet mufflers
36lb injectors, dual 255lph Fuel pumps, stock lines/rails
65MM TB
Incon 80MM mass-air
9PSI from the hairdryers
3.27 gears

Stock cam dyno was impressive, but power fell off WAY too fast.
430HP @4700rpm, 511TQ @3800rpm (rear wheel)
New cam dyno #'s:
433HP @5750rpm, 432TQ @4400rpm (rear wheel)
There were NO other changes aside from the cam.

I lost a TON of torque! Why? The stock Gt cam has ~46 degrees of overlap @.006, & -20 degrees @.050. Mr. Weak-nuts has 41 degrees of overlap @.006 @ -9 @.050. Is there too much or too little overlap? I thought turbos didn't respond well to too much valve overlap. Could it be vavle timing? Specifically were the overlap falls in the combustion cycle? Most of it is After TDC.

All I wanted was 500/500 Rear wheel. If the stock cam would've peaked higher I would've had it...or pretty close. I thought for sure this cam would've given a good power increase. Fast ramps, small heads, low overlap, retarded like a feind to get HP to peak higher in the RPM.
Please shed some light on my expensive miss-hap.

-Shaun
 

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I wouldn't expect the cam to be the biggest problem. Seems to me you have everything going right, except the heads, which are clearly a very limiting factor. They simply can't flow enough. Air in...air out. GT40's aren't horrible, but they won't support turbos very well. Ed, etc. know more about this than me, but seeing your rpm jump(at peak) makes it look like the heads have you limited.
 

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Discussion Starter #4
kim said:
call ED, you paid for the cam...... he will ensure you have it in right.
I made the 'weak-nuts' cam. I'm sure one of Ed's cams would've done MUCH better! In fact, I'll probably be ordering a custom from him within a week or so....either that or slap the stock GT cam back a little retarded. I just want to know what I did wrong.

Here are the 2 graphs. The 'weak-nuts' cam has a NICE (looking) torque curve, but it flat out didn't perform.
Pay attention to the 400TQ & 400HP marks. How long each cam held that level.

Weak-nuts dyno:
http://www.Californiafords.com/images/dyno/01_18_03/DSC02396.JPG

Stock GT cam dyno:
http://www.Californiafords.com/images/dyno/01_18_03/DSC02398.JPG
 

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Dark93

This is a pefect example of peak horsepower meaning nothing. Do you have any timeslips with both combos? The stock cammed motor clearly makes much more torque and horsepower over a broader range than the "weak nuts" combo. (average horsepower) The only time the "weak nuts" motor has an advantage is from 5000-5800 RPM. And then you're only talking around 25 horses or so. The stock cammed motor makes 75 hp more at 3600 and 50 hp more at 4200; not to mention the tremendous torque advantage!
Yes, you are correct about turbo cars not liking alot of overlap. This is exactly why you lost so much torque and horsepower throughout most of the RPM's. The "weak nuts" cam has alot more overlap at .050; bleeding off cylinder pressure that the turbo would have created early in the intake cycle. Exhaust valve closing and Intake valve opening points are crucial with a turbo. This is why they respond so well to wide LSA cams. (keeps overlap down)

The heads are hurting you also, but you would still want a better cam than "weak nuts". Go with a custom cam from someone who knows what they are doing and you will be satisfied with the results.....James :D
 

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A little addition on the situation,but your fuel curve is a little funny. Both dyno runs have it delveing into a little rich about 4000 RPM.

Blowing too much cylnder pressure out the exahaust.
 

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Kim

I was wondering if the air:fuel ratio was a little fat myself. I'm not much of a fuel injection guru, but I've read where some tuners like their power adder setups to be between 11.5-12.5 air:fuel ratio.(both curves appear pretty equal)....James
 

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Shaun,
I had this debate earlier with Mark on AIM. WHile I can't give you any insight to your cam questions I will say that from your first dyno graph you have a major restriction either in the intake or exhaust to cause that TQ to die off so quickly. Those turbo's can provide enough cfm to feed your 302 to at least 6500rpm and maintain positive pressure. The most likely candidates are the heads and then exhaust. Did you se Holdners Dyno test on Warlock mufflers and Incon kit? He unbolted the bypass in the muflers and gained 50hp at the top end. I would go back to the stock cam, maybe 4 degrees retarded, and then consider heads and possible exhaust improvements.

JL

Warlocks/Incon 10psi/Gt40 heads/Cobra/Bcam
[email protected] 5300, 483lb/ft @ 4200 rw

removed bypass, 487hp :eek: @ 5400, 508lb/ft @ 4600

one more edit- Bassani cat pipe vs. offroad H, +40hp/tq to the OR H (same combo as above.)
 

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Discussion Starter #10
So far the concensus is that the heads are too small....no doubt, but I bet I can get 500RWHP with these heads & I aim to try.
The stock GT cam installed on a 114ICL has an intake closing point of 39 ABDC @.050 lift. The 'weak-nuts' closes at 48 ABDC. Peak HP moved ~1100RPM....this is consistant with moving the IVC point 9 degrees.

redrumpony:
You believe I have too much overlap at .050 & that I'm actually blowing the air/fuel mixture out of the exhaust.... This makes sense, but I actually decreased total valve overlap..... & Plenty of turbo guys swear by the F303 which has -2 degrees of overlap @.050.
Could it be that I have too little total overlap (at .006) & too much at .050? Like the ramps are so fast that the gasses are stalling in the overlap cycle?

What's really odd is that Byron had to richen the mixture up quite a bit from the fuel tables with the stock cam. Same fuel tables were 11.5 to 1 w/the stock cam & 13.5-14 to 1 with this new cam.

As for being a little fat.... Sure, just a little, but I'm running on california 91 here. + when I get on the street & load the motor down, it should lean it out .5 or so.
 

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Discussion Starter #11
Jim, I know the exhaust is holding me back, but I want 100% smog legal....& I like my little restrictive heads.
I don't think an open exhaust (dumps after turbos) would change the shape of the power curves....just move them up ~50 or so. I want to change the power curves. Idealy, what I want is a curve that looks like the 'weak-nuts' cam, but has the power out-put of the stock cam.
EI, peak torque is ~500 or so & falls at ~4400rpm....& holds it to ~5300-5400 or so.
 

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Dark93

You only decreased overlap at .006 inches of lift. at.050 overlap actually increased. -20 degrees overlap is less than-2 degrees overlap. "weak nuts" cam has a more agressive opening ramp.
The 4 cycle engine works like this: 1.Intake 2. compression 3. Power 4. exhaust
The exhaust valve closes while the intake valve is opening. This is what produces overlap-the period in crankshaft degrees that both the exhaust and intake valves are open. The max lift on the exhaust is reached before the exhaust valve starts closing. Therefore, as the exhaust lobe descends to .050 the intake lobe will start to open in 2 more crankshaft degrees. (hence -2 degrees overlap at .050) Are you still following me? Your stock cam has -20 degrees overlap at .050 ; meaning it will take the intake lobe 18 crankshaft degrees more to reach the same .050 lift.
Yes, the stock cam may have more overlap at .006, but at .050 the weak nuts cam is still blowing off cylinder pressure the stock cam was already building. What's going to blow off more cylinder pressure, .006 or .050? And more importantly, the "weak nuts cam has actually INCREASED overlap at .050!!! Am I Thinking about this wrong?.......JAMES
 

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Discussion Starter #13
Stock cam has -20 degrees overlap @.050
'Weak-nuts' has -9 @.050

When I designed the cam I didn't really look at the .050 overlap events that way.... I tried to look at it like this:

The stock cam has 46 degrees of total overlap, the new cam 41 total. Which cam will flow more air during that overlap cycle? Given the faster ramp-rates of the new cam, it would probably flow a bit more during the overlap cycle. By most turbo cam standards, -9 degrees overlap @.050 is okay. Most have -7 to -2 degrees of overlap @.050. & they probably have more overlap @.006 then the stock cam too. I thought that a small increase in airflow in the overlap cycle wouldn't cause any harm. Perhaps I was wrong.
I think we also need to look at the valve events during overlap:
.006:
IVO: 14 BTDC
EVC: 27 ATDC
.050:
IVO: 10.5 ATDC
EVC: 1.5 ATDC

I think these valve events have a lot to do with how the gasses flow during overlap....due to piston movement. Perhaps I was overly ATDC bias with the overlap cycle.

After much thought about what's going on...for now I'm gonna have to agree with you guys & say that this cam has too much airflow during the overlap cycle. The intake air-charge is going right out the exhaust without being used. This would also probably trip-up the air/fuel meter & cause abnormally lean readings. An explination of why this cam read so much leaner then the stock cam (with the same fuel tables) without producing as much power.

I would think this cam is best suited for a stock headed 5.0. Probably give some nice gains over the stock cam on an N/A setup.
 

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It would be nice for you to post all of the events for both the stock cam and the one you spec'd. I am thinking that there is too much retard on both lobes probably and especially on the intake.

I'm not going to get into any more of my own speculation on the cam. I'll let the "real" experts give you their opinions.
 

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Discussion Starter #15
Stock cam:
.004 lift
IVO: 25 BTDC
IVC: 73 ABDC
EVO: 75 BBDC
EVC: 23 ATDC

New cam:
.006 lift:
IVO: 14.5 BTDC
IVC: 72.5 ABDC
EVO: 60.5 BBDC
EVC: 26.5 ATDC

Stock cam:
.050 lift
IVO: 9 ATDC
IVC: 39 ABDC
EVO: 41 BBDC
EVC: 11 BTDC

New cam:
.050 lift
IVO: 10.5 ATDC
IVC: 47.5 ABDC
EVO: 35.5 BBDC
EVC: 1.5 ATDC
 

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GaryJ said:
I'm not going to get into any more of my own speculation on the cam. I'll let the "real" experts give you their opinions.
OK, I lied. I want a little feedback from the experts myself.

I think that given those small ports on a 331 that you need more duration on both sides. I think the EVO is too late as well as the IVC. I also think that you are probably left with higher than desirable exhaust pressure when the IVO occurs due to the late EVO and overall short duration in addition to the turbo, which is a restriction. The end result being reversion.

Oh and one more, I think that the IVC is probably a little late, but that the IVO should also be somewhat sooner (or could be) with proper exhaust events. Again, the end result being reversion, causing your "weak nuts" torque numbers @ low rpm.

Now let the experts critique my evaluation. :) I'm anxious to hear what they have to say.
 

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Hmmmmmmmm....

OK, can I say "told ya so"???

You've got mail... :D

ED
 

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Discussion Starter #18
Shoulda' used a larger intake lobe right Ed?
Well, I can't access my home e-mail at work.....But you'll probably be hearing from me tomorrow.

-Shaun
 

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With the small exh. port area and valve for that HP level, you are opening the ex valve WAY too late. If you want to work with that cam, advance it back to straight up (113 ICL)...... otherwise, get a custom. If you want to rev that combination higher, you will have to have more head or more cam duration.

HiTech
 

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Discussion Starter #20
I think I'll put this cam aside for 'another' project.

Live and learn. Leave cams to the guys who know!
 
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