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Caballerokid 10-29-2012 08:46 AM

More TQ than HP???
 
So here's my question... How did my tq number end up so much higher than my hp number? :confused:

I was on a Mustang Dyno and put down 250hp and 317tq. (2500-5500rpm pull)

The build is a 360sbc (1995 TBI non-roller block) stock rods/crank, .060" over .125" dome(-3.5cc) speed pro hyper pistons, .055" quench, .015" shim head gaskets, 882 heads (intake ports opened up), 1.94" Int and 1.60 Exh valves, 76cc chambers, 1.6:1 S/A roller rockers, Crane 100172 274 H06 cam, edelbrock performer aluminum intake manifold, Holley 650 DP 4777-2, carter rotary fuel pump (internally regulated), MSD e-curve dizzy, MSD 6T box and blaster SS coil, 4 speed saginaw trans, centerforce dual friction clutch, Hays steel flywheel, 2.73 rear gears with mini spool and also wide open flowtech headers.

I understand that this is a torqeier setup but why so much more torqueier? Anyone have any ideas as to why the torque figure was so much higher than the hp? :confused:

Thanks

lmsport 10-29-2012 08:54 AM

The 106 lobe separation is intended to produce higher torque at lower RPM, but does sacifice peak horsepower.

Caballerokid 10-29-2012 08:58 AM

If I were to get better heads and improve the flow, I could bring up the HP figure and the torque figure would more than likely come up equally if not more in relation to the HP number? So I guess I'm saying, would it be possible to squeeze 350 hp and 400-425 tq with this cam but better flowing top end?

lmsport 10-29-2012 09:08 AM

I would guess your flywheel HP is about 300 right now. A head change could pick you up as much as 50fwHP. The low rise Performer and small headers are going to keep the max HP knocked down, as will the 650 carb. But, those parts do tend to keep the torque up which makes a more street friendly engine.

ap72 10-29-2012 09:08 AM

Quote:

Originally Posted by Caballerokid (Post 1604596)
If I were to get better heads and improve the flow, I could bring up the HP figure and the torque figure would more than likely come up equally if not more in relation to the HP number? So I guess I'm saying, would it be possible to squeeze 350 hp and 400-425 tq with this cam but better flowing top end?

Gaining 100hp is a tall order. A good set of heads, an RPM intake, and 1.6 roller rockers would probably get you around a 75hp gain- which is still damn good for such a mild combination.

A small problem is that you have a 3.5cc dome, and most performance ehads come in at 64cc's. There are a few out there with larger chambers but your selection is more limited.

Also, was this enigne dyno tuned or just ran on a dyno? If it wasn't properly tuned you could have an easy 20+hp right there.

With your highway gears I wouldn't worry too much about peak power though and focus more on getting as much tq/power as you can between 2,000 and 4,000 rpm as that's where you'll be doing most of your driving.

Caballerokid 10-29-2012 09:38 AM

It was half way tuned by me which was ok but nothing professional and it was in the car on the dyno. So those numbers where to teh wheels. Also, I already have 1.6:1 roller rockers. The rpm air gap won't make a difference accept at high end. I am thinking of modifying the performer intake (cutting a notch out of the center between the two planes. I have seen dynos pulls confim about a 20tq and and 10-15 hp gain and adding a 1" carb spacer to get a little more top end. As far as the heads I'm thinking 180-200cc intake runners, 72cc heart chambers, 75cc exhaust ports and port matching to the intake. Haven't decided aluminum or cast yet. I'm hoping to squeeze another 100 hp from all of this and then possibly thinking another 100-150hp nitrous shot to make things a little more interesting :mwink:

Caballerokid 10-29-2012 09:48 AM

What if I went to 1.7:1 roller rocker arms? That'd take my lift to .510" and make more use of the cam.

ap72 10-29-2012 10:05 AM

Quote:

Originally Posted by Caballerokid (Post 1604614)
It was half way tuned by me which was ok but nothing professional and it was in the car on the dyno. So those numbers where to teh wheels. Also, I already have 1.6:1 roller rockers. The rpm air gap won't make a difference accept at high end. I am thinking of modifying the performer intake (cutting a notch out of the center between the two planes. I have seen dynos pulls confim about a 20tq and and 10-15 hp gain and adding a 1" carb spacer to get a little more top end. As far as the heads I'm thinking 180-200cc intake runners, 72cc heart chambers, 75cc exhaust ports and port matching to the intake. Haven't decided aluminum or cast yet. I'm hoping to squeeze another 100 hp from all of this and then possibly thinking another 100-150hp nitrous shot to make things a little more interesting :mwink:

With aluminum heads you could probably use about a 70cc chamber, another option would to be opening up the chamber in a 64cc head some and/or taking some out of your piston dome. Aluminum heads generally mean you need about a point more compression than iron heads. I would go no larger than a 195cc port with that cam, the duration just isn't enough to support a larger cam.

And yes the RPM intake will pick up the most at the top- that's also where you're hp peak is so if you want higher peak numbers that's exactly where you would need to pick it up. It'll also better match a good set of heads and you can pick up a used RPM intake for $75 or less.

You should also tune your carb on the dyno, its the only place you can get an accurate measurement throughout the power band. and remember tuning for WOT is done through the PVCR's NOT the jets. jets are used for tuning at cruise- most people don't understand that. Getting a better tune would probably be worth a lot on your current combo and would be a necessity if you got all those other parts. It makes one hell of a difference.

MouseFink 10-29-2012 10:20 AM

The main advantage of 1.7 rocker arms over 1.5 or 1.6 rocker arms is faster valve acceleration rate off the seats for more cylinder filling for increased low end torque. The valve duration would be increased slightly by four or five degrees.

The increased flow and HP produced with 1.7 rockers at high RPM HP is negligible. The low end torque increase may not be worth the effort it takes to fit the 1.7 rocker arms, i.e: valve spring open height, valve train geometry, pushrod clearance and pushrod strength. Higher ratio rocker arms moves the pushrod about .060" closer to the rocker arm pivot point and places more lateral load on the rocker stud and pushrod. The rocker studs should be ARP 7/16"-20 when used with 1.6 or 1.7 rocker arms and the pushrods should be .080" wall, 5/16" chromemoly.

ap72 10-29-2012 10:35 AM

Quote:

Originally Posted by MouseFink (Post 1604631)
The main advantage of 1.7 rocker arms over 1.5 or 1.6 rocker arms is faster valve acceleration rate off the seats for more cylinder filling for increased low end torque. The valve duration would be increased slightly by four or five degrees.

The increased flow and HP produced with 1.7 rockers at high RPM HP is negligible. The low end torque increase may not be worth the effort it takes to fit the 1.7 rocker arms

Your post seems to contradict itself but I agree that at this level you'd be much better off sticking with your 1.6 rockers and maybe looking into a different cam. The one you selected is a great cam for a mild budget engine where you're not concerned with max power, BUT since you are concerned with max power you should probably consider looking into a custom solid cam- after you have the rest of your combo together of course.

vinniekq2 10-29-2012 10:44 AM

your cam is too small, use a 750 double pumper. what size primary tubes on the headers? a mild 330 horse 350 is going to have higher torque figures that engine is doing what it should with those parts.
usually if you use 1.7 rockers on a small block,the stud needs to be relocated.
your cam needs more duration more than more lift.use a cam that allows 6200 rpm and the hp will rise

MouseFink 10-29-2012 10:45 AM

More low end torque, meaning: Is five or ten lb. more torque at low RPM worth the cost of the changes that would be necessary to install 1.7 rockers.

You don't need more torque so don't consider 1.7 rocker arms. More cylinder pressure = more low end torque..... More cam duration = more high RPM HP

ap72 10-29-2012 10:51 AM

Quote:

Originally Posted by vinniekq2 (Post 1604642)
your cam is too small, use a 750 double pumper. what size primary tubes on the headers? a mild 330 horse 350 is going to have higher torque figures that engine is doing what it should with those parts.
usually if you use 1.7 rockers on a small block,the stud needs to be relocated.
your cam needs more duration more than more lift.use a cam that allows 6200 rpm and the hp will rise

cam is too small for what though? the cam he has is actually a very good match to his car- BUT it doesn't make the peak power he wants.

He either has to give up power where he uses it for power where he wants it (a dumb but often followed idea) or get a cam with relatively as small duration but more aggressive lobes.

keep in mind he's running crappy 882 heads with an untuned carb and 2.73 gears...

To solve this whole problem I'd just give up on peak power numbers (they're meaningless on the street) and focus on getting your midrange as high as possible. Build for where you drive, not for the dyno sheet that rides in the glovebox with you.

MouseFink 10-29-2012 11:03 AM

IMCA call a camshaft like that a "short track cam". High lift and short duration similar to my roller tappet camshaft..206/210 duration; .500" valve lift using 1.5:1 rockers and 112 degree LSA with "crappy" heads. .

vinniekq2 10-29-2012 11:08 AM

a mild 330 horse 350 is going to have higher torque figures that engine is doing what it should with those parts.

I thought the op wanted more horse power.
the engine is operating correctly.enjoy it


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