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More TQ than HP???

11K views 65 replies 9 participants last post by  Caballerokid 
#1 ·
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
 
#3 ·
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?
 
#5 ·
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.
 
#4 ·
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.
 
#6 ·
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:
 
#8 ·
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.
 
#9 ·
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.
 
#10 ·
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.
 
#11 ·
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
 
#13 ·
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.
 
#17 ·
aluminum heads cool better so they will tolerate more compression with other items remaining the same.If you keep that small cam I see no reason to go very big on the intake runners.180s are good enough.it depends what the heads flow,how many cfm the heads flow at what valve lift,then factor in your cam and see what you can make HP wise
 
#18 ·
How would someone go about selecting an intake runner size rather than someone just saying I should be ok with such and such? How would I know what to pick, say a 165cc, 170cc, 180cc, 195cc, 200cc, 210cc, 215cc, 220cc, 235cc etc... The 235cc will flow the most air because it's bigger. Why would 180cc be ok for my setup? Help me understand why. Thanks
 
#19 ·
The volume itself is actually meaningless. What you're concerned with is the minimum and average cross-sectional area. A typical sbc intake runner length is about 5.6" so given the volume you can easily figure the average area.

As a general rule the more rpm you turn the larger of cross-sectional area you'll need. Also increased displacement requires more area. For a street engine you want to go with an adequate volume and no more. Bigger is not better, smaller is not better- just right is better. If you do have to go slightly larger or smaller go a hair larger.
 
#21 ·
I have done some checking on this combo. Stock 350 block height is 9.020"-9.025". The rod length, 1/2 of stroke, and piston compression height don't add up to what you say. 5.70"+1.740"+1.560"= 9.0". Pistons are .025" down in the hole. For quench you have .025"+.015"= .040". You have 55" for quench. On the KB compression calculator your combo has 10.10 static compression and the dynamic compression ratio is 9.075. To run on pump gas you would want to have 7.5-8.5 DCR to avoid detonation. Keep an ear out for any pinging or knock. The 882 heads have the small 151cc intake ports is probably why it seems torquey. Here is the intake flow rates .100-70, .200-125, .300-175, .400-204, .500-205, .600-206. The exhaust flows .100-59, .200-109, .300-136, .400-143, .500-144, .600-145. A stock set of Vortec heads have 170cc intake ports and flow .500-239 intake and 160 exh. But like was said you cannot use them because they have 64cc chambers. The good news is I just finished reading an article on a 355 9.1 compression engine with 882 heads that were ported and 2.02 & 1.60 valves were swap in. The cam was a Crane PowerMax .427/.454 lift with 204/216 duration. Hold on to your hat, it produced 367hp & 442 lbs torque. Chevy Small Block Build - Mildly Amusing - Super Chevy Magazine
 
#22 ·
Ya the build is a little goofy. The pistons are .040" in the hole which is how i have .055" quench. That is some great info on those heads! I have the ports opened up pretty good at the mouth but just the way they are cast you can tell they are restrictive. I'm looking at a set of TrickFlow fast as cast 72cc aluminum heads with 180cc runners and 75cc exhaust. Those should really help the flow out along with the 2.02 int valves. I'm going to notch the intake plenum and add an open 1" spacer which should also help. Then see where i go from there. What do you guys think? Thanks!
 
#26 ·
Yeah, that's the part I don't understand. A 350 chevy block has a deck height of 9.025. Add 1/2 the crank diameter, the rod length, and piston compression height on your pistons. The total comes to 9.0". How can the pistons be .040 in the hole? The Trick Flow heads have a 72cc chamber, that will put your static compression at 10.571 and the DCR at 9.493. You will have to use 110 octane with a DCR of 9.493.
 
#32 ·
The edelbrock performer intake i have is a dual plane. Also i have seen dyno results of the very same engine with a performer and air gap. The curves were almost identical but tue air gap made more peak hp.

The crank is a stock 350 crank and i do have rebuilder pistons. I run 91 or 93 octane regularly and have ran 110 leaded initially until i was comfortable with the setup. The calculators i have used showed something like 10.2:1 static and 9.67:1 dynamic.
 
#37 ·
Caballerokid, I use this website for informational purposes. CamQuest ? Select The Perfect Camshaft & Valve Train Components Checking cams with different heads,compression, carbs, etc. I found a cam similar to yours. It a Comp Cam 12-210-2, 1500-5500, .454/.454/ 218/218 LSA 110 ICL 106. When checking it on the dyno it made 310@4500 hp and 395@3500 Torque with low perf/stock ports & valves, dual plane intake-std flo, 600 cfm carb. I guessing your cam has about 295hp and 364 lbs Torque at the flywheel. Look on your dyno sheet to find out at what RPM you made the 250hp and 317 TQ. Changing heads to HP stock ports and valves, dual plane intake hi-flow, and 750 cfm carb, the increase is 368hp@5000 and 428 lbs Tq@ 4000. Pocket porting the heads increase it to 415hp@5000 and 442 lbs tq@ 4000. Now it might affect yours a little differently because of the 106 LSA and 102 ICL. If you was going to spend that kind of money get these: AFR 180cc SBC Eliminator Street Heads 0911 - SummitRacing.com or these: AFR 195cc SBC Eliminator Street Heads 1036 - SummitRacing.com or these: I would get these. Dart SHP Special High Performance Cylinder Heads 127222 - SummitRacing.com. Then dump that Crane cam and try one of these XE262H 12-238-2 or XE268H 12-242-2. Make sure to order the heads with the springs that will work with these two cams. I have been trying to warn you about your compression that it's too high even for aluminum heads with pump gas.
 
#40 ·
I have thought about that but I'd have to tear the motor down completely so I can cut the rings for blown/turbo application. I'm worried about that to even put a turbo on it because of that. Would I even really need to worry if I ran 5-10lbs? I don't think I'd want any more than that with the compression where it is already... I'm just trying to rethink my plan on this right now. I feel stuck.
 
#41 ·
If you're going to go through the trouble of increasing the gap on your rings I'd swap in some flat top or dished pistons while you're there. A good set of used pistons would work if you're careful.

Then again you could just swap your cam into a used stock long block, which you can often find for a couple hundred bucks.
 
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