Need more torque!

[Guest zfan]

I have a 1971 240 Z with a 355 sbc,700r4,3.54 r200 rear end and 235/60-15's. Myengine build is a 350 30 over with 10.3 to 1 compression. cam is an comp cams extreme energy hyd. roller 236/244..520/540 with 110 lobe seperation. Im using 1.50 roller rockers. Cam is set straight up no degreeing. Heads are 64cc edlelbrock rpms,Victor jr. intake, Holley 750 double pumper.

All msd ign. with pete jackson gear drive. Exhaust is Hooker super comps with 2 and 1/2 flowmaster two chambers. Im running a vette 700r4 with b/m 24/2600 stall.

 

Car is a slug under 3 grand, and really is not at home until 3300 plus. To increase more lower end Ive thought about degreeing cam or changing intakes. Anyone try a torker 11 manifold?

 

Last thing I want to do is change cams as this motor and set up has less than a thousand miles on it. Ive tried checked fuel and it is not rich seems to be fine. Anyway just throwing this out there for feedback as Im not going to just jump into anything with out taking a look at all posabilities.

 

I must say I am dissapointed at performance as overall as this set up should flat out haul ass in a 2500 lb car.

 

Mike

[grumpyvette]

torque is from cylinder pressure x cylinder volume x number of power strokes per minute and depend to a great extent on VOLUMETRIC EFFICIENCY , the torkerII intake works nowhere near as well as the performer RPM intake , and you problem is not really a lack of torque its a lack of torque in the rpm range you need it in, now you can get a higher# gear ratio rear gear that will allow you to multiply torque faster and stay in your sweet spot rpm range more offten or you can lower the rpm range itself, your choice, but changing the cam (the one you have is fine) will make the engine loose power, so first choice in your case is swapping to a higher # rear gear like a 4.11 ratio would be the best choice but a swap to a PERFORMER RPM intake(WITH NO SPACERS) will move that torque curve down enough in the rpm range to improve things noticeably while only giveing up about 10-15 hp on the high rpm because the big drop from first gear to second gear in that 700r4 is leaveing you a flat spot. (don,t go spending big bucks used performer RPM intakes go for $50-$80 on ebay, if you really want to kick butt try the rear gear first then add the dual plane intake ONLY IF YOU NEED IT>

http://cgi.ebay.com/ebaymotors/ws/ebayISAPI.dll?ViewItem&item=1825662665&r=0&t=0

 

http://cgi.ebay.com/ebaymotors/ws/ebayISAPI.dll?ViewItem&item=1825627908&r=0&t=0

 

Ive posted this before but read it again,

ever wonder why your engines torque curve gets higher with the engines rpm level untill about 4000rpm-5500rpm(DEPENDING ON YOUR COMBO) but fades above that rpm level?

well it depends on several factors, first as long as the cylinders can fill completely you get a good fuel/air burn so you get a good cylinder pressure curve against the piston each time the cylinder fires,THE ENGINES TORQUE CURVE INCREASES WITH THE NUMBER OF EFFECTIVE POWER STROKES PER SECOND, at very low speeds theres not enough air velocity to mix the fuel correctly or produce a effective ram tuneing effect but as the rpms increase the cylinders fill very efficiently untill the rpms reach a point where the cylinders just don,t have the time necessary to flow

enough air through the valves to fill the cylinders , remember a 5000rpm the intake valve out of 720 degs in each cycle opens for about 250degs of effective flow even with a hot roller cam, now thats only about 35% of the time and theres 41.6 intake strokes per second , thats only 1/60th of a second for air to flow into the cylinder, I found this graph that shows the relationship between V.E.(VOLUMETRIC EFFICIENCY) and AN ENGINEs torque CURVE

http://www.n2performance.com/lectures/lect1/n2perf5.gif

 

WHAT THAT GRAPH SHOWS RATHER EFFECTIVELY is that its your engines ability to fill the cylinders that increases your power and the more efficiently you do that the higher the rpm level you can acomplish that at the more power your engine makes, remember the formula for hp is (torque x rpm/ 5252=hp)so moveing the torque curve higher in the rpm range increases hp

[utvolman99]

I agree with grumpy but I also have to think that you may have something off with your setup. Running your #s on Dyno 2000 gives the following.

 

2000 341 lbs/ft

2500 359

3000 381

3500 408

4000 428

4500 439

5000 434

5500 416

6000 381

6500 339

7000 281

 

Also, from trying it on Dyno advancing your cam would not do a whole lot for you. Something you may not know is that xtreme energy cams have 4 degrees of advance in the grind already. You may want to spend some time making sure that your timing and carb are dialed in correctly. I had a 351W with a holley 750 with very poor low range. Turned out to be the power valve. The engine was not able to keep up with the fuel supply till around 3000RPM. If that were your problem you would notice that the care was running rich. You can see that on your plugs and smell it in your exhaust!

[Guest zfan]

Grumpy, I have an almost new rpm air gap sitting in the garage already. The plugs(2) that I pulled did not look rich at all, but several two friends felt the exhaust last night and said its running rich, I must admit it sure felt and smelled like it. Wonder why plugs dont show it.

 

From a launch car doesnt seem to pull hard but as pass 3k it begins to get after it, after 4k it flat out screams. My concern is that while racing someone by the time I get rolling they will be showing me their tail lights and thats NO FUN!!

 

By the way what kind of numbers are you getting for hp/rpm's?

 

Thanks guys, Im in no hurry to screw things up so I just really want to see if I should back off and keep motor the same and maybe rear gears only.

 

The problem with gears around 4.11's is in the 1/4 I will be huffing before crossing the line.

I do not really want to go to o.d.

 

Probably will go to track and see if Im worrying about nothing?

 

Thanks again, Mike

[Mike C]

If I were you, I'd start by getting the Cyberdyne (Summit or Nordskog, same thing $29 plus a $20 parts store sensor) Air fuel ratio gauge and installing an o2 sensor. You just can't read plugs in an unleaded motor the same way you can a leaded gas engine. Next, check ignition timing. Make sure your distributor isn't stuck or the balancer slipped etc. Get a dial back light if you don't have one. My 355 with 236/236 @ .05 cam makes TONS of torque and my 3500# car hauls butt. Switching to 3.70 is a 5% increase in torque in any gear and the 3.90 are 10%. The 3.90 and the OD should be perfectly compatible. Most late model camaro guys I know run 4.10 with no problems.

[grumpyvette]

jt1

"but you probably have tuning issues too." thats fact!!

 

jap tin

"You need a looser converter. " good suggestion!

 

Mike C

"If I were you, I'd start by getting the Cyberdyne (Summit or Nordskog, same thing $29 plus a $20 parts store sensor) Air fuel ratio gauge and installing an o2 sensor. You just can't read plugs in an unleaded motor the same way you can a leaded gas engine" VERY GOOD SUGGESTION !

 

zfan

"The problem with gears around 4.11's is in the 1/4 I will be huffing before crossing the line.

I do not really want to go to o.d." look here

 

http://www.esbconsult.com.au/ogden/locost/gearcalc.htm

 

ON THE BOTTOM OF THE PAGE IS FREE SOFTWARE,USE IT!

 

youll want to cross the finish line at about 117-118mph turning about 6300rpm

[Guest zfan]

Thanks Guys! Ill look into it all.

 

Mike

[jap tin]

You need a looser converter.

[jt1]

zfan, you might want to take a look at my post "A trip to the chassis dyno". Our combo is very similar, I've got a little less cam and am using a ebrock air gap. I bet you are rich, maybe play with jets, squirters, or power valve. Also check to see that your distributor is getting all the advance in pretty quickly. I run 36 deg and get it all by 2200 rpm. If your dist is advancing slowly, it can really hurt the bottom end. Lighter springs are the answer. My car really didn't impress me much on the dyno, but it's got a 3.54 with a quaife and 225/60-15's and hitting the throttle in first or second from idle on up is a smokefest. Grump's right about the performer rpm, they are great intakes, but you probably have tuning issues too.

[utvolman99]

One last thing, if you call Holleys tech line and give them your cars weight, engine size, trans and gearing they can give you a really good starting place for your jets and power valve. The ones that come from the factory would not be what you would need for such a lite car.

[Guest zfan]

Well guys I may have found one problem. The car has all MSD ignition for starters. The engine runs relativly smooth to approx. 3 k and then begins to stumble badly,missing almost like cross firing maybe?

 

The distributor is a msd pro billet mech. advance with msd 6a box and blaster 2 coil. Has anyone else run into this problem? Im no elec. whizz so may look into a shop that specializes in this sort of thing or maybe call and talk to the engine builder and see if they do this kind of work.

 

Thanks Mike

[Mike C]

Get your self a dialback timing light and start troubleshooting. Rotate the engine around to TDC and make sure the timing mark is in correct location (inertia ring hasn't slipped or you don't have wrong year balancer for your timing tab. Some California motors have different timing point alignment). Check initial timing. Have a buddy move RPM up by about 500 at a time as you check advance with dialback light. Note how much and at what RPM. Find out what your total advance is. I think in all of this you will find something out of whack and when you fix that it'll run fine. Does it have vac. advance at all? If so, check with it both connected and unplugged and compare.