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#21
12-08-2006, 04:28 PM
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Something I can add too is the fact that I have not made more than about 550hp with a TII. That intakie is great up to that power level, but beyond, you need a larger manifold. I think you could get some power from a manifold change as well as a larger carb. The HP950 carb is a 750 with an 850 base plate. They pull lots of signal at the booster. I am not a huge fan of that carb, but they do have their place in some applications where velocity in the ports is down.
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#22
12-08-2006, 04:33 PM
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"What do you have done to an HEI that it makes 1 more horsepower than a billet MSD."
Our HEI is basically "stock", stock springs, weights and center cam. It has a positive stop welded in as described in Jim Hand's book, and a Mallory Rev Limiting module, stock cap/coil/wires. The MSD billet unit we tested had a "locked-out" advance mechanism. Even so, the timing retarded 2-3 degrees as I followed it during the dyno pulls. I don't know exactly why, tried to compensate for it by advancing the total a couple degrees, still came up a tiny bit less on power......Cliff
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#23
12-08-2006, 05:20 PM
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which comes back to the current issue...
I'm getting a new carb...but what should I get? Quickfuel recommends their P-850 carb, which is supposed to flow a true 850cfm. Many people run good with the HP950 carb. Others say AED modified 950... Others run well with a dominator 1050 carb. The real answer i'm looking for is..."how big of a carb (true cfm) should I run?" a true 850? 950? a 4500-series carb? several people with a very similar combo have actually run best with around an 850cfm carb...but then again, no two engines are identical... |
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#24
12-08-2006, 06:23 PM
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Your dyno guy should of had a vacuum gauge hooked up to your intake so you would know if you need a bigger carb.
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#25
12-08-2006, 06:46 PM
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Carb:
We are over 700HP with the Q-jets and cast iron heads. I would do a Q-jet as they out pull a Holley evertime, easier to tune at the track. Dyno: Could you publish the page that has the input numbers for dyno conditions? Did they match the dyno room? I noticed you didnt have the SCFM numbers so you didnt run the outside air through the turbines with the hat on the carb, but rather the air in the dyno room? Correction factor numbers are derived from those inputs, and are very critical for getting the right info. I always like to see when the engine stops gaining cfm pulling through the carb. It indicates issues showing up. Engine: Are you using like 1 3/4 headers on this big motor? 4300 peak torque indicates a very small header. 455's need at very least 2 inch and most of the time 2 1/4. A very fast Pontiac you all know runs even bigger! He woops on Chevys, Fords and Mopars. I ran 1 3/4 on a dyno once and got 4300 peak torque and 5300 peak HP, put the bigger headers on and got 4700 and 6200. Pontiac guys kill me when they use 1 3/4 and then want to know why their HP peaks are low. They also want to know why their exhaust gaskets blow out all the time. (probably taking 30HP to push the exhaust gases out) Another thing I would look at in this motor is valve spring, as in, you might not have enough. I just saw a dyno sheet on a big Pontiac motor after huge, I mean huge headers, man what a difference. My 455SD picked up 3 tenths when going from a 2 inch to a 2 1/4. Thinking about going to 2 3/8. Lynn Last edited by NHRASuperStock455SD; 12-08-2006 at 07:04 PM. |
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#26
12-08-2006, 07:05 PM
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the Kauffman's suggested a 1 3/4 header, because it works on their heads quite well. However, I had them test a set of 2" primaries, and the dyno results are IDENTICAL. I'm talking, within 2 hp all across. Same thing with torque, about +/- 5hp across all rpm's. Max hp/torque occurred at same values too...
does that sound strange? |
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#27
12-08-2006, 07:47 PM
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Lynn,its a 428.I just had a 428 street motor on the dyno and it made 475 HP too 6200 with a factory dual plane intake and a 700 AFB and 1 5/8 headers.Way smaller cam and less CR and 260CFM heads.Lot less HP also.Tom
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#28
12-08-2006, 08:11 PM
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Tom,
I thought this was the race section,  You are 100% correct for a street application.Formula, Race 428's have no business with a 1 3/4 header unless you want to run very low RPMs and run off the torque the engine produces like in a street car. Phil Monteiths 428 with cast iron 16 heads(mildly ported) and a old torker, made about 650HP with the Q-jet. Those heads wont flow anywhere near Kaufmans stuff. 2 inch headers (very short) Lynn |
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#29
12-09-2006, 12:23 AM
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Lynn,just pointing out my motor made HP too 6200 with way less cam,carb,intake,CR, etc.Think there is more than just headers amiss in the combo.Tom
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#30
12-09-2006, 01:05 AM
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Quote:
Cliff Ruggles just rebuilt one of my Pontiac HEI distributors for one of my 455 street engines, i had him install the Mallory rev limiting module also. Got the HEI back from Cliff and very happy with it, thanks Cliff, you do very nice work.
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"Three may keep a secret, if two are dead" ~ Benjamin Franklin ~ |
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#31
12-09-2006, 05:45 PM
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Quote:
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www.hobracing.com |
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#32
12-11-2006, 02:12 AM
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Quote:
that would be my only guess. |
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#33
12-11-2006, 10:43 PM
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Two things I see with your combo. 1, put the cam straight up. 2, try more carb. The third thing is run a bigger tube header. The KRE's have a very good exhaust port take advantage! Also you have decent .050 duration on that cam but obviously it wants more net duration (0-.050" lift cam duration) as you have seen by increasing your duration by tightening your lash. I would also be looking at 112 L/CL installed at 110 - 108 I/CL. You may also consider a single pattern cam with large tube headers if your exhaust flow is 80-85% of intake flow(avg).
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#34
12-12-2006, 12:36 AM
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i am going to get a larger carb (hence why my 830cfm is for sale). after countless opinions & alot of research, I've narrowed it down to the QuickFuel 850 and QuickFuel 950. Q series vs. Professional series is yet another question (it's another post by itself).
as far as the header sizes, I originally started with the 2" hedman headers, but found that they look very dumb with the extra mounting flange, not to mention that they hit the frame and I would have had a difficult time cutting out the port holes out of the extra flange. ouldn't find any other options for a larger header. For the cam straight up, would this affect the ability to run 93/94 octane with 11.0:1 compression (210psi)? could i still run pump gas? I guess, maybe, I'm a little frustrated because I told kauffman I wanted a pump gas engine (when I ordered the heads & had them assemble the engine). I'm not bashing them, because they did great job, but I'm uncertain why they cut it so close with the compression. I believe I originally suggested 78 to 80cc heads...but...I guess now, they could always open the chambers up a little... I have becopme worried about detonation vs. compression/octane because I already "lost" one engine's rod bearings. The upper half was into the copper layer, and the engine only had 91 miles. No harm was done, but I'm sure something bad would have happened. Even this engine, I'm still uncertain about it, almost to the point of pulling it out of the car (real quick) and checking a few bearings...maybe just for peace of mind. Last edited by formulabird428; 12-12-2006 at 12:42 AM. |
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#35
12-12-2006, 12:49 PM
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Advancing your cam usually increases your cylinder pressure! Advancing your cam also tends to lower your peak hp rpm. Again try it straight up. I wouldnt be too worried about 11:1 compression with aluminum heads and 92-93 octane. There's a lot more to detonation than just cylinder pressure.The KRE chamber is good!
Before you buy another carb put a vacuum guage on and see what you have for vacuum at full throttle 6000 rpm. If less than 1 inch (like .5-.7hg) you have enough carb. |
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#36
12-12-2006, 03:53 PM
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thanks! i'll try it out...probably in about 1 month when things slow down.
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