Big Spread??
Thread Starter
Safety Car
Joined: Sep 2005
Posts: 4,226
Likes: 643
From: Orange County Ca
Big Spread??
I ran the 69 BB through the dyno and the results were not exactly as suspected. Max tq was about 370 from 2200-4000 rpms, then started to fall off slightly, but hp was max at only 265 at about 3500 rpms, then rising slightly to 5000rpms. As I said, a 69 427 origional 390 hp car that now has 71 stock Chevy heads which give about 9.5 cr. Basically stock, slightly larger valves, slightly larger hydrallic cam, q jet and stock exhaust. Engine runs well, but runs out of steam at 5500 rpm. Is this what would normally be expected of this combination? Ran a 14.3 @ 97mph at a 2600' altitude with a 3.08 and worn out posi. Shifted into 4 th gear about 200 ' before the 1/4 mile. Comments?? PS, these are rear wheel hp and tq #'s.
Last edited by Sayfoo; Apr 24, 2006 at 09:58 PM.
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Was any tuning done while on the dyno? Did the operator use any fuel/air mixture measuring devises? What is the initial advance and the ignition curve?
The quarter mile times look pretty good with the gearing. Makes me think the dyno may be off. A 3.73 rear gear would probably have you right close to the top of 4'th gear at the finish line.
You say it runs out of breath at 5500 RPM. What are the cam specs? A compression ratio of 9.5 will not allow a large camshaft that is required for power above 5500 RPM. This is why high speed street motors use higher compression.
BigBlockk
Later.....
The quarter mile times look pretty good with the gearing. Makes me think the dyno may be off. A 3.73 rear gear would probably have you right close to the top of 4'th gear at the finish line.
You say it runs out of breath at 5500 RPM. What are the cam specs? A compression ratio of 9.5 will not allow a large camshaft that is required for power above 5500 RPM. This is why high speed street motors use higher compression.
BigBlockk
Later.....
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
I'm guessing you're running the stock intake manifold. That will limit your power peak to about 5,500. Your torque seems about right. I bet some creative tuning will get the rwhp up around 300-325.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
5500 RPM`s are about max for any hydraulic camshaft. A few claim to go a little bit higher, but not very much with a accurate tach. The only way to get big numbers is with a solid lifter camshaft. Thats where the power really starts to come on with a solid cam. 
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
Something is off,..the fact that you're not gaining much HP after 3500 RPM, tells you all you need to know,..unless you're running some sort of tow truck cam. 390 HP at the flywheel should deliver 312-331 HP to the rear wheels (with 15-20% accessory/drivetrain loss).
Some things to look for:
Stuck heat risor valve (how's your coolent temp?)
Peanut port heads (what are the casting numbers?)
Timing is retarded
A/F mix is way off
Others can probably add to the list.
Some things to look for:
Stuck heat risor valve (how's your coolent temp?)
Peanut port heads (what are the casting numbers?)
Timing is retarded
A/F mix is way off
Others can probably add to the list.
Drifting
Joined: Dec 2004
Posts: 1,345
Likes: 3
Your numbers sound about right although you peak a little earlier than I'd expect.
My guess is that you actually found an accurate, calibrated dyno. Those numbers are right on to what a G-tech would yield.
A stock 350/300 HP will put down about 165 RWHP, ZZ4 350 245 RWHP, a DOHC 350 ZR-1 313 RWHP, '93 350 -300 Net 193 RWHP, '04 505 Viper V-10 414 RWHP.
Most dyno operators give big numbers to please their customers. My heavily modded 350 with Brodix -8 Pro heads (2.055 intake valves) engine dynoed at 420, but was not much stronger than the original 350/350 with slant plug 2.02's. After raising the compression to 10.67:1 (up from 9.8:1) it measured 248 RWHP with the G-tech. Then switching to a Victor Jr intake it ended up with a VERY stong 320 RWHP. The point being dyno numbers are not usually accurate or comparable unless, like a G-tech, you can calibrate them repeatably (the G-tech reads 1G when oriented vertically).
My guess is that you actually found an accurate, calibrated dyno. Those numbers are right on to what a G-tech would yield.
A stock 350/300 HP will put down about 165 RWHP, ZZ4 350 245 RWHP, a DOHC 350 ZR-1 313 RWHP, '93 350 -300 Net 193 RWHP, '04 505 Viper V-10 414 RWHP.
Most dyno operators give big numbers to please their customers. My heavily modded 350 with Brodix -8 Pro heads (2.055 intake valves) engine dynoed at 420, but was not much stronger than the original 350/350 with slant plug 2.02's. After raising the compression to 10.67:1 (up from 9.8:1) it measured 248 RWHP with the G-tech. Then switching to a Victor Jr intake it ended up with a VERY stong 320 RWHP. The point being dyno numbers are not usually accurate or comparable unless, like a G-tech, you can calibrate them repeatably (the G-tech reads 1G when oriented vertically).
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
That 390 HP was Gross HP you are right on the money as far as rear wheel HP is concerned, could possibly be a few ponies short but not off by that much
Thread Starter
Safety Car
Joined: Sep 2005
Posts: 4,226
Likes: 643
From: Orange County Ca
Thanks for the info. Yes, stock intake (probably the biggest restrictive part, but fits under the stock hood) and stock '71 454 oval port heads. Advance curve is +36 @ 2800. Cam specs are 218/228 @.050 and.500/.500 lift with 114 lobe centers. The dyno guys said it was running rich, but when they leaned it out, the hp dropped a little. I recently put Hooker side pipes on, with their streight through glass pac mufflers, and I do believe I can feel the difference. Anyway, it seems to run well, and even with 3.08 gears, it still smokes the rice burners. Passing gear on the freeway--3rd gear--goes to over 90 mph which is pretty nice, but it does suffer off the line. Thanks again.
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