390 on Dyno (video)

[sport71]

http://www.youtube.com/watch?v=gmCqIWJma_w

I took my truck to the dyno yesterday, and was not sure of what to expect. It was tuned, and the motor ran at the tires: 246HP & 265TQ. Does that sound about right? I was hoping for 300-320HP at the wheels.

770 holley street avenger
270H Isky cam
C8AE-H heads - 2.09/1.65
edlbrock performer rpm intake
89 octane gas
DUI electric distributor
ultra 40 wires
headman headers, 3" pipes, and 50's flowmasters
I don't know what compretion or the gears on the rear end.

[r71f250]

What are your specs? Transmission, rear gear, size of axle, tire size? A truck will have a greater driveline loss then a car. Also, what compression are you running? Taking a factor of around 22-24% drive train loss is not uncommon. Also the numbers in the video differ from the number stated. I like the sound of the exhaust.... Nice truck...

Blessings,
Alan

[sport71]

The #'s on video are to throw people off here localy, just to keep them guessing..
the trans is a C6, Tires 295-50-15, I know that the rear is a postrac Ford 9", and 31 spline.
Some one said to check the rear gears is to mark the wheel and drive shaft and do a full turn on the wheel and where the drive shaft marks you should get the size gears?
I would have no idea on how to check the compretion?
The pull was done in 2nd gear..

[Ranchero50]

2nd gear, no wonder it was so quick. 246 x1.25 = 307, almost unrealistic for iron heads without a lot of port work.

My '93 pulled 390 rwhp, around 450hp at the crank but then it had excellent heads, ported GT40 intake and 6psi of boost...

Jamie

[robroy]

Good day Ruben!

This is an interesting thread you've started, and I'm sure you'll be able to identify exactly what's going on!

I'm certainly no engine expert! Yet I can think of a few more data points that would probably help the experts understand the performance potential of the engine better. You may need to ask the engine builder for these specifications.

1. Compression ratio (this has already been covered by Alan).
2. Were the heads ported? (I'm not sure if the "2.09/1.65" indicates porting work or not.)
3. Was the Edelbrock Performer RPM intake ported to match the heads?
4. Are your Hedman headers model 89810's (this may not be a critical spec to know).
5. What is the displacement of your engine?
6. What crankshaft, connecting rods, and pistons are installed?
7. If you were hoping for 300-320 horsepower at the wheels, what horsepower were you hoping for at the crankshaft?
8. What % power loss from the drivetrain had you anticipated (same question as above)?
9. Is there any chance at all that your rear brakes are dragging a little (maybe adjusted too tightly)?
10. Did you by any chance receive a printout from the dyno machine with more detail on the performance measurements, like a graph or chart of any kind?

Also, thinking this over, it makes me wonder if there's any chance that second gear on a C6 transmission might produce much more loss than high gear does. I'm not sure if that idea has any technical merit or not. If that is a potential source of increased loss, it would be interesting to see the dyno results while running in high gear.

Another thought is regarding the 89 octane gasoline. Is that the highest octane pump gas in your area? Around here (in California) it's "91," if I remember correctly. Based on the engine's comfort at that octane level, I'm guessing that the compression ratio may be around 9:1, but my guess is backed up by very little knowledge or experience.

I'll be watching this thread to see what the engine experts have to say!
Robroy

[dustman_stx]

http://www.youtube.com/watch?v=gmCqIWJma_w

I took my truck to the dyno yesterday, and was not sure of what to expect. It was tuned, and the motor ran at the tires: 246HP & 265TQ. Does that sound about right? I was hoping for 300-320HP at the wheels.

770 holley street avenger
270H Isky cam
C8AE-H heads - 2.09/1.65
edlbrock performer rpm intake
89 octane gas
DUI electric distributor
ultra 40 wires
headman headers, 3" pipes, and 50's flowmasters
I don't know what compretion or the gears on the rear end.

The Comp Cams calculator says you should be running 400/450 with that combo. That's at 9:1, figuring a 270H Comp, which I may be falsely assuming is similar to the Isky cam you're running. If you are running 89 octane, you might be at 9.5:1, but most likely not much if any higher or you'd be getting some detonation. I think the heads are your main problem. I'm in the same boat. Have you run it to see what it does in the 1/8 or the 1/4?

[ximy]

246HP at the rear wheels isn't bad.. everybody thinks they have 400 plus, until a dyno run.

The performer rpm intake works well with mega cubic inches... 428 plus.. a 390 pretty much needs a dual plane.. that would help increase your HP/torque.

Running 89 octane (without ping) means you have low compression..9.5 tops and probably lower.. a point in compression would also increase hp, but you would have to find gas.

FE's love big cams, especially with their head limitations, a 292 cam really wakes the beast up.

[Dragon]

I have seen wicked specs on many motors that still did not pull power. Your hp to weight is ratio is 17.6 lbs and hot street machines usually have 11 or 12 to 1.

The C80E Heads are basic 428 heads, C6 in 2nd is sloppy I don't see why they didn't let it hit 3rd.

How fast was it turning. Your intake and cam will pull their best power at 6000 but we still need header information. Pipe size and length of primaries.

A 390 at 6000 needs 677 cfm at 100% Volumetric Efficiency. I would give you 85% because of the Manifold and cam and that makes it 575 cfm. If you have mechanical secondaries or a light spring on the VS then the carb would be bogging and killing power. If the heads were bowl ported and the headers were tuned yo 6000 I could see 90%,

Matching the intake to the heads would really help too. Edelbrock is not good at port matching. Every Edelbrock I ever had was off. The ports on top and on the sides need to be sticking about 1/8 into the head port area. The bottom needs to be smooth. This creates and inversion pulse the stuffs the cylinder better. If the heads are smaller than the intake ports then air has a hard time getting to the heads because there is a wall in the way. Edelbrock knows this they have matching guides somewhere on their site.

The secondaries will not open by free-revving the engine. The engine needs to be under a load before they will open. If you are still uncertain if they are opening, you can take a normal paperclip and clip it onto the secondary diaphragm rod and slide it up against the bottom of the secondary diaphragm housing. Go out and drive the vehicle, making sure to get into the secondaries. When you return you will be able to look at the position of the paperclip on the rod. If it is lower on the rod, you can tell the secondaries opened and how far they opened. This is useful in determining if you need a heavier or lighter secondary spring.

The cam specs are kind of weak. 2000-6000 and max carb a 650 with 9.5 compression and stock torque converter. Intake duration is real high and exhaust is low meaning the cam is counting on the incoming charge to purge the cylinders. Funny they don't list the overlap which is real crucial to cam specs especially in the purging cycle before the cylinder gets refilled.

[DuckRyder]

• The compression is probably low (we really need to know to answer your question).
• It is a very mild cam and it a single pattern which isn't a good choice unless the heads are ported and have a good intake/exhaust ratio.
• High stall converters can be problematic on a chassis dyno.

[Dragon]

Though I do have to say that is one pretty truck.

[sport71]

Great info guys,

I think it should have been run in 3rd gear not in 2nd, also it was only run to 5500 and not 6000.

Next time I take it to the dyno I will have the intake and heads ported to match, how hard could that be? I've heard tha the exaust ports have a hump on these heads that can be removed for better flow, plus I'll take the heads to get the bowls ported to a good speed shop.

As for the Headman Elite headers, what is tunning? I'm using 3" full exaust and 50's flowmasters..

I will also be using premium fuel from now on..

The compression is probably low (we really need to know to answer your question).
How can I check the compretion?

The trans has 2500 stall feels good to me with that stall..

246HP at the rear wheels isn't bad.. everybody thinks they have 400 plus, until a dyno run(that's for sure)

I will have to agree with you all on the heads. I can get a little bit more out of them with the porting.

Also I'll see if I can get the read out on my run..

[Dragon]

Stock cam in a 65 car engine with 750 Holley roller chain 10.25 to 1 stock electronic ignition and I dyno'd 185 at the rear wheels.

http://www.ford-trucks.com/forums/42770 ... epoxy.html go to the send post in the list.

http://www.fordfe.info/HeadSections/Cross1.html Here is the port cross sections on the common heads.

[hotrodfeguy]

With that convertor I would have picked a Lunati 30507 . But still respectible numbers for what you have going on there, remember the C-6 eats alot of power post crank then so does the rear end.
Could have been worse like this guy
http://www.youtube.com/watch?v=p4l-Dl73TpM&NR=1

[hotrodfeguy]

Also you could try a one inch spacer under the carb. That you should be able to tell on the seat dyno if it helps :0)

Just out of curiousity what is your end timming? Like what numbers do you have all out with the vacume port off ? I set mine out at 37-38 total If you use the light and rev up the engine you will see where it stops going farther. Thats the end or wall time. PS you may have to make marks out there at 38 on the balancer. Last marks you will have will be 30

[Dragon]

Oh yeah I have a 3/4 spacer and can feel the diff over a 1/4 spacer.

I pull 40 with mine. I got a different base. than stock I found a dizzy that advances way more from the numbers in my book. With 12 initial I get that 40.