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Mighty 390 Dyno Test Results

April 2 2011 at 8:56 AM

Michael  (Login mhakkert)

Hi Everyone,
Well I finally made it to Panella's in Stockton yesterday to Dyno the factory original 390GT from my 1966 Mercury Cyclone GT.

This rebuild includes a set of custom JE pistons, with a slight dome to get us to 10.5:1 compression and a Comp XE274H cam with factory adjustable rockers. Crank, rods, distributor, manifold, carb and exhaust are stock factory original pieces.

We made 5 pulls on the Dyno using several interesting combinations. Here are the results:

Pull 1 (w/factory cast-iron exhaust manifolds)

Peak HP 322.6 @ 5100 RPM (Torque 332.2)
Peak Torque 376.7 @ 3000 RPM

Pull 2 (same as above)

Peak HP 322.8 @ 5200 RPM (Torque 326.0)
Peak Torque 378.7 @ 2900 RPM

Pull 3 (w/super stock headers)

Peak HP 370.5 @ 5200 RPM (Torque 374.2)
Peak Torque 432.9 @ 3100 RPM

Headers gave us an incremental 47.9 HP!!!!!

Pull 4 (w/super stock headers & carb replacement Stock Eliminator Holley 780)

Peak HP 375.3 @ 5200 RPM (Torque 379.1)
Peak Torque 441.4 @ 3100 RPM

Carb swap gave us an incremental 5HP & 8.5 CBTrq.

Pull 5 (w/super stock headers & carb replacement Stock Eliminator Quick Fuel 780)

Peak HP 378.0 @ 5200 RPM (Torque 381.8)
Peak Torque 445.8 @ 3200 RPM

While fat, the brand new Quick Fuel NHRA Stock/Super Stock legal carb gave us an incremental 3HP & 4.4 CBTrq. While still room for improvement & fine tuning, the new Quick Fuel delivers an advantage over the stock Holley.

All in all it was a great day of testing and I am very satisfied with the results, this is definitely a Mighty 390. Now I need to find something to put it in......

Will graph & post the results in the coming days.

Below are some photos & video.



YouTube video of Pull 2





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(Login F570rd)

Re: Mighty 390 Dyno Test Results

April 2 2011, 9:17 AM 

Never watched a Utube video where it was viewed once.Have fun with it.

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(Login westcoastgalaxie)

Nice numbers! that should be a stout piece...

April 2 2011, 10:18 AM 

if you run those headers. This should be some good data for Werby and his gonkulator and shines more light on output of factory motors of the day.

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John Norris
(Login John67FairlaneGT)

Super Stock headers, who makes them? n/m

April 2 2011, 10:20 AM 

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(Login machoneman)


April 2 2011, 10:35 AM 

results and I'm not surprised by the header swap. Good looking headers too.

Still wonder though...looking at a modern pro style of header, most all have least 5"-7" of straight section out of the flange and the tubes match the angle of exhaust port's roof before any bends. Check for comparison the photo of the #5 super stock tube that drops pretty much straight down and the Jeg's link. Yes, the pro headers are for a Bickel chassis car with struts but...it would be interesting to know how much more hp could be gained IMHO.


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(Login qikbbstang)

I'm with "machoneman" on the vast majority of FE Headers are inherently screwed up

April 2 2011, 2:58 PM 

Well at least the ones that go into tight FE shock tower'd cars. Not only do most FE Headers fail to have a straight section out of the exhaust port flange as is common in NASCAR and other full race engines which you have to expect by the confines of the tight shock towers but making matters even worse the header companies DO NOT do anything near fully bend the tubing fullt coming out of the head instead they simply/cheaply go with a small cheap bend and then slice the bent tubing diagonally and simply weld that to the flange. The result is there is not a straight pulse flow stabilization section coming out of the port and even worse because they took the cheaper to produce "slice" you actually have the exhaust pulses coming out the exhaust port and more like hit an angled wall and richochet vs going into a tightly curved tubular radius that is required to fit the confines of the ever to-close shock towers.
It does not seem to matter if it's Mustang, Torino etc with either big block FE or 429/460. If the car application has the 67-73 tight shock towers they simply slice the shit out of the tubes diagonally vs make up the required sharp (obviously costly/difficult) hard tubing bends required to provide a uniform tubing cross section entering the primary tubes. Sorry but if you look closely at most FE headers you will note they do not provide the seriously sharp tubing bends but simply cut the tubing diagonally and weld em on. Not only that and this obviously is because the 50s FE Engineers never dreamed of a "shock tower" they angled 1&2 ex-ports back and 3&4 ex-ports forward which aims them right at the blasted shock towers reather then away from them. So you have Ex ports that aim one way and header primaries that must immediatiately change directions on two planes to fit the confines of the shock towers. I'd just like to see what some high dollar properly mandrel bent short radius flange elbows would do on the typical FE headers.

Re: flange wonder though...looking at a modern pro style of header, most all have least 5"-7" of straight section out of the flange and the tubes match the angle of exhaust port's roof before any bends. Check for comparison the photo of the #5 super stock tube that drops pretty much straight down and the Jeg's link. Yes, the pro headers are for a Bickel chassis car with struts but...it would be interesting to know how much more hp could be gained IMHO.


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Rod C
(Login MT63AFX)

In 64 my uncle's 57 406 gained .6 sec (13.11 to 12.51) by custom building............

April 2 2011, 10:51 PM 

.......a set that went up and under the top of the fender before exiting the wheelwells, he had removed the inner fenders. People didn't rest their arms on the fenders for very long, it's a wonder the paint didn't bubble, lol, Rod. BTW, he was running the hard, 7 1/2" slicks at the time.

Mickey Thompson's 63 1/2 #997 S/S Hi-Rise 427 Lgt/Wgt Galaxie,
1957 C-600 Cab-over carhauler w/390-4V, 2-speed rear-end
FGCofA member #4908
MCGC member #75

"There will ALWAYS be an FE in my LiFE"

[linked image]

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(Login mhakkert)

This particular set of super stock headers were custom made

April 2 2011, 1:35 PM 

many moons ago to run on Jerry Mendes, SS/GA 1970 Shelby GT500 Mustang....no idea who made them originally.


This message has been edited by mhakkert on Apr 2, 2011 1:36 PM

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(Login TGenolcyC66)


April 2 2011, 10:34 AM 

What wheels do you have on your Cyclone?

[linked image]

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(Login mhakkert)

Wheels are Repro Ford Styled Steel Wheels 14x6 w/Beauty Rings n/m.

April 2 2011, 1:33 PM 

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(Login werbyford)

remarkable torque

April 2 2011, 11:13 AM 

The Gonkulator cannot match those torq readings!
For the 1st run, the Gonk feels that:
1. The exhaust pipes on the ends of the stock flat iron were hurting it a little bit
2. It was out of tune, likely too rich.

Once the headers are added the engine comes into tune, but the dyno numbers are now higher than the Gonk can match with stock c6ae-r heads and a stock "S" intake. Was anything done to the heads/intake?

The Gonk gets a great match to those dyno numbers if I just toss a 410 crank under it. Sure it's a 390?
I assumed stock bore, taking it 30-over would add about 6 ftlb and a couple horsepower but that's all. Gonk is coming in about 25ftlb below the dyno on peak torq!

If that dyno is right, the combo is so good I wouldn't even change the valve cover gaskets, it might ruin the magic!

I didn't know that stock/super stock now allows a bigger carb than factory? Maybe the rule is that the float bowls just have to look like the original ones!

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Tom P
(Login tomposthuma)

Re: remarkable torque

April 2 2011, 12:53 PM 

In my experience the headers are worth overy bit of that 47-odd horsepower. Changing the intake to almost anything else would also make a good gain. I did just that to my Z code Ranchero and changed only cam, headers and intake and gained over 100 hp. From 14.7's to 12's just like that. Power increase was obvious at part throttle and lower rpms too.

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(Login mhakkert)

I too was very impressed with the Torque!

April 2 2011, 1:53 PM 

I agree that the exhaust pipes likely hurt the first two pulls, not sure how much, but probably not as much as the bend if the engine were installed in the car.

The first two pulls were rich, but not beyond reason, I've added the BSFC numbers for the peak HP & Torque readings below:

Pull 1 (stock exhaust manifolds)

322.6 HP 332 CBTrq: BSFC = .49

Pull 2 (stock exhaust manifolds)

322.8 HP 326.0 CBTrq: BSFC = .50

Pull 3 (headers)

370.5 HP 374.2 CBTrq: BSFC = .46 (the headers certainly leaned it out)

Pull 4 (headers + Holley 780)

375.3 HP 379.1 CBTrq: BSFC = .47

Pull 5 (headers + Quick Fuel 780)

378.0 HP 381.8 CBTrq: BSFC = .46

The C6AE-R heads are stock, no modifications beyond the valve job, ss valves, etc.
The "S" intake manifold is stock as well, no modifications

Yes, it's a 390, stock crank 10/10, with stock reconditioned rods & I neglected to put into my first post that the block is indeed 30-over.

For the (2) additional carb pulls we tested with an NHRA legal factory Holley 780 & Quick Fuel 780, neither of which is correct for the 390, but we wanted to test the Holley vs. the Quick Fuel since we had everything set up. The Quick Fuel was just recently approved for NHRA Stock/ Super Stock Eliminator use. The Holley & Quick fuel are correct for the 428 CJ motor.

The first two pulls were with my stock 390GT 735 cfm Holley.

I was quite impressed with the Torque, especially how smooth the range was through 5200 RPM.

Just wish I had something to put this mighty 390 into to enjoy it on the street! That said, I wouldn't give up the 427 in my car now!



This message has been edited by mhakkert on Apr 3, 2011 10:26 AM

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(Login werbyford)

Was that 390 built loose perhaps?

April 2 2011, 2:26 PM 

A good loose build will gain 10-20 ftlb over nominal.
Or those could be just extra good headers. Amazing that is with stock "R" heads and "S" intake. Maybe it likes a slight domed piston with those "R" chambers too....

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(Login BenVZ)

735 CFM ?

April 3 2011, 8:07 AM 

My 67' S-Code came with a 600 CFM Holley but in a Mustang ,mabey Fairlanes are different ? Iwant to know as mine will be going on the dyno ina month or so . And was thinking of testing 600 VS Quickfuel 735 carbs . Stout 390 good job , congradulations! BenVZ

This message has been edited by BenVZ on Apr 3, 2011 12:54 PM

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(Login mhakkert)

The factory original 390GT Carb is a 600 CFM.......

April 3 2011, 8:44 PM 

Hi Ben,
Yes, you are correct, the factory original 1966 390GT (Fairlane/Comet) carb is a 600 CFM, C6OF-9510-N or 3557 carb.

I replaced mine in 1987 with a stock 428CJ 735 CFM C9AF-9510-N or 4280.

We also tested with a 1971 429SCJ carb which is a 780, D0OF-9510-R or 4628.

Finally we tested with the new Quick Fuel 780, an NHRA Stock/Super Stock replacement & equivalent to the stock Holley.


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(Login feme)

cam question

April 2 2011, 1:44 PM 

how much over stock is the cam and what would an intake switch do for the numbers? thanks Kirk

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(Login werbyford)

Cams 207-220 vs 230-236

April 2 2011, 2:02 PM 

The 390gt cam is 207-220-116 .480 .490
The c8ax-c cam is 220-230-116 .500 .500
Lunati cheater cam is 224-232-114 .481 .490

The Comp xe274h is 230-236-110 .562 .565
So the cam in this dyno test is bigger than the factory or even Lunati cheater (stock legal but extra duration) version

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Mike U.
(Login mtrain)

Good job, and I still love that black paint.........nm.

April 2 2011, 2:20 PM 


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(Login StarlinerRon)

Seem like I remember the 390GT

April 2 2011, 11:12 PM 

carb is 600cfm, the smallest dual feed ever used. A brand x guy asked me to rebuild one that had been on a modified BB because it was "slow" I told him it was only 600 cfm. He said "but its a dual feed!" He thought all of them were 850 cfm!LOL.

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