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:
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......
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.
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.
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.
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!
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.
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!
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....
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
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.