Custom race Tri-Y headers going lean

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ProPower engines
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Re: Custom race Tri-Y headers going lean

Post by ProPower engines »

rj4004 wrote: Thu Apr 22, 2021 9:15 am Sorry but no O2’ sensors.

Appreciate your response, was hoping someone might have had same experience but worked through problem. I’m an old guy and down on my “get up and go” and looking at easy way to figure it out LOL.

Thanks
RJ
The easiest way is to install O2 sensors other wise you are just guessing at the set up.
O2 sensors will tell you exactly where to go on the tune and get it done in a few pass's rather then beating on it to try and get it right.
The collector extensions with the bungs welded into will be a bench job and a few wires after that. Easy install and cheaper then a track pass and 10 runs of test and tune to try and get it right :D
JMO
Real Race Cars Don't Have Doors
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Re: Custom race Tri-Y headers going lean

Post by NewbVetteGuy »

I’ve seen a couple of dyno examples of overscavenging and torque losses down low when switching to tri-ys without changing the cam.

If you’ve got more exhaust velocity you don’t need as much TIME for the same total amount of flow, right?


Cams and Tri-Y swaps; anyone willing to go there?



Adam
rj4004
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Re: Custom race Tri-Y headers going lean

Post by rj4004 »

Appreciate all the info and comments, and i realize I need to get back on the dyno with O2's installed to get a better picture of whats going on.
I am trying to upload a overlay graph of the two different dyno pulls so you can see what I was trying to explain, I'm just not very knowledgeable working with computers and such.
header grahttps://www.speed-talk.com/forum/download/file.php?mode=view&id=26718ph.jpeg
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Re: Custom race Tri-Y headers going lean

Post by rj4004 »

Here is the combo info if it helps.
1967 Fairlane
390/320 hp
C6AE-R heads 2.03 int 1.55 exh (know Legal Edelbrock Alum replacement heads)
OEM rocker assy
715 Holley vac sec (can run a 780 Holley vac sec and QF 780 SS legal replacement)
Factory lift hyd cam 481/490 max legal lift
10.5 compression
C4 trans 2.75 low gear
ATI 5800 flash convertor
Two-step launch 3000-3800
4.63 rear gear
9x30 goodyear radial slick
3250 lbs with driver
10.40-10.50 good air 126 mph
peak torque 485-490 @ 4200rpm approx
peak hp 520 @ 6500rpm approx
1972ho
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Re: Custom race Tri-Y headers going lean

Post by 1972ho »

So did you ever try to jet that carburetor up and are those jet numbers with a power valve 65p and 65 a seem really low for a 715/780 vs I run 72/80 in a holley vs on a cleveland but I’m well above 6500 rpm in a stocker.
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Re: Custom race Tri-Y headers going lean

Post by rj4004 »

Jet numbers are not correct on graph, should read 65p and 76 s. This 390 combo was 7000 shift points and crossed about 7500 depending on air conditions. I pull my motors between 3400 and 6500, motor doesn’t make any power above 6500-6600 anyway, it’s all down hill at that point and I don’t like beating stuff up on dunk. Lower number is approximately where I’m at on 2 step at launch. I run 2.5-3.5 power valve on Holley as I am matted.
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Re: Custom race Tri-Y headers going lean

Post by 1972ho »

Did you talk to guys that run these motors about the triY headers combo
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Re: Custom race Tri-Y headers going lean

Post by Tuner »

There are several Holley list numbers assigned to original carbs for the 390 GT engine and they all were 585 CFM (that was before Holley changed the nomenclature to 600 CFM) and original jetting was either 65 or 66 P and 72 S, so 65 and 76 is in the ball park for a Holley that size. The same size carb is the List 2818 for 350HP 327 Chevy and they are 65P 76S. Same size carb as 600 double pumper.

How is it you get to use a larger than original carb and still be legal?

I was working at a speed shop back in the day when these cars were new we sold a lot of headers for all the muscle cars. Unfortunately, many times things didn't go the way it was written in the magazines and we got the feedback loud and clear. I recall it was not unusual that some cars with cramped engine compartments like the 390 GT Mustang and Fairlane (the Barracuda was another) would not perform as well with inside the fender headers (no cutting of fenderwells) as with the stock manifolds until someone sorted out the carb jetting. I think Bellanger headers were the best for Fords.
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Re: Custom race Tri-Y headers going lean

Post by rj4004 »

Tuner
NHRA allows replacement carbs on Stock and Superstock combos, yes the 66-67 Fairlane and Comet, 67 mustang and Cougar came with the 600 Holley.
We are allowed up to a 780 Holley, actually any carb that measures the same throttle bore and Venturi size have a air horn and choke flapper and is vac secondary is Legal regardless of OEM manufacturer. A QF 780 SS is a legal piece also with small modification. We can run a 780 from any manufacturer as long as it measures the same and is not “enhanced” or “embellished”.
I was stationed at Camp Pendleton in October of 66 and had a new 67 Mustang with the 320/390 and Belanger Bros used my car to build the first set of crossover tube headers, I think they charged me $175.00 out the door. Reverse cone collector and hooked up to my factory exhaust.
I have messing with Stock and Superstock FE motors since Noah came over on the boat.

RJ
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Re: Custom race Tri-Y headers going lean

Post by 1972ho »

RJ when you ran this 390/320 combo and had the 10:40-10:50 et @124 did you run it in E are F stock if so that’s like really quick and you still believe it can go quicker.
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Re: Custom race Tri-Y headers going lean

Post by Tuner »

rj4004 wrote: Fri Apr 23, 2021 6:08 pm Tuner
NHRA allows replacement carbs on Stock and Superstock combos, yes the 66-67 Fairlane and Comet, 67 mustang and Cougar came with the 600 Holley.
We are allowed up to a 780 Holley, actually any carb that measures the same throttle bore and Venturi size have a air horn and choke flapper and is vac secondary is Legal regardless of OEM manufacturer. A QF 780 SS is a legal piece also with small modification. We can run a 780 from any manufacturer as long as it measures the same and is not “enhanced” or “embellished”.
I was stationed at Camp Pendleton in October of 66 and had a new 67 Mustang with the 320/390 and Belanger Bros used my car to build the first set of crossover tube headers, I think they charged me $175.00 out the door. Reverse cone collector and hooked up to my factory exhaust.
I have messing with Stock and Superstock FE motors since Noah came over on the boat.

RJ
Good stuff for sure ^^ I sold some of those w/crossover for Mustang and Fairlane. He made the only good headers for FE in the narrower '57 to '59 chassis and they had pipes crossing under the engine too. A pal had a 2x4 side-oiler in a '57 wagon with a top loader. The the flywheel exploded and ruined those headers.

Did Jerry build your collectors with the spike in the center of the cloverleaf? I think he called it a "goilet" (and pronounced it goy-lay)

I thought replacement carbs had to be the same size as original ??
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Re: Custom race Tri-Y headers going lean

Post by rj4004 »

This combo 67 2dr sedan is a Natural “E” car per NHRA 10.00 lb weight break and my min weight with me in the car equates to 3360 lbs. You can take weight out and run “D” (9.5 lbs)@3200 lbs with driver or add weight for”F” @ 3520lbs with driver.
I have run all 3 classes with “D” being the quickest because of weight being less.

Weight is based on the shipping weight per NHRA.
And not the DMV or factory specs. They are pretty close on the numbers.
You then figure you natural class, in my case NHRA says”E” and that’s a 10.00 weight break class and that 3200. Then you add driver weight per NHRA and that 170lbs for everyone regardless of actual weight and that is 3360 min weight with driver across the scales.

Clear as mud huh?
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Re: Custom race Tri-Y headers going lean

Post by rj4004 »

It’s up to the powers that be.
I used to have to run the 600 Holley, then when Holley stop making the 4150 600 vac sec, NHRA legalized the 780 and everything in between.

Greg Holman @REF makes a very nice header and merge collector and I normally go through him. He is very sharp and his dad worked for Hooker in their RaceShop for over 20 years, so Greg had great guidance.
Thanks RJ
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Re: Custom race Tri-Y headers going lean

Post by 1972ho »

RJ you wouldn’t happen to have a need for one of those 390 blocks with nobs for a 427 cross bolt with 3 ribs and standard bore.
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Re: Custom race Tri-Y headers going lean

Post by 1972ho »

1972ho wrote: Fri Apr 23, 2021 9:23 pm RJ you wouldn’t happen to have a need for one of those 390 blocks with nobs for a 427 cross bolt with 3 ribs and standard bore already hard blocked.
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