dynoed hp for a 289 hipo with dealer option dual quads ?

[jk66gt350]

I've seen the original ads that claimed that swapping the original intake and carb on a 289 hipo for a holley dual quad setup and intake was supposed to provide a 45 HP boost to the stock setup but always wondered how accurate those claims were.  Has anyone with a Holley or Carter dual quad setup on their 65 - 67 GT 350 ever dynoed the HP this setup actually makes? 

[tesgt350]

I've seen the original ads that claimed that swapping the original intake and carb on a 289 hipo for a holley dual quad setup and intake was supposed to provide a 45 HP boost to the stock setup but always wondered how accurate those claims were.  Has anyone with a Holley or Carter dual quad setup on their 65 - 67 GT 350 ever dynoed the HP this setup actually makes?

That's probably to the Flywheel.  I owned a 1999 V6 5 Speed Mustang that had Factory rate of 190HP but when I Dyno'd it, it had 139 to the Rear Wheels.

[gt350hr]

  I did the swap in '75 . I used the first design Holley set up Ford offered ( and Blue Thunder repops) . I had just  done a ring , bearing , valve job on the original engine out of 6S240. I reused the cast pistons and didn't do any work to the heads. I didn't dyno it before but did with the dual fours to get the jetting correct. It made a tic over 320 ( like 322-323 ) with the original tri y's . That was at 5,600 and it fell off after that but would "run" to 7,000 where it made about 280. I was looking for 350 but it wasn't there. It "might" have been 45 better than a 271 hp engine but clearly not that much better than one claiming 306. Later that year , I replaced the Cobra intake and 715 not really noticing a difference in power.  I think 20 hp is realistic.  The later Ford offering with the Trans Am style manifold ( not reproduced at this time) made noticeably more power than the early dual four intake ( same carbs). It is easily 30 better and what I run now on 6S477.
    Randy

[s2ms]

Back in 2012 Eric English did an article for Mustangs & Fords comparing different intakes and carb setups that covers part of this question, this is Part 2....

http://www.mustangandfords.com/how-to/engine/mdmp-1207-dual-quads-twin-win-or-double-trouble-part-2/

[gt350hr]

   Thanks Dave ,
Mine is pictured in the photo gallery #15 of 19. Eric's testing was on a more modern combination and the results are a bit different because of the flow differential from the stock Hi Po heads I ran , same for the cam. I applaud Eric for the fine work he did , it opened a few eyes for sure.
    Randy

[shelbydoug]

There is always a limiting factor. Randy will tell you, the T/A manifold was designed for the GT40 heads. Compared to todays options, they are still limiting. In addition, the T/A's didn't run two 390cfm carbs. Hardy. Try somewhere around 652's like on the 67 GT500's.

As a result of all of this, in order to get an accurate ball park number, that test needed more camshaft, better headers, better heads and better carbs.

On the street a pair of 1850's will give you impressive response, performance and not bad on the gas mileage.

Of course I personally also think that it's probably a waste of time to run them on a 289. Try 347. See how that works out for you or even the Probe 355. Pick heads that show real flow numbers that match the cam lift, then dyno it.

I doubt that it's just a 25hp difference. Not unless hp is measured on a sliding scale in order not to intimidate and hurt the feelings of the 289 guys?

In addition, one of the things that make this such a nice driving combination is the design of the Ford linkage. You are basically driving around town all day on just one set of primary throttles in the primary carb up to around 3,200 rpm. Then secondary carb, primary throttles work like a 600 double pumper and the secondaries are vacuum operated by engine demand.

I wouldn't have thought there was a lot of demand a little engine could produce but judging by the whomp of the secondaries opening, the fishtailing of the rear, and the tightening of the grip on the steering wheel when this happens, some sort of demand is going on,  it's amazing.

Also the whining, squealing and grunting the engine now produces wants to make you stop and ask it "are you alright?"

You might as well throw away your rear view mirrors as well. You won't see anything there but a lot of black smoke, grey smoke, smoke of all colors and that horrendous smell of burning rubber is just enough to make you puke. Absolutely disgusting!

It may not in fact be making 500 hp but who cares? Who's counting? I'm too busy holding on. After all,  it's not how big your number is, it's how you use it! 

I vote 2x4's all the way, every day. You just gotta' be there to get it.   

[jk66gt350]

Thanks for the great replies.  My car has the Holley 2 x 4bbl OTC setup (List 3360 and 3361 dated 634).  It also has a Lemans cam and tri y headers.  I've always really liked the way this setup worked but never knew how much extra hp this setup made vs stock vs the ad claims way back when.  I've driven a stock 66 GT 350 as well.  It seemed to me that my 2 x 4 setup was a little slower out of the hole, but pulled much stronger above 3,500 rpm.  And the sound at high rpm with side pipes is heavenly!

[shelbydoug]

Thanks for the great replies.  My car has the Holley 2 x 4bbl OTC setup (List 3360 and 3361 dated 634).  It also has a Lemans cam and tri y headers.  I've always really liked the way this setup worked but never knew how much extra hp this setup made vs stock vs the ad claims way back when.  I've driven a stock 66 GT 350 as well.  It seemed to me that my 2 x 4 setup was a little slower out of the hole, but pulled much stronger above 3,500 rpm.  And the sound at high rpm with side pipes is heavenly!

Those carbs are 427 carbs and are rated at 710cfm each. That's kind of big for just a 289. I can believe the throttle response could be described as lacking crispness off of idle?

The carbs on the 67 GT500 are rated at 652 cfm each and have been criticized by some for being too large for the street.

For a 289 I'd guess that 1848's would be about right for that set up.

I'm using two 85 Mustang GT carbs. They have been converted to 1850 bowls. The idle bypass has been increased to .028 and the primaries have annular discharge venturies which help throttle response immensely over the 1850's. It's a 347 with AFR 1388 heads.

Those carbs are generically a 600cfm carb but because of the annular ventuies I think are rated at 595cfm each? They idle very very clean.

I have run a single 715, 780, 750 and 600 double pumpers. This set up is more responsive then even the 600dp is by far. The 780 was used stock on the Boss 302, and the 715 on the 65-66-67 GT350. They are about equal response wise and I would describe as being a bit sluggish off of idle.

[427heaven]

Multiple carbs are mandatory in my eyes for vintage muscle cars. I ran an original COBRA dual quad set up with vintage 500 cfm competition series Carters on a heavily modified Hipo 289. Way to much carb for just toodling around, but on the big end those hamsters felt like lions roaring... well as much as a hamster can roar It dyno'd at 360hp with a stout valley head service top end and all the best from back in the day. A stocker it wasn't, so an average hipo would make probably around a solid 300 realistic HP.

[shelbydoug]

Multiple carbs are mandatory in my eyes for vintage muscle cars. I ran an original COBRA dual quad set up with vintage 500 cfm competition series Carters on a heavily modified Hipo 289. Way to much carb for just toodling around, but on the big end those hamsters felt like lions roaring... well as much as a hamster can roar It dyno'd at 360hp with a stout valley head service top end and all the best from back in the day. A stocker it wasn't, so an average hipo would make probably around a solid 300 realistic HP.

I'd feel inadequate without at least two carbs? 

[jk66gt350]

shelbydoug - according to what I have seen / read, these are not 427 carbs - and the cfm rating is 465.  Following is one source of that info found online.   "In 1966 Ford offered over the parts counter only a small block dual quad. The engineering numbers of these carbs were C6OA-9510-A and C6OA9510-B and were listed at 465 cfm each".   Those are the engineering #'s associated with the 3360 and 3361.   

[shelbydoug]

shelbydoug - according to what I have seen / read, these are not 427 carbs - and the cfm rating is 465.  Following is one source of that info found online.   "In 1966 Ford offered over the parts counter only a small block dual quad. The engineering numbers of these carbs were C6OA-9510-A and C6OA9510-B and were listed at 465 cfm each".   Those are the engineering #'s associated with the 3360 and 3361.

Ooops! You're right. I misread the list number and thought of 3300 and 3301. My mistake. My appologies.

Those ARE the carbs from the originals set up.

Lots of info can be found at mustangtek.com.

[gt350hr]

  +1 465cfm.

[camp upshur]

Great day two thread.
The 2012 mustangsandfords article posted references of two 1968 (July October) Hot Rod Magazine AkMiller SBF articles.
Would anyone happen to have a copy of these to post? They were very influential in the day. I lost mine years ago.
THX

[jk66gt350]

Although I have no way to definitively prove it, the dual quad update to 6S1575 was supposedly done at the selling dealer on day 1.  The original owner told me this in 1987, the year after I bought the car and started contacting the 2 previous owners and diving into its history.  He said he added the lemans cam and hurst shifter the following year, which are still also installed.  He had many great stories to tell which I have documented but unfortunately he did not keep one piece of documentation from his term as owner between 1966 and 1971.  I have no reason to believe he would make up that story, so that's just one of the reasons I've left it as is.  He was quite a gear head, worked at various automotive jobs, was a manager at Roush Racing when we first talked and went on to be President of TRD - so you would think a credible story teller.  Fortunately the second owner was opposite in disposition and kept every receipt other than gas receipts.