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Holley Spreadbore 650 double pumper

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I know this is jumping the gun a little but I will start a thread on this carby I just bought from a bloke in Tassie. My mum (who lives close) picked it up for me and will bring it up next visit. So I don't have it yet.
 
I have (of course) already researched this model ad nauseum and have concluded that folks who have gotten them to work love them to bits, and those who could never get their heads around them want to hurl them into the abyss.
 
They were a slight departure from the traditional 4150 (square bore) in that the main body is a completely different casting. The differences include:
 
* Splayed boosters to suit the wider bore pattern
 
* For some reason, the primary squirters are mounted inboard, squirting outwards.
 
* Altered plumbing for the accelerator pump circuit, using a transfer tube and not a simple drilling in the metering block... Possibly so that only emissions type meeting blocks can be fitted.
 
* Metering blocks with altered drillings for specific bowls that take different locating dowels and acc pump circuit routes (for reasons above), also dedicated gaskets for blocks and bowls.
 
* Fixed float adjustments
 
* Single fuel feed in a similar location on the front bowl to where the one on a Rochester would be, with a dedicated transfer tube to the rear bowl. This is unusual for a double pumper... Normally they're dual feed.
 
* Rear accelerator pump is the big 50cc type (coupled with a suitable pump cam) to feed the huge rear barrels when they open
 
* I'm not 100% on this, but going by the type of idle screw used, it appears that the idle mixture is reversed type (screwing in equals richer)
 
These carbys were intended to be an emissions-compliant replacement for a Rochester Quadrajet back in the day, hence the lack of float adjustment, etc. This is a bit of a drawback, but not a deal-breaker.
 
The ad was taken down ages ago, but here are pics of an identical carby:

62fcdf0cc3cbe62c35253bc394e55c1b.jpg

64262f02315f5320cd46081ae3998ef0.jpg

ae5e549d35b28dae4139a478b5971080.jpg

88a81bd1426df66643830e9e81de106d.jpg
 
So as you can see, the primaries are very small compared to the secondaries, like on a Rochester or Thermoquad, which gives good low-end torque and economy. I went a step further and got a very rare 2-stage power valve for the primary side, had to order it from a place in the US.
 
The reason why I went that way is so I can jet down even more for a good cruise AFR but have a slight enrichment at part-throttle somewhere between where the normal power valves are either open or closed. I believe the one I got is 1st stage 10.5, 2nd stage 5.5. These were OEM on the 1980s 5.0 Mustangs that had 1480 Holleys (an emissions square bore). They are not recommended in a performance engine as they can't flow like a traditional power valve.
 
Anyway, I digress, it's all nice in theory but I will only know what it's like once it gets here and I strip it down. I might do an annular booster conversion, see what fuel bowls I can swap (probably none), play around with squirters and pump cams, jetting, all that lovely carby stuff.
 
I was happy with the Street Demon up until recently, when it really started drinking the juice. I'm talking 300 to a tank when it was getting 400 before, and doing identical driving.
 
I can't work out why and I can't tune it much now that my tuneup kit has gone missing (I suspect when the car went to the smash repairer). The cost of another tuneup kit landed from the US (whenever that would happen) would be close to what I paid for this Holley.
 
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these carbys came at an era of 80s usa wanna be muscle cars like trans am,and others which had a spreadbore manifold,dont really see a lot of them now a days but good score ,your knowledge should be easy to reco that fkr.

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this is what i had on My 351 i had reco'd (25yrs ago)

i asked the dyno tuner what to get for dual fuel(seeing it was on Impco LPG and the thermoquad isn't legal because of what it even did to My car.. backfired on gas through the intake, and blew a chunk of the carby bowl out.. if i flicked it to petrol like this, could have been a good fire)

 

the dyno tuner told me to get a 650DP, i just assumed because of the themoquad, get a spreadbore.. he said it wasn't ideal for the stock cast iron manifold but would work, even though they are a spreadbore style, said i should have got an alloy manifold for it also or got a squarebore.

 

anyway, he reckoned it made good power for what it was(basically stock 351 open chamber heads, i don't recall hearing a figure.) 

 

this is the first time i'm seeing a mention of one since i had mine.. must be rare.

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4 minutes ago, CHESTNUTXE said:

i can just imagine how many spready to squarebore adaptors linx and redline have sold since the xc came out with spready manifold,i know i have bought about 10 of them over the years.

from memory i couldn't find a used spreadbore to spreadbore one(to delete the EGR plate) had to buy a new one.. even then it wasn't easy to find in stock

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I remember the bulletin from FoMoCo about the TQ phenolic body cracking, when quenching the hot, dry LPG air with cool petrol. They voided all warranty if not removed. IIRC. 

Got my TQ from the FC sitting in the shed, all rebuilt and ready for the Nugget. Just a lazy bass turd. 

 

Good score there, Gerg. Looks well used.!   Check throttle shaft play for sure.

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backfired on gas through the intake, and blew a chunk of the carby bowl out.. if i flicked it to petrol like this, could have been a good fire
 
the dyno tuner told me to get a 650DP, i just assumed because of the themoquad, get a spreadbore.. he said it wasn't ideal for the stock cast iron manifold but would work, even though they are a spreadbore style, said i should have got an alloy manifold for it also or got a squarebore.
 
this is the first time i'm seeing a mention of one since i had mine.. must be rare.


I can see how that would happen on an "air valve secondary" carby like that (backfire gets trapped under the secondary flap) and the resin body wouldn't tolerate much of an explosion I imagine. I'm curious as to why he reckoned a spreadbore Holley wouldn't suit a spreadbore Ford manifold though. I would have thought the opposite true, ie square onto a spread manifold isn't ideal.

dean i blew a hole in my thermo on lpg just like you said from backfire,the black plastic area.


This sounds like it's definitely a thing

I remember the bulletin from FoMoCo about the TQ phenolic body cracking, when quenching the hot, dry LPG air with cool petrol. They voided all warranty if not removed. IIRC. 
Got my TQ from the FC sitting in the shed, all rebuilt and ready for the Nugget. Just a lazy bass turd. 
 
Good score there, Gerg. Looks well used.!   Check throttle shaft play for sure.


Thanks Bear, got it for $200 which is pretty good for a Holley these days. People want "near new" money for old junk lately.

Yeah throttle shaft is a bit of a worry, there is a fix for it but I'm hoping that this was one that someone drove for a bit, got frustrated with it and benched it for the rest of its life up to now.

A well-setup TQ is supposed to be a great carby, up there with an equally sorted Rochester. They had their issues like leaking main jet wells (epoxy fixes them), warped main body (surface plate and wet/dry should sort that) and one thing I noticed with a crappy one I mistakenly bought as a teenager was the wear in the body where the vacuum piston goes that actuates the needles wears out and leaks too much air, causing the piston to stay up all the time and have the rods on "power" (rich) mode all the time.

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3 minutes ago, gerg said:

I'm curious as to why he reckoned a spreadbore Holley wouldn't suit a spreadbore Ford manifold though. I would have thought the opposite true, ie square onto a spread manifold isn't ideal

not sure, the 302 clevo manifold is not opened up though in the larger throats, for some reason.. it makes me wonder if i had the 302 manifold still?(4 barrel still)

 

he originally said to get a rochester/quadraject if wanted it to be properly legal and tuned brilliantly (by him) he used to send people with thermoquads elsewhere.. too much time to sort them out properly. 

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the reson it is not opend up on the 302 manifold is to make more air speed ,i read this in a interview with mick webb on factory manifolds,i have used that manifold with many 351 engines and had no problems.

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not sure, the 302 clevo manifold is not opened up though in the larger throats, for some reason.. it makes me wonder if i had the 302 manifold still?(4 barrel still)
 
he originally said to get a rochester/quadraject if wanted it to be properly legal and tuned brilliantly (by him) he used to send people with thermoquads elsewhere.. too much time to sort them out properly. 
the reson it is not opend up on the 302 manifold is to make more air speed ,i read this in a interview with mick webb on factory manifolds,i have used that manifold with many 351 engines and had no problems.
That brings to mind the 3 different spreadbore manifolds that Ford Oz made from 76 onwards, the 4-hole XC one, (which is currently on my coupe), the open 2-hole and the funnelled-down dunny bowl one on the 302. The 2 latter ones would likely be from the same casting but just machined out differently in the plenum to suit. Mine started as the 302 one but as mentioned in other threads, was machined out by my brother where he discovered how hard the Aussie iron is in these manifolds.

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I used to have a 6210 650DP, was on a XE V8 parts ute, worked alright but acc pump died, it also killed the parts utes 302c when the air filter stud came lose & went into Cyl 8 breaking the piston. later put a kit in it & fitted to my black ute but started leaking from the plug above the rear needle on the bowl that had been patched before, so brought a new HP street 650DP.

DSCF6330.jpg

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I used to have a 6210 650DP, was on a XE V8 parts ute, worked alright but acc pump died, it also killed the parts utes 302c when the air filter stud came lose & went into Cyl 8 breaking the piston. later put a kit in it & fitted to my black ute but started leaking from the plug above the rear needle on the bowl that had been patched before, so brought a new HP street 650DP.
DSCF6330.jpg


That's pretty much what I got, not sure what revision it is (seems like -3 is common) but cheers for the heads-up on the plug. They do work loose over time but luckily I have Hume performance here in Sydney who will likely have those fiddly bits like meter block plugs, etc. The rebuild kits are a bit expensive, as the bowl and main body gaskets are specific to the 4165/4175 models.

When you say the acc pump died, it could have just been something like the inlet check valve failing (common on the umbrella type) or some crap getting stuck in the check ball on the outlet.

I like to wind a 1/4" nut down the filter stud and snug it to the lid of the carby to stop it from coming loose, for the reason you stated. That sucks what happened on yours by the way, I would hate to lose an engine from something so minor.

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It was the Accel pump diaphram, just leaked fuel everywhere,

Filter stud had came lose a few times was a bad fit, I was like where did it go... must of fallen on the ground. bit later, knock knock knock. was alright with a new stud,

Piston had part of the stud stuck in it after I removed the head, (RHS of broken section), block looked good & is standard bore so should clean up alright.

D2U0FXPl.jpg?1

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It was the Accel pump diaphram, just leaked fuel everywhere,

Filter stud had came lose a few times was a bad fit, I was like where did it go... must of fallen on the ground. bit later, knock knock knock. was alright with a new stud,

Piston had part of the stud stuck in it after I removed the head, (RHS of broken section), block looked good & is standard bore so should clean up alright.

D2U0FXPl.jpg?1

 

Oh I love looking at carnage... Must be a mechanical sadist thanks for sharing

 

Accel pump diaphragms are great on Holleys, so damn easy to change. I wish my street demon had that setup but they have the piston type like a Thermoquad and it sucks. Probably the worst thing about the carby. Very hit-and-miss for pumping ability. Sometimes you could move the throttle and nothing would come out. I had to stuff with the cup seal lots to get it to work ok. Both my previous Holleys were nice and crisp and instant for pump action.

 

If yours was the secondary pump that died, it could have been the wrong one. They take the 50cc diaphragm along with the bigger pump cam, and if you try and put the 30cc one in, it will punch through because it can't deal with the extra stroke of the big cam.

 

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