Flat-Top Holleys: Unfairly judged?

[gerg 10,871]

I'm eyeing off a hot run-tested 650 spread-bore Holley, 4011 series vac sec. My current carby is a 600 square, runs ok but I just can't squeeze more than 16l/100km out of it in my 302. I calculated that if I could better that even by 1 litre per hundred, this carby will pay for itself in 3 months.

 

 

 

The 4010/4011 series was based on the old Ford Autolite carbies, which have a reputation for rock-solid reliability. Holley just used their jets and power valves in their later version. Holley abandoned them when some quality issues ruined their reputation, but the current Summit brand carbies are yet another revival of this design, and get pretty good feedback from those who use them.

 

Advantages:

• I like the fact that you don't drown your engine in fuel every time you want to play with jets.

• there's no prospect of fuel leaks like what traditional Holleys are prone to on the float bowls. Granted, the modern gaskets available now are light years better than the old cork crap but the risk is still there.

• these carbies go for a song compared to traditional Holleys.

 

Drawbacks:

• you can't change squirters easily (major mod to the booster/squirter assembly

• power valve change req's carby removal

• alloy body conducts heat and vapour lock is a common problem.

 

I'm aware of the lack of interchangeability of parts, but was wondering if anybody had any major horror stories that need mentioning using this type of Holley.

[Trev Vaa 1,185]

why not just order a carb from Zok or Pro systems or Quick fuel?

16L for a 302 sounds like a lot...

[gerg 10,871]

That would be nice but mortgage, kids, blah blah usual story... I think 90 bucks is worth the gamble, unless it's a disaster waiting to happen, hence the original question.

[XES 859]

I had 650 double pumper one of these on my stock 302 and found it was a bit big. I thought it was a pretty go carby though. Easy to switch jets like you said. I ended up switching to a 600 with vac secondaries and it goes really good now. I'm currently building a 351 and ill probably try this carby on it. Loved the induction noise when those bit secondaries open up on a speadbore carb. Especially with mechanical secondaries.

[gerg 10,871]

Cheers mate, yeah I think a 650 double is way too big for a stock 302... A warm 351 would be the minimum I'd put one of them on. This one's a vac secondary so will be much tamer on my 302.

[Trev Vaa 1,185]

i wouldn't bother with a second hand carb period... even if it has been reco'd you tend to find they shit themselves/have warped bits on them anyway.... so yeah, i dunno... if its that big of an issue, shitcan it and save up, do it once, do it right.

could just got get a holley 570 street avenger too... that'd work fine on a 302.

[gerg 10,871]

I know exactly what you mean XC, I should know better as my current Holley (bought second hand) is a mongrel made up of various bits, but the one I've just bought is professionally hot run-tested and I suspect that it's a clearance from Hume Performance's old stock.

Being a spread-bore, it has to be better in some way.

I'll post some results after I've fitted it up and driven a tank worth of fuel through it.

 

UPDATE: After pulling it down, it needs a kit. Bowls were corroded, one jet had to be removed with an easy-out, and secondary diapragm was shredded. Everything else seems ok, throttle shafts have minimal play. No choke fitted.

 

Jets were 60/64, Power valves were 5.5/6.5. I found it weird to have that size in the primaries and must have been fitted by someone. As far as i know, ALL Holleys come with 6.5s

 

Rebuild kits are pricey at $89, so I just got all the gaskets I needed individually, ended up being less than $40 with a diapragm. I'd suggest going this way if you're doing up a carby, as they give you shitloads of stuff in the kit that you dont need.

 

It takes funny fittings (9/16x24) so i made some up at work by sweating some 5/16 copper tube into some brass inserts. Looks a bit ghetto but will work.

[gerg 10,871]

Still building it up now, but if it doesn't work, I'm going down this path:

 

http://www.ebay.com.au/itm/Demon-Carburetion-625-cfm-Street-Demon-Carburetor-DEM1902-/281023394001?pt=AU_Car_Parts_Accessories&hash=item416e4cb0d1

 

Plenty of rave reviews and a full-circle back to the ThermoQuad style

[gerg 10,871]

Got it all jetted nicely now at 61/68, purple secondary spring is a bit stiff (needs yellow or white I reckon), power valves 6.5/6.5. Pulls beautifully from idle in all gears, just has that dip before the secondaries decide to open at bang-on 2500 rpm.

 

One problem that aluminium carbs have is heat soak, boiling the fuel in the bowls when stuck in traffic on a hot day. Causes poor idle and stalling. Made worse by the stock air cleaner acting as a big umbrella trapping in hot air from the engine underneath. Only fix is a shaker

 

Haven't needed any choke yet, which is just as well because it came with none. Annular boosters are great for atomisation, particularly when cold. Wait till winter comes with crunchy lawns and icy windscreens... We will see.

 

Hard to tell what economy is like right now, as the 95 fuel seems to screw up the fuel gauge. Not E10 though funnily enough.

 

All round, I'd say these carbys are very good and deserved a better reputation than what they've received. I think it was people's reluctance to change that killed them in the end. they dont look like a normal Holley either.

 

If you see one at a swap meet or for sale online, and the price is right, give it a go. As long as the moving parts are all there and throttle shafts don't flop too much, you're on a winner.

[gerg 10,871]

Bitches

[gerg 10,871]

I've been getting some shitty vapour lock problems with the current winter mix of unleaded, E10 or normal. I have a theory that the stock air cleaner is acting like a giant umbrella, trapping heat under it and teamed up with my aluminium 4011 Holley, proceeds to boil my fucking fuel every time I get stuck in traffic or park for more than 10 min. Enter the Ford oval air cleaner.... Hopefully this will help by not trapping heat from the extractors down each side of the carby.

[gerg 10,871]

Midrange has picked up too. Dunno why but I'm certainly not complaining. Gotta say it only just misses the bonnet by a bee's dick, so I'd be careful just fitting this to anything.

[gerg 10,871]

so far so good, no fuel boiling yet

[Trev Vaa 1,185]

pretty sure the fuel boiling was one of the reasons they didn't take off wasn't it?

[gerg 10,871]

pretty sure the fuel boiling was one of the reasons they didn't take off wasn't it?

 

Yep, and the fact that to a Chev guy, it looked too much like a Ford Autolite (which it was based on)... Otherwise great carby