Do I need Vac secondaries or mechanical secondaries?

[Stumps 384]

still looking in to carbs for my 250 2V engine, do I want vac secondaries? or can I go with mechanical secondaries on a 4 barrel carb, will it make any real difference using one over the other?

 

I remember old street machine articles about carbs and they used to state, go vac secondaries with auto's in heavy cars and mechanical with manuals in lighter cars.

 

My XB isnt a light weight but it's certainly nowhere near as heavy as a late model falcon, and I have a manual gearbox? 

[deankxf 21,673]

44 minutes ago, Stumps said:

still looking in to carbs for my 250 2V engine, do I want vac secondaries? or can I go with mechanical secondaries on a 4 barrel carb, will it make any real difference using one over the other?

 

I remember old street machine articles about carbs and they used to state, go vac secondaries with auto's in heavy cars and mechanical with manuals in lighter cars.

 

My XB isnt a light weight but it's certainly nowhere near as heavy as a late model falcon, and I have a manual gearbox? 

if you were considering turbo or boost , vacuum secondaries are blown open in a blow through (cannot use) and i'm fairly sure they were not recommended in a draw through also.

i do recall i was told to go mechanical in a manual also, but i don't see why from more recent chatting, unless its for double the squirt of fuel when they are on a gear change to prevent a lean backfire on full throttle? or just vacuum might be too slow to react for a gear change in general when thrashed?

someone smarter than Me may have better info for you hopefully. 

[Stumps 384]

Thanks for that, mechanical secondaries make 100% sense on a turbo for sure.

 

Just dont know about the non turbo route. Most of the carbs Im looking at are vac secondary carbs like the TQ or Quickfuel 450cfm carbs. 

 

The 4360 economaster carb is a mechanical secondaries so its the odd one out.

 

Feel like banging my head on a brick wall, way to many choices...

[Stumps 384]

What about Edelbrocks, the AVS2 seem to be updated versions of the old AFB carters that Val Pacers ran....did they ever fix the hard left hand cornering fuel starvation issues those old carters had, surely 50 years on that would be well an truely sorted with the design.

[deankxf 21,673]

12 minutes ago, Stumps said:

What about Edelbrocks, the AVS2 seem to be updated versions of the old AFB carters that Val Pacers ran....did they ever fix the hard left hand cornering fuel starvation issues those old carters had, surely 50 years on that would be well an truely sorted with the design.

@Thom may know something about various brands of carby, see if he can read the few posts above and weigh in on anything perhaps 

[CHESTNUTXE 7,739]

there is way too much choice now with nok offs and copies of copies,price too now is crazy for a new carby,i went thru this in many engine builds ,see holley knows the most popular carb even thou small cfm the 465 vac is a huge seller in the states,and all around the world as it suits the 289/302 and stock other v8s ,600 650 and 750 have always been cheaper ,even consider a hume performance rebuilt carby i have bought many over the years and they are very good,they even look like new,tell them what you are doing and they can build it for you,or just buy a new 450 quickfuel d/p and be done with it,they have all the latest features built in and are very light,i had one on my 250 and pulled 210 rwhp on the dyno with room for improvement there is a video on here with it.

[Stumps 384]

11 minutes ago, CHESTNUTXE said:

there is way too much choice now with nok offs and copies of copies,price too now is crazy for a new carby,i went thru this in many engine builds ,see holley knows the most popular carb even thou small cfm the 465 vac is a huge seller in the states,and all around the world as it suits the 289/302 and stock other v8s ,600 650 and 750 have always been cheaper ,even consider a hume performance rebuilt carby i have bought many over the years and they are very good,they even look like new,tell them what you are doing and they can build it for you,or just buy a new 450 quickfuel d/p and be done with it,they have all the latest features built in and are very light,i had one on my 250 and pulled 210 rwhp on the dyno with room for improvement there is a video on here with it.

What cam were you running?

[CHESTNUTXE 7,739]

a way too big solid cam 250@50 thou was chozen by the engine builder althou i did tell him i was drag racing and i did run it at willowbank with a 4 speed single rail and 3.45 gears,but ended up putting a smaller tighe solid in it at 214@50 for more street use.i even tried a new 650 d/p holley yeah the 250 can run with it but an over kill on the street,the 450 quickfuel was much better even with the bigger cam,i ended up blowing 10k on that engine and is the only project i ever lost money on,then i found the 1971 400 engine and sold the 250

[Stumps 384]

Was the quickfuel a DP or vac secondary carb? 

[CHESTNUTXE 7,739]

holy hell i just looked on e bay and a 465 holley is $1400 wtf and a quickfuel is the same i remember i paid about $600 new ,doing up cars now is so costly .

[CHESTNUTXE 7,739]

1 minute ago, Stumps said:

Was the quickfuel a DP or vac secondary carb? 

double pumper,the other 450 ones are more daily and street driven carbs,i think the model is QHR 450 D/P and looks like a holley d/p but crome or alloy.i remember the dyno guy just changed the squirter to a bit larger one than std.

[Stumps 384]

14 minutes ago, CHESTNUTXE said:

holy hell i just looked on e bay and a 465 holley is $1400 wtf and a quickfuel is the same i remember i paid about $600 new ,doing up cars now is so costly .

Yup it sure is, im in the hole right now for $3200 for the suspension I just put in my XB...still got lots more to do..lol