carburetor size??

4speed · 01-14-09, 05:39PM

Is there a difference you will feel between a holley 750dp and 850dp when it comes to low rpm response on the street with a 4speed? wich is the better for street use with a 455 cui.

shaker455 · 01-14-09, 07:33PM

First,
That's my car on you back!

A well prepped or custom 850 for a 455 would work well even at low speeds if the unit is balanced.

How about some details of the engine build?

4speed · 01-15-09, 03:43AM

In that case, d..n nice car shaker455 !!

My engine details is

455cui 0,015
zero decked
Eagle H profil rods
Pro tru pistons
compression 10.35
E heads 87cc slihgtly ported with welded and reshaped chambers
comp XE 284 camshaft
Comp 1.52 roller rockers
Edelbrock RPM intake.

shaker455 · 01-15-09, 05:37PM

You have a good combo, are you going to do any drag racing?

What Dist & exhaust you running?

If your looking for an off the shelf unit then a Holley List # 9380 annulsr 850 is a good place to start or a nice custom built unit.

4speed · 01-15-09, 06:23PM

No only street racing, kind of popular here in sweden!!! thanks for the advice, i myself have no experiance of carburaters maybe you could help me with one?

shaker455 · 01-15-09, 07:20PM

Yes I can help, also you can PM me

Tim · 02-07-10, 09:03AM

Heres a nice little PDF file that will help show you how to choose the correct Carburetor Size..

Right click on the link below, then select save as
(better than clicking as it makes you wait until the whole pdf file downloads)

http://freeshopmanual.com/uploads/pd...Carburetor.pdf

4speed · 02-25-10, 04:54PM

Thanks but iv'e gone with a 750 DP , i think thats going to give me a advantage in low RPM,
/Leif

BILTIT · 02-25-10, 05:48PM

I run a custom 850Dp from shaker455, works well.

TIN TIGR · 03-05-10, 04:31PM

run the biggest carb that will fit on your pontiac..even to a dominator..it's all in the signal..if you have to run a small carb to get response, you cant build an engine..

guys like shaker or cliff excell becuz they understand how to get the most from the signal given to the carby..other masters, like pj, or aed, etc, have far better equipment than me to determine flow vs pressure drop..and the least restriction the better, and airspeed cant help under the carb..it has to flow smooth, like a lazy river, to the ports..

go big, go smooth..like a banana..

4speed · 03-09-10, 06:03PM

Ok i see what you meen , but since i´m running a stick and sometimes go WOT below 1500 RPM i thought it would be better to go smaller than larger to get that response from the engine i like so much, ofcourse i will loose a couple of CFM on the top but maybe the average will be the same?

TIN TIGR · 03-09-10, 06:25PM

you should learn to slip the clutch..where is my government watermelon?..

4speed · 03-09-10, 06:55PM

Lol

shaker455 · 03-11-10, 06:49PM

Old post:
Any new updates?

region warrior · 03-12-10, 04:59PM

Pontiac used 800 cfm Q-jets from 75 on up.
Even on the smaller engines.
Think about it.

4speed · 03-17-10, 06:51PM

Well the story so far ! i now have started up the engine and it sounded great but i haven't tuned it in yet, i use a #4780 that shaker455 helped me to ID. Initial timing set to 12 dgr and mechanical advance should be 24 dgr in around 4500 RPM but i doesnt it only gives around 19-21 dgrs need to spend a couple of hours to check everything before running any longer periods.