Carbureted LSX forum - Holley 850 dp too BIG?
04-28-2012, 04:24 PM
Im putting together my motor and wanted a little help with the carb.set up im running
Ls3 heads milled .30
Dynatech 1 7/8 headers
2 1/2 exhaust with 3'spintechs before axle
Cometic .40 head gaskets
I think compression should be 10:5-10:8
Now for carb choice I got a 850 dp but I wanna know if that will be to big and should I run a 750 dp instead?
Ill post a built thread as soon as get the remaining parts to assemble
04-28-2012, 08:25 PM
850 will be fine.
05-06-2012, 12:18 PM
This is from Mike Urich who (literally) wrote the book on Holley Carburetors:
"When in doubt, select a smaller carburetor... ...you can believe that you'll be happier with the smaller carburetor nearly every time. Regardless of all the evidence to the contrary, a lot of carburetor buyers 'psych' themselves into believing that bigger is better."
Holley Carburetor Handbook page 52
Pop N Wood
05-06-2012, 01:45 PM
I'm running a mechanical secondary 750 on my stock LS2 with 243 heads. Car runs perfect, no bogs or flat spots and still get 25 mpg. With your heads and cam you will probably need the extra CFM.
05-06-2012, 07:35 PM
850 will work well
05-08-2012, 11:29 PM
cool ill be getting a ls3 short block by end of month.so the lq4 will be put away for the coupe.
05-09-2012, 08:42 AM
I run a hp 1000 annular discharge on my cammed stock longblock ls2,which in reality flows 850 or so cfm because of the giant boosters. Very happy with it and its extremely responsive.
05-09-2012, 08:50 AM
I bet back to back, your 1000 compared to my 750 pro form with down legs, the response is day and night, have try one when I can, will get the chance to run a SV1, will see if I can back to back track time it as well.
05-09-2012, 09:33 AM
its probably as snappy as fuel injection if not very close. i am going to put a set of billet metering blocks in it though so i can tune out some part throttle cruise richness.
i think alot of people overlook or are afraid to try A.D carbs. because its like voodoo or something lol.
i can probably go a bit bigger cfm wise as i am still seeing about 3 inches of vac at wide open at the top of 4th. but i think its a decent setup as it is.
05-09-2012, 12:23 PM
I'm running a AD 850 on a similar combo. Haven't run it yet, but I just bought some billet metering blocks for it. Hoping to be on the track sometime next month.
05-09-2012, 12:48 PM
that 850 is only going to flow about 700 cfm, just to let you know.
05-09-2012, 01:29 PM
I wonder what the 750 pro form flows, any info on that? Never thought to look. Actually a pro form body and quick fuel base, same stuff though.
05-09-2012, 01:42 PM
they usually flow close to or actually whats advertised...except for annular carbs.
05-09-2012, 01:59 PM
Yea, i heard they can flow 800ish or close to it, but no two flow benches will dictate the same im sure.
05-09-2012, 02:04 PM
this is true. i dont worry about the advertised cfm numbers, i try to go with what works, but sometimes it isnt easy or possible to swap a bunch of carbs around.
i was actually going to go 850 or 950 once i sold my proform bodied 750 but this thing just fell into my lap. too good of a deal to pass on and if it didnt work out i can always sell it.
05-09-2012, 02:25 PM
But of course, i am hoping my car will still do ok at the track so i can compare the SC1 to what i have now, i installed the Tex700 and now, after beating it, the clutch on the floor doesnt like to shift gears from the heat to the hydraulic line, the CF clutch did not do that, so some heat shielding is a must, maybe even flush the line and put some more DOT 4 in there.
05-09-2012, 02:58 PM
I HATE HYDRAULIC CLUTCHES! LOL i spent 3 times more on headers than i would have had to if i went hydraulic. thats how much i hate them lol
i am running a block plate with my scattershield for the first time ever (aluminum block...if something goes boom in the clutch, it would probably take the block with it) and i should have punched some holes in it and one in the bellhousing for air. i think i am at the edge of what this ram 11" clutch wants to live with as it is. once it gets hot it gets stinky lol
05-09-2012, 03:31 PM
I like the hydraulic since it is factory, just dont like the heat causing the issues, they were non existent, but now, not so much, i really hope i can fix it.
05-09-2012, 05:43 PM
When I bought my Demon carb, I talked to a tech who gave me some pretty good info (or I hope anyway)...
Holley carbs are dry flow rated.
Demons are wet flow rated (claimed this is why some had carb issues when switching between the two).
Anyone back that info up ?????
05-09-2012, 05:58 PM
Most demons work better as door stops than carbs lol. Lots of metering circuit issues. I have a brand new 650 in my garage that has fuel flow issues through the metering block. Put it on my buddys car and had issues from day one. They arent all bad but it seems they have less than good quality control.
05-09-2012, 06:34 PM
I really like my 850 mighty demon, no issues. Must tune it to your combo like every other carb, if your looking for the best performance.
05-19-2012, 10:42 PM
My 750 speed demon cost me a mic 383 stroker I built 8 years ago from being way to lean the first pass down the track when I thought it was jetted on the fat side.
It was junk!
06-05-2012, 11:48 AM
805dp is goin on mine too. Hopefully it works well.