Hey guys; does this 850 Speed Demon look like it's worth $150.00 ? Thought it might be something to try, even though they have had a few issues. Guy at work is offing it. I know Devon will like the better fuel line. :grin:
Hey Marty, Those are great carbs however they had quality control issues due to metal shavings in the carb. I would ask the seller if you could rebuild the carb with a kit and try it. You pay for the kit and do the work. If it works well them buy it, if not give it back and tell him good luck. Not sure if he will go for it however he might. :TU:
yea my 750 speed demon didnt workright from out the box, secondaries never kicked in..always sucked air as certain throttle postion..prettymuch needed rebuild straight out the box. but since holley bought them i belive theres rebuild kits available imay be gettingrid of mine very soon sure has less then 10k on it
I would be after the increase in CFM. Wouldn't hurt to experiment a little.....:Brow: It also looks like the TV trans cable hookup is the right ratio, distance and arc for my 2004r
Yeah do not listen to Shurkey. The 350 loves a big carb, especially with the well ported heads you have. It may take a bit of tuning to make sure the mid RPm throttle response is crisp, but there is no question that it will add some HP in the high RPM range. As Jim W pointed out before, carbs perform better when they are not maxed out at thier CFM rating. Carbs run better when they are slightly larger than needed normally. Some engines can handle larger carbs, I was involved with dyno testing of a 551 HP Buick 350 with no power adders and it used a 1000 CFM carb.
Yep, and the venturi are very smooth and well contoured for good airflow. No choke plate or rod blocking flow either!
I would be curious to see what it would do on the chassis dyno, those well ported heads should make some power!:TU:
My 350 loves the 850 dp......only thing you'll have to do is increase the pump shot to overcome the lower vacuum. But other than that once you get it going it makes alot more power.
Gonna be a little while Sean. Car has been sitting for 2 1/2 yrs now, but it's time to get it going again. Block, crank, rods, pistons, etc. are at eng shop now getting the treatment! Bore, hone, align hone mains, rods sized, bobweight balance, decking, etc. Need to order a 10" 3,000 stall lockup from JW also. :TU: Already picked up an elec. vacuum brake pump cause this baby won't have enough vacuum.
If your roller cam is anything like the one I bought it should work great! I feel the roller cams can give MASSIVE torque in the low range and better HP in the top end. If you have the cam card you should scan and post it if you do not mind. Here is mine, I have sold the cam to a guy for testing and we expect great results as he has high compression, gessler ported heads, and a car built for the combo: And here is an actual dyno graph of a Buick 350 with 1000 CFM carb. I payed good $ for this testing bt it was worth the info we gained:
I think the two reasons why the buick 350 likes bigger carbs over other gm 350s is the longer 3.85 stroke in conjunction with. Small intake ports/runners keeping the volocity up ---------- Post added at 01:32 PM ---------- Previous post was at 11:59 AM ---------- I think the two reasons why the buick 350 likes bigger carbs over other gm 350s is the longer 3.85 stroke in conjunction with. Small intake ports/runners keeping the volocity up
You're probably right. The head porting guy I spoke to said that he would like to add material to the runners and change the shape of the ports. He said it would increase velocity. I think that's why big CFM carbs work with the runner shape that we have to deal with. We really need alum. heads with a new runner shape.
Translation: Restrictive intake manifold and head porting needs huge carb to compensate. Edelbrock lists--or used to list--a mathematical formula for determining baseline carb CFM using engine displacement, RPM, volumetric efficiency, and intake manifold efficiency. The more restrictive the intake manifold, the larger the carb recommendation. I haven't been able to find that formula on the Edelbrock web site recently. May still be there, I just can't find it. Closest I can get now is: http://www.edelbrock.com/automotive_new/misc/tech_center/install/tech_disc_cfm_rules.shtml
That is also a true point. There was a guy with a 455 who used a restrictive intake setup with 1200 CFM of carb. Then he swapped to a better intake setup and was able to drop to a 1000 CFM carb with better performance.
but yes its worth 150 as long as its complete and has no function/structure issues . even with a kit and a little time you'll have less than 200 in 'er . just sold a nice real clean 625 road demon jr. ( basically a dressed up holley 600 cfm #1850 ) at our memorial weekend swap for 175 with kit ( about $25 @ summit ) included .
For $150 buck's you can't go wrong, set up right those are good carbs and 850 cfm is a good size. Just a thought
Sean; what cam was being tested on this dyno graph? Looks to be very close in grind to the Lunati 67003, except the Voodoo is not a roller profile.
