Thanks a ton for all of the info. I will try to address the messages I received one at a time. XNTRCI-T I wasn't really fond of the silicone idea either but I had to be certain there was no vacuum leak. All gaskets are in place and sealed, and all carb vacuum ports are plugged. Like yours it does have vacuum when I turn it over. I have built every race motor I have ever run so I understand how a motor works. If the piston is on the down stroke with the intake valve open it HAS to be sucking.... This situation makes no sense. I checked for a warp condition on all surfaces, including the new intake, and found nothing. At least nothing a gasket wouldn't do it's job on plus the silicone. Also looked for cracks, nothing I can see. Keep thinking!!! Sarge

DAWG: I am going to give them a call again. On hold last time for about 20 minutes. Guess they have one guy for the entire world. Did not do a leak down. This motor runs great naturally aspirated.
Sarge

Arrowhead: It starts at about 3000 RPMS not at a normal idle. I am going to change to pullies around. XNTRCI-T has already chewed my but over that. You guys win. LOL

F-BIRD88: This motor runs about 2 seconds. How would I get a timing light on that??????

Again what cam is in it? (ya it matters) What are you setting the timing at and what rpm are you warming up the engine at? or attempting to warm up the engine at?
Have you verified that you do have compression in all 8 cylinders? (Compression test)

How are you determining that there is no vacuum through the carbs after the motor fires? By the way, what is the current carb configuration?

BTW, I would not expect the Weiand people to be very helpful. You have a very unusual problem (or you're leaving out some critical information). If anyone can figure it out, it's F-BIRD. The boy knows his motors.

I am not sure of the cam specs anymore but it is a hyd roller. I built this motor 4 yrs ago and it has been bagged ever since. I finally decided to start the motor, so put it on a run up stand and started it. After tuning, it ran and sounded great. An opportunity for a 6-71 came along and I jumped. I've always wanted to try one and I have a '68 CST orig big block chevy truck, w/air, that is screaming for me to make a change. I dropped the dist. in so I could start the motor but I can not tell you what the timing is set at because the motor has never (since the blower) run more than a couple of seconds!!! I can't tell you any temps because of the couple of second thing. I have not done a compression check because the motor ran great naturally aspirated. I know the 6-71 is a little small for a BBC, if you're looking for all out performance, but I'm just going to putt around town and go to car shows. I want it to be mild, dependable, sound good, and look cool.
Sarge

I can't feel any when I put hands over the carbs. 2 600 holleys inline. I'm am leaning on the carbs being the problem though. They are not blower carbs and I think the motor is starving. Accelerator pumps will keep it running if I really work the accelerator hard but RPM really gets out of hand. I hate running a cold motor that hard.

Aww jeez, Sarge, you better stand by to stand by... F-BIRD's gonna rip you a new one!!

Ive never built/ran a blower engine..what are the diferences between the two styles of carbs? Normally aspirated vs forced(blown)? I understand the intake signal is diferent, but is the change in metering? Idle circuitry?..

Got me!!!! This is my first try but today a local Pro-Mod racer told me the power valves will end up being a problem and I needed to jet up. He said that was pretty much the only difference. I am betting there is more to a blower carb than that.

Anyway, for y'all that have been trying to help me sort out my set up here is an update: I removed the 1" spacers from under the carbs. I opened carbs up and found #66 jets. That's right 66's. Replaced with 93's but left the power valves alone and it made a difference (imagine that). It still won't idle but it is trying. I'm going to try some 99's but that is as big as I have without drilling and tapping for alcohol jets. I have a ton of them.

Why????? I told him all I could!!!!!!!!

You are working with the wrong area of the carb. Changing the jets will have nearly no effect on the fuel delivered at idle. You need to be reworking the idle feed circuit, idle feed restriction in the metering block, and idle air bleeds.

The 93 jets you put in would be waayyy too rich in even an 850 DoublePumper. Changing jets only effects things beyond part throttle up to full throttle. 72-74 would be expected as a start point for you, and you may have to make mods to allow for more airflow at idle from the secondary barrels or by drilling an air bleed hole in each front throttle blade.

Sounds about right. Where are the idle circuits in a 600 and how would it be modified

We all are kinda shotgunning this problem. I'm surprised you haven't backfired this thing very hard. I think you really should take everything apart and start over. Something is very wrong here.


Check the bottom of the blower for flatness and also the manifold. Also you need to be very careful tightening the blower case bolts. Go in a criss cross or circular pattern starting from the middle and work out. Turn the blower by hand as you are tightening the bolts. Any change or binding and you start over or you have a problem. It's possible that the manifold is twisted so it might check flat but really be warped. Assuming the blower is flat it will rock on the manifold. It can work the other way too...the blower case can be warped. Not very likely however as it probably would lock up first.

You could just take the belt off and try and start the motor that way. It should run but throttle response can be a bit slower. More than one rod has been driven home this way. If it will start and run you may be able to set the timing and get it warmed up enough to get by the cold start problem.

I didn't notice what you have for a fuel pump but you should have about 5 psi fuel pressure. You should have at least a 'Blue' and the matching regulator with a pressure gage. If you haven't got a 1/2 in line from the tank...you need one. 3/8 lines to the carbs. Next I'd verify that the timing is close. You do have all the advance in by about 2200-2400 rpm don't you?? Try for about 28 deg total with about 10 deg adv in the distributor.


If you have a small case blower you really should turn the pulleys around for the size motor you have. I ran a large case 6-71 on our first funnycar at 50% over and it ran just fine for the day on alcohol. Also ran gas dragster (392 w/1/2 stroker) at 33 over. It was a piston burning machine. A 6-71 is not too small for this motor. A small case one just has to be driven faster.

Are the floats set right??
I think I'd get after the carbs before you go any further. It's possible the previous owner tried to trick them up by drilling things out and really messed them up. At least put a kit in them and set the floats correctly, make sure the power valves are working. I'd start with a 6.5 PV. There is also a check valve kit for the PV that needs to be there if it is not already. Put some 72 to 74 jets in them. It should at least run and idle on these. You don't need 93's.

Check any fuel filters. Over time just sitting around they can get clogged up.

Also install a vacuum gage in the manifold vac port on the carb. This will verify how much vac you have running at the carb. You can also install a port in the manifold and check the vac or pressure there. You should have pretty high vac in the manifold at idle.

OK I drilled out the brass restrictors in the idle feed circuit and changed the jets to 80' (what I have on hand). It is running but the Detroit Roll is 1200 to 3200 RPMs, after it warms up. How big of holes do I drill in front throttle plate???

I will try and hit each of your topics: The blower and intake are flat. The blower is torqued 20fp and turns freely. After doing some mods to the carb it now starts and runs but the Detroit roll is 1200 to 3200 RPM. I would like to keep the roll but 3200 is way to high for me to drive on the street. Fuel pump is small but I am pretty sure it is delivering plenty of fuel to run on a run-up stand. I do have 1/2" line to the pump and 6an to each carb. I have not swapped the pulleys yet but intend to. I'm not trying to build power on the run-up stand just get it to idle. The floats are set and the carbs are fresh. I did drill the brass restrictors out in the idle circuit which really helped. At least now it will stay running just to much roll. The power valves work but will be plugged as soon as I find some plugs.
Sarge

What size is the idle feed restriction in the metering block now?? How much throttle opening do you now have on the front and rear barrels??