Apr 19th, 00, 08:15 PM
I have a Holley Projection 670 cfm 2bbl unit on a 355 cid-4 speed (300 h.p.) I'm pretty unhappy with its performance. It doesn't seem to be as responsive or get the gas mileage I thought it would , and I've tried to tune it out, but no luck. I'm thinking on switching back to a spreadbore holley, I hear the smaller primaries give you better response.Does anyone have any experiences with the projection units? any suggestions? many thanks.
[This message has been edited by CHRIS CORCORAN (edited 04-19-2000).]
Apr 20th, 00, 03:36 AM
Is it the regular projection set up or what? What distrbuter set up and soforth do you have?
Apr 20th, 00, 06:45 AM
i'm not sure what you mean by regular, but its the one that came right out of the box. It's not a newer style, where you can hook it up to a laptop, if that's what you mean. The distributor is an HEI, with lighter springs( I forget the curve) and I set it to 10 degrees initial. I've heard a few bad things about the older projection units, I guess I just wanted to confirm with someone who isn't making commission.Thanks.
[This message has been edited by CHRIS CORCORAN (edited 04-20-2000).]
Apr 20th, 00, 08:40 AM
Referred to as the (open loop) system. I've personally not dealt with them myself. The more advanced (closed loop system) is definatly the way to go.
Apr 20th, 00, 01:48 PM
I have sold 4 of the projection units and everyone is very pleased with them. 2 were the older ones, and the other 2 the new ones. I wonder if you are running a vacuum advance distributor ? If so is the vacuum advance working properly ? It almost sounds like you do not have enough ignition timing. This will cause any motor to be "lazy" and suffer from poor fuel mileage. With the vacuum advance hooked up you should probably have 20 deg or so advance at idle.
Hope this helps,
Apr 20th, 00, 07:33 PM
The vacuum advance is a Crane adjustable unit and is set to the recommended level(just prior to detonation). I don't think its the fuel pump either because I checked it under full throttle and got about 13 psi.Also, when I first bought it,(by the way,bought it used for $500) I noticed that the throttle plates would ice up, causing them to stick open at about 1500 rpm. I then had to run the heater hoses to the baseplate to prevent this. Could this extra heat be a problem? Thanks for any help.
Apr 24th, 00, 06:36 PM
I have the same unit on my 215 Buick engine in my Vega, and the performance is lack-lustre at best. Mileage over a 600 Holley went from 14 around town to 8 mpg everywhere.
I am in the process of changing the manifold to accept 8 port nozzles, driven from the two stock nozzle drivers, left one for the left 4 injectors, right for right. I ran up to 17 lbs pressure in the setup I had, wanted more. Just not enough input for the computer to work very well on the analog 2 bbl throttle setups.
This kind of change is done by Edelbrock on 350 and 454 throttle body engines in light trucks. Makes a difference.
Your idea of the spread bore is a good one, they work, BUT you must use the correct spread bore. Vacuum secondary s/b's are for DEAD STOCK, read FULLY STOCK, no mods whatsoever, nothing. The double pumpers are great for mild to moderate engine packages.
When I say dead stock engines, I mean no K&N in the stock air filter too, nothing, thesae vacuum carbs are jetted for maximum lean, and aren't easily made to work on modified engines. Double pumpers are like regular Holleys, but a little different in a couple of circuits, can be made to work easily.
4010/4011 carbs are great on Fords, but not on GM engines without lots of work.