I have heard a lot of talk about a one inch spacer under a Carb showed results on the Dyno. Is it typical for a one inch spacer to improve the signal? Should I try this even without having it Dyno tested? They have come down in price quite a bit in the last few years. Jegs has spacers for under 40.
Is a wood spacer any good?
Seems kind of cheesy, like something I could make my self. Are they full of heat resistant glue?
Was looking at a 5/8 Phenolic.
Right now I have a fairly good Carb Signal. If I put it in the Secondaries while rolling at 30 it peels out and takes off like it was standing still.
Thanks Once again Ken. The Phenolic was the one I was looking at. Wood just seems like a bad Idea to me. I think it's just a Fad. I am sure they are cutting them out with some sort of CNC machine but they don't look to be tapered or anything. Kind of like just using a hole saw with my cordless drill on a piece of high density Chip board!
Use MDF and make one by hand and try different sizes and then buy one. MDF is good to use it will slowly leak the die through it from the fuel but its air tight for testing and ideas etc.
Thanks Shrinker. I will think about that. I could see if 1/2 inch is better than 1". Or Mock up a 5/8 by adding the plate gaskets I have now. I have some old Aluminum and gasket stackable plates that I have used for years. They are just thin sheets. I have always had then set at 3/8 or less. I only used them for clearance on an aluminum performer intake. Still haven't hooked up my Ram Air so now is a good time before I fabricate the isolation tray.
MDF is so easy to shape you can make a four hole with the fancy curved flow stuff and have a good play and even copy plates that are hundreds of dollars and find out if you can benefit from them. This how it usually goes if you persevere, once you have tested everything and start learning about carburetion you will fiddle with that then chuck everything out and just fix the carbys and be better off. The carburetor is the foundation of everything else that goes right or wrong with the combustion.
I love experimenting with different Holley's. I actually just rebuilt a 4175 and put a purple spring in the Vac Secondary. To my surprise it pulled real hard the first time. I haven't even started changing it yet. This is the first time I have tried a full Vacuum secondary Carb. I always went with mechanical. I run a Th400 with a floor shifter.
'BACK IN THE DAY" most street guys ran a 3310 Holley, which is a 780 with vac secondaries. Since money was scarce I cut a round and a half off the stock spring to make the secondaries open quicker. Much more than that and you'd get a bog when you nailed it. Got a couple of those diaphragms and a bunch of springs in my spare parts bin now. Yup, I'm a pack rat and never throw anything away that's usable.
I have an assortment of springs to try. May keep going until I bog. Holley claims that if you cut them they will only increase in strength. I see that quick fuel has an adjustable diaphragm for 30 something. Do you think that it's just a screw with a plate inside that presses down on the spring to change the strength? I saw something like that rigged on an Ebay Carb once. I have heard the 3310 mentioned many times on other sites. On some of the other sites they tell me how outdated my spreadbores are, but then they stand up for the Quadrajet. They are the same age right? I don't thing the Quadrajet ever got updated. Unless you count the Electric one. I had one on a Buick Electra and I didn't like it. Swapped it out for a Vacuum Quad and Vacuum Distributor and I lost gas mileage.
The QF unit works the same as the Holley with a spring but it also incorporates an adjustable screw that controls the RATE of opening by dampening the air the diaphragm displaces. The spring mostly determines the rpm the opening starts. If a spring is too strong and your engine is small or doesn't turn high rpm's, the secondary is late to get to WOT or never gets there. It's also important to have the little brass tube sticking out into the venturi to help activate the secondary. Some vacuum secondary carbs don't have them.
When you cut a coil off of a spring the springs rate per inch goes up. The lower the number of coils a spring has the higher is its spring rate per inch.