I was wondering if aniona has ever tried to do some porting to the throttle bore of a holley 5200 carb? I have to flow something around 350cfm to do my custom turbo setup with the chevette carb.
My plan is to put the secondary cupper coin to the primary throttle bore and find a bigger coin for the secondary one, maybe from a dualjet from rochester. It will be some porting done to the ventury, radius area keeping it proportional to the original shape. a site I found said the 5200 holley will flow 280cfm. What numbers can I expect from such a moded carb?
Post by DOCTOR FIELDS on Oct 15, 2007 14:11:06 GMT -5
It's been done for years. Bob Watts was one of the first to do it as a business, then i took over his under my own name. I don't believe you'll reach 350 CFM by enlarging the venturies and putting bigger butterflies in it. You have to be careful doing both, as the 5210 is a thin casting compared to some of the 5200 siblings. You might reach 300 - 310 CFM with extreme modifications.
Your best bet would be buying a 32/36 DGAS Weber. It is a direct bolt on, only minor throttle shaft linkage mods are needed. It flows @ 390 CFM. Of coarse you'll have to calibrate it to your settings. I'm not sure how well these carbs will do under positive pressure. It might be worth looking at an 80's model Dodge Daytona or something similar that had a turbo option. They had 5220 series carbs on them, which will also has the same bolt pattern as the 5210.
Do you plan on doing extensive port work on the head and intake? Larger valves? What kind of boost do you plan on running it at? Have you thought about head gasket failure, O-ringing the block, upgrading the bottom end (forged pistons & rods). I'm afraid if you just try bolting on a turbo, you'll either not have the power increase you were looking for, or have longevity issues (AKA Part failure). Everything has to work together.
Very interesting. I'll try to get some infos on those carbs.
To answer you Fields, I bought the head intake crank and cam of Billy Knoblett. The kit is ported and has big valves on it. The turbo I found on ebay is from mitsubishi and is a little bigger than a t25 or td04. I'll go with a blow through setup with something around 7psi. For the longevity, I'll shim the oil pump. If .063 = 65 psi, I guess that going a little higher just to be sure will be safe for my first try.
If all go right, I'll buy forged pistons from flatlanders and go with longer connecting rods. If you have good ideas for a buttom end setup I will for sure considere it while planning this step.
Post by DOCTOR FIELDS on Oct 15, 2007 19:33:07 GMT -5
Well thats good to know... The head i know is one that i did back in 2004, i believe the intake is too if it has had the back cut off it and rewelded.
You should be ok with 7 psi. If you want to go with a forged piston / rod combo i have an account with CP pistons and have had several sets of forged pistons made for the long rod combo. I would also highly recommend Total Seal rings, which CP is a distributor for them, so i can get a complete piston and ring package. Just let me know.
Post by DOCTOR FIELDS on Oct 15, 2007 19:40:50 GMT -5
One more thing... that head has been milled .130" (34 cc combuston chambers) you will have to run a dish piston in order to achieve the desired compression ratio for a turbo setup. If you had a head closer to the stock cc's, you could run a flatop piston which would give you more even flame travel and less turbulance.
I'm not sure to understand all you said about the turbulance theoric part. I always heard that turbulance is good to make power. Am I wrong?
What would be a good connecting rod? I heard about the honda connecting rod, not sure from what it was comming from.
Yes for the intake, it has been recapped and welded.
To continue with the carb issue, do you think the engine will be able to take the 38/38 weber carb? I did the math and the area of the two throttle bores will match the exhaust hole of the turbo compressor. It's why I would go with it.
I just purchased a weber 38-38 on ebay. I finally choosed to go with the big one because I already tried a dualjet from rochester a few years ago and except for the first quart of the opening, the stock engine would take it and be more powerful. I only hope that the weber carb has a smaller accelerator pump because I'm pretty sure that it was the huge amount of gas that was shooting the one from the dual jet that was killing the engine.
Thanks all for your participation on this thread.
I'll post news of the project when it will be running.