03-18-2012, 01:21 PM
From the middle of the world
Join Date: Mar 2006
Location: Ecuador, South America
Thanked 5 Times in 5 Posts
Originally Posted by RetiredHotRodder
It sounds like we're doing about the same type of hot rod project, using a six cylinder and wanting to adapt 6 motorcycle carburetors or just 6 carbs. I'll tell you a little about what I've found out so far. Maybe we can help each other as we go along.
I always like a totally different type of hot rod, something that not everyone else is doing, just for the fun of doing it. My last T Bucket was powered by a 427 set on kill. This one now with the six, is something for a totally different reason ... just to see if I can do it and hope it turns out as well as I imagine it will.
I'm making my frame from round d.o.m. tubing, my own aluminium 23 T style body and a six banger with 6 Mikuni carbs. Everyone uses a V-8, but a Six in an old T hot rod seems to get more interest. Plus, if the combination of parts is all matched properly, there's nothing that sounds quite as cool as a hot six banger when at high rpm's.
The engine I'm using is a 200 cubic inch Ford inline six with the intake and exhaust cast as part of the head. That aspect of this engine seems to be one of its Achilles heels. To me it sounds like a fun challenge.
I'm a retired machinist and welder so the head-work needing to be done, I can do here in my garage. I don't know if your Pontiac has the intake and exhaust cast into the head like my Ford does.
I'll just mill cut and mill the intake runners down flat with anything else in that area. Then make my own intake manifold from about a 3/4" plate, then weld the same size tubes to match the Mikuni carburetor and attach the carbs to the new intake runners the similar to the way they were attached on the bike. I believe these carbs are about 36mm.
Then drill and tap the side of the engine making sure not to drill into a water jacket or anything, then use screw-in studs with some good adhesive on the threads for the intake plate to fasten to. That's the plan now but sometimes plans can be subject to change.
There's been allot of questions by others about doing this project or a very similar type of project. The main question they have is about how to properly keep the carbs all tuned. I'm learning as I go on this particular project and often times that's just the way we have to learn. But if the tuning of these multiple carbs is anything like the other multiple carbs on my other hot rods, a good vacuum gauge is the trick. I am thinking that I may even need to install six smaller vacuum gauges - one vacuum gauge per intake runner. Welding a bung up above the runners so the bungs don't interfere with the intake flow. On my other hot rods I've found the value of tuning an engine with a vacuum gauge works wonders!
On most of my cars I've installed a large faced vacuum gauge inside the car under the dash and I also mounted a smaller faced vacuum gauge under the hood into a threaded hole in the intake manifold. This has worked wonders on the tuning of a Holley 4-barrel 390 cfm on an Offenhauser intake and home made headers on my AMC Eagle with the inline 258 six cylinder. It's amazing how much closer I can put a good tune on an engine with the addition of a vacuum gauge or gauges.
A computer would be able to keep a modern system like this tuned constantly but when building an old school hot rod I just prefer to leave the computers in my newer cars, and keep a tool box handy, just my opinion. So to make the tuning last longer I'm going for the vacuum gauges to help me keep everything tuned and to tell me when something is starting to go out of tune so I can make the adjustment before it becomes a big problem.
I realize going into this project the complexity of using six motorcycle carburetors for this engine and I'm okay with it. I'm prepared to make adjustments more frequently than I would on something else. But I really like the coolness about using a hot six banger with six carbs in a 1,000 pound hot rod.
Let me know how your project is going. Like I said, maybe we can help each other as we go along.
not to question your project, but why doing all that machine work for only 200 cubes? I would use a 300 cid (also known as the 4.9) inline six ford that has external intake and exhaust manifolds? plus the 100 extra inches will give you a much rewarding engine, and with the six carbs it would just look awsome.
I'm already installing an I6 300 in my son's granada, look at my pictures, or the thread I started for it :
Ford 300 inline six in a Ford Granada