Mike's Badass Quad Carb Manifold!! Build PICS!!!

[lostforawhile]

They're 38mm carbs from a GSXR750. I wasn't sure if they were going to be big enough to run a 160hp motor. But I calculated the airflow compared to a single stock throttle body and there does seem to be about 50% more throttle area with these. But that's all I really have to go on, some trial and error.

I'm not 100% sure on what mods yet. I don't think I'm going to do anything super wild yet. Compression bump, some cams, get some bottom end lightening done... Not sure yet if I want to do headwork or not. Definitely will have to have a custom header built for it. Hope to get maybe 180bhp out of it. Hopefully the carbs can keep up. Hopefully I can figure out how to jet them, and change the needles and all that. I'm hoping that the fact that they're CV carbs will let them be forgiving. The car ran and idled with the stock jetting on the carbs, so it can't take too much. Here's a video I did before I had Mike make me his badass manifold, and before I found out the engine was fucked:

http://www.youtube.com/watch?v=pPs92KrCaj8

I hardly think your ITB project was a failure. It's probably pretty frustrating for you at this point, but there's still some interesting potential there. Did you ever get videos of how your car was running, or maybe some pics of that manifold all assembled and installed on the car with the throttle bodies?

38 will be fine, the SU's flow more then a conventional carb, and they run 6 cyl all out Datsun race motors off of these , well more then 160 horsepower. that's with two,with four conventional carbs ,you have nothing to worry about. I've seen V8 hot rods run four sidedraft carbs similar to what you are running.

[cubert]

2ndgenguy:

Did you say jetting and needles?









Let me know if I can help out at all with the jetting/parts/etc..

[cygnus x-1]

I'm still trying to dream up a better vacuum manifold setup, but haven't really figured anything out for sure. As I remember, the ET2 twin carb setup runs the brake booster off of one or two ports only anyways. That system also has enough additional vacuum lines to build a large slingshot with

Nothing fancy required. All you need is a small port on each runner, each run to a vacuum can of some sort. Here's a fancy one:

http://www.go-autoworks-store.com/govalogma.html

People have even used short pieces of PVC pipe with the ends capped. All it has to do is withstand atmospheric pressure without leaking. Anything that requires vacuum is then connected to the can.

How'd the ITB's fail? Maybe I could somehow help, provided the shop hasn't permanently vetoed Al Mig gas for the foreseeable future.

They failed mostly because it was nearly impossible to keep all the throttle plates synchronized. This was exacerbated by the TBs being too large for the engine in the first place. An unrestricted 45mm bore for each cylinder means that the tiniest change in throttle opening at idle makes a huge change in airflow. It was so sensitive that even the nearly imperceptible flex in the throttle shafts (twisting) would cause a large difference in airflow between the #1 and #4 cylinders. With larger throttle openings and higher RPMs they were ok, but idle and cruising were sketchy at best.

Theoretically I could have redesigned the linkages to make them work but it was getting to the point where it wasn't worth the trouble. There were other things about the manifold and fuel system that I wasn't thrilled with either so I decided to give up on the GSXR TBs and just put together an Extrudabody setup. The cost is quite a bit higher but the design is just so much better. And this time I'll use 40mm TBs instead of 45mm.

C|

[2ndGenGuy]

2ndgenguy:

Did you say jetting and needles?




Let me know if I can help out at all with the jetting/parts/etc..

I may be bugging you soon!

[cygnus x-1]

They're 38mm carbs from a GSXR750. I wasn't sure if they were going to be big enough to run a 160hp motor. But I calculated the airflow compared to a single stock throttle body and there does seem to be about 50% more throttle area with these. But that's all I really have to go on, some trial and error.

Those will be just fine. The stock 2g Prelude carbs were I think even smaller than that and there were only 2 of them. Smaller bores make for better throttle response and fuel mixing anyway.

I'm not 100% sure on what mods yet. I don't think I'm going to do anything super wild yet. Compression bump, some cams, get some bottom end lightening done... Not sure yet if I want to do headwork or not.

At the very least get a good 3 angle valve job done. Most gains in head flow are from reworking the valves and seats anyway. Not from "porting and polishing".

I hardly think your ITB project was a failure. It's probably pretty frustrating for you at this point, but there's still some interesting potential there. Did you ever get videos of how your car was running, or maybe some pics of that manifold all assembled and installed on the car with the throttle bodies?

I don't think I ever took any pictures when I had them running. I never really got much further than roughing them in anyway. In a sense they were more of a "proof of concept" than a reliable working system. The concept being an A20 engine running on way over-sized GSXR (1300) ITBs. I think the resulting conclusion was "plausible" but not practical. And honestly I'm not frustrated at all. I had no serious expectations about the outcome and much was learned in the process. What I do know though is that I will absolutely make another attempt at an ITB setup. The individual runner idea is a good one and worthy of pursuit. But this time I'll have a much better idea of what will work and what to watch out for.

Incidentally if anyone wants to check out the thread it's here:
http://preludepower.com/forums/showt...&highlight=itb

I'll apologize now for not taking enough pictures. I'm kinda lazy and my camera is old and tired.



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[2ndGenGuy]

At the very least get a good 3 angle valve job done. Most gains in head flow are from reworking the valves and seats anyway. Not from "porting and polishing".

What do you think about oversized valves? Would I want to do some mild porting to the head to account for the additional flow through the valves? Do you know if a 5 angle grind is typically more expensive?

I don't think I ever took any pictures when I had them running. I never really got much further than roughing them in anyway. In a sense they were more of a "proof of concept" than a reliable working system. The concept being an A20 engine running on way over-sized GSXR (1300) ITBs. I think the resulting conclusion was "plausible" but not practical. And honestly I'm not frustrated at all. I had no serious expectations about the outcome and much was learned in the process. What I do know though is that I will absolutely make another attempt at an ITB setup. The individual runner idea is a good one and worthy of pursuit. But this time I'll have a much better idea of what will work and what to watch out for.

Incidentally if anyone wants to check out the thread it's here:
http://preludepower.com/forums/showt...&highlight=itb

I'll apologize now for not taking enough pictures. I'm kinda lazy and my camera is old and tired.

C|

I've been following that thread anxiously since you started it. Every new post you made was really cool! I learned a lot, as I usually do from your posts!

[cygnus x-1]

What do you think about oversized valves? Would I want to do some mild porting to the head to account for the additional flow through the valves? Do you know if a 5 angle grind is typically more expensive?

I think bigger valves are almost always going to flow better. But I known very little about the B20A. That is a 16v engine right? The 16v engines are not as restricted and the 12v engines so bigger valves might not make as much difference.
5 angle valve grinds are more expensive than 3 but the flow difference will be minimal. 5 angle would only be for an all out no expense spared race build.
Most Honda heads are pretty good from the factory. They generally don't need much more than just the casting marks cleaned up and any sharp edges removed, especially in the combustion chamber. Any more than that and you really want to make sure the person doing the porting knows what they're doing, and has A LOT of experience with Honda heads.

I've been following that thread anxiously since you started it. Every new post you made was really cool! I learned a lot, as I usually do from your posts!

That thread may sit dormant for awhile but it's certainly not dead. It will be back!


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[Ichiban]

Have gas again. Depending on whether or not I work this weekend, I'll finish up that mani. If I work, Sunday it gets done. If not, my Toyota is undergoing major surgery (front clip re+re)

[2ndGenGuy]

Dude, no hurry man. If you've got shit to do, do your shit first! I appreciate your hard work!!

[Hazwan]

Dude, hurry up man. If you've got shit to do, do MY shit first! I appreciate your hard work!!

There, fixed for you

[Civic Accord Honda]

There, fixed for you

[Ichiban]

Gonna work on it during afternoons after work this week.

[Ichiban]

Weatherford really caused afternoons to shit the bed. This weekend it is, I promise!

Also, I've been trying to get Rob to Mastercam up a simple program to CNC port the thing after I've finished welding it!

[cygnus x-1]

Weatherford really caused afternoons to shit the bed. This weekend it is, I promise!

Also, I've been trying to get Rob to Mastercam up a simple program to CNC port the thing after I've finished welding it!

CNC porting would be cool! Not sure how "simple" the program would be. I did CNC my entire ITB manifold though and it wasn't that bad. Really, coming up with the model is harder than writing the NC code. Once you have the model it's just defining the toolpaths and tools, work out the fixturing, load the tools, and press the green button.

C|

[Ichiban]

This is all you get right now.

[2ndGenGuy]

Dude sweet! I am pretty fucking giddy with excitement! Maybe to speed things along, I should find out how much that import shop in Seattle is selling those "low mileage" B20A's for. Have one to drive, and can rebuild the NZ motor...

[Dr_Snooz]

Dude sweet! I am pretty fucking giddy with excitement! Maybe to speed things along, I should find out how much that import shop in Seattle is selling those "low mileage" B20A's for. Have one to drive, and can rebuild the NZ motor...

I can't even find an A20 and you have B20s???? You get the big raspberry my friend.

[Ichiban]

I should find out how much that import shop in Seattle is selling those "low mileage" B20A's for.

What?

[2ndGenGuy]

Yeah, someone on here posted a link to an engine importer on here. Nobody but me replied to the thread for some reason. But they had 86-89 Accord motors listed... A20s and B20s.

[Ichiban]

[A20A1]

Thats very nice



I'm not sure if it's really an issue, and your manifold is pretty much a straight shot to the valves, but have you considered fuel possibly dragging on the smooth surfaces?

The only two suggestions I have for nicely roughing up the interior would be sandblasting or etching with acid, just to get a smudgin of texture to the inside.

[Ichiban]

I was gonna rough up the entire inside with a 60 grit flap wheel. I thought that might be coarse enough?

[Ichiban]

Gonna do some more this weekend! Ship soon!!

[Ichiban]

Maybe to speed things along, I should find out how much that import shop in Seattle is selling those "low mileage" B20A's for. Have one to drive, and can rebuild the NZ motor...

Go fucking find out already.

[2ndGenGuy]

Oh yeah. Sorry, I was in Mexico all last week and doing "Christmas Shit" before that.