Off center intake to an On center block

[dr_frankenstein]

I have a Off center intake, but i have no off center block....

My off center block didnt pass go and didnt collect 200 dollars.... turned out to be an expensive coffee table.

So now im looking at James's 153 on center block... I have stage heads and i understand the differences between the 2 blocks... But im very stuck on the intake.

My off center intake is made to fit a roots blower up top... a 6-71. Cool.... now find one for on center.... thats my problem...

I have a rare intake to begin with... (thanks Mike) and unless i hand fab another, im SOL.

So my question, has anyone tried or successfully used an off center intake on the on center block with stage heads? can it be done? or do i need to bite the bullet and try to build a new intake? or should I hope that another off center 4.1 block will come around?

i need some thoughts to guide my travels...

A.j.

 

[JayC]

You have two options.

You can slot the bolt holes a little and there will be some port alignment issues but its not terrible. Eric Rankin used to do this with a bunch of his stage 2 cars.

or

You can send the intake to a place like Wilson's Manifolds (Assuming theyre still in business) and they can cut it up and weld it back together and it will fit correctly. Ive seen one done by them and you couldnt even tell it had ever been welded on. I know a certain person that raced a car in a class that allowed no welding on manifolds and this manifold had been cut into a dozen pieces and welded back together. No one suspected a thing. Kenny D may be able to help with this as well. I seem to recall him cutting one down the middle and doing it that way for John Gallina many years ago.

 

[Mike E]

Is this for show or go? If your not looking for max power, just slot the bolt holes and run it as is. The ports in stage 2 heads are so massive, you won't be doing much damage buy shrouding them. It's far from ideal, but welding/cutting ports in an intake is tough and expensive.

Put up some pictures of the intake. Is it 100% custom or is it a carb intake that's been machined down and a blower plate added to it? If it's a modded carb intake, it might not be as expensive to duplicate as you think.

 

[dr_frankenstein]

this is for go..... (we hope) but there is probably enough material to port over if i have too.... but it just seems wonky to me to do it that way.

The intake is a carb manifold......... but the entire runner assembly was machined away from the sides and a new blower style "Plenum" was welded in. so not just an adapter welded to a regular carb top... but a dedicated blower style manifold built out of a carb manifold. I believe this was actually Mike Boohers first prototypes before he stepped up to the bigger blower and went crazy fast. I am looking to compete in a "gasser" style of class.

I can shoot some pics tonight of what im working with, but does anyone have an ON-Center intake that is damaged? or one to sell cheap? as i might just cut the runners out and try it like Jay mentioned above.

 

[Squid4life]

I have like four brother. I can drop one off when I drop off the block.

 

[Mike E]

this is for go..... (we hope) but there is probably enough material to port over if i have too.... but it just seems wonky to me to do it that way...

I could be wrong but I'm 99% sure the on-center and off-center carb stage 2 intakes are the same casting. The on or off center are determined by how they are ported. So porting an off-center over to match an on-center is how they were originally done. They would not dedicate a seperate casting for that little variance in port location. Unless your existing ports are really small though, you'll have to weld them up on the opposite side to match the head.

 

[Squid4life]

IIRC it is only .120" difference, so we can choose the one that I have that has the smallest ports. Then you can port to match and line up everything. Sound about right?

 

[dr_frankenstein]

well i was under the impression that they were totally different castings. Since this is the early Off center that had the long 4 ribs under the runners, while i notice most of the later On center units didnt display this same casting ribs or marks and had that wild twist for the carb pad.

this is an OFF CENTER.... And exactly the manifold mine was built from (pics 1 and 2)

and here was what I thought most ON CENTER intake manifolds looked like (pics 3 and 4)

am i way off here?

 

[Mike E]

The intake shown in 1 and 2 could be either on or off center depending on how they were ported. I've had two on-center intakes that looked like pics 1 and 2 and I've done efi conversions to off-centers that were also casting shown in 1 and 2. The twisted carb pad is a totally different setup.

 

[Squid4life]

I have on centers that have the ribs under the carb pad, and others that have the twisted top.

 

[dr_frankenstein]

ah ha!

thats what i needed to hear, Mike I could kiss ya!

Okay so its probably possible to grind the what..... 1/8" over?

I feel much better about it.

I dont have a good pic at the moment just this one.

 

[Mike E]

Well, now that you've posted a picture of it, maybe not. It looks like the only thing left from the carb intake is the flange and floor. The runners, from that tiny picture, appear to be sheetmetal. If they are sheetmetal, they may only be 1/8" thick or less. So your transition over to the on-center port may only be as deep as the flange. Any deeper and it would cut through the wall of the sheetmetal. But there is no way to know without taking some measurements of the wall, flange etc. It would work, but not be ideal. It may be no worse than the angle between the intake floor and the floor of the port in the head.

How does the size of the intake runners compare to the size of the heads? If the intake side is considerably smaller than the heads, they may just shift over when moved on-center and still fall within the port.

 

[Mike E]

There are lot's of other considerations when deciding on-or off center. I'm not sure the intake would the be deciding factor for me. Meaning, if you had to do work to the intake to make it fit on-center I wouldn't worry as much about that as I would the rods. I can pretty cheaply modify an intake, but rods can be an expensive purchase.

Here is what I found when buying rods.
on-center rods:
-Crower Billet wide Journals ($1400)
-K1 narrow journal on-center ($600)
-The occasional set of used carillo.
- BBC or sbc rods with a cut down crank

off-center:
- Crower billet
-3 or 4 choices of K1 ($500-$600)
- Scat
- Eagle
- Lots of used Carillo
-DLS
-BBC or SBC with a cut down crank.

You have more cheap rod choices with an off-center setup. There are strength differences between the two designs, but unless your pushing a lot of power either (spray on top of the 6-71) would do the job fine.

 

[dr_frankenstein]

I will post some more defined Pics later of the intake.

But I do agree, that it might be sketchy to port it over the amount needed, but I believe it can be done. I have a full machine shop at my disposal so moving the port over with weld is an easy possibility... but fabricating a new intake, even with the equipment looks long and tedious. And personally I dont rave alot about my aluminum welding abilitys so my confidence to make 1 shot no fail welds is on the low side. I am no professional - more just lucky hot-gluing stuff together .

well i have 2 sets of rods, both carillo and one for either block.... so I lucked out when i made a "lot" purchase from here awhile back... so i have extra Off center parts... if anyone needs some.... lol

I dont plan on any giggle gas, but the motor will be on meth spitting through an enderle injection unit. Im not looking to make huge power, maybe a solid 800 hp as my goals are only reliable mid 9s - thats why i began to have faith in the Repaired Block that James has. My body weighs 2600lbs and i am limited to a 12" wide "nostalgia pie crust" slick, leaf springs, 4 speed manual and have a straight axle in the front. So the motor would probably be much faster in a designed chassis rather then a farm cart with slicks.

So ON or OFF center wasnt really a huge concern as i figure both would do the job quite reliably at that level... i just chased an Off center 4.1 block because the one particular piece i had was that Intake and it was Off center..... yes a slightly stupid way to approach block choice... but when your way outside of the box for Buick stuff you have to make those compromises or spend b00-koo dollars buying one special. In 5 years of trying to find a half decent block for a resonable price ive been let down twice... once with a block who had sleeves inserts done by a machinest with a hatchet... and another with wildly spun bearings and cracks everywhere. I have been building my ride for 10 years so im ready to Race... and James has that repaired 153 block.... I have an Itch thats crazy right now.

So if by grace....... Y'all have the general opinion that i should suck it up and continue to wait for that mystical 4.1 off center block... then well i will... but if you guys think "fuck it! Build an on center and make some numbers" then im down for that too...

 

[Mike E]

If you can mod the intake and allready have rods, definitely go on-center. You could wait a while for an off-center and pay a premium for it because that's what everyone wants. Of course the day after you buy an on-center block, an off-center will show up for cheap. I'm glad I ended up with on-center stuff because I know there isn't any question that it's good strong stuff.

 

[coach]

Well, now that you've posted a picture of it, maybe not. It looks like the only thing left from the carb intake is the flange and floor. The runners, from that tiny picture, appear to be sheetmetal. If they are sheetmetal, they may only be 1/8" thick or less. So your transition over to the on-center port may only be as deep as the flange. Any deeper and it would cut through the wall of the sheetmetal. But there is no way to know without taking some measurements of the wall, flange etc. It would work, but not be ideal. It may be no worse than the angle between the intake floor and the floor of the port in the head.

How does the size of the intake runners compare to the size of the heads? If the intake side is considerably smaller than the heads, they may just shift over when moved on-center and still fall within the port.

In my opinion...you might be further ahead to build a new intake the same way they built that one. Like Mike said, they cut away everything but the intake to head flanges and the valley pan. Then fabbed up runners and welded it together. Blower intakes are the easiest to fab. They are very forgiving compared to a carb intake. Runner length used to be roughly determined by 1 inch per 1000rpms. 6000 RPMs needed 6 inch runners, and so on. Hogan intakes follow this on most engine types. Then guys started bolting blower tops to them and some killer power was being developed. The street blower manifolds are dual plane intakes to keep a better torque curve on the street.
I bet you have less work cutting that intake apart and welding it onto an on center intake as it was on the off center. Or...cut the flanges off and mill out some with the on center port pattern, shift the runners and blower top into position and weld the new flanges on.


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[Squid4life]

Doc, if we figure it out where we can meet up and give you the block (if you decide to pick it up) i can bring you a few of the intakes. Use whatever one you think will work then ship the one(s) you don't need back?

 

[Squid4life]

BTW, that setup looks bad ass brother!

 

[fuzzyGN]

If it helps any I will be traveling to Phoenix soon to dop off a car. If stuff can get that far I can get it the rest of the way.

 

[dr_frankenstein]

James,
Thanks Brother! We will figure something out... but more then likely I will take the block off your hands... just got to make sure ive crossed my I's and dotted my T's got to have a excellent and detailed presentation for the bank of my ol'lady.

Erik, Thanks for the heads up on you heading out to AZ, im sure something can be figured out when the time comes so i will keep you posted.

OKAY....

So I went home and pulled out the intake and the heads for a port size re-visit. I took more pics to show you more details about the intake. Doing some very crude port dimensions, using carbon paper and comparing the 2, I honestly think i have enough room to port it over....... depending on which direction each side gets ported and slotted over, there is barely enough meat to accomidate the shift in the manifold. The ports on the heads are already almost an 1/8" bigger then the manifold anyways, so i dont think the shift will make the transition to bad at all since were roughly moving about that much. All being said in the nature of stage 2 building, it might be more or less depending on how mock up goes.