Mismatched intake/manifold ports

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bibs
Posts: 83
Joined: Fri Jul 13, 2007 1:12 pm

Mismatched intake/manifold ports

#1

Post by bibs » Sun Apr 30, 2006 10:12 am

I made a major blunder on my motor when rebuilding it.....I must have had the wrong intake manifold (shovel type)I have STD. heads and I swear by them as they are worth an easy 10 horse power diff. over stock..........So...I removed metal on the O-ring lips of the heads to get the manifold to sit in deeper and line up with the I.D. of the intake runners,I got it really close with only a very slight difference,so that the transition....intake to head ports was barely perceptable.
AT ANY RATE...THIS IS WHERE THE PROBLEM LIES....I could not get the stock size O-RING in between the manifold and lip of the intakes!!!! So I opted to go to the rubber band set-up!! It seemed to work real nice
...It slipped, now I have a step where the intake moved out.....I need smaller thickness O-RINGS to get them to slip in to what lip is left then use the wrap around intake clamps to tighten them up......and hopefully this will solve the alignment issue
Well someone please advise me as to what, if anything I should do? Am I on the right tract in attempting to solve this problem!!??
The bike is breaking up at around half throttle and I believe this is the problem.



Cotten
Posts: 6911
Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois

Re: Mismatched intake/manifold ports

#2

Post by Cotten » Sun Apr 30, 2006 4:57 pm

Bibs!

The geometry of the chubble manifold and ports is much more difficult to install than the Pan. In spite of having assembled dozens over the decades, I still must resort to pressuretesting while installing in order to find the exact 'sweet spot' where the clamps will form the o-ring into a seal.
(Then a support must be massaged to hold the carb mated upon it without stress or bind.)
A trimmed assembly can only be more difficult.
Next time, whittle only on the easily replaced manifold!
It is a simple lathe operation to carve its o-ring spigots back to spec. (Unless it has been ruined with chrome.)
Some folks are successful with trimming the entire spigots off and using only the late bands, with a late manifold. I would consider that a last resort, and can only once again stress pressuretesting to avoid motor damage.

....Cotten

bibs
Posts: 83
Joined: Fri Jul 13, 2007 1:12 pm

Re: Mismatched intake/manifold ports

#3

Post by bibs » Mon May 01, 2006 2:47 am

uuum....I think I got 'er squared away.( I THINK)at any rate,I took the manifold off,took a good long look at it and checked into my stash....lo and behold....what do I find!!!? O-rings half the thickness of the original!!! SO..... I put 'em on the intake along with some hi temp silicone and the 2 pc. clamps....tighten things up,put the carb(S&S) back on and haul ass down the pike.....ran 'bout 20 miles and she starts breakin up again....although not quite as bad.I got 'er home and break out the C.V.carb that I sent out to RON TROCK for him to modify and put it on.....She runs MUCH smoother....havent got down the road with 'er yet but monday is the trial day.I'll see how she runs....if she aint up ta snuff she's goin out the door for whatever Ican get close to 8-9 grand.....I'm gettin REAL tired.

Billy
Posts: 781
Joined: Tue Mar 23, 2004 6:57 am

Re: Mismatched intake/manifold ports

#4

Post by Billy » Mon May 01, 2006 6:04 am

bibs-

When aligning an intake, during a build, Best to leave the base nuts loose, & twist Cly's as needed for best Fit. Then tighten things down & (of-course) pressure test intake everywhere..
Using Cotten's Tried & True method.. (then ya know for sure)...Other-wise no carb will fix a leak..
Hope things work out, adding silicone.. :-/ (time will tell)
Sounds like you're almost there. Don't give up!! You'll regret it., down the road..

bibs
Posts: 83
Joined: Fri Jul 13, 2007 1:12 pm

Re: Mismatched intake/manifold ports

#5

Post by bibs » Mon May 01, 2006 11:03 am

yeah,it was an act of frustration at the time....but not entirely unheard of as I know peaple that have done it before and had excellent results.When I put the heads on,I left them just loose enough to get the alignment with the intake.....the problem was in the size of the intake(it was probobly for taller cylinders)....oh well,ya live and learn.
Before I put the C.V. on last nite the manifold felt really solid and the alignment was spot on!!
I'm curious to see just how well she runs....the S&S I had on there was problematic on another motor......we shall see :

fourthgear
Posts: 1390
Joined: Mon Apr 11, 2005 1:12 pm
Location: north florida

Re: Mismatched intake/manifold ports

#6

Post by fourthgear » Mon May 01, 2006 1:59 pm

Bibs
Are you trying to put the o- rings between the protruding lips of the manifold ? They actually go on top of them and your clamps smash the o-rings some what to flatten them over top of the small lip. As has been said , aliening of the intake is done when cyl. & heads installed . There should be very little gap between head spigot and manifold and of course aliened as close as possible . It sounds to me like you are trying to fit the o-rings between the two. I roll the o-rings over top of the head spigot and hold the manifold in place and roll the o-rings on top of the two and then install the clamps.Of course you have to pressure test as per Cotten instructions which can be found here before carb. is in stalled. I usually mount my carb in position before I tighten the clamps all the way for alignment and then pull carb off and pressure test manifold.

bibs
Posts: 83
Joined: Fri Jul 13, 2007 1:12 pm

Re: Mismatched intake/manifold ports

#7

Post by bibs » Mon May 01, 2006 6:48 pm

Thats exactly what I did.....but the lips on the heads and intake(shovel type....cause I got STD heads) arenty as long as they once were(duh!!!) so in my INFINITE wisdom LOL.,I trimmed down the standard black o-rings and used them....I did what we all do,rolled them up on the manifold then positioned the manifold between the heads and used split clamps(I hate them damm things) cause they were all I had.I ordered the good type aircraft type along with another intake manifold just in case I needed one.
I rode the bike a little earlier and she seemed okay....just sneezing a little cause I aint familiar with the C.V. she now has on 'er.
By the way...heres a link for O-RINGS in case anybody is interested http://www.applerubber.com/library/tips.cfm" onclick="window.open(this.href);return false;
I'll let yas know if I get the problem resolved ,or if I might half to go back to the drawing board.

panster
Posts: 58
Joined: Fri Mar 19, 2004 2:07 am

Re: Mismatched intake/manifold ports

#8

Post by panster » Mon May 01, 2006 11:04 pm

Wouldn't it be good if we could get O rings that were a combination of the bands and the round section rings ?
I'm thinkng they should look like a T section, thin enough band, to use "aircraft"
type clamps, and maybe a square instead of round protusion, to better suit the step.
Any rubber moulding manufacturers out there ?
(I'll accept a modest sum for the idea).

Cotten
Posts: 6911
Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois

Re: Mismatched intake/manifold ports

#9

Post by Cotten » Tue May 02, 2006 12:19 pm

Bibs!
Modern gas eats sillycone, and often it just greases the clamps up for easy slippage later. Goo' luck.

and Panster!
Your hybrid seal idea would only be assemble-able on the chubble manifold, as you would have to remove a head to service a Pan.

Factory design works very well when assembled clean and dry, and tested.

....Cotten

bibs
Posts: 83
Joined: Fri Jul 13, 2007 1:12 pm

Re: Mismatched intake/manifold ports

#10

Post by bibs » Thu May 04, 2006 12:44 am

Just what exactly is a chubble manifold?

Billy
Posts: 781
Joined: Tue Mar 23, 2004 6:57 am

Re: Mismatched intake/manifold ports

#11

Post by Billy » Thu May 04, 2006 4:31 am

bibs-

a chubble manifold came stock on chubblehead motors. '66-'84
HD made them after the Panhead ended production. ;D
I do believe the term originated as a "Cottenism"

Cotten
Posts: 6911
Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois

Re: Mismatched intake/manifold ports

#12

Post by Cotten » Thu May 04, 2006 12:43 pm

I've never had an original thought;
My buddies from Chicago say it that way naturally.
There used to be a Chubblehead site, but I imagine it is extinct.

....Cotten

bibs
Posts: 83
Joined: Fri Jul 13, 2007 1:12 pm

Re: Mismatched intake/manifold ports

#13

Post by bibs » Fri May 05, 2006 1:33 am

BWAAAAAAHAHAHAHAHAHA!!! GOOD ONE,MY DUMB!!!Now then...back to the situation.I got the O-RINGS today they are .139 thick and look like they may do the trick.
The manifold I was operating on was a stroker manifold(chubbel)...I also scored a new stock manifold so um thinking....mebe I could use the new stock chubbel with the original .220 thick O-RINGS...I,m thinking that even if the manifold is a little loose in between the ports(heads) the aircraft style clamps will draw every thing together snug like then make up a little support bracket to hold that C.V. nice and horizontal like!!!....waya think?

Cotten
Posts: 6911
Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois

Re: Mismatched intake/manifold ports

#14

Post by Cotten » Fri May 05, 2006 12:07 pm

Bibs!

You cannot trust to blind instinct on this one; A tight and firm assembly means nothing. In fact, it is designed to have some flexibility!
Avoid tailchasing, chinscratching, and further knucklebusting by watching the bubbles.
They will tell you when the alignment is perfect, and they will also tell you if you overtorque the bandclamps, as bubbles don't lie!
Again, return to OEM design, clean and dry: no goobers, tapes, or gimmicks. Save those 2-piece 'stupor-clamps' for truck mufflers.

....Cotten

bibs
Posts: 83
Joined: Fri Jul 13, 2007 1:12 pm

Re: Mismatched intake/manifold ports

#15

Post by bibs » Sat May 06, 2006 2:01 am

Cotten....what bubbles doth thou speaketh of!!!!!! I'm dumber than a doorknob about these matters...please explain!

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