Removing Air Tubes From Manifold ?

[Carl Beck]

Try CRC "Knocker Loose" it is a copy of Kroil and is available anywhere that sells CRC products. It DOES work as good as Kroil.

Thanks - I'll find some and try it.

Carl B.

[Oiluj]

I heated the manifold area around the tubes with a propane torch, Then, while still warm, gave them a good soaking w/ WD 40. Waited 1 hour and repeated the process. Got 2 loose, but the rest were still frozen.

Took a cold chisel and cut the tubes off flush at the nut. I'm sure the impact of cold cutting the tubes probably helped to loosen the nuts.

Then just put a socket on the nuts and they all turned-out relatively easily. They were stiff, but theyall came out with minimal effort. Victory!

Now I have to get some BPS plugs. I'll try looking first in McMaster-Carr.

My only thought is what are you guys going to do when the great powers that be. Decide you have to put all that smog gear back. With the stock manifold it is a matter of bolting the pieces back on. Yes, I do own all of them. After owning this car over thirty I can not honestly say it runs better or faster with out the smog gear. I only removed it because it took some time to find a smog pump.

It is highly unlikely that this will ever occur, there are just too few old cars to make them worth the governments effort. However, I'll still hang onto the old parts, becuase if down the road when I sell the car, someone may want to make it perfect "stock". I also have an extra smog manifold that came with the car.

[Oiluj]

Or..... Just remove the manifold and get yourself a good flowing 6 into 1 header. Better air flow, looks better, allows for a new, bigger diameter exhaust pipe and all around better performance.

Dave.

When I spoke with the guys at Rebello, they told me that the stock exhaust manifold flows very well and would be quieter than headers. I can attest that this was the case when I put hearders on my MG, it did get louder. Also, you often lose a bit of low-end torque with headers. My bigger concern is as was pointed out, is heat under the hood.

Later on I can always remove the stock exhaust and try MSA's 6 to 1 headers if I want more mid-range performance. I figure it would also require a better air intake system for the headers to do much good.

[Oiluj]

I did a bit of investigation and verified that the air tube fitting threads are BSPP, not BSPT, That is, they are a straight thread, not a tapered thread. They are J.I.S., but J.I.S. is a direct copy of British standard threads).

I checked in McMaster-Carr and they have various plug forms in BSPT and BSPP in brass, 304 stainless, iron & steel. They cost about $2 each.

So here's what I plan to do. I plan to use a BSPP hex key plug, threaded all the way to the bottom of the exhaust port. I'll apply a bit of high-temp thread sealant to assure a seal. While this would be adequate, (my being a belt & suspenders kind of guy), I'm also going to use a BSPP hex head plug to cover the hole.

I also came-up with an alternate approach:

I tried this on one old fitting just-for grins...

Looking at the tube fitting, I found that the tube hole on the manifold side of the fitting is 0.203" dia. This is the perfect size for a 1/2-20 tap. I tapped the inside hole of the fitting from the manifold side with 1/4-20 threads. I coated a 1/4-20 x 1/2" threaded socket head set screw with high-temp epoxy to help "seal" the threads and inserted the set-screw into the fitting. I then used a moto-too to grind the tube sticking from the hex-head side of the fitting flush and dabbed a bit of epoxy on to look more "finished".

I'm not going this route because the fittings are quite rusted and the hex heads are rounded, but it is a viable alternative.

[sblake01]

I'd just put the manifolod in my drill press and drill them out and tap them to whatever thread that would be easy to find plugs for and not worry about BSPT or BSPP. But that's just me.

[Oiluj]

I'd just put the manifolod in my drill press and drill them out and tap them to whatever thread that would be easy to find plugs for and not worry about BSPT or BSPP. But that's just me.

I considered that as my best back-up solution, one I would have used in preferrence to tapping the original fittings with the 1/4-20 plug option. Getting the correct fittings from McMaster is less work. Call me lazy... *grin*

[sblake01]

Oh, I don't know, maybe I'm the lazy one. If I drill them out on the press, I don't have to deal with removing them. Removing them would save the threads but it's harder to do than drilling them on a press. Besides we don't have a McMaster around here, we have Fastenal and they don't have a clue about BSPT.

[Oiluj]

I phone ordered from McMaster. They typically ship the same day and are a great source for anything mechanical.

Here's the link: http://www.mcmaster.com/

[Oiluj]

Here's a pic of the exhaust air tube plugs I got from McMaster-Carr. They are 1/4" BSPT hex head and I think they look pretty nice.

With that big hex head, I'll be able to remove them if required...

[Tony D]

My mind goes weak with age... I just did this with my son on his L20B manifold in the 510 Wagon... I had pipe plugs and a tap that went RIGHT into the factory straight threaded holes. Now, I preface this by saying I MAY have had a 'flushseal' tap and plugs laying around because these babies threaded right in and went in flush, and looked slick. I know I used liberal amounts of nikel-based anti-seize so if they need to come out later....

Now, I also found some Toyota Bolts that threaded in as well, so there has to be a metric threaded plug (or metric setscrew) that will screw in similarly and then can be locked in using a 'staking' technique.

As for headers-vs-manifolds...like Carl said, unless you are tuning for a peak at a specific rpm (we altered primary lengths considerably on our L20A Bonneville Racer to get our peak right where we needed it, cut almost 5" out of the primaries!) the stock manifold, ported and cleaned of casting irregularities will function VERY well even on relatively hot motor builds. The 79 L20B manifold my son and I just put on his car had a 2.5" headpipe hole, with only about 75% of it open due to a HUGE cast-in restriction bump. Took it out altogether, and really lightened up the manifold in the process. A little port matching and bump removal at the exhaust ports as well made it look really 'flowey'... If this performs like a similarly cleaned up N42 Manifold on my 75 Fairlady Z 2/2, I think he will be very happy with the results. And the best thing: "IT ALL LOOKS STOCK"!

When the CHP pulls you over for a roadside emissions compliance check LOOKING STOCK becomes a VERY good thing!

[Tony D]

Besides we don't have a McMaster around here, we have Fastenal and they don't have a clue about BSPT.

Hey! McMaster is over in Norwalk... And if you order first thing in the AM, it will make their 9AM UPS Ground shipment...the parts will be at your door by 6PM that SAME DAY!

At least they come to me in Perris/Moreno Valley that way... And that's only if I'm not driving down the 605 any time during the week.

Fastenal is no substitute for the cornucopia this is McMaster-Carr.

And if you want the stuff in Stainless, Mc-Fadden-Dale Hardware has an outlet in Ontario, and Corona. They got EVERYTHING hardware related! Flushseal/Dryseal plugs (and the taps), button-headed stainless steel metric machine screws (think M6X1.0 and you go "Ooooh! Tasty!") Right off the 91 at Maple St, or off the 60 or the 10 at Grove, just south of Mission...

Oh, and McFadden-Dale stocks Kroil in spraycans, as well as gallon cans. They also have (believe it or not) COSMOLINE! Want to store some parts????

SanBerdoo ain't Trona! Don't be that way!

[beandip]

Anyone that owns a Z should have some kroil. I have been using the same spray can for years and it is the best I have ever used. PB Blaster comes in secound but it smells like he##. KANO Laboratories kanolabs.com Headers vs. OEM exhaust elimination of back pressure, or not is a topic for a different thread.