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Can I use Belzona to "shrink" manifold runners this much?

General engine tech -- Drag Racing to Circle Track

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V Remian
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Re: Can I use Belzona to "shrink" manifold runners this much

Post by V Remian » Wed Sep 28, 2016 12:13 pm

Wouldn't the simple expedient be just to match the head to the intake opening since they're so close anyway? That way you wouldn't have to worry about a compound coming loose. Or a huge power robbing mis-match at the interface.

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Re: Can I use Belzona to "shrink" manifold runners this much

Post by andyf » Wed Sep 28, 2016 1:59 pm

I've dyno tested that type of mis-match before and I'll say it is roughly 10-15 hp type of improvement if you can smooth it out. I don't know if I'd go to the work of using Belzona to smooth it out, all depends if the 15 hp is worth the risk of having something come loose on the drive to the track.

I have worked a lot harder for less gains before though!
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Re: Can I use Belzona to "shrink" manifold runners this much

Post by mag2555 » Thu Sep 29, 2016 6:46 am

Port match is not just a matter of effects on air flow, but also pluse tuning!

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Re: Can I use Belzona to "shrink" manifold runners this much

Post by Walter R. Malik » Thu Sep 29, 2016 9:50 am

andyf wrote:I've dyno tested that type of mis-match before and I'll say it is roughly 10-15 hp type of improvement if you can smooth it out. I don't know if I'd go to the work of using Belzona to smooth it out, all depends if the 15 hp is worth the risk of having something come loose on the drive to the track.
And I have also seen it lose power along with fuel efficiency so, every situation is different.
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Re: Can I use Belzona to "shrink" manifold runners this much?

Post by BradH » Wed Sep 04, 2019 9:12 am

Back from the dead...

Checked my Belzona 1111 batch # and found the expiration date was coming up soon, so "Might as well give it a shot!"

This was my first time working w/ that product, and that sh!t is nasty to work with. As a result, I totally botched (bodged, for our UK readers) the job on the one bank of ports I worked on. Looked at the other bank and decided "Why bother!" :(

Figured I turned what was likely to end up as an aluminum door stop into an aluminum & epoxy door stop. So much for salvaging an intake I've put a ridiculous amount of time and $ into over the years... #-o

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Re: Can I use Belzona to "shrink" manifold runners this much?

Post by Walter R. Malik » Wed Sep 04, 2019 9:20 am

BradH wrote:
Wed Sep 04, 2019 9:12 am
Back from the dead...

Checked my Belzona 1111 batch # and found the expiration date was coming up soon, so "Might as well give it a shot!"

This was my first time working w/ that product, and that sh!t is nasty to work with. As a result, I totally botched (bodged, for our UK readers) the job on the one bank of ports I worked on. Looked at the other bank and decided "Why bother!" :(

Figured I turned what was likely to end up as an aluminum door stop into an aluminum & epoxy door stop. So much for salvaging an intake I've put a ridiculous amount of time and $ into over the years... #-o
If it is for a real race vehicle, does it really matter how it looks as long as it performs...?
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Re: Can I use Belzona to "shrink" manifold runners this much?

Post by BradH » Wed Sep 04, 2019 9:55 am

Walter R. Malik wrote:
Wed Sep 04, 2019 9:20 am
BradH wrote:
Wed Sep 04, 2019 9:12 am
... As a result, I totally botched (bodged, for our UK readers) the job on the one bank of ports I worked on.
If it is for a real race vehicle, does it really matter how it looks as long as it performs...?
This isn't "not pretty", it's "grind it out and start over". :shock:

At this point I'm going to run a different intake until I (if ever) get motivated to deal w/ my sh!tty fill job and take a different approach to fixing the intake.

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Re: Can I use Belzona to "shrink" manifold runners this much?

Post by Walter R. Malik » Wed Sep 04, 2019 10:03 am

Oh OK ... now I get it.
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Re: Can I use Belzona to "shrink" manifold runners this much?

Post by Tuner » Wed Sep 04, 2019 11:43 pm

BradH wrote:
Wed Sep 04, 2019 9:55 am
Walter R. Malik wrote:
Wed Sep 04, 2019 9:20 am
BradH wrote:
Wed Sep 04, 2019 9:12 am
... As a result, I totally botched (bodged, for our UK readers) the job on the one bank of ports I worked on.
If it is for a real race vehicle, does it really matter how it looks as long as it performs...?
This isn't "not pretty", it's "grind it out and start over". :shock:

At this point I'm going to run a different intake until I (if ever) get motivated to deal w/ my sh!tty fill job and take a different approach to fixing the intake.
JB weld will kill a carbide burr immediately, one touch, dull tool. I am reasonably sure Belzona will do the same. You can grind it with abrasives, but trying to cut it with a carbide will dull the tool.

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Re: Can I use Belzona to "shrink" manifold runners this much?

Post by BradH » Thu Sep 05, 2019 8:12 am

Tuner wrote:
Wed Sep 04, 2019 11:43 pm
JB weld will kill a carbide burr immediately, one touch, dull tool. I am reasonably sure Belzona will do the same. You can grind it with abrasives, but trying to cut it with a carbide will dull the tool.
Good to know for the future. I'm going to back-burner anything to do w/ this piece for now, though.

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Re: Can I use Belzona to "shrink" manifold runners this much?

Post by Leftcoaster » Thu Sep 05, 2019 12:40 pm

In the late 70's I spent many hours filling a SBC 305's labyrinth like intake ports with JB Weld then recontouring them with carbide burrs

The burrs held their edge, and I wonder if the formulae was changed some 5yrs ago when the company was bought out and gawd knows how many "specialty" JB Weld products appeared in fancy counter displays?

Some months after completion the owner ran the 305 out of water and seized it, hot enough that oe paint blistered and peeled off the heads - - when pulled down remarkably the JB Weld wasn't affected and wouldn't budge unless gouged with a blunt screwdriver

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Re: Can I use Belzona to "shrink" manifold runners this much?

Post by Tuner » Thu Sep 05, 2019 1:36 pm

Recognizing there are several different JB Weld brand products, and several different epoxy brands similar to JB Weld, my first experience with epoxy dulling carbides was with the grey colored Marine-Tex. Close examination of the various available similar epoxies with some magnification will find that they have microscopic flecks of some shiny material. Marine-Tex MSDS lists Aluminum Silicate, which is derived from Aluminum Oxide and Silicon Dioxide. Aluminum Oxide hardness is 9 on the Mhos' scale. One of the JB Weld products lists Crystalline Silica (AKA Quartz) as an ingredient. The Marine-Tex dulled a brand new carbide instantly. Killed it. Y'all can do what you want, but I will never use anything but abrasives on epoxies. Coarse grit tootsie rolls work just fine.

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