cracked aluminum intake

so i blasted the intake for the chevelle and cleared it. in process, i found a crack. it's small, but leads from a coolant passage to the outside. also, the water ports are kinda pitted.

so someone either over tightened the water fitting or over tightened the water neck bolt. to alleviate this issue, i plan to epoxy studs in for the thermostat housing and a pipe plug in the coolant hole as the one on the other side is better for my application.

so what is the best way to go about ensuring coolant doesn't bleed up through the crack? JB weld the inside of the coolant passage? i could slather the area well and it would stick fine due to the pits.

this is not a "just go buy another one" deal, this is a vintage intake that i hunted for quite some time to get, as i wanted this specific intake for the car.

I heard something on Speedtalk about wicking Loctite... let me find the thread.

http://www.speedtalk.com/forum/viewtopic.php?f=1&t=43472#p553571

If it is particularly rare and you want some mad machinist points you can get some aluminum, copper, or brass threaded rod, a drill bit, and a tap and cold metal stitch the crack.

It's cheap and doesn't require any weird or expensive tools, but it does take patience and attention to detail. It's also about the coolest looking repair you will ever see.

Start with grinding out the crack and tig welding the crack then either tig the hole and drill and tap OR re-tap for a "J" thread adapter bushing. Diesel engine shops often had the J thread stuff on the shelf years ago the thread has a J shape not a peak V shape so it pulls the thread in as it tightens.

http://www.locknstitch.com/Default.htm

In reply to Kenny_McCormic:

I hate that E36 M3, problem is it's saved my ass a few times not only in Korea but Iraq as well lol.

The real fix is to vee it pretty deeply and TIG it. Both threaded holes will be partially welded shut, so the easy way to restore them involves fixturing the manifold in a milling machine to plunge mill the bulk of the weld before drilling and tapping.

As there's under 20 psi behind coolant, you could probably vee it out a little, get it surgically clean with acetone and a small stainless brush, heat it w/ a heat gun (or leave it in the sun) to maybe 150 degrees F and apply a thick bead of slow cure JB-Weld. Re-assemble the fittings to the holes before it cures and apply a bit more to form fillets at the fittings. JB-Weld flows beautifully and there's essentially zero load once the fittings are tight.

If I was desperate at the race track, that's what I'd do.

Upstream of the thermostat, the water pump can generate 50psi+ head pressure. Radiator cap pressure is on the low pressure side of the cooling system.

wow. this is so Fast & the Furious

It is likely that the heat cycles of expanding aluminum would lead to eventual fatigue failure of any chemical or added material type fix and the manifold as a whole at some point. The aluminum crack could extend all through the interior of the coolant passage so just sealing the outside visible crack may not solve the issue.

In the auto manufacturing industry we did implement a temporary fix of sealing the entire coolant passage with an epoxy and using a brass insert into the critical hole, in this case the hole through which coolant is flowing.

With the crack already there, it is inevitable that the whole thing will crack unless somehow you relieve all mechanical stress other than the thermal fatigue stresses. And hope that those thermal cycling stresses are not large enough to continue crack growth.

Nothing lasts forever so plan to buy or have a new one machined sooner or later.

Knurled wrote: Upstream of the thermostat, the water pump can generate 50psi+ head pressure. Radiator cap pressure is on the low pressure side of the cooling system.

You sure of that?

Are your heater core hoses under pressure before the car heats up?

Huh. Learn something new every day!

Thanks for the link!

I have no problem being educated, but searching for water pump pressure before t-stat brings up an incredible amount of useless stuff(I did attempt to search to see if there was something I was unaware of).

And personal experience shows most heater cores I've replaced for being plugged blow at 40-60psi

Those finding disturb me... pressure falls off right when you want high pressure in the heads the most. Maybe those guys who take the thermostat out and replace it with a restrictor have a point.

I got the 50psi figure as something to shoot for when sizing water pump pulleys/restrictors in circle track applications. When the water pump stalls, pressure falls off/fluctuates so you know you have to slow the pump. The size of the restrictor will affect when the pump stalls (albeit not by very much) so it's a balancing act.

new finding disturbs me, and maybe is the cause of the issue. it appears someone used too long a bolt in the t-stat housing, forced it, and blew the bottom of the hole right out into the coolant passage.

normally this i where i would buy a tig welder and do it myself, however i don't think i can afford that right now nor do i know what else i would do with it that my mig can't do. i've never been in a position saying "damn this would be easier with a tig"

talked to my uncle, he knows a guy who can tig it. probably the same guy who fixed my cracked bellhousing when he took my trans away and brought it back a few days later and said give him $20. i'm thinking about getting an aluminum pipe plug for the hole at the same time and having it welded right in.

I repaired a crack and a broken out hole in an Edelbrock intake last year.

The crack came from an over-tightened pipe thread. I ground out the crack, threaded in a brass plug, and TIG'd it closed. It is still holding. The brass didn't stick to the weld, and unthreaded just fine.

The hole was a heli-coil repair that was drilled too far. I drilled the whole thing out, TIG'd it closed, and just re-threaded it.

If you have a MIG, buying a spool gun might be an option, but beer to a friend with a TIG is cheaper.

patgizz wrote: new finding disturbs me, and maybe is the cause of the issue. it appears someone used too long a bolt in the t-stat housing, forced it, and blew the bottom of the hole right out into the coolant passage...

As an aside, that's really easy to do even with a bolt that's not too long. All it takes is some coolant or oil to be in the threaded hole, then screwing in a bolt and trying to tighten it to spec. I've blown the back out of an aluminum thermostat housing that way.