Broken lower intake bolts

Mike3 · Aug 11, 2025

I’ve got a 94 gt and upon removing the lower intake manifold I discovered that 3 of the 4 corner bolts were broken off, I’ve tried heat, I’ve tried lots of penetrating oil, and have tried easy outs over and over. I don’t know what to do as one of the bolts is drilled quite off center and another has a broken extractor in it. Don’t really want to get new heads, so what I need is as much advice as possible for drilling the bolts out and tapping the holes or what else I should do. Thanks in advance

Noobz347 · Aug 11, 2025

Drop them off at a machine shop.

They can look them over for valves, seats, seals, and flatness, all at the same time.

Mike3 · Aug 11, 2025

Noobz347 said:
Drop them off at a machine shop.

They can look them over for valves, seats, seals, and flatness, all at the same time.

I’ve got a friend who thinks we can drill and tap them coming to help me, but if all else fails, that is definitely something I’ll have to do. thanks for the reply, hopefully I’m successful in drilling and tapping as I don’t really want to pull the heads.

Noobz347 · Aug 11, 2025

Order yourself some replacement ARP bolts.

Hardware store bolts (Grade 5) will leave you right back where you are.

AeroCoupe · Aug 12, 2025

And may I suggest tapping all of the threads on the heads for the intake bolts. A little dab of anti-seize also helps with removing them at a later date. By a little dab I mean just that or you will look like this:

One further suggestion would be to use studs in lieu of bolts. Just hear me out on this as I see it through tension and torsional forces on the threads. When using a bolt you are imparting torsional forces via screwing the bolt into the threads in the heads while at the same time inducing tensional forces on the threads in the heads as the intake gets torqued down. If you use a stud you are only inducing tensional forces on the threads on the heads as the stud is already screwed into the threads in the heads with zero load on them. When you install the lower intake and then start the process of torquing it down the studs are not twisting like a bolt.

Other nice thing is the studs locate the intake gaskets so you do not get gasket shift. I also think they torque better as I do not have leaks in this area anymore. Get the motor up to operating temp and then retorque one more time and done.

https://www.summitracing.com/parts/arp-354-2103?srsltid=AfmBOoomsmtpz3a3OCb6wg2Lyg8qHWMqEc2Uto7BvHS9lRXK4AKrZlyA

KRUISR · Aug 12, 2025

Are the bolts stuck in the head or corroded into the intake?

If stuck in the head, I have always welded a nut on the broken bolt and worked it loose. Sometimes I go through a bunch of nuts before the seized bolt starts to move. Then nice part is you don't ruin the threads in the head.

Mike3 · Aug 12, 2025

KRUISR said:
Are the bolts stuck in the head or corroded into the intake?

If stuck in the head, I have always welded a nut on the broken bolt and worked it loose. Sometimes I go through a bunch of nuts before the seized bolt starts to move. Then nice part is you don't ruin the threads in the head.

They are seized into the head, also I’m not sure I’d be able to weld a nut with the heads still on the car.

Mike3 · Aug 12, 2025

Noobz347 said:
Drop them off at a machine shop.

They can look them over for valves, seats, seals, and flatness, all at the same time.

Welp tomorrow morning I’m gonna pull the heads and call around with the local machine shops, should just leave it to the pros

Noobz347 · Aug 12, 2025

A couple lists to bounce off of just to make sure you didn't forget anything:

Tools:

Item	Notes
Torque wrench	Essential for proper head bolt torque & pattern
Angle gauge	Required if using TTY (Torque-To-Yield) head bolts
Breaker bar	Useful for removing stubborn old bolts
Razor scraper / gasket scraper	Clean old gasket material from block/head
Thread chaser kit	Clean bolt holes, especially head bolt threads
Shop vac or compressed air	Clean out bolt holes before installation
Magnetic pickup tool	Save your sanity if anything falls in a valley
Feeler gauge (optional)	Useful for checking lifter preload, if reused
Engine hoist	If heads are iron and you're working alone

Parts/Supplies

Item	Spec/Notes
Head gaskets (pair)	Fel-Pro 9333PT1 or equivalent
Intake manifold gaskets	Upper & lower sets
Exhaust manifold/header gaskets	Match your setup (headers vs stock manifolds)
Head bolts (or studs)	One-time-use torque-to-yield — ARP recommended for reuse
Thread sealer or ARP thread lubricant	If using ARP bolts/studs (not all holes are blind)
Anti-seize	For exhaust bolts, spark plugs, etc.
RTV silicone	For corners of the intake gasket and end rails
Engine oil	For priming & replacing any drained oil
Coolant	You’ll lose a lot removing heads
Thermostat gasket	Cheap, always replace if disturbed
Brake cleaner or acetone	Final cleaning of gasket surfaces
Shop towels / lint-free rags	For block/head prep and cleanup

Recommended/Optional

Item	Purpose
ARP head studs	If you're planning more power, these are reusable and more secure
Oil dye & UV light	Check for leaks after reassembly
Replacement pushrods / lifters	If existing ones are worn or noisy
Intake end rail spacers (for EFI)	Helps prevent leaks from cork gasket blowout
Coolant bypass hose	May crack when disturbed during disassembly

FastDriver · Aug 13, 2025

Was this? "Intake end rail spacers (for EFI)"

I see a couple parts upon googling, but am unfamiliar. Is it just a replacement for cork china wall gaskets?

Noobz347 · Aug 13, 2025

FastDriver said:
Is it just a replacement for cork china wall gaskets?

Yes. Only difference is that they usually made of aluminum or some kind of phenolic material.

AeroCoupe · Aug 13, 2025

Just put a 1/4"+ bead of RTV that is resistant to oil ( I want to say gray in color) on the china walls and let it sit for 15 min or so. Put the intake on and torque down. Nothing to slip out and does not leak.

FastDriver · Aug 14, 2025

Wonder which holds up better when the crankcase gets some pressure from blowby. I vent to atmosphere in the cars that run boost, but I have blown out gaskets when I tried to run the EGR system. The right way to do that is apparently to run a vacuum pump.

Noobz347 · Aug 14, 2025

I run a closed system with my KB. I ran an additional line and separator and used the inlet leading to the TB as the second vacuum source.

So far, so good.

FastDriver · Aug 14, 2025

but isn't that line under pressure when boosted, too?

Noobz347 · Aug 14, 2025

FastDriver said:
but isn't that line under pressure when boosted, too?

I can't say for sure. The only time it was ever measured was on the dyno and that time, I still had negative crank-case pressure during boost.

Since then, I've added more boost, and more crank-case scavenging and have not measured case pressure.

Recall though (and you have have forgotten this part), I run a Kenne Bell and not a centrifugal so, even at WOT with my (3.5-4 inch, I've forgotten) inlet, there is "suck" in that line that I've tapped for my second crank-case vent. And that section is [after] my MAF.

With a Centri blower, I would have used the inlet leading up to the blower as my scavenge source.

I will add as a footnote that air volume is the target and not velocity. Too much velocity at the PCV port was responsible for picking up a lot of oil mist. With my second vent, it slowed the air to the PCV enough that it stopped scooping up oil mist (rather, it was greatly reduced).

revhead347 · Sep 2, 2025

Mike3 said:
I’ve got a 94 gt and upon removing the lower intake manifold I discovered that 3 of the 4 corner bolts were broken off, I’ve tried heat, I’ve tried lots of penetrating oil, and have tried easy outs over and over. I don’t know what to do as one of the bolts is drilled quite off center and another has a broken extractor in it. Don’t really want to get new heads, so what I need is as much advice as possible for drilling the bolts out and tapping the holes or what else I should do. Thanks in advance

You put a nut on the top of them, and then fill the center with a mig or flux welder. Then a ton of PB Blaster and heat, and turn off with a wrench. There must be a million videos on youtube on how to do this.

Kurt

Broken lower intake bolts

Mike3

Member

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

Mike3

Member

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

AeroCoupe

lube between the nut and the face. I know my lubes

KRUISR

Mike3

Member

Mike3

Member

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

FastDriver

I was uncomfortably high & wearing a helmet

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

AeroCoupe

lube between the nut and the face. I know my lubes

FastDriver

I was uncomfortably high & wearing a helmet

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

FastDriver

I was uncomfortably high & wearing a helmet

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

revhead347

Apparently my ex-husband made that mistake.

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Broken lower intake bolts

Member

Stangnet Facilities Maint Tech... Er... Janitor

Member

Stangnet Facilities Maint Tech... Er... Janitor

lube between the nut and the face. I know my lubes

Member

Member

Stangnet Facilities Maint Tech... Er... Janitor

I was uncomfortably high & wearing a helmet

Stangnet Facilities Maint Tech... Er... Janitor

lube between the nut and the face. I know my lubes

I was uncomfortably high & wearing a helmet

Stangnet Facilities Maint Tech... Er... Janitor

I was uncomfortably high & wearing a helmet

Stangnet Facilities Maint Tech... Er... Janitor

Apparently my ex-husband made that mistake.

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