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post #16 of 34 (permalink) Old 05-16-2017, 06:17 PM
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From my notes gathered off the net

On the small block Chevy, the rule of thumb is, that for every
.005 in. removed from the head or block deck, a hair over .006 in. must be removed from the heads intake face (or the side of the intake manifold)
and between 0.008 and 0.009 in. removed from the end mating surfaces.
IIRC this is the same for the big block.


and my notes copied from
"How to Rebuild Small-Block Chevy LT-1/LT-4 Engines" by Mike Mavrigian.

"Whenever you remove material from the combustin deck surface of the heads, you obviously shorten the head,
which can affect the sealing surface angles between the intake manifold and the cylinder head.
If the resurfacing process removes up to a max. of about .019" you will likely be ok.
If you remove .020" or more from the combustion decks, corrective material removal
from the intake port deck and intake-to-block rails will be nesessary.
Here's a handy reference to use if you need to match the intake angles.


Consider the amount removed from the combustion deck and multiply this by a factor of 1.2
in order to obtain the amount that must be removed from either the intake manifold mating surface of the head
orfrom the intake port deck of the intake manifold.

So, if .010" is removed from the combustion deck, you need to remove .012"
from either the intake side of the head, or from the intake port deck of the manifold.

You also need to remove material from the front and rear rail surfaces of the intak manifold,
where they contact the block (since now the intake will sit to high to allow proper sealing at the port decks).
Based on the amount of material you removed from the cylinder head combustion decks, multiply this by a factor of 1.7
to abtain the amount of removal needed at the intake manifolds front and rear rails.
If you milled .010" from the heads combustion decks, you would need to remove .017" from the intake manifolds front and rear surfaces.

Combustion deck removal amount X 1.2 = Material to remove from intake port side.
Combustion deck removal amoutn X 1.7 = material to remove from intake manifold front and rear rails."
----------

SO.

HOW MUCH did they take off the heads.?
Was it a straight cut or angle milled........Are the two port faces still parallel on both heads with the manifold.
My guess is quite a bit. I had the block decked 0.030 (thirty thou) and the manifold still fitted pretty well (at the top)

IF the manifold is sat on the china walls (front and back) then the manifold needs trimming.
......... You __CAN__ cut this down with an angle grinder.
Don't try to do this in 1 cut... keep checking.
It's sealed with silicone anyway so the fit isn't that important.

IF the Port faces are NOT PARALLEL then you will possibly need to reface (angle cut the manifold) You could cut the heads but i wouldn't unless they HAVE been angle milled.

When the ends have been cut down and the port faces only are touching the heads, you can measure the clearance/taper (without gasgets) with some fat plumbers solder across the valley, across the port centrelines. (That's the bit you are interested in.) and bolt the manifold up to crush the solder. You can then measure these to visualise any taper front to back & top to bottom.

Felpro do (did) a guage for measuring the face angles on heads & manifolds. You probably don't need it as the solder method works much better.
I did find it useful to confirm the Edelbrock LT4 manifold angle was wrong but i'd already guessed that.
Fel-Pro Cylinder Head And Intake Manifold Angle Guage 2520 Small Block Chevy

Mitch
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post #17 of 34 (permalink) Old 05-16-2017, 06:29 PM Thread Starter
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Wow!!! Mitch. That's some pretty damn good info right there! I am calling my shop in the morning and asking him to cut down the 2 ends to .017. He said he's never had to do those areas before, but in my mind I knew, that's the only way it would ever mate up correctly.
It appeared to me they did the combustion chamber sides and the intake mating surfaces on the heads. So it's been double milled so to speak.
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post #18 of 34 (permalink) Old 05-16-2017, 07:25 PM
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It could be more yet if he is truing up the manifold port face as that will open the clearance.

What clearance do you have between the heads & manifold now (both sides the same gap).

Not sure what to calc atm, it's 1.am and i'm off to bed now.

Other notes which i couldn't recall say
Removed RTV off China walls & Inlet Manifold. Checked clearance at front only about 0.040 at front
- Should be about 0.060 - 0.120
presume i got that out of Mike's book also.

IE you need to measure the gap now with it sat on front of manifold. shim manifold on port faces twice that to give a clearance on the front edge
OTTOMH
Say it's sat on front & you measure it about 0.050 at the ports
shim it to 0.100 and measure the front gap, say 0.030
cutting 0.030 of the front face _should_ drop the manifold to sit flush on the ports although doing that then widens the base. \__/
plus any clearance you actually want at the front & rear. (I'd go as low as possible to keep the silicone thin)

which is reduced when cutting the port faces.
If it just needs a light skim to clean up the port faces you might be ok with that.

See what your machinist recommends.

Mitch

Terminal Crazy
'95 Z28 M6
Lancashire England
"just the odd mod."

Last edited by terminal_crazy; 05-16-2017 at 07:28 PM.
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post #19 of 34 (permalink) Old 05-16-2017, 08:35 PM
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This needs to be sticky'd. Its great information.

Quote:
Originally Posted by terminal_crazy View Post
From my notes gathered off the net

On the small block Chevy, the rule of thumb is, that for every
.005 in. removed from the head or block deck, a hair over .006 in. must be removed from the heads intake face (or the side of the intake manifold)
and between 0.008 and 0.009 in. removed from the end mating surfaces.
IIRC this is the same for the big block.


and my notes copied from
"How to Rebuild Small-Block Chevy LT-1/LT-4 Engines" by Mike Mavrigian.

"Whenever you remove material from the combustin deck surface of the heads, you obviously shorten the head,
which can affect the sealing surface angles between the intake manifold and the cylinder head.
If the resurfacing process removes up to a max. of about .019" you will likely be ok.
If you remove .020" or more from the combustion decks, corrective material removal
from the intake port deck and intake-to-block rails will be nesessary.
Here's a handy reference to use if you need to match the intake angles.


Consider the amount removed from the combustion deck and multiply this by a factor of 1.2
in order to obtain the amount that must be removed from either the intake manifold mating surface of the head
orfrom the intake port deck of the intake manifold.

So, if .010" is removed from the combustion deck, you need to remove .012"
from either the intake side of the head, or from the intake port deck of the manifold.

You also need to remove material from the front and rear rail surfaces of the intak manifold,
where they contact the block (since now the intake will sit to high to allow proper sealing at the port decks).
Based on the amount of material you removed from the cylinder head combustion decks, multiply this by a factor of 1.7
to abtain the amount of removal needed at the intake manifolds front and rear rails.
If you milled .010" from the heads combustion decks, you would need to remove .017" from the intake manifolds front and rear surfaces.

Combustion deck removal amount X 1.2 = Material to remove from intake port side.
Combustion deck removal amoutn X 1.7 = material to remove from intake manifold front and rear rails."
----------

SO.

HOW MUCH did they take off the heads.?
Was it a straight cut or angle milled........Are the two port faces still parallel on both heads with the manifold.
My guess is quite a bit. I had the block decked 0.030 (thirty thou) and the manifold still fitted pretty well (at the top)

IF the manifold is sat on the china walls (front and back) then the manifold needs trimming.
......... You __CAN__ cut this down with an angle grinder.
Don't try to do this in 1 cut... keep checking.
It's sealed with silicone anyway so the fit isn't that important.

IF the Port faces are NOT PARALLEL then you will possibly need to reface (angle cut the manifold) You could cut the heads but i wouldn't unless they HAVE been angle milled.

When the ends have been cut down and the port faces only are touching the heads, you can measure the clearance/taper (without gasgets) with some fat plumbers solder across the valley, across the port centrelines. (That's the bit you are interested in.) and bolt the manifold up to crush the solder. You can then measure these to visualise any taper front to back & top to bottom.

Felpro do (did) a guage for measuring the face angles on heads & manifolds. You probably don't need it as the solder method works much better.
I did find it useful to confirm the Edelbrock LT4 manifold angle was wrong but i'd already guessed that.
Fel-Pro Cylinder Head And Intake Manifold Angle Guage 2520 Small Block Chevy

Mitch

1995 LT1 Wagon. ERE 383
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post #20 of 34 (permalink) Old 05-17-2017, 07:17 PM Thread Starter
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Ordered the felpro "Printle" gaskets from summit. And called shop and asked them to "clean -up" the intake runnersides and do a .017 mill on the two short ends. I will bring home and test fit. It I still gap on the short ends, I will grind by hand slowly until I get it to sit flush? Am I fairly correct in this line of thinking?
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post #21 of 34 (permalink) Old 05-17-2017, 09:39 PM
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Quote:
Originally Posted by Adrien95Lt1 View Post
. I will bring home and test fit. It I still gap on the short ends, I will grind by hand slowly until I get it to sit flush? Am I fairly correct in this line of thinking?
....I would use a block and appropriate sand paper vs "grinder". Aluminum is pretty soft and you can sand it.

They say .010 off the bottom..so following the advice of Mike Mavrigian in his "How to.." should be right.

I have his book and find it extremely detailed

Given the heads are on the car the easier path is to mill the intake now on the port sides in addition to the front & back
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post #22 of 34 (permalink) Old 05-18-2017, 12:12 PM
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Did you read my post above (18)?


Yeah. I tried several different ways to do it.
Pillar drill, but the manifold top isn't parallel to the two ends and it was awkward to make a pass.
Tried it in the lathe X bed but couldn't mount it securely.

I would
grind a little off the front & back so its close enough to measure the port faces and see any discrepancies between them.
The china walls are not important so long as the manifold isn't sat on them.

Light polishes with a fresh 5" grinder and filed flat afterwards is fine.
Measure the surface/thickness in a few points so you can see what you are removing as you go.

Then get the shop to face it up.

Ideally there should be a slightly bigger gap (0.001 to 0.002) at the top of the ports than the bottom so the bolts pull it down & onto the head faces.
If the gap is bigger at the bottom IT WILL probably SUCK YOUR OIL OUT.


Mitch
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post #23 of 34 (permalink) Old 05-23-2017, 04:57 PM Thread Starter
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Ok, I'm done trying to attach photos. They always exceed quota by 78kb. Anyways.

Machine shop trued up the intake runner sides of the intake, but says he can't get it turned properly to mill the china wall ends. Pisses me off. So before I had an 1/8" gap, now it'll be more. So I will just grind the 2 China ends down on intake slowly. I have a distance of 6 1/16" between base of heads on each side front to rear. On the China wall ends. Not sure if that makes any sense. I also ordered the printle gaskets.
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post #24 of 34 (permalink) Old 05-23-2017, 09:08 PM
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Sounds like they only have a surfacer not a mill!

DO NOT CUT TO THAT WIDTH.
It _should_ be to be a perfect fit but as the manifold will be lifted by the gaskets and you might give it extra clearance on the china wall, the manifold could be wider.

When you dry fit it now, are the gaps even either side & end to end?
If you can draw a guide mark on the face ends of the manifold. Use this as a reference when cutting or measure the thickness before hand.

Just take your time, bit by bit , nice smooth passes and keep checking.
The more you cut you'll see the port/head gap reduce.

**** Don't forget to factor in the gasgets ****

You can sand/file the surface smoother when it all fits.

Good luck
Mitch

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'95 Z28 M6
Lancashire England
"just the odd mod."
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post #25 of 34 (permalink) Old 05-23-2017, 09:48 PM Thread Starter
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Won't have Intake back till tomorrow. I definitely plan on taking my time. I'm concerned that the bolt holes won't line up properly now also. Should I be concerned. Will I need to drill (elongate) the holes in the intake so it will seat properly?
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post #26 of 34 (permalink) Old 05-23-2017, 09:59 PM
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Quote:
Originally Posted by Adrien95Lt1 View Post
Won't have Intake back till tomorrow. I definitely plan on taking my time. I'm concerned that the bolt holes won't line up properly now also. Should I be concerned. Will I need to drill (elongate) the holes in the intake so it will seat properly?
you may find you need to elongate the holes after your test fitting

you are having fitment issues I have not and I have had heads done twice where each time material was taken off. Same intake manifold
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post #27 of 34 (permalink) Old 05-24-2017, 04:52 PM Thread Starter
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So I picked it up today. Before I do anything. I lined up the bolt holes, measured the gap on each side on the intake runner to the heads. I can get .031 feeler gauges in there. And it's still sitting on the front and rear China walls. Should I gently sand down the China walls, or leave em and assemble now that's it true everywhere?
I'm awaiting some input before I proceed this time. Lol.
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post #28 of 34 (permalink) Old 05-24-2017, 05:30 PM
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How thick are the gasgets?
Sit the manifold on the gasgets and see what the clearance is front and back.
You need to end up with a gap after you've tightened the manifold bolts up, so if it's sitting on the China wall it'll need some taking off.
When you've done that, test the bolt fitment for any binding.
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post #29 of 34 (permalink) Old 05-24-2017, 05:30 PM Thread Starter
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And using black rtv silicone, do I need to wait a full day before I fire the car up.
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post #30 of 34 (permalink) Old 05-24-2017, 05:31 PM Thread Starter
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Gaskets are 1/8"
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