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Warped intake manifold

General engine tech -- Drag Racing to Circle Track

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travis
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Warped intake manifold

Post by travis » Tue Nov 05, 2019 12:50 am

I’ve got an edelbrock 2181 intake (351w non-EGR performer) that I bought used some 10-12 years ago. It was Jet-Hot coated by the PO but never used. I’ve used it on several engines over the years, but at some point the manifold twisted a bit and would not seal no matter what gaskets was used. I set it aside for a few years but now want to see if it is repairable. It’s not sealing on the front 2 cylinders on one side and the rear 2 cylinders on the other.

Has anybody had any success trying to straighten something like this out??

The block and heads are milled .020” each. How much needs to be taken off the intake or intake side of the heads?

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Re: Warped intake manifold

Post by ProPower engines » Tue Nov 05, 2019 1:15 am

Sound like you need to mill both side flat to start and check fit.
351 W intakes are a PITA at the best of time to get port alignment right. If you are just worried about it running
thats the easiest way to go as but if you have aluminum heads as well then they both may need attention.
Have you put a straight edge on each side to confirm how straight the flanges are yet???

That said how about the heads?? Are they straight as well??

Do you have another straight intake to test fit and check the alignment on the engine??
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Re: Warped intake manifold

Post by travis » Tue Nov 05, 2019 1:55 am

ProPower engines wrote:
Tue Nov 05, 2019 1:15 am
Sound like you need to mill both side flat to start and check fit.
351 W intakes are a PITA at the best of time to get port alignment right. If you are just worried about it running
thats the easiest way to go as but if you have aluminum heads as well then they both may need attention.
Have you put a straight edge on each side to confirm how straight the flanges are yet???

That said how about the heads?? Are they straight as well??

Do you have another straight intake to test fit and check the alignment on the engine??
This intake has only been used on OEM iron heads. The engine I’m putting together has only had the factory iron 4bbl intake on it. The intake face of the heads is straight but really could use a light cleanup cut due to some corrosion around the water ports.

I’ve got the factory iron 4bbl Holley pattern intake, I may just reuse it if the 2181 is going to be too much trouble. This is a very budget (but properly done) build that will maybe make 300hp.

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Re: Warped intake manifold

Post by PackardV8 » Tue Nov 05, 2019 10:49 am

The block and heads are milled .020” each. How much needs to be taken off the intake or intake side of the heads?
Whatever the math, just removing that amount from a warped intake won't correct warpage. Trying to "straighten" a maybe warped intake is akin to that black cat in the dark room which may not be there. It's not easy, not fun and not guaranteed.

Anyone who's ever milled heads or square-decked blocks is thinking, "what's that .015" coming off that corner and nothing off the opposite corner going to do to the intake alignment?"

An example, but during a custom Packard V8 engine swap mockup, the high-dollar stainless steel Y-pipe single exhaust fit perfectly on a junkyard core. We square-decked a block, surfaced the block and intake sides of the heads, surfaced the exhaust manifolds. Everything was shiny, square and the exhaust Y-pipe was no longer even close to fitting between the exhaust flanges. It had to be cut and welded to widen enough to fit.

Back to how to straighten your intake - does anyone else do it this way? We bolt the carb pad down to the head cradle of the surfacer, level it horizontal and with both flanges up, put a dial indicator off the surfacer head and run it over the length of each side of the manifold. It'is necessary find reference points and keep the manifold centered longitudinally. Choosing the reference point is not an exact science but once it's in line, obviously the low corners can't be cut higher, so the high corners have to be cut lower.

What other manifold milling tips can you share with OP and the forum?
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Re: Warped intake manifold

Post by PackardV8 » Tue Nov 05, 2019 10:51 am

The block and heads are milled .020” each. How much needs to be taken off the intake or intake side of the heads?
Whatever the math, just removing that amount from a warped intake won't correct warpage. Trying to "straighten" a maybe warped intake is akin to that black cat in the dark room which may not be there. It's not easy, not fun and not guaranteed.

Anyone who's ever milled heads or square-decked blocks is thinking, "what's that .015" coming off that corner and nothing off the opposite corner going to do to the intake alignment?"

An example, but during a custom Packard V8 engine swap mockup, the high-dollar stainless steel Y-pipe single exhaust fit perfectly on a junkyard core. We square-decked a block, surfaced the block and intake sides of the heads, surfaced the exhaust manifolds. Everything was shiny, square and the exhaust Y-pipe was no longer even close to fitting between the exhaust flanges. It had to be cut and welded to widen enough to fit.

Back to how to straighten your intake - does anyone else do it this way? We bolt the carb pad down to the head cradle of the surfacer, level it horizontal and with both flanges up, put a dial indicator off the surfacer head and run it over the length of each side of the manifold. It'is necessary find reference points and keep the manifold centered longitudinally. Choosing the reference point is not an exact science but once it's in line, obviously the low corners can't be cut higher, so the high corners have to be cut lower.

What other manifold milling tips can you share with OP and the forum?
Jack Vines
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Re: Warped intake manifold

Post by ProPower engines » Tue Nov 05, 2019 2:01 pm

How much difference between each ends deck to main center is there??
I have seen blocks that are off line in both directions meaning cocked to each end but in opposite directions.
Also what year of block do you have?? Some are taller then others making the error worse if the decks are not straight.

It sounds like the decks of the block or heads are slanted in opposite directions making the fit harder to do.

I have a 400M in here at the moment thats like that and after fixing the block I have to do the heads to get the intake to fit
on the ends again.
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Re: Warped intake manifold

Post by travis » Tue Nov 05, 2019 4:57 pm

The engine that killed the intake was a Jasper stock replacement reman engine that came in my ‘83 F-150. It’s been a few years, but I think it was a ‘80 casting block and heads (E0xx casting numbers). This one I am putting together is an ‘85 casting.

I kind of figured that this manifold was junk. I guess I will make a sizable contribution to my scrap aluminum pile. At this point it sounds like a $100-$125 gamble plus gaskets to try to salvage this thing.

Thanks for the help!

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Re: Warped intake manifold

Post by cjperformance » Tue Nov 05, 2019 5:54 pm

PackardV8 wrote:
Tue Nov 05, 2019 10:51 am
The block and heads are milled .020” each. How much needs to be taken off the intake or intake side of the heads?
Whatever the math, just removing that amount from a warped intake won't correct warpage. Trying to "straighten" a maybe warped intake is akin to that black cat in the dark room which may not be there. It's not easy, not fun and not guaranteed.

Anyone who's ever milled heads or square-decked blocks is thinking, "what's that .015" coming off that corner and nothing off the opposite corner going to do to the intake alignment?"

An example, but during a custom Packard V8 engine swap mockup, the high-dollar stainless steel Y-pipe single exhaust fit perfectly on a junkyard core. We square-decked a block, surfaced the block and intake sides of the heads, surfaced the exhaust manifolds. Everything was shiny, square and the exhaust Y-pipe was no longer even close to fitting between the exhaust flanges. It had to be cut and welded to widen enough to fit.

Back to how to straighten your intake - does anyone else do it this way? We bolt the carb pad down to the head cradle of the surfacer, level it horizontal and with both flanges up, put a dial indicator off the surfacer head and run it over the length of each side of the manifold. It'is necessary find reference points and keep the manifold centered longitudinally. Choosing the reference point is not an exact science but once it's in line, obviously the low corners can't be cut higher, so the high corners have to be cut lower.

What other manifold milling tips can you share with OP and the forum?
If you "know" that your engine is all true and straight my easiest way to reference high/low areas is to simply sit the intake on the engine with no gaskets, if you cant see port alignment mark up some ref points on the manifold and head faces to measure port alignment(allow for using no gasket). Find low areas on the intake face, typically you can see an end or a center area that is not contacting the head face, measure the 'gap' at the low spot, set the intake up in the mill and align to duplicate the low spot V contact areas, then decide wether to simply cut, at correct angles for your given engine, till the intake face is clean/straight OR 'just' clean up the faces till the low spots still show a witness then re check the intake on the engine for port alignment etc, find a gasket thickness that will allow for the machining, then work out if the intake then just needs a clean up pass OR something extra removed to allow good alignment with an available gasket.
I have saved a few rare intakes doing this, tedious yes but if its not a common cheap intake or is simply no longer available it sometimes must be saved. In 2 cases both alloy Cleveland Buddy Bar intakes , both warped after having been used with cheap thick gaskets and overtightened, i have had a shim laser cut to correct what i milled off, which will then allow the factory steel intake tray to be used, using 2 small pins to align the shim against the intake and stuck the shim to the intake with a " very thin smear" of Ultra Black at the time of fitting the intake.
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Re: Warped intake manifold

Post by Tuner » Tue Nov 05, 2019 8:13 pm

travis wrote:
Tue Nov 05, 2019 1:55 am
ProPower engines wrote:
Tue Nov 05, 2019 1:15 am
Sound like you need to mill both side flat to start and check fit.
351 W intakes are a PITA at the best of time to get port alignment right. If you are just worried about it running
thats the easiest way to go as but if you have aluminum heads as well then they both may need attention.
Have you put a straight edge on each side to confirm how straight the flanges are yet???

That said how about the heads?? Are they straight as well??

Do you have another straight intake to test fit and check the alignment on the engine??
This intake has only been used on OEM iron heads. The engine I’m putting together has only had the factory iron 4bbl intake on it. The intake face of the heads is straight but really could use a light cleanup cut due to some corrosion around the water ports.

I’ve got the factory iron 4bbl Holley pattern intake, I may just reuse it if the 2181 is going to be too much trouble. This is a very budget (but properly done) build that will maybe make 300hp.
When those 351w engines were new some dyno games were played with manifolds and cams and headers on the dyno at Isky (as I recollect) and reported in HRM (again, a.i.r.) and the stock iron intake was the best of the ones available in '69-'70. Why would anybody think FoMoCo would have a clue about designing an intake manifold for their own engine? I was working in a speed shop at the time and had already sold some of every sort, Edelbrock, Weiand, Offy, etc. and had some 'splainin' to do #-o let me tell you whippersnappers. I don't know if that is the case today with some fancy new thing, but things are more like they are now than they ever have been. :roll: jus'say'n

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Re: Warped intake manifold

Post by GARY C » Tue Nov 05, 2019 10:51 pm

travis wrote:
Tue Nov 05, 2019 4:57 pm
The engine that killed the intake was a Jasper stock replacement reman engine that came in my ‘83 F-150. It’s been a few years, but I think it was a ‘80 casting block and heads (E0xx casting numbers). This one I am putting together is an ‘85 casting.

I kind of figured that this manifold was junk. I guess I will make a sizable contribution to my scrap aluminum pile. At this point it sounds like a $100-$125 gamble plus gaskets to try to salvage this thing.

Thanks for the help!
You just need a belt sander, a straight edge, time and patience.
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Re: Warped intake manifold

Post by PackardV8 » Wed Nov 06, 2019 12:00 pm

GARY C wrote:
Tue Nov 05, 2019 10:51 pm
You just need a belt sander, a straight edge, time and patience.
Going to have to agree to disagree on this one. We hate doing intake manifolds on the surfacer, so nothing would make us happier than folks fixing them at home, if a fix were generally the result of their effort. However, we've had to try to save so many blocks, heads, intake and exhaust manifolds after someone has been at them with a belt sander, disc sander, Scotchbrite sander, et al. After set-up and machining, we were finding some unsalvageable and the customer didn't feel he should have to pay for the effort. Now, if we see the tell-tales, if we are forced to take it on, pay for machine time in advance. That alone has saved some grief and sends them searching for another piece which hasn't been molested.
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Re: Warped intake manifold

Post by turbo camino » Wed Nov 06, 2019 1:22 pm

Can you try re-warping it back to straight? Bolt it down to one head, with gasket, use strategically placed bolts and shims at the other head to twist it around and see if it'll take a set where you want it. Leaving the one side without gasket will make it easy to see where/how much it's out of alignment.
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Re: Warped intake manifold

Post by turbo camino » Wed Nov 06, 2019 1:34 pm

Back in the day I sent a nice virgin 4-bolt SBC block to a respected, experienced (so I thought) local shop to be prepped. Bore, hone, cut decks by the amount I'd specified. 'No problem', I thought, this shop did lots of race engines for the dirt track boyz, since back before I was born.

A few days later the shop called, said the bore/hone came out fine but they found a major problem when they went to cut the decks and I needed to stop in and see what they'd found. I walked in and saw my block... sitting with one deck down, on the freaking belt sander. Guy showed me how they had cut and cut and cut all the way down into the upper water pump bolt hole and STILL couldn't get it to clean up at the outside edge. I wonder why??
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Re: Warped intake manifold

Post by travis » Wed Nov 06, 2019 3:58 pm

GARY C wrote:
Tue Nov 05, 2019 10:51 pm

You just need a belt sander, a straight edge, time and patience.
I have all the listed items except for patience. It’s like I tell my boss...I have 5 kids, there is no patience left for anything else :lol:

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Re: Warped intake manifold

Post by travis » Wed Nov 06, 2019 4:03 pm

turbo camino wrote:
Wed Nov 06, 2019 1:22 pm
Can you try re-warping it back to straight? Bolt it down to one head, with gasket, use strategically placed bolts and shims at the other head to twist it around and see if it'll take a set where you want it. Leaving the one side without gasket will make it easy to see where/how much it's out of alignment.
I tried that...set it up on another engine and left it bolted together for several weeks. When I removed the bolts, the gaps came right back. I suspect that idea could work if you could heat everything up a bit. Unfortunately I think a 351w with heads exceeds the load rating on my oven...plus trying to explain that to the wife :lol:

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