Replacement Intake Manifold - Unfixable?

So... the intake manifold on my 305 is warped.

Any suggestions on replacements? None of the regular parts sites I use have replacement parts listed (nothing on rock auto...)
Here are the ones I have found, but I am really out of my depth on this...
I would really like to keep the rest of the stock parts and not spend a ton more cash on this.

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How did you arrive at this conclusion that the intake is warped?

Before you spend a lot of money, you can get a used one from the local pick and pull junk yard.

As phantom said, How did you determine it is warped? I have never heard of anyone having a warped intake manifold.

Well, my mechanic replace the gasket twice. Both times the amount of oil pouring out of the sides got worse as opposed to better. So we actually measured the manifold - it is warped beyond machining back to spec.

The heater control valve blowing apart on me last summer and several cut/ruptured coolant hoses in heavy traffic might have something to do with that...

I would prefer to avoid the pick-n-pull yards on this one to make sure I get a "good" part...

where did you measure the manifold??

never heard of this before,..especially on a small block chevy,.

Oil pouring out of the sides,...  not sure i understand,. if the gasket is not sealing at the sides the engine would have a vacuum leak,.and would run poorly,.

If the intake is leaking oil front and or back,. i would say your mechanic need to improve his rtv application skills,.

I have never seen an 'V' engine get hot enough to warp an intake to the point it will not seal,.aluminum or cast iron,.

IF, the engine has gotten that hot,. i would surmise you would have other more pressing problems,. i.e head gasket failures,. cracked head(s) etc,.

I personally think your mechanic is either telling you BS  or his skills are substandard, and he's telling you BS to cover up the fact,.

either way its BS,... IMHO

For what its worth,I had a 91-92 Roady with an intake that had continued seal problems. 2 mechanics,3 times.

The Edelbrock manifold for the TBI is the same as the OEM part.

If you are going to spend that kind of money, go to the junk yard and get a low mileage (135K max) LO5 and install it in place of the 305. You need the starter, computer, injectors, and ESC module, but other than that, it is a bolt in. The truck engine is the same, but the computer may be different. You might want to change the rear main seal while you are at it. BTW, if you get one from a 93 9C1. It will have a police cam and make 205 HP (you need the Y pipe for the 9C1 engine).

Since you have it apart, you should also get a set of engine compartment fuel lines from a 91-93 Fleetwood with a LO3/5, so you can check your fuel pressure.

Fred, that's the Edelbrock 2104?
Thank you.

Andebe - glad to hear I am not the only one

Phantom - Seeing I use this guy for everything, and he has never fed me any bull, I doubt it is an issue with his skill - multiple certifications and 15+ years experience.

Fred - I don't have the funds currently to do an engine swap - mainly as the labor would be too much to justify it, as I don't have the free time to DIY it.

Fred Kiehl wrote:

The truck engine is the same, but the computer may be different.

When we swapped my 92 RMW L05 into my son's 91 pickup, also with an L05, we discovered the RMW engine had roller lifters and the Sierra engine did not. My son reports that the engine has better torque and economy than the truck engine ever did.

I don't know if it's a 91 vs 92 thing or a truck vs RMW thing. But something to consider.

Car engines got the roller lifters, where as truck engines have flat tappet. You should be able to swap cam and lifters over (roller lifters are re-usable) if you go with a tbi truck engine.

You can use an LT1 cam in the LO5 as well. If you put it in the LO3, it might give it a little more pep as well. You could use an LO5 computer or a 9C1 computer with the LT1 cam and it should work on an LO3.

s1l1sc wrote:

Phantom - Seeing I use this guy for everything, and he has never fed me any bull, I doubt it is an issue with his skill - multiple certifications and 15+ years experience.

well after 40 years of wrenching everything from street cars to race cars to trucks to machines and boats,.  i know my way around motors,.
i,ve built them from 2cylinders to 12,..diesel and gas,.

my questions still stand,.  where/what was measured to come up with the diagnosis,.

kudo's to you putting your faith in one mechanic,. no matter what 2 other experienced 'wrenches' tell you,.

best of luck,..me personally i never put my eggs all in one basket,. whether its parts suppliers, specialty machining, or even the banks,..

no malice intended,. just trying to give you benefit of my years of experience,.mebbe save you a buck,.

and one further thing,.. certifications don't mean sh!t,. practical knowledge and talent is worth more,.
School smart folks are usually just that,..

everybody has a drivers license right? that makes us all certified drivers right? meh,..

i always get a 2nd opinion from doctors too,. all of them are certified right?

it usually costs me $60, to get an intake manifold cut on all four sides,.

you do what you want you're gonna anyway,

phantom, I appreciate the feedback, I know you are just trying to help, but let me elaborate...

I negotiate everything as a flat rate job with my mechanic. In this case that has been to my benefit - they do not see an extra cent from this issue.

They let me bring my own parts - mainly as I can source a lot of things cheaper online than they can through some of the local parts stores. They do charge high labor rates. Right around $100/hour. However, we discuss how long the job will take ahead of time - we all know that book rates might be 3 hours for something that can be done in 90 minutes or less by a skilled mechanic. Especially when you are addressing 2 or three related items.

They have already taken the manifold to a local machine shop that would have charged $50 to machine it back to spec - they concluded that it was warped beyond repair after measuring/analyzing it.

They will also install the replacement part at no extra charge once I get it. These guys really are very good about making things right and being honest. But they also gets a lot of business from me as well as all of the referral business I can send their way.

To give you some additional insight:
I run my own small business, selling various collectibles at fairs and events (weekends only). I use the wagon for that, as it will fit the 2x6ft metal display grids without issue.

The shop promised to have everything fixed and ready this past Friday - until they discovered that the manifold was warped they were on track to be done.

Since they could not finish the job they let me borrow their shop van (2014 Dodge Caravan Cargo) at no extra charge for two days, no questions asked. Most shops would not be willing to do that.

I really do trust these guys when it comes to my vehicles.

The saga continues - apparently the correct intake manifold for the 305 is discontinued (part number 10105141), is no longer in production and there is no aftermarket version.

The Edelbrock 2104 does not work (no egr).

The other 305 intake manifold I have (with egr) is not originally speced for the Roadmaster, so the distributor will not fit. The hole for the distributor is physically too small. And none of the 8 machine shops I have called in the local area are willing to touch the job of increasing that hole.

Is there a way to swap in a different distributor vs. what came stock? Since it is a 305 block I would imagine there are ones that will fit? Or am I missing something?

I have roughly $500 left in my budget to get this fixed (so no, a 350 swap is not in the budget), so if I can't get the wagon back up and running for that I will have to cut my losses and will part it out.

s1l1sc wrote:

The hole for the distributor is physically too small. And none of the 8 machine shops I have called in the local area are willing to touch the job of increasing that hole.

HUH? Did they say why? It's cast iron, right? It seems, in theory, like a fairly simple job: Mount it on the mill table nice and level, centre it under the spindle, and bore.

Hmmm. I wonder if I know any home machinists in your neck of the woods.

Between "we don't work on automotive parts", "We don't want the liability" and "I don't have a setup to do this" aka "too much work, doesn't pay enough" I am running out of ideas.

If you do know any I would appreciate it.

I asked on a home machinist forum that I belong to if there was anyone relatively local to you that would be interested in taking it on. I'll let you know if anyone responds.

One of the problems with manifolds can be the mating angle between head and manifold. It is  by far more common with aftermarket heads and stock manifold or vice versa though.

 There are two sizes of distributor heads. The trouble is trying to put the small distributor shaft into the small holed manifold while the manifold is still on the car. There is not enough  free angle to slip the shaft in.   The bottom of the wiper area gets in the way

You must put the dizzy into the manifold while it is off the engine, Then put them both on at time in one motion. Ofur handse to do so keeps the sealant from smearing all over everthing.

The issue I am running into is that my '91 came with the big shaft distributor, but they no longer make the matching manifold - or so I am told.
My research into that part number so far seems to confirm that.

At this point nothing would make me happier than someone proofing me wrong on that.

Or you could purchase a used manifold and be done with it already.

There are two on eBay right now for under $100.00 shipped...

JaySS wrote:

Or you could purchase a used manifold and be done with it already.

There are two on eBay right now for under $100.00 shipped...

Thank you - There were none that I could find a couple of days ago.

For future reference, in case someone else runs into this problem 2, 3, 10 years from now...
Is there an alternate fix aside from finding a good, used part or swapping engines?

Wow,is that one of those,"I missed the forest because of all the trees",kinda thing?

I had a couple of responses to my query on the machinist's forum. Unfortunately, nobody in your immediate area thus far. But everyone who did reply agrees it should be a fairly simple operation. Did you actually take the manifold to the shops, or just phone around? One fellow suggested that if the machinist could actually see the manifold, he might better understand what is required.

I mainly called around as I would need a day off from work to get there during their business hours.
Thankfully the used part that did become available worked and fixed the issue - but I worry about fixability going forward, especially as the wagon keeps getting older and used ones will become harder to find.

s1l1sc wrote:

I mainly called around as I would need a day off from work to get there during their business hours.
Thankfully the used part that did become available worked and fixed the issue - but I worry about fixability going forward, especially as the wagon keeps getting older and used ones will become harder to find.

I would still like to see where it is warped,.and unfixable,.

s1l1sc wrote:

I worry about fixability going forward, especially as the wagon keeps getting older and used ones will become harder to find.

An interesting question. I think a lot depends on how these cars come to be perceived by collectors. If they create a demand, it will be filled. I once read that there are more 1957 Chevy's registered now than GM actually built, because the aftermarket can supply virtually every part that went into them. Google "1957 Chevy parts" and look at the wealth of resources available.

My crystal ball is a bit cloudy. One one hand, there is an incipient project afoot for aftermarket floor pans. That's a good sign. We share much of the platform with the Impala/ Caprice, which is the focus of attention by the performance crowd and the spark under the aftermarket's tail fin (much like the 57 Chevy).

That said, even if the Impala/Caprice sedans attain similar cult status, the engine everyone focuses on will be the LT1. Nobody remembers the base "blue flame six"; "57 Chevy" evokes the 283. The "Corvette engine", first engine to make 1 hp per cu, subject of Nascar restrictions, etc. So it is less likely that unique hard parts your 5 litre will be available indefinitely.

The wagons are attracting some attention and interest, much like the '57 Nomad, but they are a niche within a niche, so whether there will be enough numbers and dollars to support the aftermarket remains to be seen. The 57 Chevy cult status was kept alive by hot rodders and didn't really become a collector's car until the mid-70's. We are already at or past that time frame. Is it too late? Were too many sent to China in the "Cash for Clunkers" debacle? The 57 Chev was a popular car in the 60's demolition derby circuit, but at least the frames and serial numbers survived in junkyards thereafter, awaiting discovery and restoration.

I hope these cars do attract the aftermarket suppliers. I love mine and would like to keep it forever. But it will take the interest of the monied class to achieve that. People like us, who have to worry about taking time off work, probably won't.

Maybe we should get the ball rolling: we all kick in a few bucks and send a rebuildable one to Jay Leno?

phantom 309 wrote:

I would still like to see where it is warped,.and unfixable,.

Well, just sitting on top of the engine block there is a good 1/4 inch gap on one end when the other side sits flush. I'd send you the part, but it has been sent to the scrapper at this point. I am honestly surprised it ran this long, seeing how bad it was after it got pulled. I was adding roughly 1QT of oil per 1,000 miles driven before the part was replaced.

That sounds like all it needed was a remove and reseal with fresh gaskets and silicone on the ends. An ultra common leak point on LT1s.

jayoldschool wrote:

That sounds like all it needed was a remove and reseal with fresh gaskets and silicone on the ends.

To seal a 1/8" gap at each end? That there is some thick gasket material you're using.

s1l1sc stated early on that his mechanic changed the gaskets twice. I think he's found the best option.

jayoldschool wrote:

That sounds like all it needed was a remove and reseal with fresh gaskets and silicone on the ends.  An ultra common leak point on LT1s.

It is a 1991 - has the 305, not the 350 or LT1

Sorry, replace "LT1 with "chevrolet V8s"

True though.

If it had been an LT1 engine it would not have been an issue - lots of aftermarket parts for those.

It is the '91-'93 model generation that apparently has no aftermarket support - at least as far as I can tell the stock intake manifold design was specific to those years and no longer has a replacement.

You can use a regular small block intake just fine, you just have to install the intake and distributor together.

Guest wrote:

You can use a regular small block intake just fine, you just have to install the intake and distributor together.

That is incorrect, as the distributor is of a different design compared to the regular small block... see here:
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They can be drilled out to make work.

buickwagon wrote:

jayoldschool wrote:

That sounds like all it needed was a remove and reseal with fresh gaskets and silicone on the ends.

To seal a 1/8" gap at each end? That there is some thick gasket material you're using.

s1l1sc stated early on that his mechanic changed the gaskets twice. I think he's found the best option.

Have you ever resealed a small block chevy intake? lately?

allowing for internet bullsh!t,. the gap at the back of the intake is oft times .125 or better before the intake is torqued down,. .125 looks like .250 to some folks,..

I use a a product called RTV sealer,. pretty common,. works everytime if you do it right,..comes in different colors,.

YRMV,..

So I still don't believe the manifold was warped,..INMO,...

YRMV...Your Roadmaster may very? RESULTS! Got it,not enough caffeine yet...

phantom 309 wrote:

Have you ever resealed a small block chevy intake?  lately?

Why no: I prefer to mill them flat and true so I don't have to keep resealing them.

GM specifies max 3mm in 200mm. That's about 1/10" in 7" (roughly). If the OP's was warped 1/4" in that distance, then it was out of spec. There is no basis to assume he has erred in that measurement. We have no basis to assume the mechanic was unskilled in his trade. The mechanic tried RTV twice, and failed twice. So he replaced the manifold and all is well. QED.

buickwagon wrote:

phantom 309 wrote:

Have you ever resealed a small block chevy intake?  lately?

Why no: I prefer to mill them flat and true so I don't have to keep resealing them.

Mill what flat?  please explain,..?  

After i have resealed a factory engine's intake manifolds' front and rear rails,.,. or once anyone has resealed a factory engine's front and rear rails,.,.  the problem is usually cured,..

The reason i believe and stand behind  all i have said in this thread,. is because,. if a gen 1 small block chevy is not leaking coolant either externally or internally,. and the engine does not have a vacuum leak,.internally or externally,.and is not ingesting oil into one port ,.
then the only problem to overcome is to put a barrier of RTV sealant to stop the splash oil from the camshaft from leaking out at the front or rear rails,..and the OP's manifold is not warped inmo,. because if it were it would develop either a coolant or a vacuum leak as i have explained,.,.

As for your introduction of GM specs,.

the intake manifold is a lot longer than 7" and 7" in which direction,. across which plane,.

And you have no basis for introducing that spec without basis for where the measurements were taken,.

The intake manifold does not sit flush on the front and rear rails,..

I,ve said enough,. its my opinion,. based on years of trial and error with countless engines,

Perhaps you should read the GM manual regarding applying the RTV sealant,.you go ahead and mill all you want flat,.

I await your technical in depth (as usual) explanation,. lol

Mic drop...Who says the tech conversations are boring?

phantom 309 wrote:

the intake manifold is a lot longer than 7" and 7" in which direction,. across which plane,

The measurement is a rate. It is measured at the gasket sealing surfaces across any two adjacent intake runner port openings.

My comment about milling was a bit tongue-in-cheek. (hence the smiley). There is a hard limit to how much can be milled off the intake port surface of a V8 manifold before the bolt holes won't line up any more and you have to mill the head plus the ends too. The specifics vary by the angle of the "V". On a small block Chev the angles typically work out to 5 thou off the head, 6 thou off the intake ports and 8 thou off the ends. Too much of that and it becomes a high compression interference engine. Plus you might need to shim the distributor body up off the manifold. It's worth it if you are building a race engine, but a bit over the top to fix a 5L daily driver.

RTV is great stuff. I have a variety of high temp, O2 sensor safe, etc. in addition to the versatile blue Smurf snot. But it can't cure everything, and the thicker the layer the weaker it gets. The fact remains that he tried RTV twice and it failed twice. Metal can be funny stuff -- especially castings. It might be curled up just at one end, allowing it to seal at the intake runners but leaving an excessive gap at the end. Metal will warp as part of the machining process -- removing metal changes the resistance to internal stresses, and the metal moves.

It may not even be the warp at fault. The casting could be porous or cracked near the end as a result of the overheating and/or internal stresses, appearing to leak from the joint.

The definition of insanity is doing the same thing over and over, expecting different results. He moved on to a replacement manifold, and that worked for him. Hurrah! The longroof lives to ride another day!