muffler and manifold leak advice

[tiinytina]

ok... so today on drive home... engine started acting up, surging etc. Felt like wind was buffeting us full force as I lost and gained poweer... then KABLAM.... thought we had blown a tire but had in fact giant backfire and blown a hole through the seam in the passenger side muffler...

More engine issues and the cause was that the wires to the ignitian module on the distributor cap, power harness had become loose causing cylinder misfire etc... so thats all clipped back into place and engine doesn't seem worse for wear.

To add to this we know we have either manifold leak, or gasket needed also on passenger side. Odor of exhaust is fairly strong while stopped if front windows are open.

So.. the question becomes... Should we invest in an entire Banks system for our 454 (1987) 7.4BBL or just replace the muffler and gaskets and or manifold? The Banks system at about $1200 may or may not increase mileage (currently 7.4 avg) but even 1 more mpg... would be nice...

I've found stock replacement manifolds for not too much, and will have to see if our engine has or doesn't have gaskets and or if the manifolds just need replacement.  I haven't shopped for muffler yet.

Have mechanic and elbow grease.... and may patch the muffler for now... so we can get Gone until we have down time...

Advice?

Tina

[DaveVA78Chieftain]

Tina,
From what I have read most people who have installed the Banks system were happy with the increased power (torque) but only got about 1 mpg improvement.  This is sort of one of those personal choices.  Depends on how much $ you want to invest.

Dave

[tiinytina]

Dave,
   yea.. on the P30 Yahoo forum all have suggested no Banks but to upgrade mufflers to Magna flows. for the manifolds some have suggested Thorley headers?  Lots say original manifolds are bad to begin with, some say remachining the old ones and reinstalling using a racing class gasket...
   1 mpg would extend a tank by almost 100 miles for us.. but maybe better manifolds and the 100% flo mufflers might do the same thing?

tina

[DaveVA78Chieftain]

Tina,
Let me start off by saying I am an avid DIY person.  Therefore, I would never put out $1900 for a full up banks system then adding the price of an extension kit on top of that.  On my 440-3 I am using the stock exhaust manifolds but I converted to 2 1/4" dual pipes all the way back (rear bumper) with a crossover before the Cherry bomb Turbo mufflers.  For now at least, I personally do not see what is gained by the over priced magnaflows.  My Turbo's are just fine with the only issue is that I have to go back and add heat shielding (vaporlock issues).  I also installed an aftermarket widband A/F meter and monitor both intake and ported distributor vacuum (high distributor vacuum = higher gas milage).  I wanted to know what was going on.  I will say I would not recommend Glowshift 7 color gauges at this point.  I am not able to see them easily in the daylight.

For your 454, you need to know if you have 1, 2 or no AIR pump(s).

Banks system is either 1 (96340) AIR or 2 (96341AIR) pumps.  You do not have EFI.
http://www.bankspower.com/products/show/128/67

There are smaller Banks kits which do not include everything but still start at $900.
http://shop.ebay.com/i.html?_trkparms=65%253A12%257C66%253A4%257C39%253A1%257C72%253A4726&rt=nc&_nkw=454+motorhome+headers&_dmpt=Motors_Car_Truck_Parts_Accessories&_sticky=1&_trksid=p3286.c0.m14&_sop=15&_sc=1

If you want to stick with standard exhaust manifolds, then there are plenty out there:
http://www.stevensparts.com/CHEV%20EXHAUST%20MANIFOLDS.htm#396-427-454
http://motors.shop.ebay.com/i.html?_nkw=454+exhaust+manifold&_sacat=&_dmpt=Motors_Car_Truck_Parts_Accessories&_odkw=454+headers&_osacat=0&bkBtn=&_trksid=p4506.m270.l1313
For my passenger side I purchased an off brand manifold made in China.  Only problem I have with it is the #$%&@ AIR blanking plate.  It does not want to stay sealed. Stupid design in that it only has one bolt.  grrrrr  Most new stock replacement manifolds will be from either China or Korea.

As far as headers.  They come in a multitude of flavors.  Hedman, Doug Thorly, and Banks.
http://shop.ebay.com/i.html?_trkparms=65%253A12%257C66%253A4%257C39%253A1%257C72%253A4726&rt=nc&_nkw=454+motorhome+headers&_dmpt=Motors_Car_Truck_Parts_Accessories&_sticky=1&_trksid=p3286.c0.m14&_sop=15&_sc=1
You may hear of the Doug Thorly Tri-Y which are shorty headers like used on a classic hot rod.  Being short, they would reduce heat signiture.  Headers bring heat issues as well as service life.  You want thick wall and thick flange headers to prevent early burnout as well as reduce flange warpage.   They are bit more pricey.  Coated headers lower heat radiation.   If available you want ball socket collectors (no collector flange gasket and allows soms alignment flexing).

You want to stay with 2 1/4" pipes and use a crossover pipe (either "X" or "H").  They provide a scavenging effect that helps keep the system balanced.

I built my own system using 10 foot 2 1/4" bulk pipe, plus 45 and 90 deg bends.  I now have a MIG welder so I can weld my own system. Stock Dodge was single exhaust so I converted to dual.  I did use a 2 1/4" flex sections near the engine to reduce vibration and flexing back to the stock manifolds.  I found in the past that the weight of the exhaust system results in the failure of the manifold flange gaskets.  Even Dodge added a brace near the passenger side header due to this.  You will also see this commented about in header installation instructions.  I still have to add bracing up near the manifolds to prevent that flexing.  Make sure exhaust pipe routing is clear of tanks, wiring and hoses.  A tail pipe does get hot enough to melt through a black tank or even a sewer valve assembly (I know from experience).

The additional heat genertaed in the piping is resulting in vaporlock issues for me.  I will solve that in the next couple of weeks (shielding and proper electric pump placement).  Your 86/87 GM chassis already has an in-tank electric fuel pump and routes the fuel line outboard the frame rail so that should not be a problem for you.  My understanding is that there are heat shields in the engine area though.  Make sure you retain these.

You can modify your existing air intake using home AC vents such that it provides 2 ram fresh air ports ( 3" or 4" hoses; Poor man's banks system).  Route hoses to front of grill for fresh air intake.  The Banks system increases the height of the air cleaner and installs a larger low resistance air filter.  Not sure if you have clearance under the dog house for that or not.

Which way to go is a matter of just how much effort you want to put into it vs cost.   For me cost is the driver, others is having a turn key system.

Dave

[tiinytina]

Dave thanks! 
     Current stock system on our Tiffin has 2 1/4" heat shielded pipes nose to tail, dual exhaust nose to tail.  Those pipes are all still perfect condition so "if it ain't broke don't fix it"...  I checked on the thorly site and they don't even make headers for our engine... so if anything going to go with standard manifolds if we need to replace them...
    I believe we have 1 AIR pump as the passenger side manifold has bellow insert, and one shielded end pumping heat air to snorkel.  Snorkel already has ram air to front of rig to the passenger side of radiator. 5" pipe. There is literally no room to put in a second one.
    I poked around the passenger side manifold yesterday while measuring mufflers and pipes but need to get under there with a strong flashlight to look for cracks (didn't see in daylight)... may just be warped and needs new gaskets etc... but that I"ll leave up to a more thorough inspection. I didn't have time to poke into drivers side.
    Mufflers are welded in place as part of pipe so will need to have mechanic or shop for muffler replacement....may see if Pat wants to attempt it wedged under the rig... mufflers are mid-ship between front and back of rig so no shielding on them, just on pipes.
    Engine has a edelbrock quadrajet, new in 2006 after we purchased Gone.
Tina

[DaveVA78Chieftain]

Tina,
The best tool for finding exhaust leaks is a 2-3 ft section of garden hose used as a stethoscope.  Place one end to your ear and move it around looking for the point where the leak is at.  You can get into tight places with it.  Remember though it is rubber and will melt if you touch the manifold or pipe.  Keep it 1/2" or so away from pipe/manifold.  This devices saves a lot of burnt fingers when trying to feel the pulsing air leak.  Also, you normally cannot "see" where a leak is.  You have to feel for the leak or use a sethoscope.  Additionally, the sethoscope gets you in the right spot so you can look more closely.

Single cylinder leak (head to manifold) has a steady put put put sound to it like a missing cyinder.
Down stream leak has a faster pulse to it.

Hopefully the blown muffler noise will not impeded your search so that you can locate this easily.

Headers
http://www.jegs.com/webapp/wcs/stores/servlet/MkMdlYrSearchCmd?Ne=1+2+3+13+1147708+1147708&searchType=MkMdlYrSearch&langId=-1&storeId=10001&N=1547597%204294965578&catalogId=10002&Nty=0&itemPerPage=90
Note: That link shows both Class A and Class C configurations.  You will have to filter through them.

Your AIR pump is going to be a hassel.  Most headers are mfg'd for competion use.  Hedman only made the AIR version for small blocks.  Your only choice may be to use Banks headers, stay with stock manifolds, or, if you can get through inspection with out all smog devices in MD, remove the AIR setup.  I know you live close to DC area so removal may not be an option due to emissions testing.   I live far enough away from DC such that I do not have annual emissions testing.

Good luck,
Dave

[tiinytina]

thanks! will use the hose technique this weekend when I have more time to hunt.  I had tried previously to "listen" but there is little space to do so even for someone with my "tiny" size... and once she is cranked up the whole kit and kaboodle is just noisy... I can feel the leak(s)... just can't tell where they are coming from at this point.... and thats on the passenger side... the drivers side is way tighter to get in to...

Gone is "Excepted" to MD emission testing... can't fit into testing facilities and too old etc... so AIR system may go away.. The EGR valve is bad anyway... so already talking to my mechanic(s) about removing emissions stuffs.

Think I will stick to standard/stock manifolds if indeed leak is due to warping, or maybe Banks if can get just the manifolds (and can just slide them in with no mods to pipes). 

if gaskets are bad I'm going to use silicone racing grade replacements.

I called MagnaFlow today for tech help. Current mufflers are 20" x 7" round, center in and out 2.25"... so there is room to put in larger ovals with more sound dampening, vs round flow through...  next discussion with my mechanic.... then again I love the sound of our 454.... rumbling.... 
Tina

[jbmhotmail]

Tina,
What worked for me when I replaced the drivers side exhaust manifold on my 1985 454 was this. (Engine not running) I took my old tank-type vacuum cleaner, installing the hose on the exhaust end of vacuum cleaner, then I stuck the vacuum cleaner hose into the exhaust pipe (I have duals and at that time I did not have a crossover pipe) and sealed it with duct tape, I then got my spray bottle with liquid dish washing soap and sprayed the manifold really good, turned on the vacuum cleaner and was able to see where the cracks were. I purchased a new stock manifold from a surplus outfit on the internet and with shipping I think it ran about $75.00, a new exhaust manifold gasket, new exhaust pipe donut and new stainless steel bolts and I was ready to go. I used Never Seize and a torque wrench. Also be sure to make the cuts on the new manifold between the mounting stud holes (ref Chevy Motorhome Chassis Guide?). I can find it if you do not understand what I am trying to say (about the cuts).
Good Luck

[DaveVA78Chieftain]

Tina,
Sounds like you are formulating a plan of action even though there are many options.  If you go with stock manifold, then, from what I have read, the stress relief cuts to the stock manifold JBM recommended would also be a good idea.

Dave

[tiinytina]

Nothing in concrete, except mufflers, until me and my mechanic crawl into her engine compartment Saturday morning before it turns into an oven...  For the Mufflers going with Magnaflows 7" round, 20" long, 2.25 straight throughs.  If we have to remove the manifolds will go with stock replacements but will remove the AIR system.  Decided against headers since from 3 forums more bother than worth increases in MPG.  then again on one forum I've been offered Headman shorties for $100 pair - used 35 miles...  Depends what we find Saturday morning.... I'm sort of praying its just a gasket where manifold meets pipe but I'll be bringing my garden hose.
Tina

[tiinytina]

And the results are in... Magnaflow mufflers ordered...  With a high power light we crawled around the cold and warming engine and... both manifolds have large cracks right in the "Bellows" section between manifold and engine.... soooo... After much discussion with mechanic and online research.. we bit the bullet and are going to put on BANKS torque tubes (they don't call them headers... i??)... The only replacements for "manifolds" seemed to be cast iron which have known issues on this engine with warping, no Dual/Air stainless with bellows are avail with lots of internet searches....

We will remove the AIR system and emissions stuff as we go....

PT blaster will be applied daily to manifold bolts until we start working on her.. luckily mother nature turned the oven off here in MD...

we will take pix as we go and will put a how to manual together....
Tina

[tiinytina]

Magna flows arrived today.... passenger side manifold removed, AIR system on passenger side removed, AIR on driver side disconnected.  New, smaller, belts in place...  There is some much room in there now!

Tina

[JDxeper]

Get Gone Going Y!

[tiinytina]

My wonderful friend called me.. I answered.. and all I could hear was bluda bluda bluda.... ahhhh... Gone now has a deep bass rumble... put her in drive and she crawls forward without pressing the gas at all... the Banks system looks like a sculpture! Was top notch to mount etc... mechanic was impressed with quality.   don't know yet what mileage is as no reasonable gas within home trek... but power to spare on hills, lots under pedal on flat at 60... WOW!!!    so yes if you have a 454 7.4L BBL... remove Dual AIR, Go Banks, Magna flow mufflers... and Zoom! 

Tina

[DaveVA78Chieftain]

It official

We now have our one and only

HOT

ROD

TINA

[JDxeper]

A drag strip test??? Hm?

[tiinytina]

ok cost totals....
BANKS for a 1987 7.4L BBL 454 just the torque tubes and all assembly parts including shipping.. was $1300 (guaranteed for life, stainless)
Magnaflow 2.25" dual offset 20.5" mufflers 2 - $130
Tune up parts:- wires, plugs, cap, starter shielding, battery cable redo (made longer), new belts, 2 8' sections of custom bent 2.25" exhaust pipe (no labor), all exhaust connections, new chassis battery, 2 exhaust heat valves... $435

Paying mechanic in lasagna, rockfish, and dog biscuits, a lifetime of friendship  and I will be landscaping his house.. and yes actually paid him a bit.  His total hours were probably 15+ helper friend 6+ would have been 5 less but one manifold bolt took 5 hrs to remove... professional mechanic with all tools...

DUAL AIR system was completely removed on passenger side, driver side pipes etc removed and air pump no longer in belt loop but not removed because of accessibility.

Going at speed up hills... AWESOME...  having RV that sounds like a Harley... Yehaw!...  Peddle not going to floor to maintain 55.. should = better mileage... haven't calculated on fuel load yet...  7.4MPG was average last year... 5.4 last tank... if we get 10 I will be in awe.....  Will post  it when we know as this next fill will include 250 miles of before repair....

Tina

[Oz]

It's been a long haul to get Gone where it is but, it looks like you're finally going to get to really enjoy the driving part of RV ownership! 

Go TINA... you ROCK!

[Froggy1936]

Welcome to the Vrooomm  Vrooomm club The exaust noise when pulling out makes ya feel like your lifting the frt wheels off the ground. And you can also pull out without attracting any attention if you want to  Frank

[Vince]

I was using degreaser on my Allegro with 454 with the engine cold but running. When rinsing I could see small bubbles coming from passenger side exhaust manifold where it is bolted to engine . My question is should I try to tighten with engine hot . Or is it not worth messing with and what size bolt is it . Some of my 9/16 are not tight enough one is .I don't what to do ?

[Froggy1936]

Hi Vince As far as trying to tighten , Be prepared to get into a hornets nest (broken studs / Bolts etc ) Use PB Blaster on all Find 6 point socket that fits best (metric or SAE ) Rust can make a 9/16 nut feel loose  and a metric socket may fit better. Before trying to tighten Try to loosen This will tell you wether  fastener is stretched or just loose , Replaceing all nuts with brass &  using a torque wrentch will prevent future rusting problems Good Luck Frank

[Rickf1985]

And never seize on the threads. If you use a torque wrench with never seize go with the bottom end of the torque setting for that bolts. Bolts are original 3/8" and use a 9/16 socket. As Froggy said, always go with 6 point sockets and try 9/16 and 14mm. if it is really rusty you may have to hammer on a 13mm.

[BrandonMc]

Hi. I am working through this same problem, and came upon an excellent post elsewhere. You may find this information useful yourself. My question is, what's up with a catalytic converter? Don't I need a couple of those as well? What I mean is that I believe mine were cut off, and I'm in an emissions state, CO. So right now, I'm not sure if I need one with an air port in it or both or none. Should I just assume I need two air pumps and catalytic converters with the air port on them to pass emissions?thanks

Here is the parts list:
Item# = 500-69120
Description = Hedman Hedders Headers Motorhomes Class-A 1968-91 396-454 ci, 1-3/4'' Tubes/3'' Collector

Item# = 555-30651
Description = Jeg's Universal H-Pipe Kits H-Pipe Kit, 2.5'' Dia. Tubing

Item# = 555-30561
Description = Jeg's Universal Dual Exhaust Kit w/o Mufflers 3'' Collector to 2-1/2'' Pipe

Item# = 289-17749
Description = Dynomax Hemi Super Turbo Mufflers 2-1/2'' In, 2-1/2'' Out, Offset/Offset

Item# = 720-7158
Description = Mr. Gasket Copper SEAL Exhaust Gasket BB-Chevy Square Port

I plan to buy two 2 1/2" pipes from NAPA to make the long straight run between the muffler and the turn out.

[Rickf1985]

It did not come with converters so it will not need them. as far as the pumps it depends on what type of inspection they do. If it is just an idle sniff test then you can lose the pumps and all of the associated garbage. If they do a visual you have to have ALL of the emissions equipment that was on the vehicle when it was built. You may be able to get an exemption due to age. The best way to get the correct answers is to ask at the local DMV, they will have the most accurate info. We are just suggesting based on what we have found. That can be real expensive for you if they go the full inspection route and you went by our suggestion to remove.

[BrandonMc]

Thanks for the reply.

I thought I'd update here. To follow up on the prior list of parts, I purchased:

Dynomax 15146 - Walker Dynomax Universal Catalytic Converters
JEGS Part Number: 289-15146

2-Way Super Converter
In/Out: 2.5"
Length: 18"

Super Converters flow much better than stock catalytic converters because their flow area is 26% greater than OE. These mono shell stainless steel units flow extremely free (great for engines up to 455 ci), and their single tube design eliminates all the welds common to OE for leakproof operation and greater efficiency.

Colorado where i live requires catalytic converters, so I bit the bullet and purchased the full exhaust system and 2 cats. Use the price match feature on Jegs, it should save you at least a hundred or more on a purchase like this! I hope this information is useful for someone. I've found the forums here and elsewhere to be of much help to me to get this point which would have never happened otherwise.