Blown Head Gasket

[Peterbylt]

Hi, New to board. I have just purchased a new to me older RV.



A 1985, Class C, 24 foot, CrossCounty by SportsCoach.
By any other name a Coachman.

Being an Avid, Motorcycle Touring rider with many miles on my Goldwing I was not actually in the market for an RV, but the price was right and the wife really wanted me to buy it, so I found myself the owner of an RV.

Then the fun started, on the ride home the RV overheated multiple times (Just barely made it over the Sunshine Skyway Bridge) and ended up being towed to the house. The engine, Chevy 350 with 90,000 miles, was blowing exhaust gas into the radiator.
 
I had paid too little for the Vehicle to even consider returning it (although it did cross my mind), so I knew I needed to at least change the head gaskets. I tore the engine down and discovered that the cylinder wall on #5 cylinder was scored.



Peter

[ClydesdaleKevin]

You should be able to fix that with a cylinder hone (if the scoring isn't too bad...hard to tell in the picture) without pulling the motor.  Chevy 350s are pretty easy to work on, and you should have plenty of room to work under the hood.

If the scoring isn't too bad, replace the head gasket and do a compression test on all cylinders.  If its within specs, don't worry about the minor scoring.  If its way down or varies too much, then you might want to consider a rebuild, or a Jasper rebuilt engine.  They are pretty affordable as a shortblock, since the 350 was such a common engine, and was the same for a motorhome as for a truck.

Kev

[Rickf1985]

If the cylinder wall is scored then something had to score it and my guess would be a broken or washed out ring. No matter what if the head gasket was blown and if you got antifreeze in the oil then the engine has to come out. You can't hone the cylinder without pulling the pan and the getting the rod and piston out anyway. I am not sure you can get the pan off in there. Once anti freeze gets in the oil it will wipe out all of the bearings in short order because it contains silicates, basicaly, sand. That means main bearings, rod bearings and cam bearings and you will also need to check or replace the oil pump and cam and lifters. The good part of this is that Chevy crate engines are cheap. You can get a brand new, in the box engine with a warranty for around 2,000.00 the last time I looked. Granted it has been a while since I checked so don't hold me to that price but if you got the camper real cheap it would be worth putting a new motor in it if you are planning on keeping it.
I just checked, I was off a little but not much. This is direct from GM, there are cheaper options.  http://www.gmpartsdirect.com/results.cfm?singlepart=1&partnumber=12499529

[Froggy1936]

Hi Pete Welcome to the club. I really like the looks of that rig. Seems odd the pistons are very clean & the lifter chamber is spotless For that amt of miles . The rust in the cooling syestem indicates being run without antifreeze for quite a wile ?  The oil pan will come off easily . After you get the piston out you can determine if the score is from current configuration or if eng was rebuilt with scored cly left as is . I replaced all the rod and main bearings in my 350 in place so it can be done Read special care needed to prevent rear main oil leak if you go that route . Good luck & lets see some pics of the interior etc   Frank

[Peterbylt]

Found #8 cylinder scored as well, both 5 and 8 also look like where the headgasket was compromised.
Since I have the engine this far disconnected I decided to pull it.

When pricing the machine work and rebuild parts I have decided it will cost almost the same to get one of the brand new Chevy Crate engine long blocks Rick was suggesting. Summit Racing has the best deal with free shipping.

http://www.summitracing.com/parts/nal-10067353/overview/make/chevrolet

Pulling the engine was not as difficult as I thought it would be, hardest part was taking the front of the Van off. It’s just plain silly when you have to pull the headlights to change the engine.

I have a Crane that mounts on the bumper of the Pickup that I built to change out Boat motors, hasn’t been getting much use since I sold the boat but it was just the thing to pull the engine.



I decided to pull the Engine and transmission together and do a rebuild on the transmission while I have the chance.

With the heads off the engine the clearance between the top of the engine and the doghouse was not an issue. Might be a little tighter going back in. I will probably put the intake manifold on after the engine is installed.



I had to make a quick trip to Home depot and buy a piece of chain to lift the engine by, not sure what happened to the piece I had.



I’ve never used the crane with it stretched out this horizontal before, the end of the boom was bending enough with the weight of the engine and transmission to make me nervous. I will probably either make a truss support for it or shorten the boom before I reinstall the engine.



After a little jockeying, pull forward, raise up, pull forward, raise up, pull forward, raise up, she came free, now I need to order the new engine



Peter

[Froggy1936]

Hey Pete. Take a look in the projects section of my relaceing 3 speed auto trans with 4 speed OD 4L80E Simular veh.  Look at reinforcement on crane boom to correct bending . Going back in with cly heads on will be heavier ! Frank

[ClydesdaleKevin]

Check out your local auto parts store while you are at it for a Jasper rebuilt crate engine...not sure which ones carry them...NAPA?  Autozone?  Might be cheaper and save you freight shipping than Summit Racing, and Jasper has a GREAT reputation.

Kev

[cncsparky]

The link you posted for the engine, in the notes its says maximum 7200 lbs GVW.  How much is your class C?  Have you looked at later model engines that come with roller cams?

[bluebird]

Before I'd go that route, I'd do this.
 
http://www.ebay.com/itm/CHEVY-350-383-SCAT-STROKER-KIT-2PC-RS-Hyper-Dish-Pist-I-Beam-5-7-Rods-/330797174606?


I'd build a 383 stroker engine for it. Has the block been bored yet? If not, and the heads are ok, meaning not cracked. I'd have the block overbored .030 and buy a scat stroker kit for it. The 383 will have a lot more torque than a base 350. That block should be a 4 bolt main block if it's the original engine for your coach. I've built a few 383s over the years, and highly recomend them.

I really like a 6" rod 3.75 stroke engine, and have used um in my drag cars. I have one now in my sons 96 Firebird that has close to 650 hp.  For a few hundred more you can build a stroker that will produce more than 350 hp and be perfect for your coach, provided the heads can be reused. Even if they are shot aftermarket heads a getting pretty cheap now a days.


http://www.summitracing.com/parts/nal-12530283/overview/

[Rickf1985]

That engine you link to from Summit is not the one I linked you to from Chevrolet. There is almost a hundred horsepower difference. Plus the one you picked from Summit is a light duty engine. I had picked one that was a good compromise between cost and power and dependability. I agree that the 383 is the best engine but do you really need that much power and are you willing to give up the mileage? I have put a few engines in these things and they are a pain, you will have to leave the manifold off till after the engine is in and you will need an installation plate that mounts to the intake bolts and goes down in the lifter valley and has the lifting eye in the center of the valley. That will get the crane arm low enough to clear, I would shorten the arm and truss it.

I just checked and they do have the better engine at Summit and it is cheaper than Chevrolet P/N 12499529. I tried to link to it but I can't for some reason.

[bluebird]

 Chevrolet P/N 12499529            cannot be used in vehicles with a GVW over 6,000 lbs.

I have modified my post as that engine can't be used in a MH.


A properly built 383 would be perfect for a MH, and fuel mileage wouldn't be affected much, may even be better. 

[Peterbylt]

I appreciate the responses.

I looked those crate engines over pretty good before deciding on the 10067353, this engine is the only one that lists the Chevy G30 for a stock replacement. The only difference I can see between the 12499529 and the 10067353 (besides the price) is the cam shaft.

If I did go the rebuild route it would be a 383 stroker, but the thing I was looking at was the 100,000 mile warranty if installed in an 85 G30.

The engine is listed as 195+ hp, depending on the intake and Carb you can get up to 265 hp, so if (when) I decide I need the extra HP it would not be too difficult a task to add a new intake, carb and headers and maybe later a cam.

For now though I am looking at a brand new engine, cost, dependability and maybe a warranty.

Peter   

[M & J]

Good call.

[Rickf1985]

Chevrolet P/N 12499529            cannot be used in vehicles with a GVW over 6,000 lbs.

I have modified my post as that engine can't be used in a MH.


A properly built 383 would be perfect for a MH, and fuel mileage wouldn't be affected much, may even be better.

I don't know where that info came from, I just read the entire spec sheet from Chevy and it says nothing about that. The only caveat is marine use, and emissions use, has to be an off road engine.  Nothing about weight.

[pvoth1111]

Make sure its a 4 bolt main

[bluebird]

I don't know where that info came from, I just read the entire spec sheet from Chevy and it says nothing about that. The only caveat is marine use, and emissions use, has to be an off road engine.  Nothing about weight.

http://www.summitracing.com/parts/nal-12499529/overview/make/chevrolet

Read the entire specs at Summit racing. I just did a copy/paste from their site.

[Rickf1985]

I see where Summit has added that in there, why I do not know. I also see where they say the normal vacuum is 10-12 inches of vacuum. Unless this engine has changed drasticaly since the last one I put in a couple years ago this is not so. But if this is the case then this may not be the engine for you. I would call Chevrolet Performance before believing what Summit has posted though. Those cam specs. are not high enough to give that low of a vacuum reading.

[gary19734]

IF you want the ultimate engine use a 400 block with a 327 crank  works out to be a 350 need to use rods from a ford 300 six cylinder.Have them machined to fit  = 400 hp 420 lbs of torque and would probably get about 18 miles per gallon.I put one together for about 1800 i beleve.
Had this this set up in a 73 crew cab with a 400 turbo trans and a 420 gear.Got 20 miles a gallon pulling a 35 foot race car trailor and yes it was carburated.It truly is the 350 that chevy should had built.You can look up all the tests that hot rod magazine did on this motor.  Gary

[Rickf1985]

Gary, that is interesting because you are describing an overbore engine when it is generally accepted that overbore is good for high rpm and horsepower but long stroke is the king of torque which is what you need for heavy pulling.  Low rpm torque and grunt, not necessarily high horsepower numbers but the torque band is very wide. I will have to look into that.

[bluebird]

Chevy did build this engine, started in 1958. It was called a 348, and it was a big block engine. They were originally built for truck applications, but put in passenger cars too. I sure don't remember ANY 3.25 in stroke engine having great  pulling power. Any engine can pull with the right gears, but it'll be screaming running down the road at highway speeds. Had many sbc that got 18 20 mpg in the late 60s early 70s, untill the clean air act was implemented. That's another can of worms.


The stock 400 small block would have much more pulling power than that engine. 3.75 in stroke sbc are potent engines. I have a 6" rod 406 sbc in my sons race car, and it is the stoutest sbc I've ever owned.

[MotorPro]

The last thing you want in a motorhome is a short stroke engine. It will make lots of power but only over 6000 RPM. Motorhomes are an application where nothing replaces cubic inches.

[Peterbylt]

I really have thought about building a 383 stroker engine. The Scat rotating assembly that Bluebird linked to is about perfect for a Motorhome Usage. Would keep the compression down to between 9-1 to 9.5-1 so you could probably use 87 octane the 3.75 stroke would help produce lots of torque as has been discussed.

I still think the best option for me currently would be the 10067353 350 engine.
I will be ordering the engine in the next week.

I have managed to pickup an Edelbrock 2101 performer manifold and a set of Hedman long tube headers locally off of Craigs list for almost no money. That should add a few more horse, the stock Q-jet carb will bolt onto the performer manifold.
 
Haven’t decided what to do with the exhaust yet. The current exhaust is in really good shape, but won’t really work with the headers
.
I have commenced the transmission rebuild.
First time doing an automatic transmission.
 
The few times I drove the RV, the transmission did not seem right, when you first start driving it would not shift out of first until you revved the hell out of it then it seemed to shift alright after that.. So I figured I would go through it.
   
Picked up the How to Rebuild & Modify GM Turbo 400 Transmissions book. So far this book has been real good.
Great pictures and clear easy to understand steps that have covered everything so far.
I have it all disassembled, I started to reassemble and realized the rebuild kit did not include a bushing that seemed worn so I am now waiting on a complete bushing set. Other than that the Kit is very complete. ATP master rebuild kit.

The transmission looks to be in very good shape internally (except that one bushing), looks to not have many miles on a rebuild all the parts look new, clutch disks still have the lettering on them.
I will replace everything with the new parts from the rebuild kit, all the hard parts spec out within tolerance.

I took lots of pictures and laid out the parts in the order I took them out, putting everything I could in Ziploc bags and labeling them.

The hard first gear shift looks to have been caused by a bent modulator valve that is one of the replacement parts included in the rebuild kit.

I will probably be reassembling it during the Superbowl, 50 inch TV in the shop.







Peter

[Stripe]

Nice.

[legomybago]

Pull the govenor out of the side of the tranny and inspect, it controls the upshift. It has a nylon gear that can strip, or get apple cord. Make sure the springs all move freely and not bind.

[cncsparky]

Be sure to install a shift kit.  I prefer Trans-go kits.