Cad 500 in a Chevy G30 van. Possible?

[Opus62]

Hi. First post here. :-)

I currently own a 1979 28 foot class C motorhome on a Chevrolet G30 van chassis. [For anybody not familiar with motorhomes, a class C is a standard one ton cut-away van front end with original Chevy doors, hood and glass with a camper built onto the back and overhead].

It's in very nice condition but the small block Chevy 400 just seems underpowered here in the foothills of Alberta, Canada. After thinking about the many things I could do with the engine, it occurred to me that a basically stock Caddy 500 would be the absolute best gasoline engine for this application, with it's gobs of low end grunt. They are not very hard to find in these parts and I have access to shop facilities plus I have done more than a swap or two in my days.

My question is, has anybody done this kind of swap in a van? What can I look forward to? Will it fit under the doghouse? [a 454 was optional back in the day]. Any information will be deeply appreciated.

[DV8]

It will fit. Here's a link to an album that has pictures of my install. No current picts but these are from an early mock-up so they may be just what you need. Be sure to check out page 2 of the album.

http://www.cowboyseven.us/album/index.php?cat=10026

The pictures are of a 425 w/short tail th400, but 472/500 is dimensionally the same.

Chris

[DV8]

It will fit. Here's a link to an album that has pictures of my install. No current picts but these are from an early mock-up so they may be just what you need.

http://www.cowboyseven.us/album/index.php?cat=10026

The pictures are of a 425 w/short tail th400, but 472/500 is dimensionally the same.

Chris

[DV8]

It will fit. Here's a link to an album that has pictures of my install. No current picts but these are from an early mock-up so they may be just what you need.

http://www.cowboyseven.us/album/index.php?cat=10026

The pictures are of a 425 w/short tail th400, but 472/500 is dimensionally the same.

Chris

[Opus62]

Excellent! :D Thankyou for the response. The pictures really help. That engine looks so tall compared to the Chevy 400 but the spark plugs look SO much easier to reach!

Did you have any trouble at all? What mounts did you use? I suspect that you may have had some improvement in fuel economy, am I correct?
Any problems with linkages, exhaust, etc. :?:

[DV8]

Did you have any trouble at all? What mounts did you use? I suspect that you may have had some improvement in fuel economy, am I correct? Any problems with linkages, exhaust, etc. :?:

It does make the sbc look puny in comparison.

Not really any trouble, I made my mounts from sbc mounts with plates going forwards and braced (triangulated) to the bottom (crossmember) of the sbc mounts. Just watch your side to side measurements! Not much room for error there.......

I went from about 10 mpg to 14 so I'm happy there. Vans aren't very aerodynamic.

Linkage & exhaust went very smoothly. I placed the parting line of the engine/trans at the same location as the factory sbc location, the linkage lined up very nicely that way. Only required the trans crossmember to be lowered about 1 1/2" and extended rearward 6"ish inches with a braced plate (I forget exactly how far) The crossmember MUST be lowered, I don't see how to get around this at all.

Access to exhaust manifolds from the bottom is better than sbc, and they were excellent. Just drove it to the muffler guy and let him do his thing. 2.5" duals.

There is plenty of room for the power steering pump and alt in the stock cadillac locations too. No picture of that but it works. I ran the heater hose return to below the thermostat housing, like the earlier cadillac engines were routed. Move the fuel line to the other side of the engine bay too, while the engine is out. Transmission dipstick is interesting to route. Might have been better off to fab a short one that you check/fill from underneath! Extended the oil dipstick to reach farther upwards.

Only downfall is that now I have to get out to adjust the timing on the fly. Before I could just drive with the doghouse out.....

Chris

[Opus62]

Thanx again!.

I am having trouble picturing in my minds eye the engine mounts as you describe them. Perhaps it will make sense when I attempt this project.

Since I already have a TH400 in there, could the existing crossmember location be ok? Or maybe an adapter plate and use the existing transmission might be worth considering.

All in all, it sounds like it will be well worth all the trouble.

[STDog]

Since I already have a TH400 in there, could the existing crossmember location be ok? Or maybe an adapter plate and use the existing transmission might be worth considering.

The adaptors suck, and you would need one to fit a chevy trans to the engine.

If you can find a BOP TH400 the same length, you might only need to lower it. I'm guessing you'll have to lower it because the crank center line will be lower. You've got to make room for the taller block :) I suspect the heads/valve covers are taller too.

[Opus62]

The adaptors suck, and you would need one to fit a chevy trans to the engine.

If you can find a BOP TH400 the same length, you might only need to lower it. I'm guessing you'll have to lower it because the crank center line will be lower. You've got to make room for the taller block :) I suspect the heads/valve covers are taller too.

As was shown in DV8's posting, there will be plenty of room for the taller block. I just can't seem to picture the engines mounts as they were described. As there is a TH400 in there right now, perhaps I'll be lucky [or not] and not have to modify the rear crossmember.

I won't bother with an adapter, considering how heavy the motorhome is.
:)

[DV8]

As was shown in DV8's posting, there will be plenty of room for the taller block. I just can't seem to picture the engines mounts as they were described. As there is a TH400 in there right now, perhaps I'll be lucky [or not] and not have to modify the rear crossmember.

I won't bother with an adapter, considering how heavy the motorhome is.
:)

Sorry for the confusing description on the engine mounts. I'll try again.

You have SBC (or BBC, should be very similar) in the van now? Starting at the crossmember beneath the engine, there are a pair of "stands" that bolt to the crossmember. One is taller than the other: these have the motor mounts bolted onto the top of them, then the engine bolted to the mounts. Well, for the Cadillac engine, leave the stands, but remove the mounts. Then bolt a plate on where the mounts bolted to, and have this plate extend to the front of the vehicle 4-5". Where this plate "hangs" out in space, brace it to either the crossmember or the bottom of the stand. (You might be able to get away without the brace, but it looked like a good idea to me....lots of leverage there).
Your stock cadillac motor mounts will bolt to this plate (you'll put holes directly into it where needed.) They are similar to MTS's swap kit.

Here is a picture that may help with visualizing it. (this is in a g-body regal, hope Don doesn't mind...) The picture shows how you have to move the mounting forwards, but the g-body doesn't use the stands.

I had to move the trans mount down to clear the extra heighth of the Th400 trans itself. Your mount is probably fine - you got a bonus!! I'd just swap to a BOP case on the trans & bolt it in! Lucky!


http://thumb0.webshots.com/s/thumb4/8/92/30/96089230LursUq_th.jpghttp://thumb0.webshots.com/s/thumb4/8/92/30/96089230LursUq_th.jpg

[DV8]

As was shown in DV8's posting, there will be plenty of room for the taller block. I just can't seem to picture the engines mounts as they were described. As there is a TH400 in there right now, perhaps I'll be lucky [or not] and not have to modify the rear crossmember.

I won't bother with an adapter, considering how heavy the motorhome is.
:)

Sorry for the confusing description on the engine mounts. I'll try again.

You have SBC (or BBC, should be very similar) in the van now? Starting at the crossmember beneath the engine, there are a pair of "stands" that bolt to the crossmember. One is taller than the other: these have the motor mounts bolted onto the top of them, then the engine bolted to the mounts. Well, for the Cadillac engine, leave the stands, but remove the mounts. Then bolt a plate on where the mounts bolted to, and have this plate extend to the front of the vehicle 4-5". Where this plate "hangs" out in space, brace it to either the crossmember or the bottom of the stand. (You might be able to get away without the brace, but it looked like a good idea to me....lots of leverage there).
Your stock cadillac motor mounts will bolt to this plate (you'll put holes directly into it where needed.) They are similar to MTS's swap kit.

Here is a picture that may help with visualizing it. (this is in a g-body regal, hope Don doesn't mind...) The picture shows how you have to move the mounting forwards, but the g-body doesn't use the stands.

I had to move the trans mount down to clear the extra heighth of the Th400 trans itself. Your mount is probably fine - you got a bonus!! I'd just swap to a BOP case on the trans & bolt it in! Lucky!


http://thumb0.webshots.com/s/thumb4/8/92/30/96089230LursUq_th.jpg

[Opus62]

Ok I get it now! :D Thanx a lot for clearing that up. It seems to be quite straight forward. It looks like it would be well worth the trouble.

Another thing possibly in my favor may be the fact that it's a motorhome and not actually a complete van. The floor and frame are different from a regular van floor and frame. In a regular van, the frame is part of the floor, similar to a unibody setup. In a cut-away van chassis, like in my motorhome or a freight van, there is a full perimeter frame much like a truck. I could have more overall room to work.

Believe it or not, this has led to some other parts differences. I discovered that a steering column from a regular Chevy van, same year, will not fit. Near as I can tell, GM just takes a pickup truck frame, changes the crossmembers to shift the engine/trans to the right slightly and then adds a modified van "cab". At least that's my guess.

[Opus62]

Been searching far and wide for an early to mid 70's Caddy with the desired engine. Found quite a few but not the "parts donor" types I have been looking for.

However, it's been relatively easy to find later models with a 425 that are ideal parts donors. Now I am wondering, would a Caddy 425 be much of an improvement over the 79 Chevy 400 in my motorhome? Any rebuilding I was planning would be completely stock other than a possible cam change for low-end torque.

Where is a good place to compare specs on GM engines? Comparing numbers might help enlighten me, plus any real-world experiences I can find in this forum.
:D

[STDog]

Not sure about the Chevy, but specs for the 425 in stock form:
180hp @ 4000 / 320 lbs.-ft. @ 2000(N/A)
195hp @ 3800 / 320lbs-ft @ 2400 (WFI)

Also not that the externals of the block are teh same as the 472 and 500,. So if you get it qoing with a 425, you can always change to a 500 later, and it'll bolt in with no other mods.

[MilesO]

Opus62,
The Cad 425 is not only more plentiful than its larger displeacement brothers but it is lighter weight due to a change in casting techniques.
All the parts are exchangeable. The 425 and 472 cranks are the same stroke, 4.06", the 472 is stronger. The 500 crank offers a 4.304" stroke, but no off the shelf piston is available.
If you are willing to venture beyond a stock rebuild, KB Pistons ( www.kb-silvolite.com ) offers their # 159 or # 172 in bore size 4.125" that will combine with an MTS 7.1" rod and the 500 crank to yield an engine displacement of 460 ci.
The rod journal of the crank will need to be sized to fit the BBC journal size during rebuild.
With the long stroke you will have excellent torque to pull the Class C .
Use the exhaust and intake manifolds from the 500 and maybe the small chamber 76cc heads, too.

Just a thought I had..

Miles