OK as promised I'm starting my Build thread for my 86 36' Vogue Cosmopolitan Class A Motor Home repower. I waited to start this thread until I was at the point of the swap so I can update as I remove the Detroit 8.2L Turbo engine and install the 7.3 engine. I have all the pics of the modifications to the engine and text about the reasons for some of the mods on Flickr. Please don't leave comments on my Flickr page. If you have questions about my build please ask on this thread or in a PM. Some back story might help I suppose, I am a Master RV tech and got the opportunity to buy this motorhome real cheep as it was towed into our dealership in November 08 with a "Blown" engine. when I looked at it I recognized it as a Motor Home I worked on when it was new in 86. I bought it for $500.00 plus tax and tabs. It came to $711.19 and I had it taken out of my check in three payments. The estimate for a rebuilt engine was $17000.00 at the local truck shop so the owner traded it in and we gave him a "blue sky" trade on a newer MH and I bought it right after he left the lot. Before he drove away I asked him about his trade. He said it still ran but would blow out the coolant and overheat in about 20 miles. I filled it with water and drove it 11 miles home. It has taken me over three years to collect all the parts to pull off this Build and swap. The MH is on a Gillig Bus chassis with a 22500 GVWR Running a Allison AT545 4 speed and 22.5 wheels. check out my Flickr Flickr: racer30sprint's Photostream

 

The reason I chose the 7.3 is that it is mechanical and run for ever when maintained. After finding this site and several others for info and Ideas for modifications for more power I settled on a stock bore Turbo block with lightened NA rods. I cut the pistons .030 for about 18.6 or 19.2 to 1 CR depending on how you calculate it. I coated the pistons with VHT ceramic paint. I cleaned the block removed the cam bearings and honed the cylinders then cleaned it again. Installed new cam bearings and blocked off the fuel pump hole. Did some porting on the heads, mostly in the valve seat to port area. I'm running a J2 cam to bring up my power in the top end to take advantage of the big torque converter and the "Stomp it till it reaches speed" driving of a bus application. I modified the oil pump pressure valve in the Van cooler head to give me more pressure. My thoughts here are the engine is cooled by water and the pistons by oil. give it a bit more pressure to serve the turbo and the air compressor as well as added cooling to the pistons. I am running a turbo cal pump I got through NMB2 turned up to about 90cc. I will be running a HX40w turbo on a t4 mount on a custom ceramic coated wrapped up pipes I built for the upside down reversed stock manifolds.

 

I'm using a International front sump pan that holds more than 15 quarts of oil with a PSD filter and will be even more when I go to the big Baldwin B99 filter. I won't Know for sure until the engine is mounted at the correct angle. I started the engine tonight NA on a temporary mount behind the MH. It started right up on the third try with the IP held wide open. It sounds great ,has very good response and is very smooth. The oil pressure was about 55psi at 600rpm and 80psi at 2000 or so, It was almost dark when I got everything together to start it so no pics tonight. I will get some tomorrow. Next step is to start removing the Detroit 8.2 when its out there will be 1200lbs of Iron to scrap out to pay for the intercooler pipes I will need soon.

 

I know your fuel pump says 10-14psi, but it doesn't look very sturdy.

You might want to consider buying from a member on this forum, who sells duralift pumps.

 

This pump is a GM diesel pump If it works for them in a daily driver it will work for me Too.

 

Cool build man, how did you modify the oil pump to get that much pressure out if it? My oil pressure is on the low side, I just don't know too much about the oil pressure valve you speak of.

I'm also curious to see how the hx40 works for you. I actually had one to put
On my truck but I thought it would spool to slow so I scrapped that idea. It had the larger ex housing, 17cm I believe. Which exhaust housing do you have??

 

Neat project. I just laughed at your "mild performance 7.3" -- they're all pretty mild in terms of performance.

 

Go from a screamin jimmy with no power, to a screamin IDI with no power....I like

 

It's about time you got this posted up! I've been waiting forever! Had my rods lightened by the way, it was way outta my league!

 

The engine oil pressure is regulated by a spring loaded piston operated valve that uses filtered oil pressure entering the engine to push down on a piston about 7/16" diameter that opens a port to release unfiltered oil back into the pan. By increasing the spring pressure you increase the oil pressure needed to open the return port. I carefully removed the regulator assembly that is staked into the filter end of the cooler bundle with a tiny burr on a die grinder. My cooler was from a wrecked low miles van so its spring would be less worn out than a high miles unit. I shimmed the spring with a small stainless washer about .034 thick. and I might have polished the piston and the port it fit into just a little bit to make it just a bit looser so more pressure would be needed to open the oil return valve. It seemed to work just a bit better than I had hoped for. I was looking for 40psi hot idle. I haven't had the engine to full temp yet as it was late when I got it running and it started raining here in WA just as I got off work tonight.

 

I have tried to research turbo applications on diesel engines and have found that looking at the CFM of air flow through the engine using several ways to calculate it converted to LBSM and fitting this info to known turbo performance maps to choose a turbo to fit my needs. I have seen a few guy's running HX35w's with 9cm2 to 12cm2 housing's with stock turned up pumps doing ok but I just don't want to run that small of housing in my MH because I will be at WOT or close to it a lot of the time with the Allison trany. So I have come to the conclusion that a HX40w 16cm2 housing will work for me....I hope... If it doesn't I will adjust as needed.

 

Yeah if your gonna be running the engine at high rpms most of the time the 16cm2 housing might work just fine. You might have to deal with a little lag down low but if it
Works for your application that's what matters. I decided against it because my truck is my daily driver. Slow spool in stop and go traffic wouldn't quite suit
My needs

 

Ya that's what I was thinking... I haven't found one with a 14cm2 if it is even possible.. but lag is not going to bother me, This things no sports car. most of the MH's I drive for work have 300 to 400 HP with autos and they don't spool that fast either. It rained again today so no work outdoors just did some work on the dash with my gauges and switches. I will get the cherry picker from my brothers place after work tomorrow and start removing the rear bumper and mud flaps.

 

AFAIK the HX40 has to be similarly sized to H1E's and i believe both were on 8.3 cummins in different applications. Probably a safe assumption that theyre designed for a 7-9 liter engine. I think a 40 would be perfect for a 7.3 size wise, but only having access to big non-gated housings is the sacrifice. However as youve said a big, heavy, slow motor home that spends half its time between 2500 and 3300 i think you will be just fine, especially with an auto and more so with a higher stall converter.

PS Realistically a 16cm2 housing isnt really THAT big anyway, on a stock IDI it might be slow, but with some fuel and cam i expect it would come in about the same as any of the non-gated turbo kits on a stock system. By my math a 7.3 would be able to start spooling a HT60 (something like 72/81/26cm2) by around 2400/2600.

With all of that being said, i would probably get a billet wheel for it. Theyre more efficient all the way around and lighter. Just dont bark it hehe the 40s dont like that.

How is the turbo on the Detroit? Could be suitable as well.

 

Iv heard of cummins guys building up 35/40 hybrids. Using an hx35 hot side with the 40 cold side. If the large hot side the hx40 did become an issue, which it shouldn't...you could always look into a 35/40 hybrid