Desoto 1941 get some fix with the Hemi

My Desoto need some work on the engine.



The Desoto Coupe is equipt with a 354 Hemi that i have some problems with.

For some years ago had i a big back fire in the intake manifold



It was nesesary to weld the efi manifold on place in the car



I have some problems with one of the ignitons coils.
When it is warm one chanel whan't to work, with result that sometimes it only runs on 6 cylingers.



This is not the only problem i have on the Hemi.

The big iseu is that head is to hard milled so i have copper gasket on them for the pistons not shall hit the heads.

I and my sister's son Andreas begin to disasemble the engine



We stand out door it was lite foggy yesterday



but the temp was ok

it comes more

 

I have problems with the copper headgaskets they leaks some times

and then it foams the coolant and the cooling did'nt work properly

The hemi is driven on E85 because of the high compession.

but over to the work

we removed the mainifold and the valve covers





we took of the heads (they was heavy)












Without the heads the car were lilte higher in the front.



Andreas is working with cleanig the pistons

I grind little on the sharp edges on the piston so the risk of ping will be less



I grind on the mainfold so i can paint it

/Stefan

 

What efi setup are you using? megasquirt? reprogrammed GM ECU? i've been thinking about how i want to EFI my 392 and im curious how you did it.

 

wow! that injected hemi desoto rocks dude! subscribed.

 

The efi is home made manifold with a Autronic SMC ecu

the set up is made without distiburator and have a Autronic R500 cdi box for the ingiton and the coils is 2 ford zetec two canels twin coils also it have waste spark

 

What's the C/R? Too high to use Fel-Pro gaskets?

 

The pistons are 392 +.030 with 10:1

But they are used on 354 with .095 over bore and to hard milled heads

I check how they was milled, one of the heads was milled 0.30 mm more than the other. When i checked the deck hight was one 0.10 mm higher and both were on same side so the diffrence was 0.40 mm [0.016"] and that side
hit the pistons the heads when the engine was hot with felpro gaskets.
After that bought i 1.6mm copper gaskets the felpro is only 1.0 mm high.

I have bought some new heads from Hot Heads



So they will be installed with felpro gaskets

I'm trying to see if there is some diffents in milling in them so i put right head on that side with more deck hight

/Stefan

 

392+.030 is .030 over what is usually a max 354 overbore for street work. Get a sonic check? Hope the walls are thick enough. On an unmilled block 10:1 392 pistons give 9:1. Then...the alloy heads effectivly drops your C/R down to 8:1. The alloy sucks head out of the combustion chamber, reducing power equivelent of 1 point. At www.webrodder.com they had a factory 331 block that had diffrent deck heights & the decks wern't square to the crank top to bottom or front to back. Maybe you can find here or there what the minimum deck hieght on a 331/354 block is.

 

The desoto have been out since 2001 so there is no problems with cylnder walls

But a fast calulation on the domes and the cylnder heads will a C/R of 12:1

The engine was inposeble to drive on 95 octan gas with out ping

 

1 OK
2 How did you figure 12? 12 is based on the rating of 10 or 9? & the milling? 10:1 in a 354 is only 9:1

 

I made this caluation in 2001 and it was based on that the heads have a chanber volym of 105 cc that that was milled and the messured domes
If i rember right so draw i the dome and the chamber in solidworks and take the volym from that and and calculate it from that values

 

Wait, if you're running E-85, isn't that 105 octane? Are you sure your pinging wasn't from timing?...did you re-map the fuel injection to account for the 85% alcohol content?...and I'm also confused about what got milled, the block deck or the heads?...

 

Stefan,

Great car,,that is a true hot rod.
Your Hemi should really carry the mail when you get it done.
The new heads look great and the engine will really come alive when it is put together.

I would not worry about the deck height,,.10 MM is only .004 thousandths,,you can live with that.

Let us know how it comes along.

Tommy

 

Stefan, tell us about the coupe conversion. That's a badass 3 window!

 

3W business coupe

 

With E85 worked it fine but with gas were easy to get pings

 

The car is a original bussnes coupe only change in the body is 35mm (1 3/8"] widere rear fenders on each side

 

When i dissasemble the engine fund i this



There was a crack in right exhaust manifold.
I must weld it, i'm leting a work frend do that. He had done things like this before to me

 

The fuel injection is mapped for E85 and the heads are to mutch milled to the domes on the pistons

 

Like George, I have many questions regarding the compression. 392 slugs in a 354 do not provide the same compression due to loss of swept volume and to raise the compression one-point requires cutting about 0.050" from either block or head.

Computers are nice to play with, but I'll use a physical measurement (downfill volume) everytime for accuracy. Just my preference.

.

 

I beleve there were somthing wrong with marking of the box with the pistons i bought 1989 to the engine
I think they was 13:1 or 12.5:1 or somthing in that case insted of the marking of the box that was 10:1

 

Sweet setup! Hope to see it on youtube when you get it running. Bill

 

I change the ignitons coils



They are placed under the plenum of the manifold

And the manifold have get some new paint on the plenum

/Stefan

 

Business coupe. Chrysler, Dodge, and Desoto all had 'em. I had one for a while, a '41 Chrysler I bought for parts for my '41 Windsor sedan. Duh. A buddy has a Desoto 3w in his salvage yard here in MI that I keep thinking about...

 

Looks a lot better. Good work!

 

Thanks for the comets

The passinger side exhaust manifold is now welded



I have cleaned the pistons and the other surfaces on the hemi block



Now is time for the heads



I must put the exhaust maifolds on the head before i assemble the engine



I have also gring little in the intake and exhuast canels so there is no burrs from the casting (not pollishing or porting)



Now is the heads on the motor

Time for the head studs



Andreas are screwing in the head studs on the drivers side
it is imposeble to put on the heads with the studs in the block



The have the rocker assemblys is on the heads now but i nead to torque draw the nut but i seen that i have the torque wrench on the othe garage there my shoebox is
So i stop for the night.

/Stefan

 

I have worked little more with hemi

I have put in the efi manifold and the valve covers



/Stefan

 

Stefan,,that thing is beautiful.
It should really haul,,,keep us informed.

Tommy

 

Thanks for the coment

I have put everyting togher and try to start it



But the battery that i charge last week were empty so i try to recharge it so i can test if the engie work well tomorrow. In other case will i buy a new batteri to the car

I don't wont to jump start the car if i get a stop when i try it, thats not so funny

/Stefan

 

Good luck with your engine project, Stefan! I have a 3.9 l V6 Mopar Magnum with EFI in my 3w Dodge. Just meeting the strict Finnish regulations considering engine swaps...