combo question

[plydus340]

71 440, bored .03 and decked. heads decked, trw forged pistons, six-pack indexed cam, new 91lb springs, gas ported pistons, rods installed backwards, ductile iron ajustable rockers, compression ratio aprox. 10.3 to 1. did i mess up? i can only find 91 octane around here.

[rumblefish360]

HUH?

Is this an iron headed engine? Rods installed backwards? I thought pistons were installed backwards?
Ratio seems hi for a stock cam. Whats the centerline on that puppy?
You lack some info on this. Otherwise, it seems to be like a stock rebuild.

[plydus340]

yer right, pistons backwards. 79.5 open chamber heads w/2.08 intake, 1.84 exaust. 110 centerline i beleve. im not very sharp on this stuff. im just really worried about the comp. ratio. thanks for your response...

[dirty dan]

Have you the rest of the cam numbers?
The cam grind can have a lot to do with actual running comprestion.
I`ll take a chance here and assume you are figureing your compresstion based on your machine work.
In doing so What you are actualy figureing is the max available compresstion .
The cam shaft valve overlap and duration will have the effect of bleeding of the compresstion .
The more duration and overlap you have the more compresstion you will lose.
This is why I ask about the numbers.

[plydus340]

my engine builder ordered the cam, it is listed as a six pack cam. i think the intake lift is .484, duration is .284. i didn't want to get above my stall conv. it stalls at 1800 now, i was told it should stall at 2500 w/ a 440. thanks again for your replys...

[6 packin]

I have heard of running the psitons and rods backwards before for extra power. This is not reccomended in the mopar engine manual also. It actually does turn the rod backwards and changing thus changing the rod angle. There is a down side also.......piston slap will be heard. It will be a noticable noise from your engine. For a racer OK but for someone tring to sqeeze lots of miles out of it, its not such a good deal. Besides the power lost there3 could be picked up with a better cam somthing ground with this Millinums technology. Like a racer brown, or Hughes cam.

[rumblefish360]

The actual manufactuer of the cam would help. That duration will bleed off some off that compresion. I think thats a good deal due to the HI comp. w/iron heads. It'll do fine.

i didn't want to get above my stall conv. it stalls at 1800 now, i was told it should stall at 2500 w/ a 440.

I'm not following this. Would that be a converter used in a small block now installed in a big block. If so, it looks about right. It should work well with the cam if it is accurate. Thats just the stall that cam needs.

[plydus340]

thanks for the response guys, i guess the only thing to do is put it all together and see how she does. you guys are the best!

[b-1ken]

Compression ratio seems a little high for 91 octane gas. I built a 440 for the street a few years ago with a 9.5:1 CR and it pinged badly with Hess premium gas (92 octane?). We put Sunoco 94 in it and the pinging went away. By the way, the RODS should not be turned around because the sides of the rods (big end) that don't have the chamfer should face each other on the crankpin. You could probably get away with "backwards" rods though, because the stock Chrysler crank uses undercut fillets. If you did this with a crank that had a fillet radius (any performance crankshaft), the bearings would bind up on the fillet.