OMC Cross Charge Mod questions

**bruzercomp81** · 07-14-2012, 08:16 PM

I run 27 degrees timing with my ported v4 with 150psi but I ran 1/2 111 octain and 1/2 93 octain.

**bruzercomp81** · 07-14-2012, 08:33 PM

is anyone looking for a v4 with 3.625 bore?

**930turbo** · 07-14-2012, 08:53 PM

I didn't expect the compression to be that high and I fear another failure. I prefer to use pump gas and avoid exotic blends to ensure survival. I was reluctant to disassemble the original 140 long block because it is original and runs well, however I may pull the heads off that block and put them on this one so it will survive past the break-in. I can't find any numbers on the heads currently on the motor but I wonder if they might be the '73 135's. It seems really high.

**Cavit8** · 07-14-2012, 08:59 PM

Does this mean the first one likely died of insufficient octane Tracy?

**930turbo** · 07-14-2012, 09:09 PM

Not sure, but if you look at the existing damage in the heads and historic application, there's been multiple failures. You motor was timed at 22 and it melted down, supposedly from a faulty switch box. Maybe not. I really don't want to do that again. I ran the stock 140 flat out for eight miles more than once at River Ranch. Safe to say these heads passed the test and that was at 28 degrees.

**john j 80 viking** · 07-15-2012, 12:35 AM

Most stock cross flows run between 95 and 125psi compression.

Very interesting thread.

John

**Cavit8** · 07-15-2012, 06:41 AM

Are the original heads from the "free" motor (the ones going on mine) the same as the heads from your stock 140?

**930turbo** · 07-15-2012, 10:08 AM

Originally Posted by Cavit8

Are the original heads from the "free" motor (the ones going on mine) the same as the heads from your stock 140?

They appear to be the same displacement without actually cc-ing them.

**Superstocker** · 07-15-2012, 12:59 PM

Originally Posted by bruzercomp81

I run 27 degrees timing with my ported v4 with 150psi but I ran 1/2 111 octain and 1/2 93 octain.

930, I agree w/ racer & bruzer in that I'm pretty sure that your going to need more than 93 octane w/ that much compression. I think I'd start w/ the lower compression heads if you want to stay w/ pump gas. Just my two cents... BTW, I'm happy to see you back in action!

**930turbo** · 07-15-2012, 02:44 PM

Originally Posted by Superstocker

930, I agree w/ racer & bruzer in that I'm pretty sure that your going to need more than 93 octane w/ that much compression. I think I'd start w/ the lower compression heads if you want to stay w/ pump gas. Just my two cents... BTW, I'm happy to see you back in action!

I just finished changing back to the stock 140 heads - and confirmed the high compression heads are from a '73 135. Thanks guys for all the help.