Merc 2.5 FF block deck hight question

**Matt695** · 11-29-2018, 07:36 AM

Hey guys, looking for some info, have a 2.5 FF motor in the build to run on a f1 tunnel,Have had 6 new liners with all the necessary porting, exhurst chest work ect, will be running new s3000 crank, rods and single ring f1 pistons, had top bearing journal machined to suit s3000 crank ect, also asked the machinist to take take a very light cut across the decks to level out the new liners, with some info I found online said that the deck hight difference between ff and s3000 was four thou, so told this to the machinist and said four thou max, he has not relayed this to bloke on the tools that day and they have taken 15 thou, question is what does this mean for me?Cutting the heads for the squish as now there is more piston purtrusion or is 14thou acceptable?? Have 28cc heads with gaskets, just don’t want to have to run custom heads on this motor, would like to able to have spairs with out machining them all, any info would be greatThanks

**Merc 2.5** · 11-29-2018, 07:42 AM

This seems like a advanced question for a rookie but seems to me u could deck the pistons same amount without getting to close to ring? Then could prolly run whatever cc u want? R pistons n block already?

**Matt695** · 11-29-2018, 08:09 AM

Rookie?
the rpm an being top pinned f1 pistons decking pistons for a quik fix isn’t really what I want to do considering the money spent in the rotating assembly, hence just after some technical info on dech Hights

**Merc 2.5** · 11-29-2018, 08:13 AM

Rookie statement was directed toward me. Gotcha , man I really dnt have a gud answer for ya, maybe when few these guys see this they will jump n and help ya out.

**Matt695** · 11-29-2018, 08:21 AM

Oh haha, yea I’m hoping someone has been down this road and can share some info, Havnt decked any of my previous motors so have never delved into deck hights to much

**Merc 2.5** · 11-29-2018, 08:24 AM

Mine got decked .004 just to straighten things up. Guessing that's what u wanted and he heard .014?

**Matt695** · 11-29-2018, 08:28 AM

Well maybe that’s what he heard I’m not sure what happened on there end, but I told him several times .004, too late now I guess, had s3000 port map in the new sleeves befor they went in, guess a little higher know

**Chaz** · 11-29-2018, 08:50 AM

.004 - .014 It doesn't matter what anyone says. It's up to the man assembling the motor to determine what the true deck height is.
Mock up your 4 outside corners and measure across the wrist pin line to see exactly what you have. This will also let you see if it was cut straight .

**eli** · 11-29-2018, 11:50 PM

.004 to .014. Why can't we get what we ask for now its more $ and time to fix some ones fu*k up Damm !!

**Chaz** · 11-30-2018, 08:37 AM

Eli ... so far it's just a number he was told. More importantly :

It's a block that that had all six liners changed ... Do you think it might have moved ?

It might have had a rod put thru the side and needed to welded up ... Do you think it might have moved ?

Newsflash : Brand new parts from Mother Merc are banana shaped ... what makes you or anyone think that .004 will clean up both decks and put them parallel + square to the crank centerline .. ?

Is it just easier to continually point a finger @ machinist's, platers etc. when there is an issue instead of realizing that when rebuilding engines, especially ones that have non stock parts, that it takes someone who checks and makes necessary adjustments along the way ...

**Merc 2.5** · 11-30-2018, 11:06 AM

So how would a guy putting motor together go bout fixing issue? Inquirin mindz needs know

**Chaz** · 11-30-2018, 09:18 PM

Welp .. 2.Five, that's a good question ..

Seems there's two ways to go :

You can take all your stuff home, spread it out, TURN THE LIGHTS OFF .. and put it together ... then when it grenades ..

Me ... I don't see it as a problem. I see it as an opportunity to tighten the quench up and build a little compression.

He still need's to mock it up to see what he has. Even with fresh bore's and new pistons ( non collapsed skirts ) If they really did have to / or did by mistake cut .014 chances are he will be down in the .030 neighbourhood which isn't enough to keep from printin part numbers in the head .
Cutting the piston crowns puts the top ring closer to the action making it react quicker .. good for power.
Sweeping the chamber even tilting the quench band a degree is good for power .. a little of both would be good, but then .014 wouldn't be enough, might have to go back and get another .010 - .015 lopped off

All kidding aside, sometimes it's the parts. Sometimes it's the machine's operator. And yes, sometimes it's the pressure from the "I called 48 times in the last 2 days, how come they won't answer the phone anymore" people who bring it on themselves.
There is always a solution. Sometimes if you think it thru, you can come up with something better than what you had. It's that .. Ya got lemons ... well .. make lemonade .. thing

**eli** · 11-30-2018, 09:45 PM

I believe 4 thou might not been enough but I think the machinest should of discussed it with customer before hacking
014 off and making a situation

**Merc 2.5** · 11-30-2018, 11:24 PM

So I guess now my question to the op is what's ur next step. How bout testing a stock head for compression and measuring squish band and cut as necessary??