Do you guys think this minor nick on the block deck is going to give me head gasket issues?

Been a minute since I've put a bottom end together (actually almost two years since I assmbled my last BP). Just finished regapping the rings on my backup 2.5L Duratec engine in case I decide to boost it later on. I'm currently cleaning up the block and head surfaces for the new head gasket.
Found a little nick in the block surface between cylinders 2 and 3. It just barely catches a fingernail. Barely. Can't feel it with your finger.

Block deck flatness is a hair under .002", head surface flatness is .002". Aluminum block. Gonna be using an OEM MLS head gasket and head bolts.

My gut tells me It's not going to be an issue, but I figured I'd take a couple minutes to get a second opinion before slamming it back together. Any input from the hivemind is appreciated. Thanks as always, guys!

 

I'd send it. Maybe use a MLS head gasket that comes with a rubberized coating on it. It'd probably seal fine without, but you could also copper rtv spray a gasket and rock that. My brother swears by it on his subies that are HG issue prone.

 

Yo Nate, thanks for chiming in! Luckily the OEM gasket is an MLS-type with the rubberized coating on it. I got a couple other opinions too in favor of running it as is. We shall send 'er!

Was gonna look into running copper coating on said HG until reading that the copper spray shouldn't be used on coated MLS gaskets, so I guess that solves the issue for me. I seem to recall a more than couple people on here running copper coating on their MLS gaskets but I can't find the threads now.

Onward! Thanks again.

 

The worst place possible. There is not much compliancy in the firing ring area of the head gasket. If the block has not been surfaced it would be worth the effort.

 

Welp, sh*t



The head’s back on as of current. I took all the feedback I received from various places and decided it sounded like I’m probably fine. Maybe I’ll give it some more thought after the long weekend. My original thought was to maybe put the engine in the car later this month to make sure it runs well and dial in any minor tuning that needs to be done before our race season starts back up in September.

 

Since it’s not an FI application, it might hold out.

 

Possibly. This motor is gonna be my “spare” which will be run N/A for the rest of the year. Undecided if I’m gonna go turbo or build a high-compression N/A motor next year as a power adder. I regapped the rings on this one and used stronger Ecoboost head bolts in case I decide to turbo it. Turbo application would be 7-8psi out of a G25-550 or 660 targeting under 300whp max

edit: I typed that all out before setting you edited the formatting in your last post.

 

The thing about surfacing the block is that to do it correctly it has to come apart. I stand by that the nick looks minor enough it won't matter, it doesn't look to be all the way through the sealing area either. Hopefully it works out for you! I've done some ghetto **** with sandpaper glued to a thick piece of glass to surface stuff like that in place (and it definitely works), which i considered suggesting, but I think that's small enough it's not worth doing.

I'd send it, and if it didn't hold I'd just use that block for a full build later.

 

Could be much worse

 

Took me way too goddamn long to put that joke together but when I did I damn near spit out my coffee Cat for you, dawg.

Ahh yes, I forgot to mention, I took some 1000 grit sandpaper and gave the nick an extremely light wet sand before cleaning the block just to make sure there weren't any high spots protruding upwards.

I keep forgetting that this is a "backup" motor. I do want to throw it in the car before Summer's over to make sure it runs well, but there's nothing forcing this engine to get turbo'd if I go that route. I think I'm going to slam it in N/A, and once I confirm it runs well, I'll give the ring-gapping treatment to my original 2.5, and get ready to swap that one back in as long as the cylinder walls and bearings still look good (I haven't peeked inside it once over the course of 16 track days so who knows what's going on in there). This motor will then be relegated to backup duty and might get built into a 2.4L with a 2.3L Ecoboost crank, forged rods and pistons... but that would be down the road. This scenario is first world probs to the max lol.

I texted one of my buddies who works in a speed shop as well and frequently rebuilds BMW and other euro sports car motors, including the one in his M coupe which he tracks. His response: "Dude I wouldn't have scoped the block deck closely enough to even see that. You're good." Lol.

So different answers all across the board lol, but I think I'm comfortable running it naturally aspirated at least as is. This thing's gonna get run N/A and then will be put on backup duty and built into something sick at a later date.

But for now I'm gonna crack open this Pacifico tall can and go lay out by my buddy's pool. Thanks for the feedback guys and happy 4th!

 

It should be decked before going FI. It also has some firing ring wear from previous use. Being flat is only one aspect. I have used a granite surface plate with a few sheets 400grit wet dry paper that is taped down along the sides to clean up minor imperfections. For FI applications the deck surfaces can’t be too perfect. Leaks will cause burned head gaskets and/or overheating issues. The correct surface finish is import. The head is constantly sliding across the head gasket and requires a relatively smooth finish.

 

I don't think it matters whether it is your spare - when you fire it up, you want it working, end of story. AKA do it right, do it once.