ARP head studs? + Dbilas cams + headgasket question

[Maximumtune30]

Hello,

I have a 2.8 stroker build going on, just got the block, crank and the head back from my local machine shop.

My pistons are 12.5:1 compression ratio (gonna be using E85 fuel) and i have a schrick 284/272 cam. I have noticed that the cam is way too small for my build so i'm thinking about buying a dbilas cam 292deg/11,5mm lift/108LSA or the slightly smaller 290deg/11,5mm/110LSA. Does anyone have any experience with these dbilas cams?

I also have a cometic mls headgasket (2.34mm thick), as the head and block both have been milled 0.2mm off. Did i go with a too thick gasket? Are there any downsides using a gasket this size?

Are ARP headstuds needed or am i good with just new stock bolts?

This is my first car engine build ever, (i just turned 17 years old lol). All the help is greatly appreciated, Thanks

[dvallis]

That's a 0.092" head gasket with 0.008" off the block. Stock is 0.070" so you're only 0.014" over. That's fine. Here's a parts list:

Block
ARP main studs
new bearings
main seals
sintered oil pump drive pulley
MLS head gasket
Pistons & wrist pins
Rods
Rod bearings

Head
ARP head studs
HD rockers & valve springs
Rocker shaft seals
Valve cover gasket

Who did the 12.5:1 pistons for you?
What rods?
What ECU?
12:1 CR needs a dyno tune

[Maximumtune30]

Thanks for the reply, here are my engine specs:

Block:
- 85mm JE Pistons 12.5:1 comp, from Top End Performance.
- m52b28 84mm stroke crank , balanced and all the journals polished + metric mechanic seal spacer kit
- "Eagle" 135mm h beam rods with ARP bolts
- new glyco main and rod bearings, STD size
- new oilpump
- Stock main bolts, idk if i really need the ARPs
I have ALL new seals, new waterpump, all the stuff that needs to be replaced

Head:

"885" 325i head
Ports just cleaned up no major porting done
- 43mm intake valve
- 37mm exhaust valve
- 3 angle cut valve seats
- IE hd rockers + new rocker shafts
- new valve guides
- Schrick dual valve springs + new retainers, i don't know how much lift the schrick springs can handle. I have heard that the HD rockers bump up the lift a little.
- Schrick 284/272 cam, like i said i maybe have to get something bigger
- MLS headgasket + i have new stock headbolts, ARP headstuds cost more than 300€ where i live, but if needed i have to get the ARPs
- stock 325i intake manifold, i understand that it will be a major power restriction for a bigger cam
- better flowing headers
- stock distributor ignition system

For the ECU i was thinking megasquirt pnp-gen-2 from condorspeedshop

[dvallis]

I got my JE pistons from Top End as well. They really know pistons. Gave me great advice.

All your parts look good. Should be a very strong engine when you're done. Since it's not boosted ARP head studs or main studs are not really necessary.

Stock intake manifold is pretty damn good. Intake runner length is really important for making power, not just raw CFM. The next step up would be individual throttle bodies, which starts to be $$$$.

I'm using the MS PNP Gen2 will good results on my build. Have a look at Gen3. It has new features like traction control etc.

Another upgrade would be Wasted Spark ignition.

[digger]

High compression engines should be built with some squish action and be optimised with a specific clearance between the piston and head of around 1.00mm for cast iron block and steel rods. A thicker gasket can hinder the squish motion. It will still run but may not take as much ignition timing / be a bit knock proned but likely not a big issue with e85 tuned correctly

I would ask the person who spec'd the pistons what gasket was assumed, what deck height was assumed as that is part of the process to work out the piston compression height. I'd expect it would be based on stock numbers so you probably aren't far away thought stock is 1.75 mm and +0.3 is 2.05 mm. People seem to think the 2.05mm needs to be used on a normal head refresh but not unless a lot more than usual was removed or its been refreshed several times.

Mock it up temporarily is the only way to account for tolerance stack up and it is a recommended step during assembly.

those cams are similar to a schrick 288, i'd aim for the 290 as it has a bit less duration, but it will still have a very choppy idle with stock intake and be capable of peaking at around 7000rpm if it werent for the stock intake. Dont forget to check the PtoV

[dvallis]

Mock it up temporarily is the only way to account for tolerance stack up and it is a recommended step during assembly.. Dont forget to check the PtoV

+1 for Diggers advice. Put 0.125" clay worms on each valve pocket and the highest part of each piston crown. Assemble with a throw away head gasket of the same thickness and torque the head down to spec. It's the only way to know your clearances for sure.

[Maximumtune30]

Thanks for the advice guys, how strong is the stock headgasket? if i used it i would have close to 13:1 static comp. I have a new stock headgasket too, it came with the engine gasket kit.

i have understood that when the compression increases it's harder for the spark plug to arc. Am i good with the stock distributor system, or should i upgrade to wasted spark. The wasted spark option seems like a lot of work for a little gain, am i wrong?

[dvallis]

Have a look at John's dyno thread. Lots of examples with different head gaskets.

https://www.r3vlimited.com/board/forum/e30-technical-forums/engine-drivetrain/m20/378740-forcedfirebird-s-m20-dyno-thread

[digger]

Thanks for the advice guys, how strong is the stock headgasket? if i used it i would have close to 13:1 static comp. I have a new stock headgasket too, it came with the engine gasket kit.

i have understood that when the compression increases it's harder for the spark plug to arc. Am i good with the stock distributor system, or should i upgrade to wasted spark. The wasted spark option seems like a lot of work for a little gain, am i wrong?

tuned correctly the stock OE quality gasket will be fine for a NA engine from an integrity point of view.

unless you are running a lot of boost very unlikely to run into spark problems on a well maintained system, the stock OE quality stuff is very effective, you will want colder heat range plugs though.

IMO wasted spark and fancy fuel injection is probably not worth the hassle on a mild NA engine if youre going with a PnP ECU. Reason being that keeping the stock harness makes things alot easier to get it up and running correctly during initial start-up and break-in. Can always change once things are up and running but alot of that fancy stuff is not aimed at max performance in its own right.

[dvallis]

Right. Wasted spark is only worth it for high boost, and if your engine will live at 6000 RPM for most of the time. Which street cars do not