best m20 stroker combination.

[4x4_e30]

I feel like a broken record here. The 885 head will CC the same as a 200 when shaved to it's limit. In other words, instead of having to tear your bottom end down, put different pistons in, and get the block shaved, you just shave the 885 head down to 4.909" and slap it on the ETA bottom end. 9:1 CR, cheap, easy, effective. My car would go head to head with a strong running stock 325i, while I still had a 2.93 and he was running a 3.73. We can hee and haww about squish area, cam timing, rebuild-ability but in the end you're talking about a budget build, why re-engineer the wheel for a couple variables that aren't going to make or break it, or why turn it into something other than a budget build when you're just going to end up with a motor that makes <200hp without head work. Sounds like a huge waste of time and money for a less than optimal setup.

Now that I think of it, me dropping $7k+ on building a "proper" N/A M20 seems like an even bigger waste of time and money, so to each their own!

[ForcedFirebird]

I feel like a broken record here. The 885 head will CC the same as a 200 when shaved to it's limit. In other words, instead of having to tear your bottom end down, put different pistons in, and get the block shaved, you just shave the 885 head down to 4.909" and slap it on the ETA bottom end. 9:1 CR, cheap, easy, effective. My car would go head to head with a strong running stock 325i, while I still had a 2.93 and he was running a 3.73. We can hee and haww about squish area, cam timing, rebuild-ability but in the end you're talking about a budget build, why re-engineer the wheel for a couple variables that aren't going to make or break it, or why turn it into something other than a budget build when you're just going to end up with a motor that makes <200hp without head work. Sounds like a huge waste of time and money for a less than optimal setup.

Now that I think of it, me dropping $7k+ on building a "proper" N/A M20 seems like an even bigger waste of time and money, so to each their own!

Completely wrong. The image of my dyno in a previous post had the head shaved well past the 4.909 machining limit, anf I used a half height MLS gasket on top of it (.036") That limit is in place because the domed b25 pistons will contact at the squish area of an 885 head. Also the 885 head on flat pistons starts at 8.3:1, it would take a whole lot of shaving to get another 1.5:1 compression. Check out my dyno thread in my signature, 885 on eta block (135whp) only makes a few more HP than just putting a chip in your eta (125whp), swapping pistons and spending $100 on shaving the block gets you another 45whp to total 180 - which is significant when a stock eta makes about 115.

Installing some stock b25 pistons and shaving the block 2mm is easy work, and uses all stock parts.

[4x4_e30]

Completely wrong. The image of my dyno in a previous post had the head shaved well past the 4.909 machining limit, anf I used a half height MLS gasket on top of it (.036") That limit is in place because the domed b25 pistons will contact at the squish area of an 885 head. Also the 885 head on flat pistons starts at 8.3:1, it would take a whole lot of shaving to get another 1.5:1 compression. Check out my dyno thread in my signature, 885 on eta block (135whp) only makes a few more HP than just putting a chip in your eta (125whp), swapping pistons and spending $100 on shaving the block gets you another 45whp to total 180 - which is significant when a stock eta makes about 115.

Installing some stock b25 pistons and shaving the block 2mm is easy work, and uses all stock parts.

Hmm.

https://www.r3vlimited.com/board/sho...d.php?t=334345

Looks like I took the video out of that post, here's the proof (sorry about the music)
https://www.youtube.com/watch?v=Tp43Hc0WIrU

[digger]

In fairness the difference between the usual eta with 885 head and that 180whp 2.7 with decked block is more than just the piston dome and CR. Or put differently if you were to put a flat piston with similar CR in that engine the power might reduce but nowhere near 40 whp imo.

[ForcedFirebird]

Hmm.

https://www.r3vlimited.com/board/showthread.php?t=334345

Looks like I took the video out of that post, here's the proof (sorry about the music)
https://www.youtube.com/watch?v=Tp43Hc0WIrU

Interesting. I have CC'd dozens of 885 heads (I have a proper burette with .2cc graduations), but never bothered with a 200 head. Next time I have the burette out, will have to measure....

https://www.r3vlimited.com/board/showpost.php?p=4871657&postcount=140

If you calculate the volume of a cylinder, the stock 84mm bore will decrease 1.3cc for every .010" (~.25mm) shaved off. The 885 head has a taper, so the more you shave, the less the CC's will decrease. The 885 head in it's full height is 125mm (4.921"), and 124.7 (4.909") is the minimum height, totaling .012" max shave. The 885 head starts at 42cc, the eta is supposedly 37cc (I would like to verify).

Either way, I have built and dyno'd several 885 heads on eta engines, and they always produce lackluster results. My spec-legal m20's make well into the 160's, I have never had an 885/eta combo break 150, even when writing a chip, adding a cam, headers etc. They do, however make good torque (but still only comparable to a healthy stock m20).

In fairness the difference between the usual eta with 885 head and that 180whp 2.7 with decked block is more than just the piston dome and CR. Or put differently if you were to put a flat piston with similar CR in that engine the power might reduce but nowhere near 40 whp imo.

The one with all stock parts and 272 cam made just as much, though. I dyno'd 2 on the same day. The one had a bad diff, which was repaired, and the spun bearing after the race has been repaired, plan on taking it back to the rollers. The only change was I put a thicker head gasket (+.3mm) because the quench was so close, the carbon on the pistons was leaving marks on the head.

[cornchip]

Ugh. Maybe I’ll just be happy with the stock eta and worry about getting my Ghia running instead.

[ForcedFirebird]

In fairness the difference between the usual eta with 885 head and that 180whp 2.7 with decked block is more than just the piston dome and CR. Or put differently if you were to put a flat piston with similar CR in that engine the power might reduce but nowhere near 40 whp imo.

We didn't have time to dyno the 2.7 with the cam, but did take the cars to Daytona this past weekend. The cammed engine definitely has more power. I was able to hit the 7k rev limiter in 5th gear, speedometer was buried (aero limited in the past at 134mph with a draft, hitting a wall at ~62-6400rpm), definitely pulled on the other car at the track. Will be interesting to see what the dyno has to say.