Evo 8 manley ring gap for 800-900whp

Hello. I am building evo 8 engine. It will have Manley pistons. It is going to run e85 and it will be street car with big turbo around 800-900whp. The instruction that manley included showing to run bore size x .008 on boost over 30psi. So in my case would be 3.366x.008= 0.027

Look like it is very large gap . What gap do you guys run on manley pistons and similar power level? I was thinking to set them around 0.022 top and 0.0024 bottom. What you guys think? I dont't want to have to much blow by running too big gap and also I don't want to run too little gap. Manley recommendation look very conservative to me. Thanks!

Hi. My power level now (800+) is about the same as you plan and I'm using the same type of fuel. The ring gap size i make is exactly as instructed by Manley. However, in a previous setup (700+hp) i had smaller gaps than recommended by 1 tenth of mm and i did not see any signes of pistons damage when disassembled that engine although it had seen 3.4 bar of peak boost regularly...

Thank you so much for reply. The reason why I feel like 0.027 inch look little too loose because on previous engine I used wiseco pistons and gap was 19 top and 21 bottom and it was running great for over 3 years with power at around 700whp. Now the power will be little higher and also different manufacturer of pistons (manley) and I was confused where to set them. Do you see a lot of blow by on your setup using gaps instructed by Manley? Thanks!

I also noticed different approach to ring gap by different manufacturers. Some of them recommend first ring gap larger than the second, some recommend the other way around.

I didn't face a lot of blow by with Manley. Catch can is always empty...

Great, Thanks a lot for help. I think I will go with 23 top and 25 bottom. I hope this will not be too tight.

I've found the Manley provided instructions are way too loose and do result in excessive blowby, so I feel you're on the right track.

The official recommendations will naturally be a little looser to account for tuning and operating extremes.

If you do run them a little tighter, make a point of checking the ring ends on strip-downs to check for signs of the ends butting together or any signs of bore damage.

Remember, it may only be a thou' between being fine and the ends butting up forcing the rings into the bores where they will rapidly overheat and the resulting loads on the lands will break them off, or worse, you could snap a rod and window the block.

I've seen numerous tests where ring/piston manufacturers, and engine builders, have experimented with different clearances and it would seem to only become any sort of issue in the 50 thou', 1.25mm range.

If it's that much of a concern, perhaps a change to the two-piece "Total Seal" rings would be a good idea? They're even available in many sizes with shallow gas-pressure grooves in the top rings.

Indeed, Total Seal is the way to go. I purchased their "gapless" rings for my other 4g64 with 600+ hp...

Thank you for answer. I have never used total seal rings. Do I gap them same as regular rings? Are they worth to buy? I see they are selling them at around 120 us dollars so price is not bad. Also are they wearing faster than regular rings? Thanks

You might want to write to Keith from Total Seal - he is very educated person and I'm sure he will give you all the answers you need about their rings better than anybody else...

You should find the literature here of use - https://www.totalseal.com/support-and-downloads

Thanks guys for reply. I am leaning toward .0022 top and .0024-.0025 second ring even that manley recommend .0027 which seems pretty wide. I would love to hear input from Andre as he got ton of experience about those specific 4g63 engines.

@Krystian87 I would like to hear from Andre too, but that will not happen!

krystian keep in mind people will have different opinions on this, and there is a range of valid answers.

People have made more power on tighter gaps than you are planning, and looser ones.

You had great experience with similar material pistons at 19 and 21 gaps, and your increase in gap for the additional power you are planning on makes sense. I don't think you're making a bad call.

Semi related, my experience is you'll have more blowby with the Manleys vs. Wiseco even if you run the same gaps you used prior. Whatever you choose for gaps, if you end up with more blowby, remember the ring gap wasn't the only change from the old engine.

And also semi related, Total Seal gapless test amazing in static leakdown tests compared to standard rings, but that doesn't mean dynamic sealing is as magical. If you meter crankcase flow you may find something surprising... Your mileage may vary, there are many factors at play.