redtacoma31

I am putting together a LQ4 based 408 Wiseco motor. I have their ring gap specs. What is everyone's opinion on this? They have 2 different measurements. Street Moderate Turbo/Nitrous .0050 top and .0055 second. Then blown race only .0060 both. Where is line drawn with boost when you want to gap more? I will be installing 4.030 pistons. I was thinking .021 top and .023 bottom. Will there be a lot of blow by?

svslow

That will be fine.

Forcefed86

iTrader: (4)

Depends on the piston material, fuel used, tune up, oil squirters, water/meth, etc.

Error on the large side IMO. I'd run more than that if you aren't running alcohol based fuels and plan on pushing it very hard.

3 window

iTrader: (1)

There's an article out there where they used different ring gaps on an engine and measured leakdown and noted blowby. They were up to .100 and the results weren't as bad as you'd think. Not sayin it's a good idea, just sayin.

JoeNova

.021/.023 is pretty low IMHO.
Gap is also dependent on bore size. More ring material = more expansion, so larger bores need more gap.

I would probably add .010 to those numbers.

redtacoma31

Forcefed86- The piston material is the 2618 forged Wiseco units. No oil squirts, Might use a little water meth if needed. I do not plan on alcohol fuel as it is tough to find around Utah and this will be daily driver.

3 window- I will try and find that article. I bet it is an interesting read. Was it a forum or mag/website page?

JoeNova- Those measurements are what I got with the calculations Wiseco said to run for Street Boost/Nitrous. And if I added .010 to them that would be .007 more than the full blown calculations.

What is the line in boost pressure with standard 93 octane fuel. Where you would consider your setup to go from street boost/nitrous setup to a full out blown setup. To me 20psi seems like the ticket, but then again my factor stock Audi with 9.5 c/r is running 24lbs on 93. Doubt Audi gapped those rings crazy big. Or maybe they did and I lucked out on blowby.

Thanks for the opinions I have so far. Again I am not trying to create an argument, but simple small talk on the subject. JoeNova do you have a bad experience?

stevieturbo

blowby has very little to do with ring gap given how small all gaps are, and the fact there is more than 1 ring.

The gap is such a small percentage of the overall seal...even 10, 20thou too big is still almost negligible.

If you have excessive blowby either your engine is fucked or the bores were not prepped correctly to allow the rings to seal.

Forcefed86

iTrader: (4)

I ball honed a 3.78" bore with .028/.030 and had a noticeable amount of blow by. Since dropping to a .022/.024 on those engines I don't have any issues. Thats a baby bore compared to what your doing. Just throwing my experience out there. (was also a bone stock cast piston motor). Also run the same .022/.024 on my 4" bore with mahle pistons.

stevieturbo

I'd say mine are around 35-40 thou lol....zero issue with blowby. In fact it's lighter than many previous engines !!

It's easy to get carried away when filing sometimes lol especially with a powerfile.