<6,000 RPM Street SBC Hone: Sunnen 818

[NewbVetteGuy]

All,

I'm looking for a "third opinion". I took my low mileage (14k) SBC 350 L82 to a local machine shop and had them to a few things to it, including giving it a "power hone" (no torque plate). I'm building a street SBC 350 using the stock forged crank, pink "x" rods, and forged pistons, and am just refreshing it with some new rings; I'm using a long-runner intake so anything beyond 6,000 RPM is really pointless.

I called Total Seal to get a ring set and they asked for information from the machine shop on how they honed the cylinders. The machine shop says that they used an 818 Sunnen Stone.

Total Seal indicated that this is something close to a 400 grit finish that's hugely inappropriate for a street motor and that my rings will have a hard time breaking in and getting a good seal. They said I should take it back to whoever honed it and have them rehone it correctly with a 280 grit stone...


-I've had a number of challenges with the machine shop and would rather not have to take my block back to them again, so I'm looking for a "third" opinion on how big of a deal this is.

--Do I really need to take the block to get re-honed with something closer to a 280 grit finish? Is this going to screw up my piston to bore clearances? (I obviously have no idea how much material a quick hone removes.)




Thanks,
Adam

[ClassAct]

If you want the rings to seal, use the stones and geometry Total Seal says to use.

I can say as an engine builder I almost never used a 400 grit finish in anything, unless I KNEW the tuner had his shit together. With that finish there isn't much oil there and it doesn't take much to kill ring seal. Plus, it had to be gasoline only. No alcohol based fuels get that fine finish. You need the oil to seal the rings.

[NewbVetteGuy]

If you want the rings to seal, use the stones and geometry Total Seal says to use.

I can say as an engine builder I almost never used a 400 grit finish in anything, unless I KNEW the tuner had his shit together. With that finish there isn't much oil there and it doesn't take much to kill ring seal. Plus, it had to be gasoline only. No alcohol based fuels get that fine finish. You need the oil to seal the rings.

I just got off the phone with Ed @ TotalSeal one last time. He said it will seal fine with 400 grit; it just won't have enough oil and oil control will be bad and longevity will be bad in a street motor.


Adam

[Newold1]

For the great honing equipment available in the auto engine machining industry it is a problem when these shops won't come into the new uses and technologies in these great new bore finish techniques and results.

What you have asked them to do is not rocket science and many operators of shops on here have been doing this type of quality boring and honing for years!

If you are using a shop that is not availing and training itself in the new bore finish specs. and tools you should probably look at finding a shop that does. They should be using torque plate honing, using plateau hone finishes, understand RA, RVK, RK and such finishes. They should own and use a profilometer as well as the trained expertise to know what finishing tools to use and how to create the best finishes as todays ring types need for great sealing and longevity.

Oems that are building engines that they warranty for 4 -10 years and have engines that run 150,000 to 250,000 miles or more without using oil tells us its not some dark science and can be done by any good shop.

MY opinion is you need a new shop period.

[NewbVetteGuy]

For the great honing equipment available in the auto engine machining industry it is a problem when these shops won't come into the new uses and technologies in these great new bore finish techniques and results.

What you have asked them to do is not rocket science and many operators of shops on here have been doing this type of quality boring and honing for years!

If you are using a shop that is not availing and training itself in the new bore finish specs. and tools you should probably look at finding a shop that does. They should be using torque plate honing, using plateau hone finishes, understand RA, RVK, RK and such finishes. They should own and use a profilometer as well as the trained expertise to know what finishing tools to use and how to create the best finishes as todays ring types need for great sealing and longevity.

Oems that are building engines that they warranty for 4 -10 years and have engines that run 150,000 to 250,000 miles or more without using oil tells us its not some dark science and can be done by any good shop.

MY opinion is you need a new shop period.

I agree about a new shop.

-They did say that because I'm not going with an overbore that a torque plate hone won't remove enough material to really give me the benefits of torque plate honing. They said that if I was going with an overbore- then by all means I should have it torque plate honed, but just honing a stock block and reusing stock pistons, no.


I'm not sure whether they're right or not, I just know that's what they said.


Adam

[pdq67]

May I ask if he might be able to use a, "coarse", dingle-berry hone, a 1/2" electric drill and lube and just re-crosshatch the cylinder walls and go?

pdq67

[houser45]

If you want the rings to seal, use the stones and geometry Total Seal says to use.

I can say as an engine builder I almost never used a 400 grit finish in anything, unless I KNEW the tuner had his shit together. With that finish there isn't much oil there and it doesn't take much to kill ring seal. Plus, it had to be gasoline only. No alcohol based fuels get that fine finish. You need the oil to seal the rings.

Wrong, with over 75 to a 100 alcohol injected 305/360/410 engines i have machined and assembled over the years with a 500 grit finish. I will call bs on this one.

[houser45]

Just a thought? Is it possible he ment a “518” stone

[ClassAct]

If you want the rings to seal, use the stones and geometry Total Seal says to use.

I can say as an engine builder I almost never used a 400 grit finish in anything, unless I KNEW the tuner had his shit together. With that finish there isn't much oil there and it doesn't take much to kill ring seal. Plus, it had to be gasoline only. No alcohol based fuels get that fine finish. You need the oil to seal the rings.

Wrong, with over 75 to a 100 alcohol injected 305/360/410 engines i have machined and assembled over the years with a 500 grit finish. I will call bs on this one.

Then the tuneup has to be dead nuts on. Ever do a back to back dyno test? Call BS all you want. Doesn't matter to me.

[Keith Morganstein]

818 is 400 grit for a CK-10/CV-616. IDK how much they removed from the bores. It’s not uncommon to finish with a few strokes (4-5) of 400.

518 is 220 grit

[houser45]

If the bores are finished round with a torque plate they dont need to be that rough with a thinner ring set (1.0 x 1.0 x 2.5 mm) on alcohol. If its rougher all it is doing is wearing the rings out during break in.

[Keith Morganstein]

Dart block honing instruction

Hone block to finished size with 220 grit @ 40 amps of load on sunnen hone.
Make 3 strokes on each cylinder with 280 grit @ 20 amps.
Make 3 strokes on each cylinder with 400 grit @ 20 amps.

[modok]

Ohhh, nice Haven't heard that one before from dart.
I'd say to de-glaze..... 8-12 strokes with 518 (or 512)
then 6-7 strokes 623 or 818 (which I would choose depends on the rings)

[NewbVetteGuy]

Thanks for all the replies!

I talked to the owner of the machine shop yesterday evening and he said that he doesn't know what Total Seal is talking about and this is just how he's been doing it for 30+ years and his race customers have no problems running 500 laps with this finish, so it should be good enough for a street motor....


I've confirmed that they definitely used a Sunnen 818 stone only it's even on my invoice.


For what it's worth, I'm looking to reuse my stock forged pistons with a 4.5 thousandths piston to wall clearance, and use a 1.2, 1.2, 3/16" ring set with spacers. Gapless steel top, napier 2nd, standard tension 20 lb oil ring.

-I'm mailing one piston to Total Seal to leave nothing to chance because as my forum name says I'm a complete Newb and I just don't trust myself to do anything fully right the first time.

Total seal recommended the cylinders be honed with 280 grit, medium pressure @ 50 strokes a minute with 3 full strokes.





Should I just buy a 240-280 grit aluminum oxide flex hone and go through each cylinder 3 times to try to get more depth on the cross-hatches to retain more oil, or am I better off leaving the cylinder wall finish as-is? It's a street car so longevity is kinda important...

(I'm honestly done with the machine shop; they've been nothing but trouble; they tried to give me someone else's heads back and tried to convince me they were mine, too... ??? The crank was polished beautifully, though.) -My options are:
1. Pay someone else to re-hone it
2. Run it as is
3. Flex hone it myself


Adam

[NewbVetteGuy]

If the bores are finished round with a torque plate they dont need to be that rough with a thinner ring set (1.0 x 1.0 x 2.5 mm) on alcohol. If its rougher all it is doing is wearing the rings out during break in.

No torque plate was used in this case; the machine shop said that it wouldn't do any good on a stock SBC that hadn't been overbored. (I don't know whether that's true or not; I just know it's what they said.)


Adam