View Full Version : Main stud girdle for Navistar blocks
Good idea or unnecessary? If my existing engine is a small bolt, then reusing it is kind of a no-brainer. But if my current is a big bolt, then should I spend the $$ on a girdle for the new block?
DmaxMaverick
05-11-2016, 12:01
All Navistar blocks should be small bolt. I can't imagine a circumstance where it wouldn't be. The effectiveness of a stud girdle in older (weaker?) blocks isn't conclusive as it is, and still subject for debate. A Navistar/GEP block shouldn't see an advantage with one, except, perhaps, in the case of competition (racing, pulling) or very heavy duty use. If you have one and it isn't inconvenient, it wouldn't hurt. Otherwise, I wouldn't bother.
Thanks! One less thing to worry about.
My only suggestion on even a Navistar block
DEHORN THE ENTIRE BOTTOM END.
Go through and break every sharp edge and lightly chamfer every bolt hole.
Do not leave anything sharp in the bottom end.
Sharp edges create stress risers and can lead to formation of cracks.
Chamfer the oil holes in the main saddles too.
Use a countersink and just break the edge to about 1/64"
All the holes in the saddles are nasty nasty sharp.
This sort of stuff is "Blueprinting 101"
I would not worry about the girdle unless you are in a position to toss it in.
Won't hurt.
Dehorning will likely do more to help stop cracks.
When I did my AMG block I even used a very small carbide ball bur in the die grinder and made a tiny radius in the bottom corner of the step the main caps sit in.
SHARP CORNERS KILL
My only suggestion on even a Navistar block
DEHORN THE ENTIRE BOTTOM END.
Go through and break every sharp edge and lightly chamfer every bolt hole.
Do not leave anything sharp in the bottom end.
Sharp edges create stress risers and can lead to formation of cracks.
Chamfer the oil holes in the main saddles too.
Use a countersink and just break the edge to about 1/64"
All the holes in the saddles are nasty nasty sharp.
This sort of stuff is "Blueprinting 101"
I would not worry about the girdle unless you are in a position to toss it in.
Won't hurt.
Dehorning will likely do more to help stop cracks.
When I did my AMG block I even used a very small carbide ball bur in the die grinder and made a tiny radius in the bottom corner of the step the main caps sit in.
SHARP CORNERS KILL
Thanks Robyn. I do plan to spend some quality time removing all the sharp edges, and especially checking to make sure they didn't hit the bottom of the bores when they drilled the piston spray holes. I also like to clean up all the drainback holes in the valley. Fun times.
Little DUMORE grinder, some stones, carbide burs, fine cut file, emery rolls and a mandrel for them.
A full bucket of ELBOW grease. :D
Buttttttttttttttttttt, it's worth every ounce of time and blood sweat and tears you put into it.
Taking the time to debur the bottom end can make the difference in an enginE that lives a loooooong time and one that does NOT
Have fun and good luck
Little DUMORE grinder, some stones, carbide burs, fine cut file, emery rolls and a mandrel for them.
A full bucket of ELBOW grease. :D
Buttttttttttttttttttt, it's worth every ounce of time and blood sweat and tears you put into it.
Taking the time to debur the bottom end can make the difference in an enginE that lives a loooooong time and one that does NOT
Have fun and good luck
Now if I could just come up with some 18:1 pistons, I would be in great shape...
What about the P400's ?
Are they ready to go w/o all the aforementioned elbow greeeez ?
My 95 Sub is awaiting a new power plant and that's what I want to put into it.
Jeeps.
18:1 slugs are readily available items
.........
TGVET
The P400 has a built in "Girdle"
All 5 of the main bearing caps are cast into a single unit that bolts not only to to main webs, but to the pan rail as well.
The oil pan is a cast aluminum unit that is really part of the entire structure too.
As far as the P400 having been hand "Dehorned" ahhh nope.
The factories do not do this stuff.
These are old race car shop tricks that take time and effort.
Albeit, these tricks drastically reduce/remove the inherent stress risers in the lower end, they are not something you will find in a production engine.
Now, installing the P400 in a 95 Burb is quite easily done, TO A POINT
Unless AMG has started offering the P400 with an oil pan that will fit down around the front differential on these rigs there needs to be some serious mods made to the pan to make things fit.
I know that a few folks that frequent TDP has dropped the P400 into GMT400 series rigs, but as far as a "Drop in" goes ????????
ASk questions before you drop the coin for the new P400
If there is a drop in model then you're set, and if not then a little whittling on the pan is needed.
This is likely why many go for the Optimizer 6500 as it is a direct bolt in and go engine.
The only difference is the Optimizer does not have the heavy cast girdle, but does have all the rest of the block mods.
The P400 has the forged crank shaft though (Real plus)
Have fun
Jeeps.
18:1 slugs are readily available items
Yes, Peninsular's pistons, with the higher pin height which are available in std size only. I found one other retailer that has Mahle 18:1 in 020, but they also use the relocated pin to drop the piston into the hole to give the lower compression ratio. Maybe I have been around gas engines too long, but dropping the piston down into the hole and opening the quench area doesn't sound like a good alternative to me.
I've been in touch with Kennedy and he hasn't produced a set in quite a while and lost the machinist that was doing the work on the crowns. I'm pursuing one other potential source for having the old JK style pistons made, and if it doesn't work out then I may just sell off the NAV blocks and pursue a 4bt. ;)
Dropping the piston by moving the pin C/L up or by cutting the top of the piston or by any means that gives slightly more room between the top of the piston and the head reduces the compression ratio.
The other way would be a piston with a Bowl in the crown.
The 6.2/6.5 uses the recardo bowl style piston crown to achieve the best swirl action of the flame front as it progresses from the pre cup port into the cylinder.
No worries about Quench area.
This is a gasoline engine issue and in the indirect injected diesels the combustion takes place inside the pre cup in the head.
I would opt for the pistons with raised pin height.
A set with the hard anodized coating on the crown is the way to go.
A link here.
Complete set with rings
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0ahUKEwjaz7zsjYLNAhVL02MKHXflAAwQFghfMAM&url=http%3A%2F%2Fwww.amazon.com%2F6-5-6-5L-Diesel-MARINE-18%2Fdp%2FB016APSV2W&usg=AFQjCNFQzZq7gSPpikPDwXGBifqn5WXmVg&sig2=xVkp3AP_hEf3vmldasMp0g
Another option
http://www.ebay.com/itm/6-5-6-5L-Diesel-18-1-MARINE-Pistons-020-MAHLE-Coated-set-of-8-w-Rings-/141795284233?hash=item2103a85509:g:a-sAAOSwIrNWFWZm&vxp=mtr
Have fun
OK, something to consider with the quench not being an issue. I still like these though...(with a ceramic coating)
http://www.kennedydiesel.com/images/lowcomppist_lrg.jpg
arveetek
06-01-2016, 06:53
Over 10 years ago I had the Diesel Depot (Avant Salvage in Georgia) make me a set of custom 19:1 ceramic-coated pistons. I didn't want the full 18:1 drop due to possible hard starting in winter weather. I was pleased with the product and the resulting engine. I ordered .040" over pistons, and then had the block bored (6.2L red block) to match the pistons.
I'm not sure if this is something they still offer or not.
Casey
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