401 to .060? How realistic?

aallison28

Bad news for me. The block is currently .030 and needs to be bored. It's .007 out of spec from what I understand. Dude said it could go .060 with no problem I'm not real sure. But I see Bulltear sells .060 pistions for a 401. They even go to a .085. Do they have .040 or .050 that I missed? My understanding is over .030 you really risk the motor getting hotspots. THis is going into a CJ and the motor is being built for torque. Any thoughts???

jeepsr4ever

People do it all the time. A quick sonic check will tell the tale but it isnt uncommon to go .085 or 4.250 bore on a 401 block. Generally speaking the earlier the block the better the chance but you never know how the casting went or if the mold box had any displacement or core shift when they were cast.

jeepsr4ever

I will also add that it is the availability of the ring size that sets the bore and piston size. Check summitracing.com for rings stock 4.165, .010 = 4.175, .020 = 4.185, .030 = 4.195..ect and keep in mind with a 401 AMC we are talking about stock rings that are 5/64 5/64 3/16. As long as the corresponding bore and ring thickness is availalbe for your bore we can make a custom piston for you in any compression for $660 shipped so maybe you onyl have to go .040 or .050 over. Factory TSM's are litterally a good bathroom read but not much more when it comes to block guidelines.

aallison28

The mechanist said the the bore was .007 out of spec and he needed to bore it double that to clean it up. So from .030 to .044. He said all he could get was a .060 piston so that was what he was going to use. I've found some .040 pistons. I think bulltear has some .040 in stock. So if I get the 40 over pistons and go with that, do you guys think it will be OK or do I need to go a custom .050? I found a set of rings that can be fit. At least I think I did. But it seems if we bore to .040, the most it will be out is .003 and that is in spec IIRC. If I go 40 over, do I still need to sonic check the block? I tired to call a Bulltear and talk to them today but I kept getting the asnwering machine and I am not in any position to get a call back.

jeepsr4ever

We dont have an answering machine you got our voicemail. Most likely due to someone else being on the first phone line. If you can find rings for it we can get a piston done for it....any bore size.

Old Rugged Crosser

Hey aallison28, is your tag memorializing the Allison stock car guys?

aallison28

Old Rugged Crosser;129392 wrote
Hey aallison28, is your tag memorializing the Allison stock car guys?

No. My name is Arthur Allison and when I got my first MSN account I was 28 years old......

aallison28

jeepsr4ever;129386 wrote
We dont have an answering machine you got our voicemail. Most likely due to someone else being on the first phone line. If you can find rings for it we can get a piston done for it....any bore size.

These will work for a .040 over http://www.summitracing.com/parts/SLP-E-302K40/

Based on everyhting I've read, my plan is to have it sonic checked and bore it as little as possible. If it will clean up to within tollernace at 40 over, that is what I'm going to do. If not, I'll have it bored as little as I can to clean it up as long as the sonic check is good. I'll match the smallest bore size with the pistion rings avaliable since you can do any bore size. I hope to stay under 050 so I can get anothe bore out down the road. I'll only go to .060 if it checks out on the sonci and I have no other option.

I realize I'm making this over complicated but 401 blocks are darn hard to find in Florida and i don't want to mess it up.......

jeepsr4ever

Yes:glasses2:

aallison28

block is being sonic checked to see if it can go .060 over.................

aallison28

Here are the results of the sonic test. You guys know AMC's. Based on the numbers, am I OK going to as much as .060 over? Thoughts on how far I can bore it? Going to .045 over will clean it up completely but will require custom pistons. Feel free to make comments pro or con............ Results of Sonic Test, AMC 401 bored .030 over. TF = Top Front of each cylinder LF = Lower Front of each cylinder TR = Top Rear of each cylinder LR = Lower Rear of each cylinder ET = Exhaust Side Top of each cylinder EB = Exhaust Side Lower of each cylinder IT = Intake Side Top of each cylinder IB = Intake Side Bottom of each cylinder Piston Number TF 0.185 TR 0.185 ET 0.180 IT 0.240 1 LF 0.270 LR 0.220 EB 0.220 TB 0.300 Piston Number TF 0.240 TR 0.165 ET 0.175 IT 0.245 3 LF 0.180 LR 0.250 EB 0.270 TB 0.270 Piston Number TF 0.165 TR 0.190 ET 0.175 IT 0.220 5 LF 0.180 LR 0.240 EB 0.280 TB 0.290 Piston Number TF 0.150 TR 0.215 ET 0.180 IT 0.160 7 LF 0.160 LR 0.300 EB 0.240 TB 0.320 Piston Number TF 0.200 TR 0.180 ET 0.160 IT 0.200 2 LF 0.230 LR 0.210 EB 0.230 TB 0.300 Piston Number TF 0.170 TR 0.160 ET 0.170 IT 0.200 4 LF 0.230 LR 0.200 EB 0.240 TB 0.300 Piston Number TF 0.220 TR 0.170 ET 0.190 IT 0.270 6 LF 0.270 LR 0.220 EB 0.270 TB 0.300 Piston Number TF 0.150 TR 0.210 ET 0.170 IT 0.270 8 LF 0.200 LR 0.240 EB 0.280 TB 0.290

wyrmrider

your machinist has torque plates for an AMC? (what equipment does he have- he's not trying to do this with a kwik way is he???) any reason he can't bore .007 and hone .003? AMC blocks are much harder than chevy's In general the smaller over bore the better ring seal makes up for a few cu/in I have finished bored AMC 199 sixes .010 to make a class where the rule was 210 cu in max... 3 3/4 +.010 x 3 inch stroke either Armasteel (like Pontiac) or 52,000 PSI cast nodular iron cranks = indestructible engine)

aallison28

OK, so after all the work, here is where we are.......... I'm a little paranoid. 'Bout to drop close to 2k on motor stuff and I want to make sure it will be what I want. Going in a CJ6, T-18 tranny with 6.32 first, 4.56 gears and 40" tires, give or take. I am building the motor for torque. Most of my driving will be street but some off road with mud and sand. Motor is a 401: .040 over Forged speed pro pistons with 9.5 compression Moly Rings Comp cam 268 kit (260H?) (XE256H?) Performer intake Holley truck avenger carb, 660 cfm Doug Thorley headders and duel exhaust with a cross over if I can get it to work Some sort of high energy ignition (thinking about the ford TFI using the stock motorcraft dizzy) To be blunt, I want as much torque as I can get. This will not be a high RPM motor. Bet it almost never sees over 5K. So is there any suggestions to increase the torque out of this motor? I know it will have plenty of HP for what I want. Make me feel good that I'm doing everything right.......