New member here. I unable to locate a thread on maximum boring on a 383, so here we go. I obtained a 383 for my 70 RR. Once I pulled it apart I noticed some corrosion in cylinders 7 and 8. I have not yet measured the bores, but is +.060" a possibility? I see that kits are available, but do not with to have issues down the road.
383 Maximum Bore Size
- Thread starter Hoofty
- Start date
69hemibeep
Sponge Bob Square Wheels
Heat would be the main issue if the block can go over that far, have it sonic checked. What is the bore now? Is it a #s match block ? If so you could sleeve it
droptop
Well-Known Member
The 400 is basically the same block as the 383 with a bigger bore dia. You should be able to go to that dia without any issues at all. This chart is from Allpar.
Bore Stroke CID Bore Stroke CID
4.06" 3.38" 350 4.18" 3.75" 413
4.12" 3.38" 361 4.25" 3.75" 426
4.25" 3.38" 383 4.32" 3.75" 440
4.34" 3.38" 400
Bore Stroke CID Bore Stroke CID
4.06" 3.38" 350 4.18" 3.75" 413
4.12" 3.38" 361 4.25" 3.75" 426
4.25" 3.38" 383 4.32" 3.75" 440
4.34" 3.38" 400
69hemibeep
Sponge Bob Square Wheels
I do believe the 400 is a different casting to allow for the large bore
1778ppr
Plymouth Owner
According to the Direct Connection book I have, it’s says +0.060” is max overbore from standard 383 bore of 4.250”. So, max bore dia for a 383 would be 4.310”
droptop
Well-Known Member
The casting is different for the added strength around the mains because of the cast crank.
69hemibeep
Sponge Bob Square Wheels
Recommended max bore of 60 over on any big block depending on core shift. If the core is crooked 40 over max so a 60 over 4.375 piston for the 400 and a 60 over 4.310 for the 383. I looked at allot of sources today to edjimacate myself 
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Goon
Well-Known Member
I'd find a different block. 383's are not hard to find. Plus you'll have peace of mind.
then stroke it out.
then stroke it out.
69hemibeep
Sponge Bob Square Wheels
You need to measure the holes first they may clean up if it is standard or 30 over. Worst case If its a numbers match block sleeve the two holes, if not do what Goon said
moparchris
Well-Known Member
I sonic check my blocks always when I bore them. Cheap insurance. I have a 440 that at .030 over is too thin. I have several engines that are .060 over with zero problems.
quikbird
Well-Known Member
Chris, nice to hear from you again. Been wondering what you have been up to. Hope all is well.
I agree, sonic check the block, go from there after results
I agree, sonic check the block, go from there after results
69hemibeep
Sponge Bob Square Wheels
First find out what the bore is, it might be standard.
Russ69Runner
Well-Known Member
Yep that is the first thing I do. Measure from top to bottom to make sure you don't have a taper. Check the top for ring made by the lower being worn larger may have to get a ring cutter. Have rebuilt many and engine. If I needed one bored then took it to machine shop for that but did the rest at my shop. Good to have the block boiled to clean all the gunk out of the journals and oil ports. Find a machine shop you trust ask around to find a good one. Good luck Russ.
