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#1
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Some time ago I posted info on my 318 and every one said you cant bore a 318 to 4.25 I didnt have the numbers off the block then but have the engine out of the car now
here are the numbersfront of enginr left side CM318R 34566859 right side of block 2-25-71 left side of block2538030 318-12 does that CM 318 R mean racing engine ? the stock 318 i have just says 318 Any help will be apreciated Bill ------------------ |
#2
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You can't bore a 318 to 4.25", period. Even the new siamese-bore R3 blocks can 'only' go to 4.22" MAX. Your 318 can be bored 60 over to 3.97" and that's it. The 'R' in the stamped numbers means a Regular fuel engine.
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#3
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Sorry, Tim's right on the "R"egular fuel. It is also a "G" if it is a 71 motor, cast in the Mound Road plant 3,456 day of production and the 6,859 engine produced that day (wow, that cant be right!!!) The 2538030 is the block casting number
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#4
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If I remember correctly, the bore spacing of the SB is 4.46". A non siamesed block and a 4.25" bore doesn't leave a lot of meat in to the cylinder walls, does it? The first race blocks were produced in the mid seventies, and even they had a 4.10 maximum bore; the blocks had more meat elsewhere, not in the cylinder walls. I have bored a ca '70 318 block to 4.04" and run it several years, the cylinder walls were so thin that once I screwed a too long timing cover bolt and it went right through the cylinder wall without much effort. With a 4.25" bore you would not have had any cylinderwalls at all.
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#5
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You can bore it to 4.25......there just wont be anything left except a BIG ASS hole....couldnt resist.......PRO.....
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#6
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I recommend trying it and then reporting the results back to us. It's good to share information and ideas within the Mopar family.
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#7
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There is a machine shop in Uvalde Texas that talked to me about a 4" bore regular 318. He said it worked and is still running. BUT, it is a low budget, low performance street engine. I would absolutely NOT do it to a horse power making engine.
I agree with CudaMike. If someone could find the time to bust the cylinder walls out of a wasted block and measure the thickness, we would have more knowledge on the subject. I did this (accidentally) to a 69 Ford 302 block that was .040 over 4". It had cylinder wall thicknesses on the same cylinder that ranged from .045 to .120" Not too thick! Billy |
#8
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Billy
Hows that car coming along. I know the shop you are talking about in uvalde. My buddys 360 block is over there right now getting a sleeve in one cylinder that had a crack and the rest are getting sonic checked. I have seen a 318 bored out to 340 specs. Meaing from a 3.91 to a 4.04 bore. It has extremely thin walls and is used only when necessary to whoop some smart a$$ kid. It also has a 360 crank in it. It also runs an experimental oxygen injection system on it similar to NOS but pure O2 compressed higher. All in a D150 pickup. I would love to have this truck but my biddys dad in North Carolina wont let it go. I have thought about it with my 318 but I would have it sleeved also. This other 318 in the truck may have been sleeve I can't remember. You would be better off with a 360 and boring it out to 4.04. The only way to get a small block to 4.25 is to cut the block open and recast it with wider bore spacing. You can't even sleeve the block tthat big if you could actually get sleeves for it. BTW why on earth would you want to do this?? Or are you not on earth? Christian ------------------ Http://ThunderRacing.Knudstrup.net/ 68 'Cuda 383 Best of 8.363@83.78 in the 1/8mile which is a mid 12 with a 1.89 60ft Formula S recreation not original but making like they should have at the factory) Working on adding EFI 69 'Cuda Race Parts Car 76 Duster 273 recent transplant 95 Neon 2.0 SOHC best of 16.96 84 Dodge Ram D50 transplanting 360 |
#9
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He has posted this and swears it to be true. If so, let him do it. We told him so, so many times that a 318 can not be bored out to 4.25.
Let him do it and post pics to prove it. |
#10
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Im sorry I screwed up the 318 is bored to4 1/8 in.
Sorry to get you all sturred up Bill ------------------ |
#11
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I was going to ask you if you did'nt mean 4.025--which might be feasable
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#12
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Thanks for your reply
I Just pulled it out of the duster and put in a 1964 426 wedge engine in last night with shumacker mounts ang headders. It fits pretty good but I( have to cut some steel off the K member by the oil filter so its not touching, . Amityville, didnt mean to stur you up so much My son and I are doing all the work hes 21 im 65 so cut me a little slack lol. The 426 is a rare engine but we are going to run it in the Duster anyway,it will be a good tire kicking conversation piece, and ought to go pretty well. the Duster with driver is 2900 lbs. Thank you for helping out a gear head from the 50s Bill R ------------------ |
#13
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"Amityville???" I guess thats me. <G> Not stired...shaken
And that Duster w/ the 426 sounds better than sliced bread!!! (envy!) Just tryin to help. Sorry if I came on poorly. You'll get all the slack ya need w/ none of the flack. Nobody here is perfect. rumblefish360 |
#14
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Thanks Rumblefish can use all the help I can get.
Im getting up to speed here ,read a lot and listen . That 426 is a HP with a S stamped over it , I hope I can get fuel for it, im thinking it may be 13:1 compression. Going to hold on tight on the first run with it lol ------------------ |
#15
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13-1!! WOW! One of them old time eng's huh. Let me know about that one! Holy heap Sh%#! It's gonna be a lil'hard to feed that on the street! <LOL> Lots of vists to the track for gas for you.
Good luck |
#16
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318 with 4.04 bore......
Hi guys i have been following this topic some time...
I have actually bored a 318 to 340.... but i did not want to reply before i started up my engine.... Boring the 318 to 340 std has been a topic for many moparfans on the web... Some say it cant be done and some say the opposite so i decided to do some mythbusting on this..... I used a 318 PRE 75 block..... The casting number starts with 25..... What is special for those is that they have 5 mm(1/5 of an inch) thick cylinderwalls I have heard that the higher amount of mangan and nickel in the castings make them more suitable to run with thin cylinder walls...... To be sure that u have one of these blocks ....whack in the center freeze plug measure the gap between the cylinders ....then take a slide guage and measure the distance between the same cylinders on the deck..... Subtract the gap result from the result from the deck and divide with 2 Then u have the cylinder wall thickness...... Having a good cooling of the engine is very important... Be sure to use the best components u can find.....The thin walls wont lead away the heat as good as the thicker ones..... I used a high flow water pump , a 16" electric fan and a radiator from a big block... Forged pistons rods and crank will also help leading away the heat better...... During the break in of the camshaft i did not notice any defects in the engine unless the tendence of running hot...... After the break in i have done some tuning on the engine and it runs just perfect so far..... Spec for my engine.... 318 block Forged Speed pro 340 std pistons 10.5:1 comp 318 efi heads(also known as 302 heads) with mira cut and 360 intake valves .... 340 Forged steel crank Eagle forged i beam Rods Comp cam 270h camshaft..... (470/470 lift and 270/270 duration) Rpm 340 airgap intake.... Edelbrock 750 carb....... This far the engine runs great i guess time will tell how long it lives....... One thing is certain if the engine will hold together (wich i believe) i have built a hi performance 340 for a very low cost........ DONT EVEN THINK OF BORING IT MORE THAN STD 340.... Made in sweden /Swede 67 |
#17
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Swede 67
Since my post on this thread seven years ago, I too have bored a 318 to 4.040" as well as invested in a nice little sonic thickness tester. After seeing what some of the .060" over 350 Chevy & Ford engines look like, I have no issue at all taking a 318 to .090" over. I know I should not compare Mopar cylinder wall thiskness to Ford & Chevy because the cylinder length is also different, and the length has a lot to do with cylinder strength. |
#18
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Im doing it to a 68 318, 4.04, Just havent done it yet, I actually havent done anything this winter, just been to damn cold out. I also havent been up to the machine shop that I know has a sonic tester to do it, and I am not sure, But I dont think they have torque plates, but I dont think I really need to do that to this motor, I already have the rods and pistons and crank, just havent got the block done, digging it out of the shed when it is ten degrees and colder just doesnt sound like fun.
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#19
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Just remember that a block with thick cyl. walls & straight bores will allow better ring seal = more power. I wouldn't go more than .060 either. If a bigger bore is needed, the 340 or 360 block would be best.
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#20
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Has anyone ever sonic checked a 318-3 truck engine??? I have wondered if there was any difference in wall thickness.
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#21
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I have heard of someone doing that and finding zip.
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#22
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Quote:
I would bore it to 4.0" and use one of the 3.51" mopar forged cranks you can buy on ebay,give you some where around 355".wayne this is a dead thread.. |
#23
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Unless your hung up on bearing speed, just buy a 3.31 stroke 360 main crank & run 360 block.
4 inch pistons for a 318 3.31 stroke =$$$$$$$ And with thin walls What's the point? YOU COULD HAVE JUST BOUGHT A CRANK. |
#24
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Billydelrio... interested to know what your sonic testing results were and what you reckon is okay for wall thickness... thrust and non thrust sides included...
We're close to selecting a block to bore for our Poly 318 project. So far, all blocks that Ben has sonic tested have shown significant core shift and he reckons they're beyond boring to the 4.0" he wants as he doesn't want to offset the bores at all. Also, with reference to comments about nickel content... the word used to be that high nickel prices about 1963 led Chrysler to cut or reduce nickel content in castings. Now we're saying 1975? There's the results of a metal analysis test somewhere on the Forward Look forum that shows there is zero nickel in everything they tested. |
#25
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To each his own...
We have a customers 318 here out of 69 Model Power wagon...walls sonic out at 0.355". We're gonna safely go to 4.00" and possibly more if we needed to. Just have to check every block on a case by case and I think ya'll be surprised.
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#26
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One theory is that industrial and truck blocks had thicker castings...
That's why I tracked down blocks out of Case combine harvesters. |
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