383 Engine BUild
Thread Starter
Le Mans Master
Joined: May 2008
Posts: 9,063
Likes: 2,736
2022 C3 of the Year Finalist - Modified
383 Engine BUild
Question for any engine guys. I am building a 383 from Chevy 880 block bought from Summit Racing. It is advertised as bored to .030 over, mains align honed, and cam bearings align bored. I have two problems. One is easy buy annoying, in that the cam bearings installed are not fulled centered in there bores, which I can move them into position to get the holes properly aligned with the oil groove. The hole is at 3:00 oclock position, which I guess is okay.
Main issue is that the main bearing bores are about 0.0004 too large, based on the specs I have found. They are supposed to be 2.6410 with plus tolerance of 0.0006. They are at plus 0.0010 measured with dial bore indication (spent all weekend measuring, again and again). My guess is the align honing was a little agressive.
So, I went ahead and put all the bearings in place and measured bearing clearance. The bearing clearances are 0.038 inches for several, some of them slightly lower. I would prefer around 0.025-0.030. From what I read, this is definitely on the high side.
What do you all think?
Main issue is that the main bearing bores are about 0.0004 too large, based on the specs I have found. They are supposed to be 2.6410 with plus tolerance of 0.0006. They are at plus 0.0010 measured with dial bore indication (spent all weekend measuring, again and again). My guess is the align honing was a little agressive.
So, I went ahead and put all the bearings in place and measured bearing clearance. The bearing clearances are 0.038 inches for several, some of them slightly lower. I would prefer around 0.025-0.030. From what I read, this is definitely on the high side.
What do you all think?
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
I would call summit ask them to to make it right. You spent your hard earned money at a reputable vendor and expect to get what you paid for, what they advertised. Sure its probably an easy fix but they should foot the easy fix.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
There shouldn't be any "align boring" of the cam journals...that's a red flag for me right out of the gate.
You can adjust main bearing clearances by using oversize bearings and mixing bearing oversizes (article linked below) but IMHO bad machine work is indicative of other problems you won't see until the build is done. I'm not a fan of these "pre-machined" blocks - I expect the deck height is also wrong and/or inconsistent and a bunch of other stuff too. Send it back and work with a good local machine shop.
http://www.carcraft.com/techarticles...e/viewall.html
You can adjust main bearing clearances by using oversize bearings and mixing bearing oversizes (article linked below) but IMHO bad machine work is indicative of other problems you won't see until the build is done. I'm not a fan of these "pre-machined" blocks - I expect the deck height is also wrong and/or inconsistent and a bunch of other stuff too. Send it back and work with a good local machine shop.
http://www.carcraft.com/techarticles...e/viewall.html
Thread Starter
Le Mans Master
Joined: May 2008
Posts: 9,063
Likes: 2,736
2022 C3 of the Year Finalist - Modified
Summit
I spoke with Summit today and they agreed to take the block back. With all of these problems, I am rethinking the whole plan. I appreciate the idea of getting a local machine shop, but it requires the same level of trust I had with the Summit block. I may just buy a GM short block assembled, even if does cost more.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
The key points for a machine shop are getting referrals, not references - ask to talk to folks they've done work for in the prior 30 days - and make sure they want to work with a home rebuilder. Post in the forum for your home area.
There's nothing wrong with a GM or GMPP shortblock, but make a careful choice. In the end, if you're going to do engine stuff, you're going to need to find a good shop even if you have to drive a while to get to it.
There's nothing wrong with a GM or GMPP shortblock, but make a careful choice. In the end, if you're going to do engine stuff, you're going to need to find a good shop even if you have to drive a while to get to it.
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
I spoke with Summit today and they agreed to take the block back. With all of these problems, I am rethinking the whole plan. I appreciate the idea of getting a local machine shop, but it requires the same level of trust I had with the Summit block. I may just buy a GM short block assembled, even if does cost more.
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
The bearing to crank clearances are 38 thousandths? And you like them at 25 to 30 thousandths? 0.025 to 0.030?
They have 6 tenths tolerance and you have them at 1 thousandths over size. I think I must be reading something incorrectly here.
They have 6 tenths tolerance and you have them at 1 thousandths over size. I think I must be reading something incorrectly here.
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From: Chino CA
Thread Starter
Le Mans Master
Joined: May 2008
Posts: 9,063
Likes: 2,736
2022 C3 of the Year Finalist - Modified
Decimals
Forget about where the decimal point is, just to make it clear. Information I read is that a desirable bearing clearance is 020 - 030. Mine is at 038.
The 0.0006 number I mentioned is the plus tolerance allowed on the main bearing bores (meaning the holes the bearing are inserted into). The specifiaciton is 1.6410 +0.0006 / - 0.0004. This means 1.6404 - 1.6416. My bearing bores are at 1.6420 plus.
Fortunately for me, Summit and Skip White have agreed to allow me to return all these poor quality parts and start over.
The 0.0006 number I mentioned is the plus tolerance allowed on the main bearing bores (meaning the holes the bearing are inserted into). The specifiaciton is 1.6410 +0.0006 / - 0.0004. This means 1.6404 - 1.6416. My bearing bores are at 1.6420 plus.
Fortunately for me, Summit and Skip White have agreed to allow me to return all these poor quality parts and start over.
Thread Starter
Le Mans Master
Joined: May 2008
Posts: 9,063
Likes: 2,736
2022 C3 of the Year Finalist - Modified
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
Before you buy any of these pre built engines, get the name of the manufacturer for each part they intend to use in the engine. Do a little research and see what issues people are having with each company.
Remember, Less costly parts generally mean less quality. Yates doesn't use eagle cranks.
Remember, Less costly parts generally mean less quality. Yates doesn't use eagle cranks.
Drifting
Joined: Jan 2012
Posts: 1,908
Likes: 129
From: Fredericksburg Virginia
There HAS to be a decent speed shop around there. My guy is top notch and VERY **** retentive...a good quality in an engine builder.
He isn't the 'big guy' in town. He's the person that has been building engines with his dad since he was 5. His dad owned the shop, now he owns the shop.
My radical 350 build JUST went on the test stand tonight and I am 100% confident that it will run like a banshee. Not a question in my mind.
Work with a person. Not with Summit. Not with Jegs. They may MAKE it right, but I'd rather it BE right.
An **** retentive engine builder. That's what you need.
He isn't the 'big guy' in town. He's the person that has been building engines with his dad since he was 5. His dad owned the shop, now he owns the shop.
My radical 350 build JUST went on the test stand tonight and I am 100% confident that it will run like a banshee. Not a question in my mind.
Work with a person. Not with Summit. Not with Jegs. They may MAKE it right, but I'd rather it BE right.
An **** retentive engine builder. That's what you need.