When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
i know you said you made your mind up on a 400 sbc, but for the rpm range you drive in, IMO you would be way happier with a big block. I've read your other thread, im semi local to you (ive seen your parts for sale on marketplace), drive the same kinda roads you describe, and your driving style does not match the type of engine you build. its like have a foot long dong and only using the first 4" of it, doesn't make any sense.
I hope this time you find a local builder to work with you, there are still plenty of them in the PGH area.
I disagree with your comment that a 400 SBC is not right for me...why? Because, both the original 406, and the second 408 rebuild, had ALL the torque and power I wanted. The problem with the Mark Jones build, was the cam was 10 degrees duration more than the first built, and IF you pushed the pedal hard enough, and got the RPM past 4000 RPM,....it came alive, but by then I was exceeding speed limits and going too fast to make the next curves in the roads of PA. And had I been on a track, and more road in front of me, I am quite sure it would have continued accelerating to far faster than I care to drive the car. All that high RPM power is absolutely useless to me.....unless I were to drive around in first gear everywhere,....which would be more than annoying.
I don't want to have to resort to that high RPM to create the power I want. In my opinion, that kind of engine is PATHETIC...I want max torque and power off idle and through 4000. Just like a Harley, not like a screaming *** race bike. Said it many times....and here I am saying it again.
The first build, with the 224/228 cam did just that very well, and I was very satisfied with the performance aspect of the engine. And what you all will find out soon, when I post the cam choice,....is I am now at even less duration, .and should make the engine even better for me off idle through 4000 RPM. It will idle better, smoother, more vacuum,...and more carb signal....and is going to accelerate the car in the lower RPM ranges FAR better than first two and finally deliver exactly what I wanted from the beginning.....but the racer boys just don't get it. It seems they are unable to comprehend it. Its got to be some sort of mental block or defect??
So....point is, a 400 is more than adequate, and meets all my wants and needs, proven by the 9600 miles I drove the car with those two engines installed. I just need one that isn't going to self destruct and burn tons of oil.
As for a big block, I posted my reasons why not in Post #1. Not repeating it again. Yes....big blocks deliver what I want, but they come with the compromises I listed. And I am not going to bicker about the truth that a big block does it better and easier, versus a 400 SBC.....I know they are not the same. But again....lots of compromises.
And as for all these engine builders in Pittsburgh you mention......I found none, nor do I know any, nor would I trust any of them even if I found one. If you ask them,any of fhem will tell you how great they are....because thats what they do. That means nothing to me.....as proven by two builders who did just that, and obviousy that was a mistake. Not doing that again.
Last edited by Torqued Off; 03-06-2024 at 08:10 AM.
Definitely looking forward to your updates on this thread. do you have a projected time line as far as when the engine will be done and in the car?
Pat
Thanks Pat. Glad someone is interested in my nonsense. The timeline is unknown. My first priority, between my hectic work schedule, is to get my Harley back on the road with its rebuilt engine, and after two years of it off the road, I can't have another summer without it. Once that is done, then I move to the 77 engine rebuild. I hope I will get the car on the road this summer....but as I said...Harley first.
Last edited by Torqued Off; 02-29-2024 at 07:59 PM.
So, as I began the thought process, the first questions and considerations came up, i.e. what do I start with?
- I have no choice but to pay someone to do the block machine work, because I can’t do the machining. That means buying a new block, and having it machined. I am not interested in starting with an old worn-out Chevy 400 block.
- If I can find a shop that I could trust with the machining, can I also trust them installing a crankshaft, pistons, and rods correctly? Or do I do it myself?
- I “could” assemble the short block, but I do lack some of the tools, and I admit I lack direct SBC experience at it, and don’t want to make any mistakes. While I am confident in my ability, I also recognize that I don’t know everything.
- Several companies sell un-assembled short block kits. Still leaves me with the assembly. And the actual assembly charge is a small increase over the cost of machining and parts.
- There is some potential “warranty” from the right shops on the assembly versus no warranty on assembling it myself. If something happens that can be directly related to the short block assembly, it’s more likely with an ethical company, I could get some consideration?? Maybe.
- Another reality of my life is that I am working all the time, often away from home for days. If I end up doing everything, the completion date is just that much further down the road. THIS is probably the biggest factor to consider.
THIS DECISION SETS OFF WARNING FLAGS IN MY HEAD……since I have come to NOT trust anyone. Do I make the decision to trust someone to assemble a short block??
My decision, after considering all the above, is that this falls under the category that some jobs should be left to more experienced people, with the correct tools, and hope they get it right. And it deals with the reality of the lack of time I have available outside of work.
The key to this is finding the right machinist and builder.
So, with that the plan, the next step is to find the best builder who can machine and assemble a high-quality short block. At least I can control the quality from that point forward and I am very confident that I can do that as well as anyone. The challenge is to find that quality company, which included my requirement that I make all the decisions on the components used, or at least approve them. I am NOT letting anyone else make those decisions ever again. And that became the plan I began working on late last year.
I searched most of the shops across the country that advertise short blocks, and settled on CNC Motorsports from Brookings, South Dakota.
They are a low volume engine builder, with a full and well-equipped machine shop and an engine dyno, building and dyno testing complete race and street engines, as well as providing short and long blocks for Chevy, Ford and Mopar. They are also a large engine parts supplier, selling most of the brands. They have one guy who does all the machining, and one guy who assembles the engines, both have been working for the company for some 25 years. Based on my research, they reportedly produce high quality work, at a slightly higher cost than others. Their website provides massive numbers of engine build packages…but allow you to substitute different components if you want. I started with the package closest to what I was looking for and made several substitutions.
Their main sales contact is Chris Carlson, and I have had lengthy discussions with him about what I expect, about how they build engines, about the problems I have had with builders in the past, and what I am trying to avoid with this new build. He assured me that I would be happy with their work. The conversations I had with Chris did give me the confidence to go ahead and buy an assembled short block from them.
I chose CNC Motorsports after considering Chevy Performance, Shafiroff, Blueprint, ATK, Tristar, Skip White, Ohio Crankshaft, Smeding and several other smaller shops. I have “reserved” confidence in CNC Motorsports, but I had to make a choice and I decided they were my best choice. Only time will tell if I made the right choice this time. It’s just another gamble at best…..yeah, I am a pessimist….earned the hard way.
I ordered the assembled short block on December 20th, and it arrived in my garage February 26th. About two months, which is what they estimated when I ordered it.
Last edited by Torqued Off; 03-07-2024 at 12:17 PM.
My understanding is that you may go thru your entire thought process on this build, as well as document it for others.
Nice!
It should help preserve our hobby just a little bit for the next guy(s).
Because as we all know, expertise in these old cars is getting scarcer every day!
And some lessons / experience can only be learned the hard way, by trial and error.
I'm interested to see what cam and head/piston combo you've chosen.....a cam with less than 224 degrees will be pumping up the dynamic compression ratio for sure
I don’t know if I will get the car running this year or not. My work schedule is only getting more intense and seems to be no reason to change or slow down. Even at 65 years old, I like flying high performance jets too much to retire and I still need the income to pay for all this nonsense.
My priority now is getting my rebuilt Harley Road King engine reinstalled, and the bike back on the road as soon as possible. Two years out of my life have been lost with the bike off the road, and that is not acceptable any longer. My 137,000 mile relationship with this Harley is way more important and valuable to me than this car. In fact, I finally put the rebuilt engine back in the frame a few weeks ago….so I hope I will have the bike reassembled by the first day of spring. THAT comes first over this Corvette. Once the Harley is back on the road, I can work on the Vette….and unfortunately, I like riding it so much I will probably spend most of my free time this summer riding and not building this engine.
I also intend to be extremely methodical, and careful building this engine. I am going to use all the 40 plus years of my technical experience, combined with extreme care and patience, to assemble the engine to have the best chance it will work properly when I put it in the car. Every failure of the first two builders is, and has been, considered as I will build this engine. I can only hope CNC Motorsports built the short block properly. I am confident in what I will do to take it from there to a fully running engine, but as I said, only time will tell. I have become a very pessimistic person when it comes to this engine in this car. Two highly recommended engine builders failed to provide me with a functional engine, which is an unfortunate and sad fact. We shall see how I do…this third, and final time.
Last edited by Torqued Off; 03-02-2024 at 09:10 AM.
It's been an observation of mine that it's amazing how fast cast iron blocks rust. Maybe they have come upon some super spray coating that I don't know about.
The second item is assembly lube. I liberally coat everything rotating. Then proceed to the first firing. I have a spare motor in a engine shipping box, but it's been dyno breakin run and then drained and bagged up.
I totally understand priority lists.
Some day you'll have to give us all your engine build spec's
It's been an observation of mine that it's amazing how fast cast iron blocks rust. Maybe they have come upon some super spray coating that I don't know about.
The second item is assembly lube. I liberally coat everything rotating. Then proceed to the first firing. I have a spare motor in a engine shipping box, but it's been dyno breakin run and then drained and bagged up.
I totally understand priority lists.
Some day you'll have to give us all your engine build spec's
CNC Motorsports sprays the short block with protective oil before shipping. I will use all the proper lubes. And I will be providing all the component information, in detail, and why I chose them. Coming soon.
The CNC Motorsports Short Block I bought and is in the crate in my garage, and in the above picture is CNC Competition 400 Short Block, Scat 3.750 Crank, 6.0 H Beam Rods, Dart SHP Block, SRP 10.2:1 Pistons, PN CNC-9347-S. Price - $5,649.95. The shipping charge was an additional $480 to my house. Since I ordered this short block in December I got the price listed.....this years price is $150 higher at $5799.
I made several substitutions to the above parts listed, including pistons and rods, that did NOT change the price. I will list the components and substitutions in upcoming posts. The picture below is their generic picture of the 400 SBC short blocks they sell....those are not the exact pistons I chose, but similar with D shaped piston deck.
Description
CNC-Motorsports, has quickly raised the bar to a new level in offering high quality short blocks at an affordable price. Our short blocks have become a huge hit among racers and performance enthusiast all over the world. We have the ability to custom build you just about any combination the way you want it. All our short blocks are 100% machined, CNC Machined and blue-printed to our race wining specs. We never cut corners like others just to lessen the price.
Small Block Chevy Short Block Assembly New Scat 4340 forged steel crankshaft (3.750 Stroke) New Scat H-Beam connecting rods bushed fit pins, ARP 8740 bolts (6.000 Length) New SRP forged -16cc dish pistons High performance plasma moly piston ring set ACL/Clevite 77 Rod and Main Bearings Dura Bond cam bearings Dura Bond finishing kit Brass freeze plugs Fel-Pro rear main seal New Dart SHP block Compression Ratio with 64cc Heads: 10.2:1
*Professionally Machined, Balanced, Assembled and blue printed in house by CNC-Motorsports. Balance card and blue print sheet will be provided to the customer. All short blocks are standard bore unless otherwise noted. We can custom build any short block assembly to meet your needs.
Last edited by Torqued Off; 03-02-2024 at 09:06 AM.
I wouldn't let that short block sit around too long. I'd be concerned with rust/corrosion a bit. If it's all been coated with something I guess that would last for a little while.
You maybe could use a large garbage bag and a vacuum cleaner to create a sort of vacuum seal environment for it. I did this on a 400 block I have to store it just to minimize rust over time.
Getting a pre-assembled short block is still quite a leap in faith that it's done right. Let's hope it is.
It is a bit more involved than just assembling top end components. For that reason I wanted to assemble my bottom end. Ensure the ring gaps were correct, rod bolt stretch was correct, bearing clearances were correct, piston to cylinder wall clearances, end thrust , etc etc. There is a lot of important stuff in that bottom end assembly that is of concern to me, thus the decision to do it myself.
I installed a stock 400 in my 69 about 10 years ago. Short block was low mileage original. I had the stock heads milled to remove 0.050 inches. Installed big valves. Used a Crane nigh energy cam. Still runs great sounds great. Good luck with yours.
Getting a pre-assembled short block is still quite a leap in faith that it's done right. Let's hope it is.
It is a bit more involved than just assembling top end components. For that reason I wanted to assemble my bottom end. Ensure the ring gaps were correct, rod bolt stretch was correct, bearing clearances were correct, piston to cylinder wall clearances, end thrust , etc etc. There is a lot of important stuff in that bottom end assembly that is of concern to me, thus the decision to do it myself.
I said all I am going to say about this in Post #24. There is risk either way.
I like the fact that only one guy does all the machine work, and another does all the assembly, and they both have 25 years experience, a good reputation and good reviews.
Short of knowing them for 25 years that is the best you can do.
A small one or two man shop lives, or dies, based on it's reputation.
That is obviously how your first engine got fouled up, even if it was a good machine shop, the "main guy" obviously did not do the work.
He let someone else do it, and without enough supervision. Sad.
I don’t know if I will get the car running this year or not. My work schedule is only getting more intense and seems to be no reason to change or slow down. Even at 65 years old, I like flying high performance jets too much to retire and I still need the income to pay for all this nonsense.
My priority now is getting my rebuilt Harley Road King engine reinstalled, and the bike back on the road as soon as possible. Two years out of my life have been lost with the bike off the road, and that is not acceptable any longer. My 137,000 mile relationship with this Harley is way more important and valuable to me than this car. In fact, I finally put the rebuilt engine back in the frame a few weeks ago….so I hope I will have the bike reassembled by the first day of spring. THAT comes first over this Corvette. Once the Harley is back on the road, I can work on the Vette….and unfortunately, I like riding it so much I will probably spend most of my free time this summer riding and not building this engine.
I also intend to be extremely methodical, and careful building this engine. I am going to use all the 40 plus years of my technical experience, combined with extreme care and patience, to assemble the engine to have the best chance it will work properly when I put it in the car. Every failure of the first two builders is, and has been, considered as I will build this engine. I can only hope CNC Motorsports built the short block properly. I am confident in what I will do to take it from there to a fully running engine, but as I said, only time will tell. I have become a very pessimistic person when it comes to this engine in this car. Two highly recommended engine builders failed to provide me with a functional engine, which is an unfortunate and sad fact. We shall see how I do…this third, and final time.
It is " funny" how not riding ones bike puts you in a fowl mood almost in a withdraw state. I was without my mine for a year and couple months upgrading and rebuilding my topend during covid. I have RoadKing with a S&S 124 and changed the heads out to an old set of Hemi design heads (2.080" 300cfm) after the originals valve guides gave up. Custom ordered Ferrea Valves sent back twice as they wouldn't close on the seats, Third time I sat at my lathe for an hour to finish them correctly. Custom poured/molded pistons were never right as the company didn't even use my mold I sent and there wasn't enough squish area imo in their final design (11:3.1). Threw out 2 sets of rings as my prestart leak down was @ 8 percent. Couldn't find correct MLS gaskets thickness so I played the base gasket numbers game. Plus a few other technical issues like Baisley Rockers and offset support plates/pushrod math and machining. Then behive spring install height issues due to spring avail from Pac. I have rode my bike 1K since the overhaul and now. Its "funny" I work more as well to find the time to even enjoy the bike ever sense covid happened.
On a good note I picked up my Dart block yesterday to begin my mock ups. It never ends . Some days I feel I should sell everything and retire so I can have enough time to enjoy my hobbies.
Summit Price on bare block is $2944, CNC Motorsport price on bare prepped block is $3549.
Dart SHP Special High Performance small block Chevy cast iron bare blocks are designed for high performance and heavy-duty applications. These SHP blocks are an ideal starting point for hot rodders, drag racers, circle track competitors, off-roaders and high performance marine enthusiasts.
Key features of SHP small block Chevy bare blocks are:
* Priority main oiling system
* Siamese cylinder bores with extra-thick walls
* Extra thick decks to ensure reliable head gasket seal
* Blind head bolt holes (don't go through water jacket)
* Scalloped water jacket walls for improved flow around cylinders for better cooling
* Clearance for 3.75 in. stroke with steel rods
* Splayed outer bolts on middle main bearing caps
* Provisions for OE stock roller lifters and cams
* All OE bolt holes starter, clutch ball, etc.
* Uses 1981 to 1985 stock style oil pan and passenger side dipstick
* Uses stocked stamped steel or plastic timing cover
THEN….CNC Motorsports takes that Dart SHP block and does the following:
CNC-Motorsports takes great pride in offering a fully race prepped Dart SHP block blue-printed to race specifications that is ready for you to assemble
Check and align hone mains if needed, chamfered main parting lines
Bell housing surface squared to crankshaft centerline
Stroker clearance to 4.000 stroke
Parallel square deck the deck surface to your desired deck height
Bottom of the cylinders chamfered
Top of the cylinder bore chamfered
Block de-burred to eliminate sharp edges and casting slag
Freeze plug holes and rear cam hole are chamfered
All bolt holes and oil galley holes chamfered
Oil galley holes tapped
Head and main bolt holes tapped
Chamfered distributor hole and lightly ball honed to eliminate high spots
Hone the block with torque plates to your piston bore size and verified with a profilometer
Top of lifter bores chamfered
Lifter bore checked and honed to your set of lifters you will be using in your build
Install Cam Bearings and Freeze Plugs
Block is cleaned and ready to go
As listed above, CNC Motorsports preps their blocks to a great detail level, much better than both the builders on the first engine block. Their block prep is the same on all their short blocks and engines, whether for a street or race engine. Their attention to detail is indicative of their quality, assuming they do what they advertise. It was a sign of quality that helped make the decision to use them. It’s the way I would prep a block if I had the equipment. None of the other engine builders I considered advertised this level of detail, nor do I think many of them do…. especially not the big production shops. That level of detail takes time…. which costs money and lowers profits.
This is the same part number block I started with on the first engine, but instead of boring out a new block to make a 406 (4.155 inch bore), and then the second time to 408 (4.165 inch bore) I am only boring to 4.125 inch for a 400 cubic inch displacement, when combined with the 3.75 inch stroke. It’s not worth 6 cubic inches to bore away new material on a new engine block. I should not have done it the first time with the first brand new block but was hung up on the “406” word.
Last edited by Torqued Off; 03-04-2024 at 02:18 AM.
One problem I discovered on the teardown of the rebuild was the shadowing on the cylinder walls, at multiple head bolt hole locations and on multiple cylinders. This shadowing indicated that there was distortion, caused by the head bolts, creating a less-than-round bore, and the rings marked the spots on the cylinder walls at those high spots, but more importantly is the resulting LOW spots on either side of the high spot.
Common sense would tell you that round piston rings will not seal well on less-than-round bores and will allow blowby and oil consumption, only getting worse over time as the engine wears. I have seen pictures of engines with this problem, showing clear paths of oil-to-head blowby on both sides of the high spots. Remember, I only had 1600 miles on this engine, and this shadowing was already evident. The engine guys over on a popular engine forum clued me in on this, stating that this is typically caused by improperly boring and honing without a torque plate, and/or applying excessive torque on head bolts.
This is the main reason I did not intend to salvage the first block/engine, which was only one bore size away from the Dart 4.185 limit. There was no easy or inexpensive way to fix this on that block. Some folks say this is not an issue. I disagree. To me, it’s common sense. Why do we go to the trouble of boring a circle and honing it, if it ends up with multiple high and low spots for rings to try to seal against? Some people also said this clearly should not occur on the stronger Dart block, more likely on factory block, but nevertheless, it happened.
So, on my new block, keeping the bore smaller at 4.125 inch gives me the best chance to minimize that issue on this larger bore engine. Remember the original SBC 327 and 350 blocks had a 4.00-inch bore…. leaving more steel (and the original engineered strength) between the piston bore and the bolt holes. Every bore size larger than 4.00 inches just makes that area more prone to this distortion.
The proper industry process is to bore and hone the cylinders with torque plates, AND using either bolts or studs, whichever are to be used when mounting the cylinders. The intent is to simulate the actual stresses placed on the block, so the boring and honing is accomplished with the same stresses as the cylinder heads apply, thus creating a perfect, undistorted round bore for the round piston rings to seal on. No high and low spots. It makes sense to me. CNC Motorsports uses torque plates, with bolts properly torqued, for boring and honing. And I will install head bolts to the proper torque.
Last edited by Torqued Off; 03-07-2024 at 12:19 PM.
The deck was machined to a 9.00 inch / zero deck so I could select from the much larger variety off-the-shelf pistons and gaskets to achieve 0.040 quench and static compression I want. The Dart SHP decks are thicker than stock Chevy, so I am not compromising anything. I could have left the deck taller, and had custom pistons made with taller compression height, but I decided to go to 9.00-inch deck, saving money and time, and it’s obviously a very common thing on SBC engines, with lots of pistons and gasket sizes to choose from to get compression ratio where you want it. It was very difficult to get the pistons and specs where I wanted them, without making it even more difficult with a taller deck height.
Decisions
What I don’t like about the Dart SHP block is the lack of coolant bypass provisions a Chevy block has, nor do I like their design of big block style oil drain slots in valley center, versus the multiple drain holes on front to back of an OEM SBC block. I am not sure what they are trying to “fix” with these changes over the original SBC design.
But looking at available choices and my intended use, no other block makes better sense, especially given the cost. I considered the more expensive Dart blocks, GM Performance, Brodix and World blocks, and even considered an old Chevy 400 block, but all were much more expensive, and in the case of the Chevy 400 block just too risky dealing with availability, age and machining costs. The Dart SHP block is simply the best solution for my application, despite several features I don’t like. It has a lot of great features.
I also considered going to one piece rear main seal block, which Dart also sells in the SHP Line, but it is more expensive and I would need a new flywheel, and just decided against it. The one good thing about a two-piece rear main seal is if it leaks, you can replace it without pulling the transmission. But I sure hope CNC Motorsports can install a leak free two-piece rear main seal.
The short block comes unpainted……and I will paint it either Chevy orange or possibly RED to match the Chevy Performance valve covers I used on the previous builds. I had great luck with Eastwood Two Part engine paint on the 350 engine I built so I may use that, but it is sure much easier with Duplicolor spray cans. I guess it will depend on my mood when the time comes. The Eastwood Two Part engine paint is very high quality and durable and looks great.
Last edited by Torqued Off; 03-04-2024 at 02:20 AM.
02-29-2024, 05:19 PM
