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Old 07-19-2019, 03:18 PM
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408 build

Ok so here it goes...I’ve signed up for this site to find out what my future holds....I’ve been taken advantage of mechanically for most of my hot rod tenure...and have decided to build my own motor...IDK WHAT IM DOINGGGG😩😩 lol...here’s the rundown on what i do know
400 sbc bored .40 5.7 scat rods Stock crank, maybe polished 🤷🏾*♂️ Also has been stroked, but unaware of the actual figures 😩 Motor has been balanced and decked, to what height??..no clue 🙁 Trans is built bm 350 with either 2500 or 2800 stall Ford 9’ rear with 3.73 gears 84 Monte Carlo base Comp cams double timing chain So this is my issue...the motor had flat top pistons made by a non popular brand...hyper whatever...but not forged...they suffered a small crack around the ring area which is why the motor was pulled...they were equipped with stock iron heads that had been worked with bigger springs, valves, and been ported...I’ve been doin a ton of google research and at this point...i just want to start over...i bought the motor from a friend who did all the block work, however, my google research suggests maybe his compression was too high???....did he need race gas??...he was running a Howard™s cam 299/299 510/510
Now about the next step...after frivolous spending...i now have those worked stock heads, sum dart iron eagle 230, and edelbrock rpm aluminum heads....I’m leaning towards the edelbrock because i here that will be better with compression...the dart and Eddy’s are both 64 cc chamber....I’m aware that makes compression higher...but that’s what i got lol...i only want to be a street car...I’ll prolly NEVER go down a track to be realistic lol...but i want to be better then the guy at the light ....I’m looking for the “most usable power” as they say on the street...which heads should i go with??? Which cam is recommended??...also have a complete cams drag race cam 305/305 525/525 brand new...should i keep it???...or go with a cam that matches the heads better...idkkkk...i also have to buy new pistons...can i get away with flat top forged???? With aluminum heads???...how much would i lose with a dished piston???...so many questions lol and i know I’m everywhere...also looking for 450 horses at least....can i get that with dished?? Any info will help...i don’t have any real motor heads that i can ask straight up...I’m not looking to change my rear end and stall too much...so was trying to build around those aspects....I’ll have my eyes open to any reply good and bad

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Old 07-19-2019, 03:25 PM
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Do everyone a favor and re-post your information without the graphics or whatever it is youre trying to use. Its very difficult to read.


Second, telling us that you want a certain level of performance without details about what the engine is going in, weight, gear, tire size, etc is basically impossible. What will work in a light vehicle will not do well in a heavy one.
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Old 07-19-2019, 03:34 PM
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Sorry about that...i realized that you cant use emojis and evidently any punctuation when you post but I’ll edit
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Old 07-19-2019, 03:38 PM
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Ok so here it goes...Ive signed up for this site to find out what my future holds....Ive been taken advantage of mechanically for most of my hot rod tenure...and have decided to build my own motor...IDK WHAT IM DOINGGGG lol...heres the rundown on what i do know

400 sbc bored .40
5.7 scat rods Stock crank, maybe polished
Also has been stroked, but unaware of the actual figures
Motor has been balanced and decked, to what height??..no clue
Trans is built bm 350 with either 2500 or 2800 stall
Ford 9 rear with 3.73 gears
84 Monte Carlo base
Comp cams double timing chain

So this is my issue...the motor had flat top pistons made by a non popular brand...hyper whatever...but not forged...they suffered a small crack around the ring area which is why the motor was pulled...they were equipped with stock iron heads that had been worked with bigger springs, valves, and been ported...Ive been doin a ton of google research and at this point...i just want to start over...i bought the motor from a friend who did all the block work, however, my google research suggests maybe his compression was too high???....did he need race gas??...he was running a Howards cam 299/299 510/510
Now about the next step...after frivolous spending...i now have those worked stock heads, sum dart iron eagle 230, and edelbrock rpm aluminum heads....Im leaning towards the edelbrock because i here that will be better with compression...the dart and Eddys are both 64 cc chamber....Im aware that makes compression higher...but that’s what i got lol...i only want to be a street car...Ill prolly NEVER go down a track to be realistic lol...but i want to be better then the guy at the light ....Im looking for the most usable power as they say on the street...which heads should i go with??? Which cam is recommended??...also have a complete cams drag race cam 305/305 525/525 brand new...should i keep it???...or go with a cam that matches the heads better...idkkkk...i also have to buy new pistons...can i get away with flat top forged???? With aluminum heads???...how much would i lose with a dished piston???...so many questions lol and i know Im everywhere...also looking for 450 horses at least....can i get that with dished?? Any info will help...i dont have any real motor heads that i can ask straight up...Im not looking to change my rear end and stall too much...so was trying to build around those aspects....Ill have my eyes open to any reply good and bad
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Old 07-19-2019, 03:41 PM
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And its an 84 Monte Carlo 3.73 Ford 9...idk how to respond to you specifically but I will learn lol...
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Old 07-19-2019, 07:50 PM
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Your second big post helped with the graphics...stuff posted from an I-Phone or Pad often doesn't translate punctuation marks or emoji's well and the post ends up full of Cyrillic/Arabic looking hieroglyphs.
Posts from desktop computer don't have that problem.

OK, 400 block, .040" overbore. We can work with that.

Big question about the crank, as you mentioned "stock, maybe polished" and then said it was "also been stroked". Stroking the stock crank would require either welding up the rod journals and offset regrinding to a different stroke, or switching to a different connecting rod bearing bore size and grinding the crank undersize and offset to that smaller diameter bearing. Both are expensive operations not often done on a stock crank, and especially not on a cast crank....it just isn't worth the cost.
It would also require a custom height piston, which doesn't exist in the hypereutectic style....
So I have a hard time believing the crank was also stroked.

So we will assume the crankshaft is stock, unless you can provide further info to show otherwise...

As far as the flat top pistons in the previous build, yep, you guessed it, pretty much too high compression for pump gas. This ain't no little peewee 340, flat top pistons in a 400 push the compression ratio between 1/2 and 3/4 of a point higher than a similar 350 build,and many fail to realize this.

just a rough compression ratio calculation, since we don't have definite block deck height dimension but we do know it has been cut some, puts a flat top, stock open chamber head 408" SBC in the range of 9.9 and 10.3 to 1 compression....to make this live on pump gas takes very careful carb and ignition tuning, along with cam choice. For a lot of guys, it is a disaster waiting to happen even with tougher forged pistons, but with hypereutectic pistons it is almost always going to break them, as you can relate.
If we move the same flat top assembly under a 64cc head chamber, then compression ratio jumps to somewhere between 11.2 and 11.7 to 1 , again depending on just how much the block was deck cut and what thickness gasket is used.

Considering the parts list you have, and what you want for power along with the weight of the vehicle and intended use, this is what I'd do.

Use the Edelbrock heads. The aluminum makes them more tolerant of compression on pump gas, and the port size matches up well to the intended application and your torque converter stall limitations.
You'll have to use a dished piston, preferably a D-shaped dish rather than a full round dish in order to preserve good quench action plus the dish will be necessary to get the compression ratio down to a point it will live reliably on pump gas. You'll need a dish in the 16 to 22cc range to land the compression ratio into the 9.5 -10.0 to 1 area.
Flat-tops, 64cc heads and 400+ cubic inch under them puts the compression ratio well into the mid-11 to 1 area....not going to work on anything out of the local pump except E85 or AvGas.

The "worked" stock heads really aren't worth using unless that was all you had, and the Dart 230's are way too big a intake runner volume for the low stall converter, mid-weight vehicle(in race weight terms), and the fact this doesn't shape up to be a 7500 RPM build.
Same with the 305/.525" camshaft, its way out of line for the stall converter and vehicle weight, as it would need 3500 rpm+ stall, a deep rear gear and a light vehicle to be a good cam choice. It's a bracket race type cam.
For a hydraulic flat tappet, or hydraulic roller to match your converter stall, you will want something in the 275-288 advertised duration, 224-238 @.050" duration and as much lift as you can find per the design(flat tappet or roller)...500"+ lift on a flat tappet or .550"+ on a hydraulic retro-fit roller cam would be great.
If you wanted to sneak into a small solid lifter cam design mimicking the old LT-1 Corvette type streetable behavior solid lifter cam, add 10-15 to those @.050" duration specs.

This will get you something will run on pump super unleaded, and probably even mid-grade in all but the hottest weather, with very strong midrange torque, stout low rpm torque to pull well with your moderate stall converter, and still have a great top end charge right up to 6000+ rpm, 6500 rpm max. 440-460 HP @6000 rpm no problem, 480-500 ft lbs torque peak @ 4400 rpm and will be making 325+ Hp and 400+ ft.lbs at your converter stall rpm.

It'll be enough power to make you start worrying about the life span of your TH-350 if it isn't built with some race grade internal parts upgrades.
Good thing is you've already got the 9" rear, or we would be worried about the stock 7.5" living very long too.
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Old 07-19-2019, 08:28 PM
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The motor is out, correct? Pull a piston and get some numbers from the crank, rod and piston. Measure the rod length. Post pics if you can't find numbers. Maybe a pic or number off the Dart heads as well.

IMO, you have way too many unknowns to make an educated decision on what to do.

You can easily make 450 with a 408 with the right parts.
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Old 07-19-2019, 09:00 PM
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I would be glad to pitch in and help on the stack and block deck height questions but I would need some more information.
1. The block has been bored and honed +0.040". Has it been run with pistons on that bore or is that a fresh, never-run bore? Was it honed for cast iron rings, moly rings or what?
2. What is the block deck height? (centerline of the main bearing bore to the flat surface of the block where the heads bolt on). You can measure from the lip on the bore at one end of the block up to the deck with a 8" or 12" caliper, then add 1/2 the diameter of the main bearing bore to your measurement. If you take your time doing this, you can measure at the #1, #2, #7 and #8 cylinders and determine if the block is cut catty-wampus. (a highly technical term that has to do with tree stumps and hammers).

These questions need to be answered before you go any farther. You can't buy pistons and rings before you know. There is a possibility that the rings you have now can be used, but I don't know that yet. What is the width on the rings? Have they been run in this motor?

"IMO, you have way too many unknowns to make an educated decision on what to do.
You can easily make 450 with a 408 with the right parts."
Times 2

.

Last edited by techinspector1; 07-19-2019 at 09:15 PM.
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Old 07-20-2019, 07:11 AM
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Find yourself a reputable engine builder and take your stuff there. Pay the man or forget about it. The accumulation of tools that you need to even perform the measurements will probably wreck your budget. There are tons of books and articles on the internet about how to properly measure an engine, how to assemble one, how to tune it but that means putting in the effort to read, learn, understand and apply the concepts.



As an alternative, you can get a crate motor 383 ci, 430 HP, 450 lbs torque with aluminum heads long block that sells for $4000 from Jegs, it will work with your current converter/trans, bolts in and runs on 91 octane. Sell off the stuff you have and you can put those funds towards it.
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Old 07-20-2019, 07:45 PM
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Quote:
Originally Posted by chasracer View Post
Find yourself a reputable engine builder and take your stuff there.
Too many horror stories.
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Old 07-20-2019, 09:14 PM
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Quote:
Originally Posted by techinspector1 View Post
Too many horror stories.

Guess I have been lucky then - I have a 45 year relationship with one of the best machinest/performance builders going. He is a multi-time NHRA Record Holder and Class Champion. Helped out a team from Sweden just a few years ago with a Pro Stock project.


Like I said - reputable.
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