Author Topic: Grassroots 400, think it will crack 350hp?  (Read 1898 times)

Offline Flatdad

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Grassroots 400, think it will crack 350hp?
« on: February 01, 2017 - 11:57:11 am »
Winter boredom has set in, so thought I'd upgrade the 400 a bit for the fun of it.

The engine that's in my challenger when I bought it is a mystery 400 that ran and idled well enough to drive the car on a trailer but sounded one cylinder off. Found one of the header pipes smashed shut almost. I have some old wedge parts lying around that I couldn't sell last year so here's the plan:

Swap the 452's for a fresh set of 915's with .020 gaskets, port match an Edelbrock tm7, swap in an old Summit cam and lifters, and replace the smashed header with an old flowtech. Not sure which carb to run though, I've got a 600afb and a 600 vac holley both need rebuilt.

Cam specs: 298/303 224/234 @.050, .466/.488 lift and a 114LSA.

Think it can make 350? Think it can put a stock E-body into the 13's?
'70 Road Runner-B7 383 Auto, now with more cubes
'97 Ram 1500 Sport 4x4-Bright Red 318 magnum
'67 Belvedere II-Dark Blue 318 Auto, now owned by my brother
'73 Challenger Rallye-B5 318 Auto, had a 360 in it, SOLD :(
'42 Harley Davidson 42WLA-U.S. army green 45ci flathead
'71 Challenger R/T-B5 383 Auto, now 400 powered and rusty!
'86 W100-Yellow 318-2bbl 4x4 4spd, off road toy




Offline 1 Wild R/T

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Re: Grassroots 400, think it will crack 350hp?
« Reply #1 on: February 01, 2017 - 12:38:04 pm »
The TM-7 & the cam both are a little hotter than a low compression 400 likely will want... Swapping to the 915's certainly helps but your likely going from 7.8-1 up to 8.2-1....  Personally I'd consider milling the 915's .050-.060.... That would take you close to 9-1....   Another .5 would be nice but not worth the cost.... A true 9-1 should make that cam allot happier...

What gear are you running? 4 spd? Auto? Convertor?
JS27N0B 70 Challenger R/T Convertible  FJ5 Sublime, Show Poodle w/90,000 miles since resto
WS27L8G 68 Coronet R/T Convertible  PP1 Bright Red, Project
RM21H9E 69 Road Runner Coupe R4 Performance Red, Sold...
5H21C  65 Falcon 2 dr Wagon... Dog Hauler...

Offline Flatdad

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Re: Grassroots 400, think it will crack 350hp?
« Reply #2 on: February 01, 2017 - 01:36:10 pm »
Don't know the current rear gears, probably still an open diff, have a 4.57 suregrip lying around and a 3.23 sg in a Road Runner, also a spare set of 28.5" tall slicks that barely fit the Road Runner. I bet the torque converter is whatever came with the 400 since its still externally balanced. Figured the head swap would bring it from maybe 7.2 to 8.0:1. Originally ran that cam in a 440 with a whopping 7.0:1 compression, seemed pretty mild.

If I had the heads milled, would need new pushrods. So far the only costs involved for this project are the various gaskets, seals, motor oil, etc. Open to suggestions like that though, like I said this build is just for fun.

Which carb should I try on this turd?
'70 Road Runner-B7 383 Auto, now with more cubes
'97 Ram 1500 Sport 4x4-Bright Red 318 magnum
'67 Belvedere II-Dark Blue 318 Auto, now owned by my brother
'73 Challenger Rallye-B5 318 Auto, had a 360 in it, SOLD :(
'42 Harley Davidson 42WLA-U.S. army green 45ci flathead
'71 Challenger R/T-B5 383 Auto, now 400 powered and rusty!
'86 W100-Yellow 318-2bbl 4x4 4spd, off road toy


Offline RCCDrew

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Re: Grassroots 400, think it will crack 350hp?
« Reply #3 on: February 01, 2017 - 04:32:44 pm »
Mild hand porting is free and can help. Anything else you can do to help the compression will help too. Milling deck or heads. A matched cam for your application would be worth it as well.

Or just run all your stock parts and find some take off Cummins turbos lying around. Problem solved!

Offline 734406pk

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Re: Grassroots 400, think it will crack 350hp?
« Reply #4 on: February 01, 2017 - 06:30:51 pm »
The 400 is very strong block but the stock piston compression height is very low.  IMO i would replace the pistons with something taller to achieve near zero deck height and go from there. Use a .040" + - compressed thickness head gasket for some quench and you will be happy!
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive

Offline Road_Runner

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Re: Grassroots 400, think it will crack 350hp?
« Reply #5 on: February 02, 2017 - 04:13:33 pm »
I ran an old Edelbrock DP4B dual plane intake on my mostly stock 383 before I built it and was very happy with how it ran. That intake or its modern equivalent the Performer RPM would be my choice for intakes.  I ran both 3.91 & 4.10 gears with the original 10.5" converter and the car was very strong off the line, even more so after I rebuilt it with new 'pop up' pistons, cam, etc.  The 383 loved to rev like a small block so your 400 should like the same kind of mods.

Later, Jim
1970 383 Roadrunner Tor Red
1973 318 Barracuda Mist Green
2014 Mustang GT/CS Convertible All Black

Offline 1 Wild R/T

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Re: Grassroots 400, think it will crack 350hp?
« Reply #6 on: February 02, 2017 - 06:16:26 pm »
I ran an old Edelbrock DP4B dual plane intake on my mostly stock 383 before I built it and was very happy with how it ran. That intake or its modern equivalent the Performer RPM would be my choice for intakes.  I ran both 3.91 & 4.10 gears with the original 10.5" converter and the car was very strong off the line, even more so after I rebuilt it with new 'pop up' pistons, cam, etc.  The 383 loved to rev like a small block so your 400 should like the same kind of mods.

Later, Jim

DP$B is closer in design to the Performer than the Performer RPM.. :2cents:
JS27N0B 70 Challenger R/T Convertible  FJ5 Sublime, Show Poodle w/90,000 miles since resto
WS27L8G 68 Coronet R/T Convertible  PP1 Bright Red, Project
RM21H9E 69 Road Runner Coupe R4 Performance Red, Sold...
5H21C  65 Falcon 2 dr Wagon... Dog Hauler...

Offline Flatdad

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Re: Grassroots 400, think it will crack 350hp?
« Reply #7 on: February 03, 2017 - 08:46:57 am »
The tm7 is actually what came on the car so it stays, unless I see a low deck intake for stupid cheap. The 600 afb is taken apart, cleaned, and just needing gaskets now. Wanted to run the holley, but the afb is just sooo much easier to rebuild. Put a big order in @ Rockauto using the the discount code (thanks cuda-challenger!) a whopping 694 bucks in sheetmetal, parts, and gaskets!

Cost of engine parts so far:
$13.16 Intake gaskets
$1.89 PCV
$34.60 New set of exhaust valves 1.74"

Yet to purchase:
.020 Steel head gaskets
Exhaust gaskets
New fuel hose
Hose clamps
Oil filter
6qts motor oil
Push in breather
+other unknowns

Yet to pay for:
Clean and mag, cylinder heads (they're crack free, woohoo!)

Might just start a build thread for the whole car heap of rust soon...with pics of course!

Here's a pic to show the junk I'm dealing with, and why I'm not too keen on investing too much time and $ in the engine. (the carb in the pic has been repurposed elsewhere)
'70 Road Runner-B7 383 Auto, now with more cubes
'97 Ram 1500 Sport 4x4-Bright Red 318 magnum
'67 Belvedere II-Dark Blue 318 Auto, now owned by my brother
'73 Challenger Rallye-B5 318 Auto, had a 360 in it, SOLD :(
'42 Harley Davidson 42WLA-U.S. army green 45ci flathead
'71 Challenger R/T-B5 383 Auto, now 400 powered and rusty!
'86 W100-Yellow 318-2bbl 4x4 4spd, off road toy

Offline Cazbah362

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Re: Grassroots 400, think it will crack 350hp?
« Reply #8 on: February 05, 2017 - 12:03:22 am »
I think you are spot on to your approach, just a thought.  I would probably do a leak down test before starting on this just to check health.  Yes, there may be a cylinder head issue such a burnt valve, but at least it would be a good start before ANY money goes in.  Those 915's are worth a bit on the market, so you could just sell them and re purpose the funds to milling and the push rods the 452's.  I would suspect you'd be a little more overall compression in the end the just the .020 gasket with the closed chamber 915's plus some cash back. 

And rent a steam cleaner, wire brush and Krylon can fix the overall appearance of the bay.

A little more down time and work, but 452's milled or even sell them both and get 440 Source heads?  Personally - 915's, gaskets and port match will perform well. especially for the price. 

Offline Flatdad

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Re: Grassroots 400, think it will crack 350hp?
« Reply #9 on: February 07, 2017 - 03:26:50 pm »
Updates: Had to order 4 more exhaust valves. They come in packs of 2, so I ordered 4 thinking 8 would show up...Nope! -$35.

The intake is actually a TM6, as TM7 is for RB's.

Committing to using the 600afb, unless I spot a cheap Holley 3310 on craigslist.

Just moved into a new place, and the Dodge can come out of storage hopefully in the next couple of days! I've got a pile of metal and engine parts waiting!

In response to Cazbah362, I actually tried selling the 915's back in the fall. Listed 'em on CL for a whole 200 bucks but nobody wanted 'em beyond a couple calls and texts. I figure even if the engine turns out to be junk, the 915s will be more sale-able with the bigger exhaust valves now anyway.

Ended up with a full 2.25" exhaust system off a '69 RR, I'm going to shorten it to fit the dodge. $100 with mufflers and hangers.
'70 Road Runner-B7 383 Auto, now with more cubes
'97 Ram 1500 Sport 4x4-Bright Red 318 magnum
'67 Belvedere II-Dark Blue 318 Auto, now owned by my brother
'73 Challenger Rallye-B5 318 Auto, had a 360 in it, SOLD :(
'42 Harley Davidson 42WLA-U.S. army green 45ci flathead
'71 Challenger R/T-B5 383 Auto, now 400 powered and rusty!
'86 W100-Yellow 318-2bbl 4x4 4spd, off road toy

Offline Flatdad

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Re: Grassroots 400, think it will crack 350hp?
« Reply #10 on: February 13, 2017 - 09:56:37 am »
The Dodge is out of storage and in the garage! Exhaust valves went to the machine shop Friday afternoon too.

Visited my brother with my dad over the weekend, he was going to be cleaning and painting parts for his Belvedere project so I brought the Holley 600 along for something to do.

The local O'reilly's happened to have a kit in stock. Was expecting a grubby mess, but instead it was the easiest Holley rebuild I've ever done! Except for a couple small issues, I think this Holley would have almost ran the motor BEFORE the rebuild.

Specs: 1850-2 (probably mid '70s) 600cfm vacuum secondary. 66 primary jets, standard secondary plate is 69 jet size. 6.5" p-valve, standard white pump cam (installed in #1 position), .025 accel pump nozzle, and standard secondary spring.

Thinking of upping the primaries to 69 or 70 jets and a .028 pump nozzle. Have to wait and see what it wants for a p-valve, but I think the 6.5 should be darn close.

Trailer rental+light adapter: $77
Holley 4160 rebuild kit+2 cans carb cleaner: $37
'70 Road Runner-B7 383 Auto, now with more cubes
'97 Ram 1500 Sport 4x4-Bright Red 318 magnum
'67 Belvedere II-Dark Blue 318 Auto, now owned by my brother
'73 Challenger Rallye-B5 318 Auto, had a 360 in it, SOLD :(
'42 Harley Davidson 42WLA-U.S. army green 45ci flathead
'71 Challenger R/T-B5 383 Auto, now 400 powered and rusty!
'86 W100-Yellow 318-2bbl 4x4 4spd, off road toy

Offline Flatdad

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Re: Grassroots 400, think it will crack 350hp?
« Reply #11 on: February 24, 2017 - 10:44:28 am »
Not much to update: Waiting on my heads (and the bill) from the machine shop. Pulled a valve cover and verified the old heads were 452's as suspected. Discovered the gas tank had a leak at the top. My cousin and I dropped it down so I could redo the trunk and I managed to spill the smelliest gas ever on the floor.

After these next couple swap meets, the plan is to order the rest of my gaskets and more sheet metal including a fuel tank. My brother has an old digital camera to donate to the project so hopefully you guys should have some pics soon!
'70 Road Runner-B7 383 Auto, now with more cubes
'97 Ram 1500 Sport 4x4-Bright Red 318 magnum
'67 Belvedere II-Dark Blue 318 Auto, now owned by my brother
'73 Challenger Rallye-B5 318 Auto, had a 360 in it, SOLD :(
'42 Harley Davidson 42WLA-U.S. army green 45ci flathead
'71 Challenger R/T-B5 383 Auto, now 400 powered and rusty!
'86 W100-Yellow 318-2bbl 4x4 4spd, off road toy

Offline joes74challenger

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Re: Grassroots 400, think it will crack 350hp?
« Reply #12 on: February 24, 2017 - 02:55:56 pm »
 :popcorn:

Offline Chryco Psycho

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Re: Grassroots 400, think it will crack 350hp?
« Reply #13 on: February 24, 2017 - 07:20:16 pm »
The cam is actually a decent choice the 114* l will help a lot with the low compression .
 The package should work OK .
I would never use an AFB over a Holley , both are too small but the Holley will be more responsive

Challenger - You`ll wish You Hadn`t

Offline Flatdad

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Re: Grassroots 400, think it will crack 350hp?
« Reply #14 on: March 02, 2017 - 03:33:05 pm »
MMMH! Tasty Crow, my favorite! I had the heads redone with new exhaust valves, claiming it would still be worth it over aluminum heads or keeping the questionable 452's...NOPE!

$687 which included: clean & mag, 8 new oversize exhaust seats, 8 new guides, and all machining associated with installing guides, grinding seats and valves, making them all the same height installed, freeze plugs, etc...

I have a long list of the work they did. I would have been perfectly happy if it had been less than $600, but gee wizz it was almost 7!

To total the cost of the heads, for all to see (and ridicule):

200 initial purchase in 2014
  70 for new exhaust valves
687 in machining
_____
=$957 still needing stem seals!

Cost of new 440source heads: $998 pair + shipping + having them gone through.

Downside is I just barely beat the cost of new aluminum heads, they weigh more, and flow less. The few upsides are: I know everything on them is "right", none of it is made in china, and the money spent stayed in my local economy.

I can usually admit mistakes pretty easily, but this one hurts my pride a bit, lol. Think I'm going to run these heads for a loooong time to get my money's worth. What kind of beer goes well with crow?

Next time: CC'ing and port work! stay tuned...
'70 Road Runner-B7 383 Auto, now with more cubes
'97 Ram 1500 Sport 4x4-Bright Red 318 magnum
'67 Belvedere II-Dark Blue 318 Auto, now owned by my brother
'73 Challenger Rallye-B5 318 Auto, had a 360 in it, SOLD :(
'42 Harley Davidson 42WLA-U.S. army green 45ci flathead
'71 Challenger R/T-B5 383 Auto, now 400 powered and rusty!
'86 W100-Yellow 318-2bbl 4x4 4spd, off road toy