Looking for easy power from 426 Hemi

[Cranky]

Turn up the timing.

Turn it up until it PINGS!

 

[wyrmrider]

which edelbrock carbs?
what rear end Dana or 8 3/4
original hemi car?
fan clutch- how many blades and what pitch - measure next time you have it off
headers do help but not much stoplight to stoplight where you are traction limited
so do you drive it where they would help?
what 5.7 said do this and carb tune first
did they put a mechanical cam back in it? which one? (since originals are no longer available nor are the special lifters (or were the special ones race only- I forget)
what springs did they use- did you get a parts list?

 

[426rt]

On all my other BB mopars I always had a good set of headers but they were stroked/ calmed motors with after market heads making 650-700hp . . Just didn't want to spend around 2k for an exhaust and headers with a 10-15hp gain if that's all it is . If stock hemi gains are on par with nicks stroker I would do it in a second

 

[426rt]

Originally a 440/ 4spd/ Dana 60 car. Has an original date correct 68 hemi now that was rebuilt to stock specs using a reproduction cam of the 490 something lift that was in the hemi's . Also has the hemi crash box course spline with a good clutch

 

[wyrmrider]

for hyd cams
http://victorylibrary.com/mopar/mpcam-tech-c.htm#hemi

"During its eight year production life, the street 426 Hemi saw updated camshafts (more duration was added in 1968, and a hydraulic bumpstick was used beginning in 1970)"
1966 “Street” 426ci Hemi: Solid cam with 276 degrees of duration and .480-inch lift (intake) / .460-inch lift (exhaust).

Late Mopar performance engines catalog
For 426-based HEMI® Engines. Duration @ 0.050" 241° lntake/241° Exhaust. Intake Centerline 106°. Lift 0.484" Intake/0.475" Exhaust. Recommended Springs P/N P3690933
Hydraulic, 1970-1971 Street, Purple, P/N 1P4529315AE. . . . . . . . $415.00 Mechanical, 1966-1969 Street, Purple, P/N 1P4529316AE . . . . . . $415.00

I know of nothing with the lifts you mention
10.25 Heavy TRW Pistons stock really less than this unless blueprinted
run a compression test and post back whenever
undoubtedly the head gaskets have been changed to from OEM steel shim

 

[426rt]

Its the 484 lift cam , I was told the compression is 10 1/4 to 1 . I don't think it's that critical to split hairs on a basically stock motor as far as the specs are concerned . Only want to know what easy mods would be beneficial and how much of a gain headers / 3" exhaust would be approx

 

[6PKRTSE]

Anything you do can only help. For a cruiser, I say go for it. It's your car, do whatever you want with it. Have fun and enjoy it. That is what this hobby is all about, making our cars OURS.

 

[dvw]

Big heads (Hemi) need rpm. Rpm needs camshaft. Camshaft needs gear and converter. Simple formula. The stock cam (or similar) is no where near adequate for high output.
Doug

 

[wyrmrider]

What Cranky said then back it down a bit
BVVC on big short headers for a street car
I even question 3" collectors with a stock motor
take a look at
https://www.msn.com/en-us/autos/enthusiasts/426-hemi-crate-rebuild-and-dyno-test/ar-BBt7gY5
and other similar and see how much difference headers make on a mild motor
post up a compression test when you get a chance
did you confirm solid cam
thanks for the clarification I was questioning the 490 lift statement

 

[wyrmrider]

If thinking of headers I strongly recommend that you find someone working with PIPEMAX or learn it yourself
google pipemax header design
overview here
https://hotrodenginetech.com/pipemax_header_design_software/

https://www.speed-talk.com/forum/viewtopic.php?t=57087&sid=02988a1e0a33dba211917180f8924266

 

[wyrmrider]

for that custom cam
https://www.speed-talk.com/forum/vi...8&p=826451&hilit=controlled+induction#p826451

https://www.speed-talk.com/forum/vi...5&p=818135&hilit=controlled+induction#p818135

https://www.speed-talk.com/forum/vi...8&p=817641&hilit=controlled+induction#p817641

AN fyi
tight lash(.008"/.009") acts about 4-6 degrees bigger then a cam with .020" lash.

 

[Challenger340]

Its the 484 lift cam , I was told the compression is 10 1/4 to 1 . I don't think it's that critical to split hairs on a basically stock motor as far as the specs are concerned . Only want to know what easy mods would be beneficial and how much of a gain headers / 3" exhaust would be approx

Might be well advised to START splitting hairs ?
Because it depends on who's interpretation of the stock 426 Hemi specs the engine was rebuilt to ?

I've seen Forged replacement 426 Pistons that didn't even yield 8.2:1 when actual "poured" CC Downfill Volumes were done on Engines !
But those guys swore up and down it can't be.... it has to be MINIMUM 10:1 !
So....
we brought 'em in the shop and did it with them standing RIGHT THERE !
8.15:1 being "generous".

Most of the so-called Crate Engine Forged replacement piston offerings being the WORST !

Just say'in....
I don't care WHO told you it's so-called rebuilt to "stock '68 specs".... it could be anything !

Without you knowing anything POSITIVE about the Engine other than here say...
Stick to Headers, Carbs & Timing.... and NO telling "theoretical" gains on an UN-known Engine , but should help.

 

[wyrmrider]

a compression test would help determine stock which is most likely around 9.5 especially if felpro type gaskets replaced the stock shims
Once we sorta nail down the compression I'd have AJ/FormS (maybe at FABO) run the numbers for you If compression is lower then a cam change would make more difference than Headers
on headers think real hard then select 2" or 2 1/8
NO 2 1/4 SUPER COMPS on a stock engine
no dropping a grand on headers
Also check out TTI
there were near me here in So Cal as were most other header builders

 

[Challenger340]

a compression test would help determine stock which is most likely around 9.5 especially if felpro type gaskets replaced the stock shims
Once we sorta nail down the compression I'd have AJ/FormS (maybe at FABO) run the numbers for you If compression is lower then a cam change would make more difference than Headers
on headers think real hard then select 2" or 2 1/8
NO 2 1/4 SUPER COMPS on a stock engine
no dropping a grand on headers
Also check out TTI
there were near me here in So Cal as were most other header builders

You intend a "cranking" type compression test with an accurate(measured) ABDC Intake Closing Point and elevation factored in ?

I haven't seen many "426" Crates that yielded an actual static CR much above 8.5 ? Making Cam pressures difficult on the small engines ?

 

[wyrmrider]

absolutely correct challanger
That's the intention B4 spending money on headers

9.5 on a rebuild is quite a comedown from the expected 10.25 which is what a NHRA type blueprinted motor would be with shim gaskets
the reality of 8.5 with minimum cut decks and fel-pros is closer to reality

Which is why the stock 284 degree cam
(and that's at around .008- more like a 290+ degree Comp cam or a 300 degree Crane
may be the wrong cam
low compression and that cam looses low end big time and while you can get higher rpm HP you have to rev it up- no fun
If lucky OP will have a parts list and we can see what pistons were installed

 

[Kern Dog]

There is no power to be found in an MSD ignition system if your current setup is working. Once the fire lights, the combustion takes care of itself. The MSD may be easier to tune, adjust the advance rate, etc but it will not make the car faster.
Exhaust will make a noticeable difference, likely 35 HP or more.

 

[Beach Goat]

Long tubes
Passon 855 overdrive manual
Single plane manifold with a single big four barrel

 

[wyrmrider]

Good points
get an ignition system that does not let the plugs foul. We used to put hotter plugs in as the sales people would take a superbird or hemicuda to lunch and bring it back barely able to run. Had to go back to stock when the car was sold- During the gas crisis we could not even give these cars away.
I do not want to get into single plane vs dual plane without knowing usage but there are more modern carburetors or you can get EFI for about the same cost as headers and I'd go there first.
Would make it fun to drive and not a PITA.
Do your research on headers based on usage
long tubes- right GOAT and bigger is not better especially through the mufflers
Get it to run right before worrying about 35 mostly top end (but some everywhere) horsepower.
Figure how to boost your entire torque curve

 

[Hemirunner]

This is actually my first post and also first time experience with the 426 hemi . I've had RB & LB based engines making lots of power in the past but never the hemi . I just got into a 68 rt 4spd car with A freshly rebuilt hemi to factory specs . The only additions are edelbrock (I think 650cfm) carbs and an msd distributor . I didn't want to open the engine up and was looking for easy / easily revers-able mods to boost power . I was thinking along the lines of headers , msd box, electric fuel pump , anything else ? Also was going to put 4.10s out back . Any help / advice is appreciated . Thanks

Given the constraints of not wanting to open the engine, you’re limited to a few options.
1.)The 4.10 gears are a great idea as hemis like rpm even in stock form with the small cam. I really doubt you bought a 4spd hemi car to make highway cruises to the mall or road trips to see aunt Betty two states away.
2.) Headers and a free flowing exhaust will let it breathe easier and rev higher. Goes well with the gears.
3.)MSD ignition box and matching coil is a great idea and a big improvement over stock and MP electonic units. Just be sure to dump the ballast resistor as it’s not needed with the MSD coil.
4.)Carb and Ignition tuning. Optimize both and it’ll run crisp and strong. A wideband O2 sensor setup can help with tuning. Good luck and let us know how it all works out.

 

[biomedtechguy]

Passon 855 overdrive manual

THEN add the 4.10 gears!
That's what I did on my 70 Roadrunner.
440 6bbl, went from 3.54 to 4.10 with the 5 speed. 70 mph RPMs went from 3,500 in 4th w/the 3.54+4 speed to 2,750 in 5th w/4.10s
BIG ? before you do anything...
Can you get traction now??
I don't regret changing to the 4.10s because it was the time to do it w/the transmission swap, but I have been fighting wheel spin forever.
If anything, the 4.10 helps because I roll off the start and floor it.
Once I get hooked, I believe I'll be in the 12s
Get traction FIRST.