408 Stroker build (what heads)

Hi,
Very sweet ride! Ouch, oil pump. No, these questions are very welcome! Couple questions to know where it needs to Rev & CFM flow & Cam spec’s, based on C.R.
4 Speed Car?
Auto..Stall?
Gears?
This a stock block? No probs, 351’s aren’t vulnerable like 302’s, wondering if it’s aftermarket.
Threaded freeze plugs?
Running an ARP studded bottom end,?
4 bolt conversion?
Lower Stud girdle?
Internal balance?
Rod’s (Mfg./series) used?
Floating Pin pistons?
—Trying to Calculate your static C.Ratio for ideal Cam size with 26cc I/Dome .040 over pistons installed 0.005 @TDC in the hole, 4.0” Stroke & I’m just guessing these are 0.040 the head gaskets, & Heads are uncut Pro 1 Dart Inconel Exh Valved Heads, 62cc, 58cc Chambers(?)
62cc.. Around 9.62:1 C.R.? Seems low.
58cc...Around 9.98:1 C.R.? More likely.
351w Stroked & bored to 408’s are usually -.030 square.
—Certain you’re 0.040 over? Norm is +0.030 with a 4.0 Crank throw.(040 over & you’ve 410CI.).
Where are you idling, about 850-900RPM’s?
Running stock ratio Rockers?
— If this is the Cam I think it is... well, you can get much more out of it with a few event changes.
Pistons have relief’s that will work with Twisted Wedge Heads?
—In the > 400 CID category, for a hot yet Streetable build like this, a 200cc port will serve you best, but at this point you’re not outflowing the heads as the Cam’s insufficient @ barely 1/2” lift.
— Regarding the “500BHP” comment.. ABSOLUTELY. Not difficult to pull 400-425RWHP & slightly greater Torque is a given with a 408.
— As you’re not relying on vacuum signal to pull fuel from annular boosters in a Carb, the advantage of positive injected fuel you need not be as concerned about no low end due to more duration & overlap & can run a hotter Cam. I’d absolutely consider a custom H.R. or S.R. grind, off the shelf could be better, not that there isn’t a good Cam available.
—That could grab near 25HP, on top of what a more aggressive (but highly streetable) profile would yield you, as is.
—Instead of going with 205’s, having the Intake & Exhaust flowbench ported, bowls blended, port matched to the S/P Victor Jr’s runners, & removing the flash on the runners will also help. (A Dual plane Stealth or Airgap RPM II intake would give you the tire melting mid to top end with less effort)**.
What headers are you running, tube diameter, tuned? Exhaust system?
Ok, I’ll check back in a bit. Sorry for the 1,001 questions, but difficult to give you solid suggestions if I don’t know the specifics. TY.
Best.
-John


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** Don’t get me wrong, Victor Jr’s are great. It’s the runner length & configuration that you’ll be fighting to keep the power where you want it on the street.

if you have 195cc heads on now, they will do fine. the 205s are a small step up. this is based on your choice of cam for the engine. where the 205s would help is on the top end, where you really dont need the power anyway since you wont be racing, as you have said this is basically a street engine. besides the amount of power you would gain with the bigger heads with you combination would not be worth the outlay of cash. personally i would freshen up the dart heads and run them

Mach1969 said:

Thanks for the thorough answer! That helps a lot. For more background on the build I have had a local shop do the engine build for me. I havent been real happy with their work. The shop deals with a lot of newer mustangs and work more bolt-ons while running a dyno. I went to them for suggestions and they initially suggested the 205 heads and when I asked them more about why they suggested those heads they didn't have a good answer other than they would move more air. I wont be going back to that shop but want to make sure the next place I find has reasoning behind what suggestions they provide.

I dont have answers to all your questions but here's what I do know:

5 speed manual- tremec TKO
Detroit locker 9" 3:55
Block is 351 from '72 (basically stock but from another mustang)
ARP bolts throughout
Internally balanced
all I have is the rods part number and cost: part #300-780-8 ($118) hope that helps
not sure about the pin pistons
Idle is set at 900rpm
I was having hood clearance issues with a taller intake manifold so had to go with the vic jr single plane manifold. The air filter I have now just slightly touches the hood when I close it and I had to remove 2 bolts from the hood scoop to make it fit. I previously had a dual plane but the EFI wasn't running right and the idle would jump all over the place. The single plane has since fixed that issue.
headers are long tube hooker super comps (recommended to fit with my rack&pinion setup)
exhaust is magnaflow 3 1/2" x-pipe

other mods include wilwoods all around
ridetec level 2 coilover suspension with front sway bar
rack & pinion steering

Again, thanks for all your help and information

Click to expand...

Hi,
Great follow up answer! Hard to help without a history. Sounds like your motor, exhaust & drivetrain are solid. Gorgeous car, I must add. The info you relayed about the shop sounds bleak.
Btw..That’s quite something, regarding the dynoshop’s answer when confronted with your query regarding the benefits of running the 205cc Heads..”they’ll move more air”... Thats pricelessini!! lol.!Too technically advanced to comprehend on my end, I’d have never deduced that response- you? lol. Agree with you, I’d move on to another more “seasoned” nostalgic motor/car setup, as you suggested.
Specific application is within much better reach, financially. You're shifting about 6K- correct? Existing Cam is Comp’s 4,800 RPM spread (1,200-6.000) XR282RF-HR. a Versatile grind I’ll mo your setup if seeking the 500HP mark. Can you pls confirm this is the Cam you’re running:
https://www.compcams.com/xtreme-energy-230-236-hydraulic-roller-cam-for-ford-351w.html
The Cam is holding you back a bit, it has long duration & events that are similar to, & would be best served with increased lift.
Swapping to a 1.7 rocker ratio alone for this is not so cut & dry, not a “bolt on” process.
A clay-test to verify Piston to Valve clearance is required for the extra lift, especially running slightly aggressive duration, Ergo: Head removal.
At least one Head. I check more cylinders than one, randomly, if they're on the close side. (clearances, P to V Intake clearance; minimum is 0.060, Exhaust 0.100) full lift, solid roller lifter(s) installed in the Cylinder you choose.
There’s an alternative method leaving Heads alone. pulling 2 Valve-springs & running light compression springs & running a Borescope into the plug hole & running the pump to pump up the Hyd.lifters for full lift. If it’s something you want info on, just ask.
Head removal, on the other hand, since you should consider some light porting, bowl work, port matching (2) solid lifters is a proven & therefore the best for the clay test, no error possibility, and you can freshen Heads up up while removed. A Flowbenched & a person that’ll work with you is helpful, those specs are important for a new Cam grind, should you pursue that.
GEARS:
Since its not driven on the highway daily & you have a 4 speed with an OD Gear with the 5 speed...Motor runs & performs well, slightly less than optimal output..... have you considered gearing lower?
4.10’s may offer your App. not only the typical mechanical advantage, it also may allow your motor to hang in it’s optimally existing Torque & power-curve RPM’s while accelerating hard through the gears on the “backroads” lol.
Though 5 Speeds aren't labeled as 4 speeds w/OD, by definition- tis’ what they are. A 1960’s Muncie M-22, a Saginaw, Top loader all share a 4th Gear ratio of 1:1, as does 4th Gear in a 1990 T-5, a late 90’s T-45, 3650, etc.. Overdrive= Any drive assembly where input RPM is exceeded by output RPM. Whether a Blower or a Bicycle, physics are unchanged.
5th Gear’s tall Ratio is generally 0.67 or 0.68:1 in a 5 speed trans.
You’d see around 300RPM’s greater @ 60MPH with 4.10’s VS the 3:55’s, so it won’t devastate a leisurely cruise on the freeway, but will really wake it up getting there..easy to use RPM calculator below.
Best bang for the buck. You’ll need all (3), purchased separately at LMR:
1) FRPP Ring & Pinion gears, of Ratio desired.
2) install kit with the Vent. Friction modifier & Royal Purple gear oil.
2) Axle bearings and seals.
Parts self purchased & a shop install averages around 800$.
You’ve a good combo going, be absolutely certain the fuel & ignition system is as should be, timing advance is at its peak without detonating, fuel is 14.7:1, AFR’s around high 12’s when it needs/may use fuel the most. An A/F gauge is useful, using any injection, whether DP or TBI. Dizzy curved to add all your advance in by 3K RPM’s is also important. So, aggressively yet safely tuned, then decide what works best for your needs. .
CAM:
You can grab some extra lift by running 1.7 RR Rockers, as also mentioned above, but you’ll need to be certain of adequate Piston to Valve clearance. It’s not all about lift, the combo if it and duration are what cause issues. That means removing the heads & performing a simple Clay test.
Uncertain if your piston notches/reliefs are “Twisted Wedge friendly”, as they moved the valves to the combustion chamber’s midline.
If you wanted to go up a sizable notch in HP/TQ, and were after replacing a few things, I’d have your existing heads ported & portmatched to your intake on a Flow-bench, or buy a set of TrickFlow’s CNC ported 190-210 11R Heads & a custom Cam grind.
OTS, a TF stage (2) Cam, or a Comp.’s HR 292, I’m not suggesting buying all new parts, such as Heads brand spankin’ new, rarely can you trust a set of new heads without a tear down, if you find a set of used heads- you can get a good price & tear them down yourself, do a bit of port cleaning with a handheld with some decent burrs, sanding tips, match the ports & rid casting flash on the intake. Little goes a long way.Truly.
What’s your actual head cc’s, and /or what was the ratio they (shop) told you it was? I can check against that to verify, chamber cc’s are the only calculus I’m in need of.
Btw, awesome Mallory distributor, still a dual point system, or electronic? Looks great! What tube size is your Hooker Headers, and what length are the pipes to the collector to the motor flange (part number is fine). You can pick up significant TQ, HP with collector extensions, if too short.
Talk soon!
Best!
John.