408 stroker build

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racerbob

racerbob

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I finally have laid out the cash and bought a 408 stoker rotating assembly to build my next engine for the dart. I have been racing the Dart Sport the past 5 years using 340 based power. Car currently goes as fast as 11.896 @ 112mph using a hydraulic flat tappet cam, "U" (#915) head, steel crank 340 I bought used for $1000 three seasons ago. Engine is still running strong, but I want to see if I can get car to run low 11's or even high 10's with a 408 engine.

I started this process by researching the market and arriving at buying a 4" stroker, forged steel crank, H-beam rod, dished JE forged piston balance rotating assembly kit from Ohio Crankshaft for $2000 (actually $2065.00 shipped to me in La Plata, MD). I had a few early 360 standard bore blocks to use, so I ordered the kit with 4.030 bore pistons.

Once I got the kit home, I installed the crank in the block, installed the rod with a mock-up piston and checked the rod bolt to block clearance. Had to grind out small notches at the base of each cylinder bore, otherwise the crank/rods cleared everything else. I was using a milodon main cap stud kit so I bottom tapped all of the main bearing cap retaining threads in the block. See notched cylinder bore shown in picture 1.

Set block to Clinton Auto Machine in Camp Springs, MD to be cleaned, checked for cracks, bored .030 over and have engine plugs and cam bearings installed (all for $385!).

Got block home and installed the main bearing retaining studs, main bearings and rear main seal (as shown in picture 2).

Gently lower the 4" stroker crank into place (picture 3).

Install the main caps and torque in three steps. (picture 4).

More to come later.

Bob
 

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so all the caps stayed put, cool.
Most line hone for studs.

what was the main bearing part number you used?
Standard main bearing hit the radiuses on my ohio crank and I ended up with .002 end play, so I lathed them to get .006
 
I think its highly recommended to line hone when using studs, i could be wrong
 
Looks good Bob.
I'm building a flat top 400 inch engine for my wagon this year.
My 360 went an 11:07 with burnt up high gear at last years Mopar race.
Going to use the same heads, intake, cam. New 950 HP car.
Hope to have it in for the Mopar at MIR race and run mid tens.
 
Double check the main bearing bores with a dial bore gage. Studs tend to distort the cap differently than bolts, and it's recommended to align hone them when they are installed.
 
TurdFerguson said:
so all the caps stayed put, cool.
Most line hone for studs.

what was the main bearing part number you used?
Standard main bearing hit the radiuses on my ohio crank and I ended up with .002 end play, so I lathed them to get .006
Click to expand...

Not sure of the part number, but the bearings that came with the kit were listed as Race bearings and they are bit narrower than the standard oem bearings. Looked kind of weird at first, but considering the radius on the crank journals it makes more sense.
 
moper said:
Double check the main bearing bores with a dial bore gage. Studs tend to distort the cap differently than bolts, and it's recommended to align hone them when they are installed.
Click to expand...


We actually installed the studs and then measured the bores, nothing changed when using the studs and was aligned well.
 
It looks like you are going to have clearance problems with your oil pump and the stud/s on the rear main. A lot of people just remove the stud and use a bolt, not the ideal scenario. I usually get the main cap spot faced down and cut the stud back to suit, a bit of time spent on this is way better than using a bolt.
 
I just ground mine down during mock up [ the main stud under the oil pump]
and I used the 12 point nut that is a lil smaller.
 
raymond said:
It looks like you are going to have clearance problems with your oil pump and the stud/s on the rear main. A lot of people just remove the stud and use a bolt, not the ideal scenario. I usually get the main cap spot faced down and cut the stud back to suit, a bit of time spent on this is way better than using a bolt.
Click to expand...


Yes This is the case. Next time buy the stud kit that comes with a high strength ARP bolt for this position (Hughes engines sells them).

I replaced the stud with a high strength bolt, that seems like a better (safer) fix to me then machining the cap and shortening the stud.
 
TurdFerguson said:
so all the caps stayed put, cool.
Most line hone for studs.

what was the main bearing part number you used?
Standard main bearing hit the radiuses on my ohio crank and I ended up with .002 end play, so I lathed them to get .006
Click to expand...


I measured the end play and came up with .003-.0035, which is within the .002-.009 spec. I think it will be fine since it is above the .002 minimum and will only get larger when the engine breaks in.
 
Nice work!Your gonna love the new torque from the 408.What cam will you be using?I run a solid roller cam(custom grind)252,258 with .631 lift dialed at 106.good luck.
 
pettybludart said:
Nice work!Your gonna love the new torque from the 408.What cam will you be using?I run a solid roller cam(custom grind)252,258 with .631 lift dialed at 106.good luck.
Click to expand...


I called Comp Cams and by thier recommendation I will be using a XS282S grind cam (mechanical flat tappet with .520/.540 lift).

bob
 
Once you feel the torque of that 4" crank you'll never build another stock stroke engine again.
 
racerbob said:
I called Comp Cams and by thier recommendation I will be using a XS282S grind cam (mechanical flat tappet with .520/.540 lift).

bob
Click to expand...

Bob - If you'll pardon me for saying - I'd doubt you'll make 10s with that stick in a full weight A body.

I know of a 3500 lb Valiant that ran a 408 with that cam - with unported Edelbrocks and 3.89 gears and it made 11.9.

My own car ran the same cam with a stroker 318/390. Cast heads (flowed less than OOTB Edelbrocks) ...best ET with that was 12.3.

Its a great stick but not a ten second cam I don't believe.

In my limited expereince, ten second A bodies generally run flat tappet cams in the 250/260 / .550+ lift ball park.

2c.
 
Rat Patrol said:
Bob - If you'll pardon me for saying - I'd doubt you'll make 10s with that stick in a full weight A body.

I know of a 3500 lb Valiant that ran a 408 with that cam - with unported Edelbrocks and 3.89 gears and it made 11.9.

My own car ran the same cam with a stroker 318/390. Cast heads (flowed less than OOTB Edelbrocks) ...best ET with that was 12.3.

Its a great stick but not a ten second cam I don't believe.

In my limited expereince, ten second A bodies generally run flat tappet cams in the 250/260 / .550+ lift ball park.

2c.
Click to expand...

Torque is for trucks, race cars want HP.You just gear for torque. Why 4.88 gears were used at the strip.

Maybe you should have went with a solid cam for the 340 and more gearing and rev the piss out of it. That is how it was done in the old days...well even today, BMW V 10 uses under a 3 inch stroke crank but has a 8,500 rpm red line

I agree 10 seconds with a SBM is going to be tough to pull off. Losing some weight on the car would help
 
I was thinking of runnig a bigger cam, but I also wanted a Pump Gas friendly engine. When I dropped the compression, the cam experts told me to run a smaller one. I race enough, weekly basis, that buying race fuel can be very painful.

Yes you are right, I probably will not get into the tens with it, but I hope it would be faster than my current setup:

.030 340 with flat tops (10.5 comp),
2.02/1.6 J-heads,
MP .509" Hyd cam,
Weind single plane intake,
650 Dbl pump Holley,
MP electronic ignition,
Hooker 1 5/8" Comp headers through 3" dynamax bullet mufflers
10" Turbo Action 3600 conv,
727 trans with Manual valve body,
4.56 ratio rear
10/28X15 slicks
3400 lb 1973 dart sport (with me in it)

11.89 @112mph in cold air and low 12's all summer long.

so I guess with a engine with 60 more cubic inches, A bigger cam, A bigger intake (Victor 340) , Bigger headers (Hooker 1.75" super Comp) and a bigger carb (750 DB with Proform body & QF metering blocks), maybe I can run mid to low 11's and maybe get into the 10's after I lighten the car (or maybe just buy a lighter car to put this engine in??)?
 
viperredduster said:
What heads are going on this bad boy?
Click to expand...
To start out I am taking a set of 2.02/1.60 J-heads (915's) I had on my street car several years ago to the shop to have them rebuilt. The comp cams kit comes with springs, retainers, keepers and seals, so they will be all new except the castings and valves.

I was hoping to buy something nicer, but am starting to run out of resources.

Maybe later I can upgrade to something better: eddy's, RHS-X, W-2, etc.
 
Well, you do what you can with what you have…you can swap out for better heads later, just remember you are handicapping your engine combo a LOT with stock heads, small cam, small carb, ect. As long as you’re having fun, that’s all that counts. When I built my motor, I put too small of a cam in it…..but it still boogies.

BTW, 10’s on pump gas can be done without too much trouble….see sig below for my grocery getter.
 
I have built 4" arm engines with iron heads that were built with low compression and the future plan of upgrading heads. They have enough steam on iron to run into the tens with a hydraulic cam... But that's with porting the heads, race gearing and tires, and that car has to be a bit lighter... including adding in the weight of the safety stuff (cage, belts, etc).
 
Good job 408 I think I use rhs heads and HUGHE CAM I HAVE HUGHE CAM JR CAR. SEE YOU AT MIR.
 
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