318 stroker

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The .090 over 318 has been done for years... In terms of a stroker - it's cheaper because it uses a 4" 340 crank, and a std bore 360 piston.
 
I'm not doubting anybody here,but on a street motor I would be hesitant to go more than .040 over.
 
R4Sedan said:
I'm not doubting anybody here,but on a street motor I would be hesitant to go more than .040 over.
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Especially in a street application.

I wouldn't hesitate to run a .090" bore in a siamese block, or in a race only application, though. (As long as it was sonic checked).

The smaller bore will live longer in a street/strip build, though.
 
moper said:
The .090 over 318 has been done for years... In terms of a stroker - it's cheaper because it uses a 4" 340 crank, and a std bore 360 piston.
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I can see where it would be easier to get pistons, I just personally have not seen a 318 thick enough to go .090 I know they all vary but my fathers 67 318 cylinder walls were between .150-.180 @ .060 over. Another .030 would be to much IMO to put a 4" crank in it. I do like the idea, I would build one myself. 318s are everywhere and very cheap. Any particular years the thickest? A square motor would be cool.
 
The poly motors had thicker walls, but the LA and Magnum blocks aren't going to have as much cylinder wall thickness.
 
w7smallblock said:
This was my 390 combo
1988 318 roller block .030 over
scat 4"cast crank and I beam rods
Icon pistons-IC847 9.4:1 static comp
Indy LA-X heads 1.92x1.62 valves bone stock
custom HR 516/516 237/241 @.050 on a 109 LSA in at 105
LD 340 intake with 2" open spacer
Quick fuel SS-830 carb
mopar dist with 24deg initial and 34 total
hooker 1 5/8 headers with 2.5 inch full exhaust
3500 converter
3.73 gears with 275/60/15 drag radial

This motor was in my street car F-body aspen that weighed 3600lb with me in it and ran 11.70's at 115 on pump 93. There was nothing fancy just a good combo. This car also has power steering and factory water pump which was robbing a few horsepower.

I hope this helps if you have any ?' feel free to pm me.
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Nice, basic combination.
 
Yes I like your combo,are you running power brakes ? Good time in the 1/4 mile ! I might need alitte more cam sound,how does your idle ?
 
sleepyswinger said:
rnaz, is 11" of vacuum enough for power brakes ? How does that cam soung at idle ? Thanks, Mike
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I had that motor in a Dakota before the Dart, and it ran power brakes fine.

I love the idle of it.

[ame="https://www.youtube.com/watch?v=NUDjZAiDILA"]1970 Dart HD Walk around after polishing - YouTube[/ame]
 
sounds good,looks good,nice race with the mustang,did ya smoke em ? You have a roller motor, I'm going with the LA style, will there be any differences with hyd. Flat tappet ?
 
sleepyswinger said:
sounds good,looks good,nice race with the mustang,did ya smoke em ? You have a roller motor, I'm going with the LA style, will there be any differences with hyd. Flat tappet ?
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Thanks!
Yeah. I put him away by more than .3, and I let out of the throttle at the 1000' mark. I was just making shakedown passes, and he wanted to make a few alongside me.

I have changed the gears, and wheels/tires since then too. It should run 11's this season.
 
A 318 bored. 030 over with a 4 in stroke should yield 390 cubes.
I think that would be a 3.910 bore.
Would 340 J heads with a decent port and 2.02 intake valves work well in that combo?
I am thinking a 9.2 comp. Ratio, a cam with about 236 duration on on
Intake, 240 exhaust at. 050.
Also, shouldn't valve lift be in the range where it can take full advantage of the heads maximum flow? I mean if your heads flow best at. 560 valve lift then shouldn,t your cam opev open the valves. 560?
 
A couple years ago I bought a 390 smallblock (318 stroker) off craigslist.
It seemed like a good deal at the time. It was a fresh build still on the dyno, using many
Stock factory parts.It had a 4" EAGLE crank , factory conecting rods, custom forged flat top pistons,
6 quart oil pan, old 360 heads, a factory cast iron four barrel intake, and a thermoquad carb, and a
Mopar Performance 509 lift hydraulic flat tappet cam. The dyno said 431 hp and
454 ftlbs. Torque.
Brought it home, put it in the Demon, hooked up everything, even the exhaust and got it fired up.
It run well sounded great and idled a little lopey. I kept an eye on the oil pressure and it was about 60 lbs and would drop to about 20 at idle.Satisfied that every thing was good I thought I was done. I ran it several more times over the next month. When I went to change the oil I noticed some metal filings in the bottom of the drain pan. I didn' t throw anything against the wall but.....
Anyway, I pulled the engine and tore it down. What I found was the corners of all the
main bearings were worn down to the copper. Apparently the radius on the main journals of the Eagle crank is bigger than the radius on the bearings.
I was going to use the good parts over in a fresh build so I ordered the
correct bearings for that crankshaft -.010 and had the crank reground -.010. I have not done anything else with that motor sinse. I know it could be built into a real strong street engine.
 
The radius issue is very common. In fact, the 496 I'm doing was "completely prepped and ready to bolt in" by a highly regarded supplier. I found that the 7 & 8 rods had no side clearance... Both rod bearings were hitting their respective radii. Once I chamfered them - no problems. The other 3 crank throws were fine and went together with .011" side clearance with no special chamfering.
 
The Eagle forged cranks have that radius back cut a little bit to solve that problem.
 
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