i have a motown block that i recently purchased, and i need to build the rotating assembly for it. the engine is the 400 bore/350 mains

heres what i know is goin in it so far
- air flow research 195 heads
-edelbrock rpm air gap intake
-750 double pumper
- compression ratio of 10.5-11.0 (pumpgas motor)

since i have to buy a crank/rods/pistons i was wondering would i benefit from a stroker crank over stock? i could go with a 3.85" stroke or the 4" stroke.

i have some 5.7 i beam rods right now, would those work with either stroke or would i need some 6"

the cam i want to run is the compcams 274xe solid flat tappet. but would be willing to buy the 282xe solid if it was recommended over my current choice.

rundown of questions:
1. would stroking it give me any noticable power?
2. could i use the 5.7" rods if ido stroke it or do i need 6"
3. would the cam i want to run be too small, or my heads not flow enough for that stroke?

oh and i dont want the engine seeing over 6500 rpms ever if that has anything to do with it.

thanks in advance.

rick

I will throw this out for consideration just to get the ball rolling!

Hopefully some of the guy's will chime in here that are more up on this then I am since I have went over to the "Dark Side" with my 496..

Decide how big a motor you want to build and go from there, but I suggest settling on a bore size before you look at the stroke b/c the block you are talking about CAN go out to 4.20" easy and 4.25" at MAX. And a 4.25"b x 4.00"s equal's a 454!!!

Think 6" rods need to be used to hold rod angularity to a more managable number??

Guy's talk of using 220 cc heads and bigger on big SB motors due to just shear size alone?? Kinda like BB's!!

Mention of the 282 cam seems like a winner to me but like I said, I am not up on big SB's all that much but I do stay away from solid rollers b/c of the longevity issue thing if street driven!!!

ANd don't over CR. it so that you can still run pump gas unless you want to feed a her a steady diet of octane booster or racing gasoline, imho///

Hope this is of help, come on in guy's...

pdq67

i would pick a cam in the 250 to 260@.050 range it would benefit the heads more. the 282 cam would be the most i would run on vortec head because of the lower 170cc ports and you can easly run 93octane gas on 10.5 compression with 36 degree timing. with this combination you should be 11 second crusier with know problem just some tuning to get it there.

what is set in stone, is the afr 195 heads, intake, bore (4.125), carb, and compression ratio could not be higher than 11.0 for pump gas reasons.

i know my heads are small for such a big motor, but the combo has done well so far (406 with the 274 cam, and above mentioned heads, intake, carb, with a 3.90gear and 26" tire, and 3000 stall) has run a best of 12.64 at 8000+ density altitude, so id ont think it would take much more to run low 12s (combo was untuned at the time)

is it worth it to stroke it to 3.85 or 4.0 to gain the low end torque, and i dont want a high revving engine.

any ideas?

I would leave it at 3.75" stroke. The extra stroke will just move your power lower in the RPM band without making any additional up top IMO. Although the AFR195's are excellent heads they ARE slightly undersized for a 400 so they would be way undersized on a 434 (4.00" stroke). Just not enough bang for your buck to make the bottom end bigger --- you'll be limited by the cylinder heads anyway IMO.

Here's what I'd do (I'm building one similar for a friend).

The CR and heads are fine for a 400/406 as long as you don't want to rev it to the moon --- I'd shoot for an even 10.5:1 compression if you can do it. Then I'd look for a solid FT cam with a fairly tight LSA (106-108*) and high 24x - low 25x duration @ .050 lift for the intake. With bigger heads I would say great - go for more compression, a larger cam, and rev it; but with the right cam the AFRs will make your engine a midrange-monster :D

If you plan on keeping the revs to say 6500 RPM or less the 5.7" rods would be fine. If you really want to spin it then a 6.0 rod would be much better, but you probably need more cylinder head anyway.

Here are a couple ideas for cams:

Isky Z27: 282* adv duration, 247* @ .050, .507" lift, 108* LSA. This would be good if you plan on a lot of street driving.

Comp 285-B6: 285/296 adv duration, 250/260* duration @ .050, .532/.555" lift, 106 LSA. This would be good if you want a more radical idle and want to rev it a bit more (3500-6500 power band)

I think some of the Crane Saturday night special grinds have a tight LSA with shorter duration that would fit nicely too.

Just a couple ideas.

i was not looking to get any rpm out of the combo, my max rpm is still 6500, how are those cams better than the 282xe solid ft? i am not too smart on cams yet so if you could explain the characteristics i could expect from these cams id appreciate it.

im considering having the heads ported, even if i do stay at 400ci.

thanks for the info again, its much appreciated, and keep it comining

rick

The Comp XS282s is a good choice too, duration @ .050 is right there with what I was suggesting. It would work just fine.

The big difference between the Comp XS 282s and the first Isky Z27 cam I suggested is that the Isky is a single pattern cam. The single pattern cams are good if your heads have an excellent exhaust port (yours do) and if you are wanting to build max midrange power.

The Isky also has a tighter lobe separation angle. The Comp XS 282s is 110*, the Isky is 108*, the Comp 285 is 106*. The tighter lobe separation angle creates more overlap and more cylinder pressure. This causes a narrower power band and a rougher idle, but usually more peak HP and TQ. It also helps IMO if your heads are on the small side, but that is just my opinion.

The bottom line: the Comp XS282s would idle fairly well in a 400 (probably a slight lope at around 700 RPM) and would have a fairly wide/flat RPM band (roughly 2500-6000 RPM).

The Isky Z27 would probably idle a little rougher in a 400 (more of a lope, at about 750-800 RPM). The power band would probably be from about 2800-6000 RPM with more peak HP and TQ than the XS282s grind.

The Comp 285-B6 grind would idle rough at I'd guess 900 RPM. The power band is higher and narrower than the other two running from about 3500-6500 RPM. I think this cam would make more HP than the other two but would be less driveable.

Hope that helps - sorry so long.

thanks for takin the time to explain that to me, ill consider all this when picking stuff out

rick

Well heres another suggestion, Keep your 400 block and run that combo for a while and casually build up the new motown block to some oddball big bore shorter stroke {4.250 bore/3.48 stroke???}with a 6.25 rod, Brodix 18 degree setup on top, a wicked roller cam and such and have yourself a naturally asperated pump gas 9 second street car... that would be cool. and probably very streetable if you stuck a jerico 5 speed behind it. Just an idea, not really realistic though unless you have some very deep pockets. Its what i would do on a high budget.... not that ill ever have one smile.gif
But really you could just run the 400 block and casually build the mowtown over a period of time hell that new 454 Hardcore motor is making 600 hp and 600 ft/lbs of torque with somthing like a 230/235@.050 cam and there 220 heads and a dual plane if im not mistaken??? just think of what that 454 would put out with a real cam, some better heads and good port work