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#1
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has anyone used the new cast 4" stroke crank that MP has put out for the 360?
I know you need new pistions (also avil from MP), but what else do you need to do? any clearancing required? |
#2
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Yes, a notch in the block at the bottom of the cyl. is required. The Machine shop can handle this easy.
Once you have the crank, piston & rings and the bearings, your ready to go.(if your useing stock rods, otherwise its what ever you buy in addition.) Grab some quality bolts and gaskets. |
#3
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360 Stroker
This is my first visit here, but I thought I would join in on this one..
I didn't go with the 4.00 crank because... With 6.123 rods, the rod angle was an unacceptable 19.06'. Unless I filled the block, the cyl walls would go oval. The rod ratio (1.53) was outside of my target design of 1.75. New rod costs were high New piston costs were way high... Here's what my alternative is... (16.27' rod angle:1.78 ratio) Chev 6.5 rods (2/3 the cost of Mopar) SRP-170232 Pistons (less cost than Diamond) Cut crank for 2.00 journals and balance All this was a net $205.00 LESS than the 4.00 stroker combination plus the other benefits... Maybe this will help your decision... |
#4
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etvolare;
help me out on this one. I've neverheard of this ovaling thing unless it was a hi mile eng. Then its simply a worn unit. Also, whats the stock rod angle? and why is the new angle not good for you/what your doing. I understand the rod ratio thing. That can be personal pref though. One more ? for you. The pistons you give by part #, but not by manufacter. Who makes them and what are they made of? Thanks for the info and in adv. for the ans. to the questions I asked. OH, almost forgot, jump into a thread anytime. It beats bench warming! You'll never know what can pop up when you do. |
#5
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Rumblefish360
I meant most of these references to an engine used exclusively for drag racing and not necessarily for a street driven engine. Although, a street driven engine might have the problem made worse by the fact that it may see 2-3 runs from light to light (why else have a stroker on the street!!) and then some low rpm cruisin... The oval thing is not as literal as the phrase would indicate. When you have a long stroke and a short rod, the piston exerts a lot of unnecessary side wall pressure on the cylinder walls when it makes the transition from BDC to the upswing. The cylinder walls are not completely stationary and actually flex (microscopically) when running at hi rpms. Most 1/4 runs are max out and there is time for the engine to cool but over a period of time, the bottom of the cylinders will go ovoid in shape instead of perfectly round and the extra drag causes lost power and skirt scuffing. This is another reason water jackets are filled with hard bloc etc... def: The rod angle is the number of degrees that the rod is when it is half way thru the stroke cycle, measured from a perpendicular line thru the center of the bore to the center of the crank pin. The stock 360 rod angle is 16.99' and has a rod ratio of 1.71. As a comparison, the 340 has a rod angle of 15.68' and a ratio of 1.85. There is an inherent relationship between the rod angle and rod ratio and I suppose that would be an individual preference. The SRP pistons are JE. The are listed for a 351w Ford stroker application, but have a .927 pin diameter (same as the Chevy rods) and a 1.280 pin height. You end up with around 11.8-12.3 CR depending on head cc etc... Hope this helps étvolar |
#6
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etvolare
What crank are you using? |
#7
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Basic 360 cast crank, offset cut for the chevy rods.
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#8
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thanks for the info guys.
a cr of 12.5:1 is too high for my target. this will be a daily driver and I don't want to pay for premium fuel. MP has a set of pistons available (made by federal mogul, hypereutectics) that are supposed give a 9.25:1 with 68cc heads, as well as forged pistons for higer cr's Rumble, have you built this combo (or simmilar)? 402 ci sounds pretty neat. |
#9
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Just talked to the MP tech support hotline, and they say you need to do a little clearancing to the oil pan rail with the 4" crank.
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#10
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clearance.........
Talked to a friend to is building a 360 with the 4 inch crank...and he is using Eagle 3D 4340 steel rods....he had to do minor clearance on the bottom of the cylinder walls to clear the rods.....he said he dummy up the engine with stock rods...the saw where they hit...notched block....and the eagle rods cleared easy....he is building the engine to go racing also...
tony |
#11
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Dwayne
Just a little more food for thought... You didn't mention what heads you would be using but a 72cc chamber head and a .060 head gasket shim will get you a 9.22 (approx) cr. If you build the bottom end strong, you always have the option of a raising the compression by swapping the gasket and/or heads for more HP. In the mean time, you can still tear up the street and not have to worry about another major rebuild (like replacing the block and/or pistons) in a year or two... As you may have guessed, I do not think the 4" crank is a good investment for either a street or strip engine. |
#12
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stroker 360
etvolare,
Is this the recipe for the 383 cu.in engine like Koffels has for sale? Have you built and run this combo? Sounds interesting! '71 Duster no electronics bracket racer 11.62@114.00 360,904,83/4... |
#13
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Hi Racerjr
I'm not familiar with the Koffel 383, but I would venture a guess that their combination may not have the Chevy spec rods and Ford spec pistons... but I could be wrong about that. Yes, I'm running this combination (372 CI) with a little more compression. I had the piston tops fly cut, ceramic coated and decked the block a tad to square it up. I have unported (gasket matched) Edelbrock alum heads that were shaved enough to index the chamber cc's. The only time my car sees the street is when I sneak out on the highway to do a jet change check or some other full run type test. So far I've gotten back to the shop before I was collared: Knock on wood. |
#14
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stroker 372
etvolare,
This combo sounds like it has alot less rotating weight than even the stock 360 much less the rotating weight of the 4.00 stroker crank! what cam are you running in it? Did you dyno it? Thanks! '71 Duster no electronics bracket racer 11.62@114.00 360,904,83/4.... |
#15
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Racejr
I'm running an old Moon solid lifter cam that I had reground at Elgin's in Ca. Lift: .560-I .540-E w/1.6 Roller rockers Duration: 254-I 264-E @ .050 Never had it dyno'd - those results aren't much good at the track anyway! Best time in 3200# Volare @ 5000 ft was 11.98 @ 112 |
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