D Algozine Posted June 29, 2009 Share Posted June 29, 2009 Brief history: After three years of racing I had my engine freshened this past winter. We found a cracked #2 main cap and a crack in the webbing at the #2 cap. It was still together, so it must had been cracked for a short time. Here's what I have: 331 - Production block, machined, prepped and assembled by reputable and capable race engine shop Eagle rotating assembly, forged parts, zero balance Dart Pro 1 Heads - Solid roller lifters Custom cam - Dont have the info in front of me, but nothing crazy Just before Nationals 08 I replaced the transmission and installed a new clutch (Centerforce). I raced one more weekend in 08, then it was torn down and we found the cracks So, upon finding the cracks this past winter, we prepped a new production block and reassembled with new bearings, rings, valve job..... Second weekend this year the webbing at the #2 cap blew apart. The bearings, all looked good. Coincidence, or related? This week the entire rotating assembly, with balancer and flywheel, was just checked for balance and it was fine. So, I don't know if the two incidents are related or just coincidence. The second replacement block was not magnafluxed. Could it be something in the transmission? It shifts fine and I haven't noticed any vibrations in the shifter handle. Clutch assembly be bad? Can the Centerforce weight system on the fingers be a factor? Some type of harmonics issue? Anything else? I purchased a DSS race prepped block and plan to re-install my rotating assembly (balance just verified). Ideally, I'd like to find the smoking gun, but nothing yet. I'd hate to throw more money away and have it happend again. Thoughts and ideas appreciated. Quote Link to comment Share on other sites More sharing options...
nape Posted June 30, 2009 Share Posted June 30, 2009 My car only emits #2 main cap cracking sonic waves from the front. If you let me pass you sooner, the damage will be less. What balancer are you using? Any chance it's worn and not doing it's job? If the bellhousing isn't indexed correctly, I know it will cause the trans to wear, but it shouldn't put strain on the crank. Nor should the clutch as long as it's balanced. Is it a 2-bolt, 4-bolt, or 4-bolt splayed block? The GM ASedan guys quit machining 2-bolt blocks for the extra bolts because the main webs seemed to be too weak in the 305 blocks. Quote Link to comment Share on other sites More sharing options...
D Algozine Posted June 30, 2009 Author Share Posted June 30, 2009 It's a Romac SFI balancer that's less 2 years old. 2 bolt main block. Nice try on the sonic wave deal. Quote Link to comment Share on other sites More sharing options...
swhiteh3 Posted June 30, 2009 Share Posted June 30, 2009 I would STRONGLY suspect the balancer. I've seen things like this come and go like a lightswitch with a balancer change. Balancers are tuning items like a shock or a spring. If it's not tuned right, you're going to have issues. Quote Link to comment Share on other sites More sharing options...
Grizlbits Posted June 30, 2009 Share Posted June 30, 2009 The rotating assembly should be balanced with the balancer, even on a zero balance motor. Quote Link to comment Share on other sites More sharing options...
D Algozine Posted June 30, 2009 Author Share Posted June 30, 2009 Scott/ Chris Thanks for the input. To clarify, just last week the entire rotating assembly including the balancer and flywheel was checked, and found to be ok. As it's been explained to me, the balancer could be in balance, but not dampening properly. At this point, I plan to install a new balancer, and I haven't decided if I should change the clutch, yet. Quote Link to comment Share on other sites More sharing options...
BOC- Beau Posted June 30, 2009 Share Posted June 30, 2009 Dave, I had five roller blocks fail in the same spot(#2 main web). My engine is a 306, neutral balance with a pretty light rotating assy. I turn it 6500 rpm. I went from a Romac dampener, to an ATI Superdamper. I had failures with both. I run solid engine mounts. One theory is that the lack of flex in the engine mounts puts too much stress on an already weak block. Do you run solid Engine mounts? I also had a main girdle with ARP bolts. Another theory is that the girdle just holds things together if something fails, and that the higher torque spec for the bolts adds stress to the block in the main thread area. The thought is that studs, or even the stock torque spec would be better. Another supposed fix is to add splayed 4-bolt caps to your stock roller block. Pro-Gram makes a set of caps specifically for this application. I know that some people have had success with these caps and polyurethane engine mounts. I bought a set to try, and never used them. I would sell them if anyone is interested. Ultimately I decided to buy a Boss block to remedy the cracking. That seems to have worked. I also lost a Mexican block to a crack in the #2 main web, but It broke on the right hand side. All of the roller block failures that I had were on the left side. I contribute the loss of the Mexican block to a wreck which stressed the right side of the block heavily. Fortunately, I never lost an engine. I always had a "funny feeling" that I better tear it down and look. I hope this information helps. I can't say that I ever really found the problem. I just came up with a bunch of theories. In the end, I decided that I was just over stressing an inherently weak block. Quote Link to comment Share on other sites More sharing options...
D Algozine Posted July 1, 2009 Author Share Posted July 1, 2009 Beau, Very interesting. I have solid mounts. I only spin it to 6400, and put out 335 hp at the wheels. Drag guys get a hell of alot more reliable hp out of the production block. I like the solid mount theory. Oddly enough, I have a brand new set of poly mounts. I bought them a few years ago for a street car and never installed them. I think I'll give it a shot. My engine builder told me to pony up for a Dart block. He also said that 4 bolt mains on the Ford production block do very little, because the webbing is so thin. I just picked up a DSS block today. Thanks Quote Link to comment Share on other sites More sharing options...
gbrown8439 Posted July 1, 2009 Share Posted July 1, 2009 Dave, I have also broken 2 production blocks in the same place you have. We always found the cracks at the end of the season when the motor was torn down to inspect everything. A new block became an expected expense. I never had solid motor mounts so I'm afraid switching to poly mounts won't help you much. I do know of one person that was using the 4 bolt main caps on a stock block with good success so that may be the most cost effective fix. Good luck. Quote Link to comment Share on other sites More sharing options...
b_tone Posted July 1, 2009 Share Posted July 1, 2009 What rpm are you guys spinning these things to? I have used production blocks with success, only breaking one and that was due to a dropped valve and the sudden stop of the engine. I run relatively low rpm though, never spin it past 6k. Just wondering. Quote Link to comment Share on other sites More sharing options...
D Algozine Posted July 1, 2009 Author Share Posted July 1, 2009 What rpm are you guys spinning these things to? I have used production blocks with success, only breaking one and that was due to a dropped valve and the sudden stop of the engine. I run relatively low rpm though, never spin it past 6k. Just wondering. I've got a 6400 chip. Shift light is set at 6200. Quote Link to comment Share on other sites More sharing options...
swhiteh3 Posted July 1, 2009 Share Posted July 1, 2009 As it's been explained to me, the balancer could be in balance, but not dampening properly.Calling it a balancer is what causes the confusion. "Balancing" the system is only a very small, and rather incidental parts of it's purpose. The main purpose is to dampen crankshaft torsionals. Quote Link to comment Share on other sites More sharing options...
swhiteh3 Posted July 1, 2009 Share Posted July 1, 2009 What rpm are you guys spinning these things to? I have used production blocks with success, only breaking one and that was due to a dropped valve and the sudden stop of the engine. I run relatively low rpm though, never spin it past 6k. Just wondering. Is that the crank snout & dampener that you attacked a Ford Focus with? Quote Link to comment Share on other sites More sharing options...
b_tone Posted July 1, 2009 Share Posted July 1, 2009 No, when the crank broke the block was fine. When the valve broke at 6100rpm it split the block. Quote Link to comment Share on other sites More sharing options...
Members Jay A. Posted July 1, 2009 Members Share Posted July 1, 2009 Dave, The stock blocks are very likely to crack where yours did at the power levels we run, as stated by Beau and Greg and others. My shift lights are programmed between 6000-6300 with the chip at 6500. We have had great success with the block with the Splayed 4-Bolt main form Paul’s Automotive Engineering in Cincinnati. Paul has quite a few of them out there that are performing well. He has a road race customer that spins his a lot higher than we do. I think in the 7,000-8,000 range. kind of crazy. Stock rubber mounts for sure. Jay Quote Link to comment Share on other sites More sharing options...
Burnett Posted July 1, 2009 Share Posted July 1, 2009 Dave, end it all now......"Boss Block". Call Capaldi racing and have Leo sell you one of these things. A true 4 bolt piece for racing. Robin PS Ran AS for years with 310hp but making what you make will kill those stock blocks. Quote Link to comment Share on other sites More sharing options...
D Algozine Posted July 3, 2009 Author Share Posted July 3, 2009 Picked up a splayed 4 bolt from Paul today. Also, going with a new ATI balancer for good measure. Anyone have a Canton road race pan and pickup for a 302 they want to get rid of? Also, anyone want a DSS level 10 block, bored 30 over ? Still boxed up, never been opened. Quote Link to comment Share on other sites More sharing options...
ST#97 Posted July 6, 2009 Share Posted July 6, 2009 There is always the 6 bolt aluminum mod motor! j/k... Dave, also check the manufacturer's spec for rpm range on the dampeners. My old engine builder told me once that MOST aftermarket dampeners are "street" spec and are only good for up to 3k rpm on "street" motors. The higher torsional loads we put on the motors at sustained high rpms, loaded/unloaded with down shifts AND lighter clutch/flywheel assemblies requires a better harmonic dampener. I think he quoted me a $450 dampener as opposed to a $99 one. I bought the $99 one and it lasted one season before it spilled it's guts and trashed some timing components on the front of my motor. I have a middle of the road one now and it has lasted 3 seasons. Harmonics of the rotating assembly is a funky thing...especially on stroker motors like the 331/347... good luck! Quote Link to comment Share on other sites More sharing options...
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