VictoryLane Posted July 23, 2004 Report Share Posted July 23, 2004 I know my theory to this question , but I am wondering what others think ....... Why do we see twice as many late model motors blow up than street stock motors??? The bottom end in both motors can be the same. Same Carb... The main Difference is the heads (also cc's) & intake. It is not a huge difference.... You have twice the number of street stocks running than you do late models ( at most tracks). Victory Lane Link to comment Share on other sites More sharing options...
Modracer Posted July 23, 2004 Report Share Posted July 23, 2004 Im sorry to say but the bottom end is not the same in both cars. Most late models will run a light weight assembly. The parts that the Street stocks typically will run a more of a "stock" combination. Maybe some of the engine builders will get on here and explain it in more detail. Link to comment Share on other sites More sharing options...
Chuckman77 Posted July 23, 2004 Report Share Posted July 23, 2004 Modracer the rules for the bottom end on a LM are the same as a SS Link to comment Share on other sites More sharing options...
VictoryLane Posted July 23, 2004 Author Report Share Posted July 23, 2004 The rules for THR SS & the LM as well as TSRS the lower end is basicly the same. Link to comment Share on other sites More sharing options...
txtom Posted July 23, 2004 Report Share Posted July 23, 2004 Without getting too technical, I think the better suspension of a late model coupled with more tire creates more load or strain on the LM engine. Link to comment Share on other sites More sharing options...
hobby74 Posted July 23, 2004 Report Share Posted July 23, 2004 Dang that must be my problem then this year. I need to take out the light weight latemodel motor since my HS is so dang heavy it is just twisting things apart. Link to comment Share on other sites More sharing options...
tqj3 Posted July 23, 2004 Report Share Posted July 23, 2004 Well, dang, Hobby74. You ain't helpin' the thing stay together by trying to knock down the front straight wall. (There ain't but one wall on the whole track, and he manages to find it. Son-of-a-gun!) Think about how much stress that puts on the old chassis. No, not your personal chassis, the one under the car. But come to think of it... Keep truckin', Bubba. Some of us like both your rants and your whacked sense of humor, which, oddly enough, are usually in the same package. Link to comment Share on other sites More sharing options...
hobby74 Posted July 23, 2004 Report Share Posted July 23, 2004 Tq well they have done one hell of a job redoing the track and I was just trying to do my part in making the track bigger on the front straight since the back was done this year. Well I was trying to scare the crap out of randy to see how close I can hit the wall underneith him...lol Link to comment Share on other sites More sharing options...
Modracer Posted July 23, 2004 Report Share Posted July 23, 2004 To answer your question yes the rules are written somewhat the same, however, the rules are not written the same. In the street stock it says that the rod must be stock length for the engine being run. In the late model is says that you can run the 6in rod. Also it says in the street stock rules that the rods can be shot peened and polished , ie: a stock type of rod. I doubt very seriously that the the late models are running stock rods. Its been my experience that the late model cars are running more of a light weight assembly than that of the Street Stocks. Street Stock PISTONS The pistons must be dished or flat top. The flat top may have 2 or 4 valve relief. No part of the piston may extend above the top of the block. RODS Steel rods are required. The rods must be stock length for the engine being used. Polishing and shot penning of the rods is allowed. Six inch rods are not allowed. Steel wrist pins are required. Late Model PISTONS Flat top or dished pistons are required. Valve relief are allowed in the piston top. No part of the piston may stick up above the block at any time. Steel wrist pins are required. RODS All rods must be steel. The maximum rod length is 6-inches. Link to comment Share on other sites More sharing options...
VictoryLane Posted July 23, 2004 Author Report Share Posted July 23, 2004 ModRacer, So do you think that running a 6" rod with Reduced clearances is whats making all the motors in LM blow, or is it the Lighter weight parts that are being used? Victory Lane Link to comment Share on other sites More sharing options...
rsowell Posted July 23, 2004 Report Share Posted July 23, 2004 Seems to me the 110# seat pressure limit on the THR SS is the pin on the hand grenade. When people get the handling in order they start turning the motors higher. It would be interesting to see of the last 10 blown motors, what started the chain reaction. Link to comment Share on other sites More sharing options...
VictoryLane Posted July 23, 2004 Author Report Share Posted July 23, 2004 yep, If I had a SS I would change the Valve springs every 3 weeks. Link to comment Share on other sites More sharing options...
Bandit Posted July 23, 2004 Report Share Posted July 23, 2004 Given the combination, there should be almost 0 failures (with proper maintenance). Probably put too many laps on it without pulling it down and checking it. Link to comment Share on other sites More sharing options...
Chuckman Posted July 23, 2004 Report Share Posted July 23, 2004 You got that right Banbit Link to comment Share on other sites More sharing options...
Crazyhorse Posted July 23, 2004 Report Share Posted July 23, 2004 yep, If I had a SS I would change the Valve springs every 3 weeks. whew-you wanna sponsor a s.s. daddy warbucks!!!!! what springs are you running that you would have to change every three weeks??? Link to comment Share on other sites More sharing options...
Poohba Posted July 24, 2004 Report Share Posted July 24, 2004 The last place to scrimp is the valve train and the next is rods. A good set of well cared for springs will last a season or 2 in SS and at least 1 season in LM. 550 lift/6800 rpm is possible at 110 seat pressure (done it) and most power in these engines is well below that anyway. Spring life can be extended by backing off the few tight rockers during the week too. It's a pain but so is building a new engine. Link to comment Share on other sites More sharing options...
jp17 Posted July 24, 2004 Report Share Posted July 24, 2004 The vast majority of LM engine failures I have seen have been valve train related. Keeping everything on the top end cool and well lubricated is a big part of making these things live. Use good parts, good lubricants, adhere to a meticulous PM schedule and go through everything regularly. For us that's at about 1000 laps. jp Link to comment Share on other sites More sharing options...
ups88john Posted July 25, 2004 Report Share Posted July 25, 2004 i have seen a lot of motors this year loose timing chains. seems to be a problem with the maker of the chain, and it seems to be the same chain, i could be wrong. on the ss valve spring deal, if you back the cam down a little the springs will live. i believe the ss motor we did had 10 or 11 nites on it and springs didnt hardly loose any seat or open pressure. maintnence is the key in any race motor, you cant expect to run the same motor all year without any problems. if you make the whole year without problems, you probally got lucky. big john Link to comment Share on other sites More sharing options...
colgate Posted July 25, 2004 Report Share Posted July 25, 2004 dont get me started on this issue!!!!!!!!!!!!!!!!! lm and ss have the same bottom end...... the only diff. is the rod. you can make a 5.7 rod motor run better than a 6in motor. we have done it. it is in the vale train. that is where the problem is. I think we have found something that will be a big improvment in that area to reduce friction. Link to comment Share on other sites More sharing options...
supertx Posted July 26, 2004 Report Share Posted July 26, 2004 Cologate You are wrong about the 6 inch rod motor if you have the right cam intake and ex. system. Valve spring failure should not be a factor on an engine in SS AND LMS that run in the 7000 rpm range if the proper valve spring, retainer,and keepers are installed right. We have engines with 745 lift turning the motors 8800 to 9000 rpm that we get 1500 laps on before we change valve springs . I think it was Bandit or JP said the key word you have to keep an eye on your engines every week.Also you have to run quality parts and lubs. friction {HEAT} is the killer of motors. Link to comment Share on other sites More sharing options...
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