1955chevy33 Posted June 13, 2010 Report Share Posted June 13, 2010 I was curious. I read rules at different tracks and I read circle track articles and they all usually say GM crate engines are legal to run. I was wondering if a brand new GM crate engine would handle running many 1/4 mile feature races in a car that turns between 5500 and 6500 RPM. Let me hear from some of you experienced racers. Link to comment Share on other sites More sharing options...
jwmbishop Posted June 13, 2010 Report Share Posted June 13, 2010 Any of the three CT crates will easily give you a season - or two if maintained right - between teardowns. If limited to 355 inch the CT355 (tech sheet)or the CT400 Tech Sheet are very dependable - the spec max of 5800rpm is forgiving of a few more and the hyper pistons are quite forgiving compared to forged or cast. The cam is dropping off sharply after 5500 anyway so staying down there is better for ya! Just run good racing fuel - don't go the av gas with your own stuff. If you do not have to keep it sealed the scat i-beam rods are a good upgrade to make it go 6000 - but why your already out of cam... In the "unlimited" classes the LS based CT525 Tech Sheet is quite the screamer - its good for even the occaisional 7000 rpms. It'll go more but thats where the power curve starts really dropping off anyway. I have not personaly dynoed any one of em - but the guy I used to work for has all three and he's just flat in love with em. He has three 400's and a 355 that he keeps going for clients and the worse thing he has found in annual teardown and inspect on these is valve guide wear is a little faster than some of the other options - as soon as he sees .0075 he changes to a harder bronze. take a while to get there, the first pair was after three seasons. But the guides he uses will go six or seven if not running too hot (no more than 210-215 - over that you pay more in wear). The bearings were flawless but he replaces them just because he's already there and he gets good prices (he's a distributor for many lines of parts). the 525 he runs is on its second season and has not yet been torn down. The oil analysis done at end of last season showed no issues so they decided to keep it running with out tear down. As a matter of fact the bottom end became the standard for most rotating kit sellers. Link to comment Share on other sites More sharing options...
Crazyhorse Posted June 13, 2010 Report Share Posted June 13, 2010 the 602? they recomend you do not exceed 5800. but i ran one for 19 races a majority of the time taking it to 6400.....never less than 6000. it didn't make the 20th race. but one hell of a motor,,,,it won the ARTS natl. championship, and lonestar region/ USRA. Link to comment Share on other sites More sharing options...
Truck99 Posted June 14, 2010 Report Share Posted June 14, 2010 We've been very pleased with our 602, even having to run it with the 4412 carb. They don't like or need to be twisted very tight, but within it's limits, it's a smooth running little motor. I would recommend keeping it between the bottom to mid point of the range you mentioned. It makes the most power in that range anyway. Link to comment Share on other sites More sharing options...
txtom Posted June 14, 2010 Report Share Posted June 14, 2010 A couple limiting factors in these motors are the valve springs and the connecting rods. The springs are fine to the rpm's they are allowed to turn. The bigger factor is the rods. They are manufactured using the "Powder Metal" technology. While they are more uniform or consistent in their manufacture, they will not take much more rpm than the high 6,000's. Chipping them at 6300 is very safe, wouldn't want to have to race them at 68-7000. Like Chase stated, find the power band and stick to it. An hour on a chassis dyno will tell you a lot about your particular engine. Link to comment Share on other sites More sharing options...
jwmbishop Posted June 14, 2010 Report Share Posted June 14, 2010 Can you even get the 602 from GM any more? the CT350 (602) was being phased out last I heard - the replacement being the CT355 (603). Link to comment Share on other sites More sharing options...
Truck99 Posted June 15, 2010 Report Share Posted June 15, 2010 Can you even get the 602 from GM any more? the CT350 (602) was being phased out last I heard - the replacement being the CT355 (603). We heard the same thing, but found them to be readily available from various dealers. Link to comment Share on other sites More sharing options...
jwmbishop Posted June 15, 2010 Report Share Posted June 15, 2010 Ahh - so they are there until inventory depletion. I am not even sure what the 5hp diff is - I believe they have the same cam effective profile. Link to comment Share on other sites More sharing options...
Truck99 Posted June 15, 2010 Report Share Posted June 15, 2010 Ahh - so they are there until inventory depletion. I am not even sure what the 5hp diff is - I believe they have the same cam effective profile. That could be the case, but I'm not sure. We ordered ours in Oct 09 and the tag showed it was produced in Aug 09. Link to comment Share on other sites More sharing options...
jwmbishop Posted June 16, 2010 Report Share Posted June 16, 2010 September is retool. Link to comment Share on other sites More sharing options...
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