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We had a little accident last night at the track while testing our Outlaw figure 8 car and lost a motor. We are thinking a cracked piston from over-revving it due to someone forgetting to shift to high gear. Anyways, we have our biggest race of the season on Saturday and need to get the new engine together. The original engine is an aluminum block 5.7 with flat top pistons, 241 heads, an ISKY cam(don't know specs but it picked up about 50hp on an LS6 cam), Edelbrock Victor intake, and a 650 carb. before last race it put down 410hp at the wheels. We have another aluminum 5.7 that we are putting together but aren't sure which heads are better. We have 241 and 706 heads. Which are better? Cam is also going to be slightly smaller but it is sitting at CBM so we don't have specs on it either. Car has the limiter set at 7k but we don't plan on it spinning more than 6600 under load.
Garrett
Last edited by SSpeeDEMONSS; 11-06-2014 at 09:43 PM.
I would get some better springs and get the valvetrain under control 6600-7000 rpm's is not really high rpm's.
IMO at 7000 you should be more worried about rods, than the losing control of the valves. So get the valvetrain sorted out so your not replacing the heads again.
It didn't ruin the heads as far as I know. The engine is up at the race shop in Hesperia and we are down in cerritos. We are headed up the hill with a new short block, fresh heads, and a new cam. The other engine had LS6 springs, same that this engine will get. Here is a pic of the new cam that we just got from CBM, pricey little thing.
Got the engine apart friday night and it did trash a head and the block too. We're thinking the high RPM(7000rpm sustained on the limiter) as well as high oil pressure(130-140psi) caused the piston to valve contact. No other piston had a mark on it from the valves. Put the new cam in a new 5.7 and a new head with the same LS6 springs and put it in the car. had it going Friday night and we raced it all day. Still in the 400-405rwhp range. I guess this off season it is going to get a better bottom end and some head and valvetrain work. Here's some pics.
Put the new cam in a new 5.7 and a new head with the same LS6 springs and put it in the car
Two things that need to be remedied for your next engine:
1.)That cam above is designed with Comp's XER cam lobes. Those things are really hard off of the seat and are known to be hard on springs and have acceleration rates that are not smooth.
2.) LS6 springs are not a good choice for sustained high RPM.
Combine those springs with that cam and it is a recipe for disaster. Not to mention that you likely were losing power at high RPM if due to valve float.
If your rules allow, get yourself some good double springs like the Tooley Racing springs. They are meant for what you are doing. If your rules don't allow double springs, get some good PAC beehive springs. They are far superior to the LS6 springs.
When you buy a cam for your new build, I would suggest you call Cam Motion and tell them what you are doing with the car. They have lobes that are very very good at sustained high RPM. They also sell Brian Tooley Racing valve springs.
I did not know this. I don't pick any of the parts for the car, I just work on it. I will pass this info to the owner. We already talked about building a more stout engine for next season anyways so springs will definitely be on the list. Thank you.
Where can I get the PAC beehive springs? The engine is coming out of the race car next week and going into the sand car and going to Glamis for a week. I told him he can't take it without putting some new springs into it.
We carry PAC beehive springs as well as Brian Tooley Platinum dual springs. The duals are better suited for what you are doing, although the PAC beehives are an upgrade over the LS6 springs for sure. Give us a call to discuss the details: 866-461-9536
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11-06-2014, 09:34 PM
which heads to use? rather urgent, 241 or 706? 
