Valve spring pressure

Ian Hill · 05-18-2010, 06:39 AM

I run a 350 crate engine in IHRA with a hydraulic flat tappet cam shaft and lifter set. i ran regular style valve springs last year and ran the engine past the finish line to check top end rpm limits. the engine pulled no problem to 7400 rpm. Normally i was crossing at 7100. All this while running a 4.88 rear gear set and true hydraulic lifters. Now i have gone to the solid style hydraulic lifter (call it what you will), bee hive valve springs and lighter weight retainers. I put a set of 5.13's in the rear and can only pull 7200. i am running out of steam about 80-100 feet from the finish line. i have the valve springs setup for 125 lbs at the seat and 320 over the nose. i also was down 6 pounds of tire pressure from where i normally race as i thought the track was marginal.

i know that pumping up the tires will make them grow in diameter, but it will also reduce rolling resistance to the tune of almost 2 mph and .005-.007 as tested last year. i still have 30 pounds to put into the car which also will reduce top end rpm. i am at a loss for what to do to help the rpm situation without going back to the 4.88's other than shimming the valve springs for more pressure. What is normal, what is too much valve spring pressure on a hydraulic cam shaft?

thanks
Ian

randy wilson · 05-18-2010, 06:55 AM

it doesn't make sense. only one of three things could cause this. first, put a .030 shim under each spring and see if the extra pressure picks up rpm, second, check timing, i know it sounds simple, but double check it, third, check cam intake centerline. your car should be turning tighter not less as you know. my bet is that you don't have the spring pressure you had earlier for what ever reason.

Mike Taylor 3601 · 05-18-2010, 08:11 AM

Did you check heads for installed spring height,to make sure your springs have that pressure and check springs to verify they are pressure they are supposed to be?
With cam & lifters broke in should be able to run around 140 seat and 375-390 open
without any problems. You don't have a hard surface lifter correct if you do you can crank
pressure on up.
You have some valve lash correct you need .003-.007 lash.
Mike Taylor 3601

Ian Hill · 05-18-2010, 02:41 PM

i do have .003" clearance checked hot. My timing hasn't moved, the float was happening on the first run and the next four. richening the fuel helped but slowed the car down. I am wondering if anyone has info on going from standard style springs to bee hives. can you expect to use the spring pressure set up or is it natural to have to increase spring pressure with bee hives.

Ian

randy wilson · 05-18-2010, 02:45 PM

there's your problem. go back to your old style springs.

M&M Motorsports · 05-18-2010, 03:31 PM

Changed from regular springs to beehive. I have 200 lbs seat pressure and that is good to at least 7500 rpm. Hope this helps!

05-18-2010, 06:39 AM	#1
Ian Hill Member Join Date: Sep 2008 Posts: 216 Likes: 0 Liked 6 Times in 3 Posts	Valve spring pressure I run a 350 crate engine in IHRA with a hydraulic flat tappet cam shaft and lifter set. i ran regular style valve springs last year and ran the engine past the finish line to check top end rpm limits. the engine pulled no problem to 7400 rpm. Normally i was crossing at 7100. All this while running a 4.88 rear gear set and true hydraulic lifters. Now i have gone to the solid style hydraulic lifter (call it what you will), bee hive valve springs and lighter weight retainers. I put a set of 5.13's in the rear and can only pull 7200. i am running out of steam about 80-100 feet from the finish line. i have the valve springs setup for 125 lbs at the seat and 320 over the nose. i also was down 6 pounds of tire pressure from where i normally race as i thought the track was marginal. i know that pumping up the tires will make them grow in diameter, but it will also reduce rolling resistance to the tune of almost 2 mph and .005-.007 as tested last year. i still have 30 pounds to put into the car which also will reduce top end rpm. i am at a loss for what to do to help the rpm situation without going back to the 4.88's other than shimming the valve springs for more pressure. What is normal, what is too much valve spring pressure on a hydraulic cam shaft? thanks Ian

05-18-2010, 06:55 AM	#2
randy wilson Senior Member Join Date: Jan 2007 Location: N/A Posts: 882 Likes: 0 Liked 22 Times in 22 Posts	Re: Valve spring pressure it doesn't make sense. only one of three things could cause this. first, put a .030 shim under each spring and see if the extra pressure picks up rpm, second, check timing, i know it sounds simple, but double check it, third, check cam intake centerline. your car should be turning tighter not less as you know. my bet is that you don't have the spring pressure you had earlier for what ever reason. __________________ don,t have one

05-18-2010, 08:11 AM	#3
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,374 Likes: 358 Liked 308 Times in 103 Posts	Re: Valve spring pressure Did you check heads for installed spring height,to make sure your springs have that pressure and check springs to verify they are pressure they are supposed to be? With cam & lifters broke in should be able to run around 140 seat and 375-390 open without any problems. You don't have a hard surface lifter correct if you do you can crank pressure on up. You have some valve lash correct you need .003-.007 lash. Mike Taylor 3601

05-18-2010, 02:41 PM	#4
Ian Hill Member Join Date: Sep 2008 Posts: 216 Likes: 0 Liked 6 Times in 3 Posts	Re: Valve spring pressure i do have .003" clearance checked hot. My timing hasn't moved, the float was happening on the first run and the next four. richening the fuel helped but slowed the car down. I am wondering if anyone has info on going from standard style springs to bee hives. can you expect to use the spring pressure set up or is it natural to have to increase spring pressure with bee hives. Ian

05-18-2010, 02:45 PM	#5
randy wilson Senior Member Join Date: Jan 2007 Location: N/A Posts: 882 Likes: 0 Liked 22 Times in 22 Posts	Re: Valve spring pressure there's your problem. go back to your old style springs. __________________ don,t have one

05-18-2010, 03:31 PM	#6
M&M Motorsports Member Join Date: Mar 2008 Location: Jerome, Michigan Posts: 119 Likes: 0 Liked 0 Times in 0 Posts	Re: Valve spring pressure Changed from regular springs to beehive. I have 200 lbs seat pressure and that is good to at least 7500 rpm. Hope this helps!