Crate Motor Camshaft..

Hemiparts · 02-01-2010, 07:43 PM

I have studied several Mopar crate motor cars and have several questions, after reading the IHRA spec sheet the biggest crate motor cam i see listed is .520 lift and these cars make a lot more thump than than any normal .532 lift cams cars is there any variance as far as lift allowances ?? It looks like they allow 1.6 or 1.7 rockers is that where they make up the excess lift ??? It also says " carb w/ choke plate" do they need to be operational or just in place ???

Woodro Josey · 02-01-2010, 07:50 PM

Choke Plate just has to be in place,,,,,,,not sure i understand what your asking about the Thump, but the duration is what makes the sound and the power, not the lift, however you want as mutch lift as you are allowed, within a few thousandths of allowable specs according to the sanctioning body!

Myron Piatek · 02-01-2010, 10:13 PM

Some of the combos, like the Magnum 360's, came with higher ratio rockers. The listed cam lift specs are the max you're allowed with those rocker ratios.

Hemiparts · 02-01-2010, 10:39 PM

so if it says.532 for the 360 it has to be .532 no mater if you use a 1.6 or a 1.7 rocker ??

ps.. also for any guys using stock magnum heads i saw a bulletin this afternoon before i left work about 5or 6 magnum cylinder head numbers that chrysler is wanting us to send back for Quality control reasons i'll check the pn's tommorrow and post what they are.

Myron Piatek · 02-01-2010, 11:10 PM

Yes. Some get cams with a little more lift to compensate for bad valvetrain geometry or less-than-advertised rocker ratios. It takes a little time, money and proper tools to figure out what you need to order to get as close as possible to the legal limit without going over.
Little things like valve length, pushrod length, measurement set-up, etc. can make little differences, but enough to put you over or keep you under. Double & triple check eveything and not just one cylinder.

Magnum heads are prone to cracking. But I'm not familiar with them because I run the older Commando version with the original style shaft mounted rockers.

02-01-2010, 07:43 PM	#1
Hemiparts Member Join Date: Mar 2008 Location: Raleigh, N.C Posts: 212 Likes: 0 Liked 0 Times in 0 Posts	Crate Motor Camshaft.. I have studied several Mopar crate motor cars and have several questions, after reading the IHRA spec sheet the biggest crate motor cam i see listed is .520 lift and these cars make a lot more thump than than any normal .532 lift cams cars is there any variance as far as lift allowances ?? It looks like they allow 1.6 or 1.7 rockers is that where they make up the excess lift ??? It also says " carb w/ choke plate" do they need to be operational or just in place ???

02-01-2010, 07:50 PM	#2
Woodro Josey Senior Member Join Date: Jul 2007 Posts: 805 Likes: 0 Liked 3 Times in 1 Post	Re: Crate Motor Camshaft.. Choke Plate just has to be in place,,,,,,,not sure i understand what your asking about the Thump, but the duration is what makes the sound and the power, not the lift, however you want as mutch lift as you are allowed, within a few thousandths of allowable specs according to the sanctioning body! __________________ Woodro Josey 2002 STK

02-01-2010, 10:13 PM	#3
Myron Piatek VIP Member Join Date: Nov 2001 Location: Florida Posts: 1,542 Likes: 34 Liked 138 Times in 51 Posts	Re: Crate Motor Camshaft.. Some of the combos, like the Magnum 360's, came with higher ratio rockers. The listed cam lift specs are the max you're allowed with those rocker ratios.

02-01-2010, 10:39 PM	#4
Hemiparts Member Join Date: Mar 2008 Location: Raleigh, N.C Posts: 212 Likes: 0 Liked 0 Times in 0 Posts	Re: Crate Motor Camshaft.. so if it says.532 for the 360 it has to be .532 no mater if you use a 1.6 or a 1.7 rocker ?? ps.. also for any guys using stock magnum heads i saw a bulletin this afternoon before i left work about 5or 6 magnum cylinder head numbers that chrysler is wanting us to send back for Quality control reasons i'll check the pn's tommorrow and post what they are.

02-01-2010, 11:10 PM	#5
Myron Piatek VIP Member Join Date: Nov 2001 Location: Florida Posts: 1,542 Likes: 34 Liked 138 Times in 51 Posts	Re: Crate Motor Camshaft.. Yes. Some get cams with a little more lift to compensate for bad valvetrain geometry or less-than-advertised rocker ratios. It takes a little time, money and proper tools to figure out what you need to order to get as close as possible to the legal limit without going over. Little things like valve length, pushrod length, measurement set-up, etc. can make little differences, but enough to put you over or keep you under. Double & triple check eveything and not just one cylinder. Magnum heads are prone to cracking. But I'm not familiar with them because I run the older Commando version with the original style shaft mounted rockers.