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Camshaft Selection for your New Engine
Cliff Ruggles:
Bump
73ss:
Cliff, I am new to the world of roller cams and would like to ask if you have a favorite in mind for a BBC? This is a gen 6 block with a factory roller. I am putting together a 489, Scat stroker kit with Brodix race rite oval port aluminum heads. Block has been decked and pistons are 10 in the hole. Compression should be right at 10:1, depending on gasket. Edelbrock Q-jet RPM intake topped with of course, a q-jet.
I am very pleased with my old flat tappet 454 set-up. when I put this motor together 15 years ago I fell victim to the magazine hype and installed a Comp extreme energy. I experienced everything you have posted above. What a piece of junk!!!! I called comp for some help and they blamed??? You guessed it, The Q-jet. Based on your forum posts I removed it and installed a Summit 1302.https://www.summitracing.com/parts/sum-1302. This is a 114 LSA cam, the comp was a 110, very similar lift & duration specs between the 2. This is by far the best cam I have ever run in a mild street BBC. Perfect blend of vacuum, idle speed, Very quiet, and would not wash down the cylinders at an idle. This has been a great combo for me over the years but it has gotten boring, and I am starting to lose a lobe. I got 10 yrs out of it but I'm done with the flat tappets. I would like to find a roller that would behave the same way. Any recommendations? Thanks for any help.
Cliff Ruggles:
A hydraulic roller cam is chosen in the same manner as a flat tappet. They compare pretty close except many roller camshafts push the envelope a bit for opening/closing velocity and will require pretty strong springs to keep thing in check.
I use and prefer older lobe profiles with slower ramps and I run less spring on them. I've taken some criticism for this, but have had zero issues. When I've strayed over to faster ramps we've seen the engines take "nose dives" on the dyno at higher RPM's. At first I thought it was simply the heavier parts but have found out that it's the ramp profiles and inability of the springs to keep things from getting "stupid" at high RPM.
Going to a HR camshaft is not any sort of guarantee that you woln't have lifter/lobe issues. There are a LOT of lifters being sold that will not go the distance and we're seeing quite a few failures. There are several suppliers, Johnson, Morel, Isky, etc. The better HR's are quite a bit more expensive than others but superior in quality so avoid any of the cheaper retrofit HR's.
I'd also avoid running a lot of spring pressure and stick with "softer" lober profiles. The factory is able to get away with using HR set-ups and they will go hundreds of thousands of miles w/o issue and guess what, they don't get stupid with super-quick ramps and don't use a lot of pressure on them either.
Maybe there is something to be learned from this?
My current HR cam uses Comp Magnum roller lobes, advertised is 289/308, .050" is 236/245, LSA 112. I decided back in 2009 to run Crower HIPPO solid roller lifters on it because we were seeing so many problems with HR's. I set the lash at .005" and it's not only been pretty much maintenance free it's the quietest engine that has ever sat between the fenders of the Ventura.
I just checked the lash couple of days ago, haven't even looked at it in at least 3 years and they were right on the money. I'm not recommending using the "hybrid" set-up, but I would get good HR lifters if you plan on going that route. Hylift Johnson would be my first choice.
I'd also mention that there is nothing wrong with flat camshafts and no need to worry about loosing a lobe. With all the problems we've been seeing with this sort of thing I've been sending our cams off to be "coated". They come back looking like black chrome and will last just about forever. Ion Bond did the last one for us, excellent work and reasonably priced. We topped it with genuine Johnson lifters......Cliff
73ss:
Thank you for the info. I already bought GMPP factory style lifters for it. I figured I should be ok since this is what is used in the 454/502 crate engines. I will avoid radical lobe profiles and too stiff of a spring. Comp does not offer a "standard" cam for this engine. They have the extreme energy & big mutha thumpa line. Howards looks like they have a nice selection, I've contacted straub as well.
This engine was a few miles shy of the 200K mark and the roller lifters were starting to wear a groove in the lobes, but they were not going flat over the nose like a flat tappet set-up would do. From the looks of it, oil changes were few and far between, probably once it hit beater status. Still ran good and was quiet.
Thanks again for the insight.
Cliff Ruggles:
Comp also grinds just about everything on a "tight" LSA. This is done more for the "bling" factor than anything else. Wider LSA isn't going to produce a "choppy" idle, stinky exhaust and reversion at lower RPM's. The target audience typically prefers that deal compared to a smooth idling engine that is efficient at lower RPM's, clean exhaust and smooth/broad/flat power curve.
I'd add here that I get butt-loads of complaints from folks who went to XE lobes and even more from those who did the 107LSA Thump-ya-mutha stuff.....FWIW......Cliff
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