If you run BBC rocker arms on a chevy 292( I was planning on Comp Cams roller-TIPs) do you have to use 3/8 pushrods? or can you use stock 5/16?
thanks.
You can use stock diameter 5/16 pushrods. You will gain some power is you use a full rollerized rocker. Tom
Tom, is there a need for guide plates with a full roller rocker? I'm running a mild hydraulic cam, nothing big.
No need for guide plates with the full roller rockers.
They will become needed with high rpms and big spring pressures, then the 3/8 pushrods. Tom
I disagree as to the value of having the rocker pivot on needle bearings.
The rocker does not actually rotate in use, it only oscillates perhaps 20-25 degrees, and only about 1/3 of the rollers at the bottom of the trunnion carry the load. This is expensive overkill for most engines, they don't last as long as bushings, and a failure showers broken needles into the oil drain and in between the spring coils - meaning, don't buy any knock-offs for $115. on eBay). Somehow, eBay hasn't heard that "all products made outside the US must be identified as to country of origin", so none of them say "Made in China", and if you ask they won't answer you. "Gold Series" does not mean Crane Gold Series. Some are not self-aligning and need guide plates, they generally say so.
For a motor with stud rockers, full roller also means much more money than just roller tip since the entire fulcrum is now completely different (not a ball and cup) and has a miniature individual shaft or trunnion.
I've run Crower investment cast stainless full rollers that sure seem stout to me. Not running high spring pressures or racing, just street duty. They were 3-400 bucks though.
Agree some of the crap you find cheap on line is a total waste of money. I've had to learn this lesson more than once. I mean, how bad can they really be? Then I find out. I trust used OEM parts more.
The Crower stuff is excellent, lasts forever, but as you said $$.
It's certainly cheaper to have stuff made in China and they could turn out a quality product at a competitive price, but there's more money making junk that looks bling and sells in far higher volume.
Thanks for all the input. You all have good and valid points. I am building a solid street engine, no racing. I was looking at the 1.72 Magnum roller tip rockers from Comp as a street upgrade for about $150. From there, it looks like Harland Sharp makes a good made in USA 1.75 aluminum full roller for $250. Comp cams 1.7 BBC go for more, and they also have a 1.75 in a quantity of 12 but that kit is $450.
Heater,
I have used these.
http://cgi.ebay.com/ebaymotors/ws/eBayIS...RK%3AMEWAX%3AITRecently on the dyno 250. They are 1.7 ratio and require a 7/16 rocker stud. Valve cover clearance will be a issue as with most aftermarket rockers. They will fit under a mercruiser cover with the front and rear clearanced out abit.
Tom
Those are also investment cast, which is a great way to get a quality product without breaking the budget. The only penalty is a few extra grams of weight, harmless for anything you'd be doing. IMHO they're also much safer to buy used, since steel lasts almost forever and can be rebuilt by the manufacturer if the rollers get sloppy. Sometimes you find an incomplete set for very cheap because he trashed 1 or 2 - but you only need 12!
I know the dyno tests couldn't do everything, but based on work done to other Chevy engines the intake can use more ratio (the exhaust not so much), which is also a method of adjusting the intake/exhaust bias in the cam somewhat.
Does a 1.8:1 BBC rocker clear the pushrod relief holes in the 250 head?