I am helping a friend fix his 347 Stroker that broke a couple of weeks ago. Luckily it stopped in his driveway. This is a show car that only has maybe a few thousand miles on it over the last six years. So, I thought I would post the damage and what was most likily the cause to possibly save others from this fate. The parts were all supplied by the machine shop that did the work and measured everything for the owner who wanted an engine with around 400 HP.
The heads were Edelbrock Vistor Jrs. #77189. The cam and lifters were from CompCams. The lifters were OE design with the spider and wishbones. Lift on the cam was around .565 as I remember. The machine shop charged the owner for checking the spring pressures but I suspect they really didn't. These heads are rated supposedly for 8,000 RPMs. Spring specs were 145 lbs. @ 1.900 closed and 380 lbs. @ 1.300 open. I took one of the springs to three different machine shops and got three different readings but the shop that did the work measured the springs at 145 and 380 lbs. this time.
Edelbrock has an installation note:
“Check cam manufacturer's specs for compatibility with valve springs. Recommended valve sizes listed.” There is no way Edelbrock knows what cam and lifters you are going to use, assuming the springs, lifters and cam are compatable can be a big mistake. In this case the #831 lifters cannot handle that high of spring pressure.
Comp's recommended spring for the cam was 120 lbs. @ 1.800 and 290 lbs. @ 1.259. The other issue was the lifters. In this case the stock style comp lifter might handle up to about 340 lbs., but at 380 lbs. in those heads, if you had a cam with .600 lift, you need a better tie bar lifter.
In summary, there are lifters and then there are lifters. They need the right spring for the right cam. I went with the Morel OE style from Howards Cams #91213, which is far better quality. However, be aware that with some after-market heads you have to remove the head to get them in. The lifters are about 1/8” taller than stock. This is not mentioned in the Howards calalog or on Summit's site. So, you may be in for another 100 bucks for gaskets. I called CompCams and was told they have redesigned the #821 lifter. The cost of fixing this engine in parts alone was about $900. The owner was really lucky the block was not ruined.
Someone else's engine:
[ame="https://www.youtube.com/watch?v=dcvWtQtsm-Q"]https://www.youtube.com/watch?v=dcvWtQtsm-Q[/ame]