Valve train parts selection

rhende454 · 01-16-2010, 12:19:26 PM

Looking for some advice on building a set of 186 casting heads. I bought the 186s bare and plan on using a Comp 12-210 cam with 218/218, 454/454 duration and lift. These heads are 1.94/1.50 with 64cc chambers. I also have two sets 487 heads, 1.94/1.50 with 75cc chambers, which are complete but need rebuilt. I definitely plan on buying new valve springs and lifters for the 186s, but my question for the group is, should I buy all new components for the 186s, or can I reuse any of the pieces off the 487s, like retainers, rockers, valves, locks?

Next question: I am planning on using Comp Cams 981 springs, which is their recommendation for the 12-210 cam. These have 370lb open spring pressure. However, Comp doesn't sell a kit with all of the needed components, i.e., springs, retainers, rockers, lifters, valves all offered separately. Summit sells a kit for significantly less $$, with springs which have 350lb open pressure. Their Summit brand valves are also a good value and would match up with the other components. Has anyone had experience with using Summit brand valve train parts, and would there be any issues mating the Comp Cam with Summit brand cam accessories?

These heads are going on a 350, will be using a 300-36 intake, Holley 3310, and am shooting for 350hp with 99% of the use being under 5500 rpm. I want the motor to handle a beating, but won't spend much time at the track.

Thanks!

chevyseve71 · 01-16-2010, 03:31:59 PM

1 out of 20 with the summit brand has a problem but summit sells name brand products with their name on it so dont worry about them. you can mate them with comp cams perfectly because alot of summit is comp cams. worry more about the installation. your gonna have a good 300 HP @ the wheels with that combo.

spicewood1 · 01-16-2010, 03:47:08 PM

With that small a cam and under 5500 you aren't going to break many parts of the valvetrain. Fine to reuse all the stock retainers and locks in my opinion. In fact those springs sound a bit stout with that open pressure. Are you sure the quoted open pressure is at YOUR open spec? For example they usually give the specs at say 125# @ 1.700, 350# @ 1.200, but you aren't going all the way to 1.200, only 1.246. And for starters you may set your heads up on a 1.750, further changing the spring loads. As far as the valves, their reuse depends on what they are, stainless or carbon steel, 21N alloy, condition of the stems and tips, etc.. Sounds like a good high vacuum mild mannered motor. It may idle at over 25"hg.

Damon · 01-16-2010, 04:00:01 PM

Agreed with spicewood- feel free to swipe the retainers and locks off the other heads. I've used that exact cam with stock locks and retainers + Comp 981s before. Many thousads of miles on it before I sold it. Never a valvetrain issue.

Not sure if 186 heads ever came with exhaust valve rotator/retainers, but if they did, check your installed height closely on the exhaust side (whether you use rotator/retainers again or not).

rhende454 · 01-16-2010, 04:43:38 PM

Quote:

Originally Posted by spicewood1

With that small a cam and under 5500 you aren't going to break many parts of the valvetrain. Fine to reuse all the stock retainers and locks in my opinion. In fact those springs sound a bit stout with that open pressure. Are you sure the quoted open pressure is at YOUR open spec? For example they usually give the specs at say 125# @ 1.700, 350# @ 1.200, but you aren't going all the way to 1.200, only 1.246. And for starters you may set your heads up on a 1.750, further changing the spring loads. As far as the valves, their reuse depends on what they are, stainless or carbon steel, 21N alloy, condition of the stems and tips, etc.. Sounds like a good high vacuum mild mannered motor. It may idle at over 25"hg.

rhende454 · 01-16-2010, 04:53:07 PM

Thanks for the advice. I'm way past my level of schooling on the spring load specs. Just quoting off of the spec sheets I saw on the Summit web page for their kit versus the comp cams 981 springs, which is what Comp recommends for that cam. The cam is a bit small, but it was free, and I'm going to need the $$ to hire a good head builder. The valves are stock GM pieces circa 1971, so whatever they were using in their 250 hp truck motors is what I've got - 16 of each to choose from so maybe I can find a good set out of that. What about the rockers? Summit sells their stamped steel rockers for around $40, which seems like pretty cheap insurance if the old GM ones are prone to failure.

Damon · 01-16-2010, 05:09:50 PM

They aren't prone to failure. You can run then a billion miles with a mild cam.

Just check the pallet area where it touches the valve, thr fulcrum area where the rocker ball rocks back and forth against them and the pushrod cups. If they're smooth and shiny with no pitting, crack or obvious wear then you're probably good to go for many more tens of thousands of miles.