Another cam question???

[carls72dart]

Hey Fabo, in need of some help once again. I purchased a 340 engine with .30 over trw forged pistons. It has a crane cam with .484 intake/.484 exhaust. It's a hydraulic cam.

My question is: I picked up a lightly used howard's cam with .531 intake/.547 exhaust. How do I go about making sure i don't have a valve/piston clearance problem? This is new to me and am trying to make sure I don't ruin my engine. Any and all help is always greatly appreciated!! Thank you in advance.

 

[70aarcuda]

going to need to know what valve springs you got...plus spring retainer to top of guide clearance also.

 

[krazykuda]

First, the duration numbers are a better way to compare than just lift. It's better to get lift and duration to compare cams. Duration determines the power band.

Second, if you use the Howards cam, you need to check piston to valve clearance when to make sure that the valve won't hit a piston or your engine will be junk. Especially when you get over .500" lift, you need to check piston to valve clearance.

 

[67Dart273]

Uh, I think he's asking HOW you check that. There are two ways. One involves clay in the combustion chamber.

But you can do so without removing the heads. You'll have to come up with a method (spring compressor) to remove the no1 springs. Replace them with "checking springs" which are simply very lightweight springs.......you can punch down with your fingers. I think the Summit cam degree kit comes with these

Then you "rig" the thing so you can check at zero lash........that is with hydraulics, compensate for a fully extended lifter......and check valve clearance with a dial indicator on a valve retainer while wrenching the engine over.

I bet.........there are youtube videos to explain this

Modeling clay method:

[ame="https://www.youtube.com/watch?v=Y66lvdHbm60"]Piston to Valve Clearance - Summit Racing Quick Flicks - YouTube[/ame]

HotRod, "heads on" method

http://www.hotrod.com/how-to/engine/hrdp-1303-checking-piston-to-valve-clearance/

https://www.fordmuscle.com/fundamentals/pistontovalve/


Covers both clay and dial indicator method. Indicator method starts at 4:05

[ame="https://www.youtube.com/watch?v=ifoGVT4G0m0"]StreetLegalTV.com - Dart University: Piston-to-Valve Clearance - YouTube[/ame]

 

[carls72dart]

Tony, thanks for the reply. Here are the springs that came with the cam:
Howard's 98441 dual spring
Outside diameter 1.437 in
coil bind height 1.050 in
Spring rate .375 lbs/in
Inside diameter of inner spring 0.800 in

Tony, I'm not sure what's in the car now. I can take a look tomorrow. I'm sure it's only a single spring with under .500 lift/exhaust.

Do I need to use a micrometer to measure the retainer top to guide clearance? Is that the point where the valve enters the top of the head? This is all new, sorry if not responding with the right answers or asking the right questions. Would the info your requesting be with the new cam springs or the ones in the car now? Thank you

 

[carls72dart]

The cam in the car now (crane cam) 222 int/222 exh. Howard's cam 230 int/236 exh at 050 inch lift. Hope this helps. 67dart273 that's exactly what I'm asking. Have never done this type of engine work, but very willing and excited to learn how. I'll watch the video, thank you!

Krazycuda, thank you for the reply. Hope these numbers help.

 

[67Dart273]

Just use your head and think this out. you have at least 3 important dimensions, just for the valve.

1...valve to piston clearance. I forgot to mention the minimum does NOT happen with the piston at TDC. At some point with the piston "down" the valve is open "enough further" that this is actually LESS. Important to check I don't know, 20* or so before and after TDC, so, as the piston is coming up, up and over, and going down.

2...Retainer to guide or SEAL distance, obviously at max valve lift

3...Spring coil bind. If this uses spring shims, don't forget them, and don't forget to recheck if you change springs or retainers.

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Then there's the possibility that "other stuff" in the valve gear is AFU. There can be all sorts of things, poor rocker geometry, and related is rocker "sweep" of the valve stems. Pushrod bind in the PR holes. Interference between rockers and "some" valve covers.

Welcome to the world of "big," LOL