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Can someone tell me the correct setting for my valves (1964 327-375 fuelly).
I would like to set them cold, therefore, the setting may be slightly different than on a hot engine. How much would the clearance change (thousandths) from one at normal operating temperature to a cold engine?
I've never measured a difference between hot and cold clearance on a SB. The steel pushrods and CI block/heads expand/contract about the same amount with temperature change.
Send me an email, and I will send you a paper on how to set cold clearance on all OE SB mechanical lifter cams. Your OE cam is what is referred to as the "30-30".
I was glad to read your response Duke. I have observed that their was no difference when setting hot and cold or warm. I always felt I was not using feeler gauges properly because I had always read that the adjustments should differ due to temperature. It sure makes it easier to do when it is not hot.
Some claim there is a difference. I have made numerous measurements and never found a signficant difference on cast iron block/head engines.
It also depends on what "hot" means. At idle the exhaust valve stem is relatively cool and there is little stem expansion. When you shut down a hot engine, the exhaust valve cools rapidly.
At sustained WOT the valve will heat up considerably and the head may run at 1000 degrees F or more. About 80 percent of heat transfer is through the seat, however, the exhaust stems will run hotter and expand more that the inlet stems under high load, but it's tough to measure measure valve clearance at WOT and high revs!
This is why exhaust lobe clearance ramps are typically taller than on the inlet side. This gives the valve more room to expand without running out of clearance that will hang the valve open.
The setting clearances I recommend are the MAXIMUM running clearances that the engine should see in order to take up all the lash by the end of the clearance ramps to not shock load the valve on opening and slam it into the seat on closing at higher than clearance ramp velocity. Tighter operating clearances are okay. That's why mechanical lifter cams are usually designed with generously tall clearance ramps.
Thanks Duke,
My email is: larryschuyler@hotmail.com
I should also mention that after warming up, if I listen down at the end of the 2 tailpipes, I hear a "shhssk-shhssk", sound ( thats the best that I can discribe the sound) from both pipes and I think slightly more, after the engine is warmed up to regular operating temperature. I dont hear that on my friend's 327- 365HP car. Could this be that the valves are not totally closing and leaking a bit? The car has a 4-speed/3.55 rear-end but seems to be 'lazy' on initially taking off from a stop (until you get up over 2500-3000 RPM) The engine was totally rebuilt about 500 miles ago.
Thanks for your thoughts.
I can't make anything out of your exhaust noise description. Since the FI engines have no exhaust crossover, they have a somewhat different sound than a carbureted engine where the heat riser connects the two sides. They are completely isolated on C2 FI engines.
The only way to determine if the engine's health is okay is to run a compression and/or leakdown test.
The poor low end torque is a characteric of the 30-30 can due to its high overlap and late closing inlet valve. It's also exacerbated by the "single plane" architecture of the FI manifold. The combination will result in substantial top end power, but not until the heads are reworked for better flow.
Click "send e-mail" if you want the valve adjustment paper.
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