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  #16 (permalink)  
Old 07-29-2010, 10:11 AM
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Well I like the 1st idea of getting rid of the domed pistons, but that is not an option right now! I bought this motor as a quick replacement of my worn 327 for my 66 impala & I just need to get buy till winter when I plan to rebuild my 327 then I can mess with changing these pistons out.

As for when it was running if I drove a bit then played around with the distributor I almost got rid of the noise, but it still comes under a load. Actually the only time I had the noise was under a load... It just gets worse or less depending on where I set the timing? It ran fine & even reving it up in neutral wouldn't have the noise...

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  #17 (permalink)  
Old 07-29-2010, 10:29 AM
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It sounds like with a bit more attention to the timing, you can likely get rid of the knock. If you have a vacuum advance dist, I'd disconnect the vacuum and play with the initial and max timing first. Just one less thing to complicate your test results.

If you can get rid of the knock that way, then re-connect the vacuum advance and try again. If the knock comes back, hopefully the vacuum canister is adjustable, or you'll have to give up on some of the mechnical advance.
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  #18 (permalink)  
Old 07-29-2010, 11:08 AM
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Quote:
Originally Posted by yttaf
Well I like the 1st idea of getting rid of the domed pistons, but that is not an option right now! I bought this motor as a quick replacement of my worn 327 for my 66 impala & I just need to get buy till winter when I plan to rebuild my 327 then I can mess with changing these pistons out.

As for when it was running if I drove a bit then played around with the distributor I almost got rid of the noise, but it still comes under a load. Actually the only time I had the noise was under a load... It just gets worse or less depending on where I set the timing? It ran fine & even reving it up in neutral wouldn't have the noise...
OK, reving it in neutral won't cause detonation, even if the timing is way advanced, so don't try to use that as a guide of any sort.

You need to do a couple things. One is to determine what the air/fuel ratio is averaging. This can be done by checking the plug for the color along w/what heat range they are.

You also need to check what the vacuum at idle is.
Then, you want to see where the initial timing is set, w/the vacuum advance disconnected and the line from the engine plugged off. You will also want to know where the total timing is at and at what RPM it is all in by.

Knowing all of these things will allow the timing to be optimized for the best performance w/o detonation, using the existing parts.

This all involves some work, but will get you the most bang for the buck and will assure the engine doesn't damage itself.

A couple things you can also do, is to DETERMINE TDC then MAKE A TIMING TAPE. The temporary timing tape allows you to see where the total timing is, w/o having to rely on a dial back timing light. Use the tutorial on finding TDC if there's ANY question as to the accuracy of your existing timing marks.

As for the heads, if the 2.02 set has a larger chamber than the 305 heads (which can be as small as 53, according to F-Bird'88) they'd be a much better choice. If they don't have accessory holes and you are using a long water pump set-up, this can be a snag, though.
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Old 07-29-2010, 08:54 PM
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A few more Distributor Install & Timing Tip links/sites.
Distrbutor
http://www.corvette-restoration.com/...stallation.pdf
http://www.chevytech.com/3c1o1.html
Timing
http://www.corvette-restoration.com/.../Timing101.pdf
http://www.corvette-restoration.com/...ine_Timing.pdf
http://www.chevytech.com/2c44o3.html
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Old 07-30-2010, 02:50 AM
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Out of the4 box camel back heads can vary in chamber size. Theya re not all 64cc. Some are as big as 68cc. The bigger the better in your situation.
CC your camel backs and see.
Otherwise hunt for some large chamber heads for true pump gas compatability. The better 441, 487 920 76cc smoggers are not too bad.
(especially with some porting)

Other than that the best you will do with this situation is to create a
compromised ignition timing curve to make the best of a not ideal situation
on pump gas.

The best you can do with a engine with excessive high compression ratio :

You need to recurve the distributor. You need to limit the mechanical advance travel to allow a healthy initial at idle (for throttle response) yet modest, reduced less than stock. less than ideal limited timing at full throttle and rpm.

On this motor:

You want to limit the WOT timing to around 28deg BTDC.
The bigger the cam the more initial timing it will want at idle.
Thus the short limited mech timing curve.

If you just retard the timing to avoid knock, the throttle response sucks.

You could determine the cam in this motor by measureing the cam lobe/lifter lift using a dial indicator on the lifter edge.
That spec combined withe idle vacuum @750rpm will tell you the cam size pretty close.

.260" lobe lift or less= stock or very near stock mild cam
.300 to .305 moderate "torque RV cam"
.320" and higher hot rod cam 230@.050 and bigger.
.333" or higher race hyd or solid. .500+ lift

The manifold vacuum at idle (750rpm) is a good indicator of the camshaft size. test with say 14deg timing at idle and see.
Big cam= less then stock manifold vacuum and needs big idle timing.

Then: vacuum advance will have to be custom modifed also.
The excessive cr will want a very limited conservative vacuum advance curve to avoid pinging. The biggest issue will be rolling into the throttle
from part throttle at hiway speeds to full throttle.
A stock vac adv will need to be limited in travel and adjusted for rate.
A typical common vac can from stock smog era GM distributor from a car with EGR will be way way too aggressive for this high compression motor.

Limit vacuum advance to a max of 8-10deg max.

If the cam in the motor has a rough broken idle I suggest 18 to 24deg at idle.
a short-limited mech advance curve limited to about 28-30deg at max advance occuring around 3500rpm.

A milder, more moderate cam will allow less idle timing say 10-12deg at idle but will still want the limited max advance. 28-30deg. This is not ideal but about the best you will get from this motor on pump gas.
If you want to see what this motor really like , run it on 100++ octane gas and 36deg timing.

Camming the hell out of will not fix it.

Water/methanol injection (even home built, when done right) works and helps a ton. Google search it.
A functional egr system will help too.

New quality cast flat top or dished pistons are not expensive.

The stock application bread and butter spark plugs for the 305 heads are way to hot for a high compression ratio engine. Use a cooler champion RV8c or equal. AC R42T..... R44TS and R46TS is way too hot.

Last edited by F-BIRD'88; 07-30-2010 at 02:58 AM.
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  #21 (permalink)  
Old 08-03-2010, 07:19 PM
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Well I found some 882 casting heads with hardened seats & had them cleaned up & umbrella seals installed on them. Got most of it back together today... would have had it done today, but found the majority of coolant passages in the block where the head mounts were plugged up with crud! So I had to clean them out real good... Now just need to finish her up tomorrow! I'll post back up here how she runs when I'm done! I'll even add a couple pics of the car too.

And thanks to all for the awesome advice!
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