Smooth Idle on 360?

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bwhitejr

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I don't have any experience with this so bear with me. I have just fired off my 360. I have set the timing and adjusted the carburetor. It has Edelbrock performer RPM heads and intake, a 625 AFB and a cam with 60 deg of overlap. I am idling it down 900 RPM. It isn't a smooth idle. It shakes ocassionally, like it suffers from poor fuel distribution problems at low RPM. It sounds good and strong when you get to 2k and smooths out. Is it normal for an engine like this shake at idle? Will the motor mounts handle this (stock rubber mounts)?

bwhitejr
 
Kinda a big cam to expect a smooth idle from. More tuning will help. Its going to want around 12 to 14* initial timing and 32* total. I would also replace the carb with either 750 double pumper or 3310 Vac Secondary.
 
definitely not a smooth idling cam, but a great one. i am getting the same one. my buddy ran it in his 340 and that thing pulled to 6k and kept going. go to schumacher creative services( www.engine-swaps.com) and get either the magnum mount or the new polyloc mounts. so there is no worry about breaking the mounts.
 
Could you be running a little lean? Richen your idle mixture some and see if it helps any. How about your plugs? Are they in good shape, clean and gapped right?
 
AdamR said:
Kinda a big cam to expect a smooth idle from. More tuning will help. Its going to want around 12 to 14* initial timing and 32* total. I would also replace the carb with either 750 double pumper or 3310 Vac Secondary.
Click to expand...

I needed 15 degrees BTDC with an XE268H in my 360 to get the best idle. I would expect that you would need that much or more with the XE274H especially if your compression is below 10:1. Also, unless you have magnum heads you generally need 35-36 degrees total.

The 625 carb is not hurting you. If your plans are primarily street driving the 625 is better choice than a 750 double pumper or a 3310. It may give up a little power above 4000 rpm to the 750 carbs but will have much better throttle response below 4000 rpm where you will actually drive the car. If you do plan to get a new carb a 670 Street Avenger would be a much better choice for anything that is not primarily a strip car.
 
I had the same cam in my 360 w/eddy heads. It ran the best w 18degrees on the bottom and 36 on top. I agree you might be a little lean at idle. Back the mixture screws out a little at a time... I run the Schmacher torque strap..
I'd swap out the plugs for NGK's and open the gap up to .045

Bob
 
BobsDart said:
I had the same cam in my 360 w/eddy heads. It ran the best w 18degrees on the bottom and 36 on top. I agree you might be a little lean at idle. Back the mixture screws out a little at a time... I run the Schmacher torque strap..
I'd swap out the plugs for NGK's and open the gap up to .045

Bob
Click to expand...

i agree with you on the timing and the plugs and the gap. i am about to run the same cam( i have the 284/484 now) and i run 17* initial, 35 total with an msd distributor.

tell us what the plugs read RIGHT AFTER a wot run, not after idling it back to the garage. you have to pull over right away and pull a plug.
 
I know I should have checked the clearance between the valves and the pistons to make sure, but I didn't. So do I have any reason to worry using The Eddy Performer RPM heads, stock rods, Speed-Pro H116CP30 hypereutectic pistons (5cc valve notches) and normal head milling (for trueing). The compression height is 1.67 in. I should have above 10:1 compression.

bwhitejr
 
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