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Aka Force Fed Mopar
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Discussion Starter #1
Anybody have any experience in tuning an engine w/ the swirl heads? I have a 4bbl on an '85 318 w/ the 302-casting "swirl-port" heads (the ones w/ the heart-shaped combustion chambers), and I'm working on curving the distributor for it. However, no one really seems to know what those heads like timing wise. I know on the 2.2/2.5 4-cyl engines, the swirl heads use a less aggressive timing curve than the old bath-tub heads, but even the bathtub heads had quench areas whereas open-chamber 318 heads do not.

So I know they need different timing curves, but what they are I don't know. Anybody have any specs on a swirl head distributor, as in what governor, springs etc they use?
 

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4 Wheel Power Disc Brakes
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I can say from what I have read and my experience with Edelbrock heads with 9.1 to compression ratio and a tight quench that you need will slightly more timing at idle (I'm at 20 degrees) to get the fire to lite in the quench zone and less total timing 32-34 degrees at 3000-3500rpm. I have another ~10 degrees of vacuum starting at about 15", all in by 5". (This is what an early 2bbl canister runs.)
 

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Aka Force Fed Mopar
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6,120 Posts
Discussion Starter #3 (Edited)
Right now I have it at 10*, if I increase the revs slowly it sounds good until the timing hit about 30*, then I hear a slight break-up. I was unsure which way to go on the base timing, up or down. I went to 12 but didn't seem to make a difference. I did have it at 20* base, but it would stutter pretty bad in the upper revs. It was hitting about 38-40* total. I may turn it down to 8* and see what it does. BTW it currently has a stock 70-something dizzy in it, not sure what governor or springs, and the vac adv isn't working.

I have 5 dizzy's tore apart for parts, so I can build one to suit once I figure out it's needs. I have a couple 11R governors, I was thinking to use one of those w/ the lighter springs that were on the 15R units to get the timing in quick w/o getting too much total. I think that would make 22* mechanical advance, correct?

Also, I have a 7R, 8.5R and 11.0R vac adv cans. I was thinking to try out the 8.5 can.

Other relevant info is I'm running the 318/340/360 4bbl hyd cam and an old factory "tarantula" low-rise single-plane 4-bbl intake, probably off an old 273 or something. Cam specs are .429/.444 lift, 268/276 duration (adv), 114 lsa. Carb needs some tuning, but has settled into a decent tune, 750-800 rpm idle.
 

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4 Wheel Power Disc Brakes
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Since it breaks up at about 30* that's probably the total of initial+mechical you should shoot for. ( I used an article on how to build a long rod Ford 351 as a starting point.)
I had to decrease the mechanical advance from 26* to about 20*. I did this by heating and anealing the outer edge of the distributor shaft were the weights slot in. Then used a center punch at the outter edge to reduce the length of the slots. (An electric welder could be used to do this with a spot of material added.) As for springs I used the light spring (with 2 coils cut off to stiffen it). The 2nd spring is a modified light one with a loop on it that slows the last 3rd of the advance similiar to the factory heavy spring.
 
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