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Here's some measurements of a few common cams. The K cam is about 5° smaller than the D were it counts + but kinder to the valvetrain because of the slower velocity at the clearence ramp. (.003 for the C grind, .023 K & .017 D)
5° smaller effective duration knocks about 10HP from the top end of a B20E, but it's very good from idle & matches the D up to 5000, in a B20 (higher in a B18)
.017 of the D cam is similar to the Isky cams & they sell theres with dual springs to maintain control. The D cam was designed orininal for Volos 1st B18B Rally kit & that included a modified head & dual springs. If you are staying with a B18 head, I recommend spending as little money as possible on it because they flow bad compared to a B20F head. That makes K the the choice because it works with everything else stock & bit the old A, B & C cams EVERYWHERE. Those were developed in the 1950's, The D in the early 1960's & The K in the early 1970's. If you were building a B20 & had some money, I would bypass the D & go straight for a dual pattern from Phil Singher with whatever he recommends for springs & lifters. (High lift, short duration for the inlets, stock lift longer duration for the exhaust + a good exhaust:- B20E engine pipe into a 2.25" exhaust system)
I find conflicting information saying that "D" is recommended for fuel injected engines.
D is for D-Jet cars 1970-1973, K came out for K-Jet cars.
That was also IPD's recommendation too.
IPD sucks, avoid them. They sell stupid stuff like "heavy duty" oil pump springs when the stock spring is plenty & the stupid pump shaft strengthing collar.
All I want out of the rebuild is an engine that still offers decent power and excellent fuel economy.
Ultimately, power & economy comes primarily from GOOD head porting. Intake porting gives more power, exhaust porting gives more power & economy. I've dropped a semi-ported B20 head with stock 44/35mm valves on a B18 & it was vastly better that the B18 head even though the compression dropped from 10:1 down to 8.5:1 because of the oversize chamber, but ports that flow are worth vastly more that compression.
Here's a few I have personally used & measured for comparison during installation & degreeing in. If you plan to build engines, you must have a degree wheel & dial indicator. 4° advanced is always a good place to start for just about anything that is a 2 valve engine.
And what are your thoughts about making the exhaust ports larger on B18 heads for B20 valves? Just a wild idea in my head.
Same size head, 35mm, just the stem is one size smaller which requires special guides. Just ask the machine shop for a good 3-angle valve job with a quick blend job of the the throat cuts in to the ports + add a small radius to the SSR of the exhaust. DO NOT remove metal from the spark side of the exhaust port, that kills flow & makes the head a throw away.
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Three 164's, Two 144's, One 142 & a partridge in a pear tree.
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