Volvo O H V cam grinds

Volvo B20 Cam grinds

(Compiled and maintained by Ian R.)

This is a working version - let me know if you strongly think I need to tweak or proof read some figures. Still, no figure should be out by much more than about 3 degrees, but some are educated guesses.

IMPORTANT: One of the more common reasons for dispute between my figures and others' is that people have used the "setting spec for intake opening point" from the Volvo factory manuals (and supplied in Haynes manuals). This is not the intake opening point that a cam manufacturer would supply or a machinist uses to check cam timing when assembling a bare block, as it is measured at a different clearance for each engine, none of which are the SAE standard clearance of .020". I've attempted to standardize to a .020" LIFTER RISE point, which means that the rocker ratio and valve clearance setting have been taken out of the equation. This is standard way all North American made O.H.V. camshafts are measured. Specs here are directly comparable to those from Competition Cams, Crane, Crower, Lunati, etc. for a GM/Ford/Mopar V8. However, Volvo uses a smaller base circle (30mm/1.18", stock), as the cam bearing that the lobes must pass through is 1.69 " diam, whereas the domestic v8's that the lobe shapes are designed for use cam bearings in the range of 1.86 to 2.13" diam. For reasons of the geometry involved in eccentric motion, if using a mechanical lobe master to grind from, the duration drops about 4 degrees from the design value when ground on the smaller base circle. Your cam grinder might need to be reminded of that, if you were to have a cam custom ground...though with "masterless" CNC grinding becoming the norm this is becoming an obsolete concern.

Cores are available to have custom ground cams made or certain grinds of used cams in good condition might be reground. (I will buy used ISKY or IPD cams for more than you might expect, as long as the no lobes are critically worn). Please e-mail me if you want to discuss doing any regrinds, as I have done my homework and can send you to the right places.
My most recent personal project in the area of regrinds was based on an Isky VV61 that I had found a bit big when put in a low compression carbed b20, and subsequently removed for future use.
Ironically, with 19% more displacement, a subtly higher compression ratio, 2 deg advance positioning, and maybe my ears developing a bit more tolerance for engine revs, I am now planning on exceeding that spec of cam. The regrind I've chosen is with the 256/262 CompCam XtremeEnergy Solid lobes, & I expect to be very pleased. Also a contributing factor is that the stroker kit I pieced together lowers the rod ratio from 1.81 to 1.69. Contrary to the opinions of a few self-styled engine experts, this is beneficial, giving better midrange output and better throttle response, but it does create a need for-"soak up" is how one engine builder worded it- additional cam duration.

On the smaller duration cams I've had most experience with, I have adjusted down some overlap figures on the slow-opening cams so those figures are more "subjectively" comparable to faster-acting cams. This is important as the total area the cam is open is the key, and especially the overlap, when both valves are open. This is defined by the opening ramp of the intake and closing ramp of the exhaust. The same principle of subjective adjustment can be applied to the longer duration cams by watching the .050 figures more carefully than the advertised.

Some advice on knowing what the info in the charts means:

* the longer the duration the greater ultimate horsepower potential. However, the peak torque is not raised, merely moved higher in the RPM range.

* the duration at .020 rise is called advertised duration and is usually used to 'name' cams.

* the longer the duration, the higher rpm the engine will have to spin before it becomes efficient

* a duration change of eight degrees is noticeable in the way a car runs. If the overlap has been changed by 6 to 8 degrees that counts as well, even if it is caused by any combination of a couple degrees of lobe center change, a couple degrees duration change, or several degrees of advance or retard.

* Purists will say I am overstepping what can be quantified, but it is a vague rule of thumb that with reasonable modifications going along with each cam, at minimum one horsepower will be gained for every added degree of duration at .050.

* generally the less the difference between the advertised duration and the at .050 duration the better. Current state of the art in cam lobes is 24 ° between .020 and .050 - that is, 12 ° on each the closing and opening ramps. Ideally it would be about twice that quick, which isn't possible with conventional valvetrains. As air has mass, and therefore inertia, it is believed that instant openings are not really worth pursuing. For the curious, disc valve engines as used in snowmobiles and some recreational vehicles have very close to instant openings.

* As cam technology advances, the ability to open valves faster is achieved. For this reason there exists a large number of otherwise well informed people who will suggest a larger cam than you need. This is because a 260 ° cam of today is equal to a 278 ° cam of 30 yrs ago in terms of the actual amount of time the valve is open.

* the greater the lift, the greater the power at all RPM, within limits practical with today's technology. You cannot currently buy a cam with so great a lift that you will experience performance loss.

* Lifts greater than .430 may require non stock valve springs. Lifts greater than .470 will require guide modifications on b18 cylinder heads. Lifts greater than .515 may require grinding of the cam core for creation of a sufficiently wide base circle. Factory cylinder heads do not flow well enough to benefit from lifts over about .450 but in modified form can flow well enough to benefit from close to .600.

* The better the port, the higher lift and shorter duration you require.

* the knowledgeable cam buyer is also interested in geting the "fattest" lobe of a given duration and lift. As cam opening rates are somewhat fixed by lifter face size, it is a matter of which manufacturer is most willing to trade off lifter wear. However, careful engineering by the larger cam manufacturers has seen some improvement in speed of opening without compromising lifter wear, through precise analysis of lifter-to-cam loads. The only available way to understand the overall lobe shape is to get duration figures for either .200 or .300 cam lift. Most aftermarket cam manufacturers have this information in their catalogs, but short of measuring all available Volvo cams in a jig, I have no way to get those figures. Safe to guess that the higher the peak lift -and the faster opening- a lobe, the greater the high lift duration.

* greater lift on a given duration means more wear on the lifter face, as it has reduced contact area on the lobe. The same function can be achieved by increased rocker ratio-(those who follow Winston Cup racing may know that ratios used there are over 2:1 as compared to Volvo's 1.45:1), but this is not entirely free of adding risk of wear as it feeds proportionally greater valve spring force back at the lifter. It may sound like I am unusually concerned with lifter wear and with preventing it, but it has been a known weakness of the OHV Volvo engine design. More recently another factor has been compounding this: with passenger car engines switching exclusively to roller lifters or overhead cam designs, it became reasonable for motor oil to have some of the potentially environmentally/biologically harmful additives taken out. These additives- mainly compounds of zinc, along with some molybdynum and other trace metals, were found to be "coating" (on a microscopic level) the internals of catalytic converters, and to a smaller degree, the spark plugs. Environmental concerns and the declining "need" for these additives has caused the oil producers to phase them out. Unfortunately, they were the additives which best prevented metal on metal contact as occurs when the lifter-cam contact area becomes over-loaded. The additive requirement is very specific, as the lifter bore is located off center on the lobe, and so causes the lifter to rotate against the cam lobe with a friction-based "bevel-gear" effect. If there is insufficient friction to start the lifter turning, this will cause failure, yet if the oil film fails to keep the metals apart on a microscopic level, this is worse yet. CompCams, CraneCams, and GM (as "EOS") offer very worthwhile break-in additives. Long term, it seems far more than the more publicized issue (non-issue, as it turned out) of the removal of lead from fuel, owners of non-current production cars would be very smart to research engine oil additives. The one I've seen the most scientific back up on is OilXtreme, if you can get past their snake oil sales pitch. (Would you buy anything produced by "Jet Set Life Technologies"? Yeah, me neither.)

Possibly the ultimate solution is to use carbide lifters, as produced by Schubeck, or lifters of a larger diameter - Chrysler V8's use ones .062" larger (one sixteenth-inch). This small amount can make a major difference. International truck motors from the early 70's use a larger size yet. I am eventually going to investigate the cost of having the lifter bores opened to the Chrysler .904". Volvo OE lifters are .842" (27/32nd's minus oil film, copied from Chevrolet small and big block v8's, who knows how GM picked such an odd size!). Also, when installing new lifters, it is becoming a habit among professional engine builders to texture the lifter contact face slightly by rubbing the lifter in a 'figure-8' motion on sandpaper, folowed by some final radial etchings..

* the narrower (smaller numerically, also called 'tighter') the lobe separation (the average of the two lobe center figures) the more powerful the cam will be in its power range, but the lower the mileage, and the higher the emissions. It also will likely have a rougher idle, and somewhat poorer off-idle throttle response, even if it's not a long duration cam. These effects become pronounced when the value falls below 108 °.

* conversely, the wider the lobe separation, the power curve will be wider, but not as high peaking. Typically, values over 111° will have, logically, benefits of the opposite of those negative effects mentioned in regard to smaller lobe separations. Most all original equipment cams use a wider lobe separation to give a smooth idle, smooth off-idle throttle reponse, lower emissions, and better fuel economy, at the the expense of mid & upper-mid range torque.
Turbo cams also require wider lobe separations, as do some very long duration race cams. In both these cases it is to avoid excess overlap.
In Non turbo applications the difference in torque curve will generally follow the pattern shown here

* the stock volvo rocker ratio is rated at 1.5 but is actually a bit less. Under less than ideal circumstances, it can be as low as 1.44. The factory rockers can be modified for higher lift or completely new items can be adapted from other engine makes. I will be trying both ways of rocker ratio increase during summer '01. Email me if you are interested.

* Update nov2001: I ended up learning a bit while fooling around mocking up rockers on a spare cylinder head and observing the resulting geometry, but ended up running an OJ Rallye-sourced Enem/Unitek 248 ° cam with stock rockers. I have a photo in the tech photos section showing an option or two.

* Update #2 fall '04- as much as the engine runs well as is, I'm going to try a CompCams' fairly minor regrind of an Isky VV61 (also sold by IPD as Street Torque) , coupled with 1.6 ratio rockers (a .15:1 boost in true ratio, with measured lift going from approx .430/.430 to .485/.490"). I'll post impressions when I finally get to that (May/June 05, likely).

* The colored highlighting (the grey is purely for readability of the lines) on the first few indicates cams I have presently in my cars, or have had in the last couple of years.
The big one further down is on the horizen for a couple of daydream-projects- a T5-transmission-backed, stroked, h-beam-rodded, possibly nitrous'd, possibly aftermarket-headed "ultimate" b20 .. or more realistically, it may get offered to a friend of mine for use in a IMSA GT3 class 1800E he races locally.
* The cams below are chosen with a U.S.-centric slant. IE, cams from Euopean companies having active websites and distributors in the US are added among the base list of products of the main US manufacturers. The cam cores used by European manufacturers are US-made, so the separation is not as pronouced as might seem.
* I am slowly adding the lobe dimensions of the main European brands in text form following the chart, as well as the lobes successfully used by Volvo racers & enthusiasts in the custom grinding of cams.

GRIND
NAME
.050
Duration
Advertised
Duration
Overlap
lift
w/1.5
lift
w/1.6
lobe centers
intk / exh valve events @ .050
intake / exhaust
btdc . abdc . bbdc . atdc . valve events @ .020
intake / exhaust
btdc abdc bbdc atdc

Volvo 'A' 194 245 (18)* .355 .379 109 / 113 -12    27    31 -16 13    52   56 9

Volvo 'B' 200 252 (22)* .386 .406 109 / 111 -9 30 31   -11 17    55 57 15

Enem A10-248 215 248 35 .460 .490 107 / 109 1 34 36    -1 17    51 53 15

Volvo 'C' 210 260 (32)* .395 .421 109 / 113 -4 34 31    -3 23    57 63 17

Isky VV61 216 256 40 .425 .453 108 / 108 0 36 36 0 20    56 56 20

Comp 256XS-8 218/224 256/262 43 .466/469 .498/502 107 / 109 2 36 41 3 21    55 60 22

Paeco 266 220 266 50 .400 .427 106 / 110 4 36 40 0 27    59 63 23

Enem K16 260 222 260 44 .472 .504 108 / 108 3 39 39 3 22    58 58 22

Volvo 'K' 222 277 (46)* .420 .448 111 / 111 0 42 42 0 27    70 70 27

Volvo 'D' 222 280 (48)* .420 .448 111 / 111 0 42 42 0 29    71 71 29

Paeco 270 224 270 54 .435 .464 106 / 110 6 38 42 2 29    61 65 25

Isky VV71 228 268 52 .446 .477 108 / 108 6 42 42 6 26    62 62 26

Enem k17 272 232 272 56 .472 .504 107 / 109 8 44 44 8 29    62    64 27

KG 10 238 280 60 .440 .469 110 / 110 9 49 49    9 30    70    70 30

Isky Z322 242 280 64 .480 .512 108 / 108 12 48 48    12 32 68 68 32

R-Sport 'f' 241/250 291/300 69 .440 .469 112 / 111 8 53 56 14 30 81 81 39

KG 17 243 285 71 .440 .469 107 / 107 15 48 49 14 36 69 70 35

Enem K18 284 242 284 68 .472 .504 107 / 109 14 48 50 12 35 69 71 33

Isky VV81 244 286 70 .446 .477 108 / 108 14 50 50 14 35 71 71 35

Paeco295 248 295 80 .480 .512 106 / 110 18 50 54 14 42 73 77 38

W.G.1171 242 288 86 .450 .480 99 / 103 22 40 44 18 45 59 63 41

R-sport 'r' 245 287 86 .460 .491 102 / 100 21 44 43 23 42 65 64 44

Comp 6234-5683-8 248/252 274/279 60 int .515 w/1.6 exh .510 w.1.7 105 / 111 19 49 57 15 32    62 71 28

Isky91/z349 254 300 84 .507 .541 108 / 108 19 55 55 19 42 78 78 42

Enem K19 296 258 296 80 .472 .504 108 / 108 21 57 57 21 40 76 76 40

Isky vv101 260 310 88 .507 .541 111 / 111 19 61 61 19 44 86 86 44

KG 19 262/248 312/292 92 .488/443 .520/473 104 / 106 27 55 50 18 52    80 72 40

R-Sport 's' 254 300 98 .510 .544 101 / 101 26 48 48 26 49    71 71 49

Enem K23 308 262 308 96 .472 .504 106 / 106 25 57 57 25 49    79 81 47

Isky V111 264 320 98 .507 .541 111 / 111 21 63 63 21 49    91 91 49

Isky Z309 264 314 98 .538 .574 108 / 108 24 60 60 24 49    85 85 49

KG 6 260 312 102 .488 .520 105 / 105 25 55 55 25 51    81 81 51

Enem H3 312 262 312 102 .492 .525 105 / 105 26 56 56 26 52    80 82 50

R-Sport'u' 260 312 108 .510 .544 102 / 102 28 52 52 28 54    78 78 54

KG 5 268 320 112 .508 .542 104 / 104 30 58 58 30 56    84 84 56

Enem 320 270 320 112 .509 .542 104 / 104 31 59 59 31 56    84 84 56

Kg mr3 274 320 114 .547 .583 103 / 103 34 60 60 34 57    83 83 57

KG mr1 274 320 118 .547 .583 101 / 101 36 58 68 36 59    81 81 59

R-Sport T 274 336 125 .510 .544 100 / 111 37 57 68 26 68    88 99 57

Also useful are the lobe specifications of the main European brands, other than KG & Enem already listed:

BOA ( Bengt O Askanius ):
BOA3 277°, lift 12,6 mm (.496) (all with 1.5:1 rocker)
BOA1 279°, lift 12,4 mm (.488)
BOA7 284°, lift 12,6 mm (.496)
BOA5 289°, lift 12,8 mm (.504)
BOA6 295°, lift 13,1 mm (.516)
Combinations of #3 on intake/7 on exh, as well as #5 on intake/6 on exhaust are common and effective.

Nisse Hedlund :
NH 139 258° 10.4mm (.409) comparable to A-cam
NH 44 272° 110 11.0mm (.432") comparable to C-cam
NH 48 275° @107+1 11.6mm (.458") comparable to K-cam
NH 23 272° 106 12.1mm (.476") possibly comparable to K/D-cam, but having reduced lobe sep
NH 49 278° 108 11.7mm (.461) comparable to F-cam (older lower-lift profile)
NH 163 284° 11.5mm (.453) (older lower-lift profile)
NH 62 282° 11.4mm (.450") (older lower-lift profile)
R 2 = NH 74 in NH 62 ut 298°/282° rev split (.493/.450)
NH 191 282° @107+1 12.7mm (.502) comparable to R/S-cam
NH 220 281° @104+2 12.8mm (.505) comparable to R/S-cam
NH 20 291° 105 12.6mm (.496") (older lower-lift profile)
NH 192 288° @104+2 (102-106) 12.7mm (.502)
NH 232 291° @104+2 (102-106) 12.9mm (.508)
SMR 294° 12.8mm (.506")
NH 12 290° 105 13.2mm (.520")
NH 113 288° @ 105+1 13.4mm (.529) Impressive!
NH 193 296° @103.5+2.5 (101-106) 13.0mm (.511)
NH 74 298° 12.5mm (.493) (older lower-lift profile) (R 8 = NH 74 Volvo B20 Alternativ till H3)
NH 101 287° Turbo 10.6mm (.417) ---?? VERY LOW LIFT!
NH 125 306° 104 11mm (.433) ---?? VERY LOW LIFT!
TG 4 = NH 88 in, NH 125 ut 314/306 rev split (.540/.433)
NH 77 305° 104 13.4mm (.529)
NH 88 314° 13.7mm (.540) Custom for Ronwill Racing

TG Motor They are the souce for steel cam cores, and prefer to grind all their cams using them. The price is a very reasonable 1900 sek (approx $235 US). Items marked with an asterisk are for use with aftermarket springs and their proprietary lifters, presumed to have an altered face finish, and/or metallurgy.
My understanding is that the item numbers refer to a lobe area figure, probably mm².

Tg 761 280° 11.4mm (449") (I'd guess Lobe sep @ 110°) Similar to D, works with EFI, CIS, SU's, Weber DCD/DGAV or DCOE.
TG 765T 281° 11.45mm (.451") (I'd guess Lobe sep @ 113-4°) Altered ramps (and lobe separation angle) compared to previous, for better results with turbo.
TG 774 296° 11.6mm (.457") (I'd guess Lobe sep @ 108-110°) Low lift, not recommended.

*TG 876 282° 12.59mm (.496") (I'd guess Lobe sep @ 108-110°) Evolved from the older TG761, similar rev range, but allowing better VE
*TG 880T 288° 13.1 (.516") (I'd guess Lobe sep @ 114-5°) Recommended principally for maximum effort turbos, but lobe design could be used to good effect in a naturally aspirated motor having significant porting. Similar to the Nisse Hedlund NH113 in the previous block of text, but without quite as high a peak lift.
*TG 858 298° 12.75mm (.502") (I'd guess Lobe sep @ 108-110°) In spite of 10° greater duration, note that this has lower lobe area then the previous cam. Recommended by them for NA motors, I think it's somewhat of a compromise.
*TG 984 318° 13.85mm (.545") (I'd guess Lobe sep @ 108-110°) Their big cam. In fact, I believe it holds the title as the largest commercial off-the-shelf lobe, in both lift and duration, for the b20. The cam was used in the Lindqvist 122 to make a probaly record-holding 230 dyno'd rear wheel horsepower, but even this duration could not permit the maximum-ported b20 head to create an power range extending much over 7000 RPM. The airflow needs of his maximum-effort race state of tune multiplied by his 2497cc displacement overwhelmed even his relocated & welded ports. In the Lindquist motor, 1.6 rockers bring peak lift to 14.77mm, or ~.580"

Also useful is this chart decoding the factory grind codes:

S733 = A
S758 = C
S760 = D
S764 = F (accessory/R-sport)
S772 = K
S759 = R (accessory/R-sport, & widely copied)
S761 = S (accessory/R-sport)

Paul's Cams

A series of ever larger cams used by an Australian racer in a 140 with a much modified cylinder head (filled exhaust floor, extensive porting). Used in a series of builds with 92mm bore & sometimes using just longer rods, and sometimes using both longer rods & longer stroke.He found two things which contradict the efforts of others: one being the the factory single springs are inadequate even for stock cams, having a resonance around 5400rpm, the other being that he ran the cams straight up or retarded, and when trying the more usual advance, didn't get good results. He sought reasonable cam life while using off the shelf lobe masters & using stock rockers so lift was typically relatively modest. dur @ lash
@.050" dur
@.200" dur
max lift @ lobe
/ with 1.49 rocker & net of lash /
with 1.5 rocker rated

An Australian ground (as are all these cams) street performance cam, being a fairly faithful copy of a "D grind". 286 °
219 °
118 °
.280"/.399"/.420"

A small bump up from the D-copy, having slightly more duration & lift. 292 °
220 °
124 °
.290"/.417"/.435"

An attempt to use a lobe with a slow initial opening ramp and a large nose radius. I am in slight doubt that this lobe master was supposed to be used as an .842"lifter OHV, flat tappet lobe. Performance was reported as not impressive and lobe caused lifter-face failure in short order. 311 °
235 °
144 °
.317"/.456"/.476"

A big block Chev V8 intake lobe master. Good power reported, good top end, yet decent streetablity with 42DCOE's. 290 °
237 °
130 °
.287"/.405"/.431"

Ok overall, though not really superior to previous cam. Replaced mainly because evolving spec of motor and increased motorsport activity seemed to suggest to go larger in lift and duration. 299 °
239 °
140 °
.295"/.425"/.443"

Similar to previous two, but with less lift, while having slightly more low lift duration. 301 °
246 °
132 °
.274"/.393"/.411"

A big block Chev V8 exhaust lobe master. Originally combined with above BBC intake lobe, it strikes me that it would be nice with the slightly more aggressive lobe just following that in this chart. Good power reported, used more than once, and recommended by Paul to others. 298 °
247 °
141 °
.295"/.417"/.443"

Again with less lift, while having slightly more low lift duration. 317 °
260 °
147 °
.287"/.413"/.431"

similar to previous but more lift, especially in terms of nose radius. To be run with only 11-12 thou lash. 313 °
258 °
152 °
.297"/.434"/.446"

similar to previous but more lift yet, & again especially in terms of nose radius. Is to be run with 24 thou lash. Possible lifter wear issues. 308 °
257 °
158 °
.333"/.472"/.500"

progressively larger duration, less lift. More durable(?) 304 °
262 °
162 °
.316"/.448"/.474"

Again trying Chev lobe masters, this time from the exhaust side of a race small block. Uses a slightly scary .030" lash. Paul said he did not experience issues with the rocker tip pads chipping or wearing, as they "felt the hit", due to fairly gentle ramps. 301 °
264 °
164 °
.346"/.486"/.519"

Again a Chev exhaust side race small block lobe master, this one with slightly more duration...in fact as a point of interest, when measured at .010" this cam has 378° duration. This is possible because duration figures always refer to crank degrees, which are twice measured cam degrees. It was used @ .027 lash, yielding the shown 320° figure. 320 °
268 °
169 °
.336"/.473"/.504"

Final and largest grind. Lobe was apparently custom. Again uses slightly scary .030" lash. I feel that somewhat like the Lindqvist motor, you may not see a power range that is radically high RPM oriented, because you've reached the limit of the head flow, and additional duration provides diminishing returns beyond 300°. Also worth mentioning is that the peak lift in use, allowing for rocker ratio & lash, is no more than equal to my 218/224° cam which has small lash losses and works through 1.6 rockers. 325 °
282 °
183 °
.339"/.475"/.508"