camshaft comparisons Web vs Megacycle 894cc gs750 street/racer

[Chuck78]

Can you all help me compare the pros and cons of a few aftermarket cam options? I'm looking for a wide powerband for a very fun street performance bike built for riding twisties and an occasional track day. 894cc GS750 8v going into Rickman CR900 frame & VTR1000F forks (although I may do a gs550/650 with 750 sleeves & 789cc 10.9:1 to save weight).
I know higher lift means less durable, more wear on the cam, valve guides, and valve due to the aggressive lobe angles and faster valve speed, but higher lift is better for street manners down low and bigger power. Longer duration doesn't affect durability but does lose low end power/response at the expense of gaining high-end horsepower.

With that said, I'd like to know opinions on how big I can go and still have a very fun reliable street engine with good power 4500+. Can I run the .380 or .395 lift cams and just advance them or play with lobe seperation angles to bring the power on earlier, or is that touchy with higher lift cams & piston to valve clearance?

I did read one guy saying the basic .365 lift grind was really the best for tight racetracks and fun street machines on a GS450 race bike. Could be due to the lower cc's lacking torque below the optimal power band of the cam, & the bigger street cams would have better tendencies on 800cc and 900CC GS four cylinders?



From the Megacycle Cams catalog:

Grind # 381-70
.380" lift
261° duration @ .040"
107.5° intake lobe center
108.5° exhaust lobe center
23 btc/58 abc.004" INTAKE OPEN/CLOSE
59 bbc/22 atc.004" EXHAUST OPEN/CLOSE
.004" running valve clearance
All around road & road race performance. Top-end power. Use spring kit. Stock pistons OK in 1000cc, must use modified pistons in 750 and 850.
Same grind for the gs550/650 says:
Best all around street/road performance. Use modified pistons and springs. Mid-range and some added top-end power increase.


Web Grind #118
.365/.365
286°/286°
245°/245° @ .050" lift
High performance street profile for stock engines. Very broad power range. Stock base circle. Price Per Set (2).

Web Grind #110
.395/.395
284°/284°
256°/256° @.050" lift
Good mid and upper end performance for hot street. Requires Exhaust System, High Compression Piston / Big Bore, and Performance Valve Spring Kit. Price Per Set (2).

[Chuck78]

Hard to compare them apples for apples with .040 vs .050 lift duration figures!
The Megacycle 380 lift sounds like a GREAT cam & is much cheaper at $450-475 vs closer to $600 for the webs. Will the .395 lift Web be my best bet though for most power? It seems to have slightly less duration than the .380 lift megacycle, & more lift. Is .395 pushing it for longevity on lobes, valve adjustments, valve guide and seat wear???

I missed a $200 new set of the base model 110 grind Web cams on ebay new in box, major bummer there..

[Chuck78]

There's also this Megacycle grind that looks pretty great for an engine that needs to have good street manners, but when my buddy at the local Vintage Japanese salvage shop talked to the awesome tech support girl at Megacycle, she swayed us towards the .380" lift grind for my application, and said I'd be most happy with it. This one is shorter duration (near stock?) But more lift, almost into shim under bucket territory. Probably not as good for pushing high rpm's with shim over bucket setups...

Whaddya think?

Megacycle Grind #381-10
.410" lift
250° duration @ .040" lift
108° lobe centers
17 btc/53 abc
53 bbc/17 atc
.006" running intake clearance
.008" running exhaust clearance

Best street/strip cam. Use modified pistons and springs. Maximum throttle response, mid-range added top-end. Good with oversize valves.

[BadBillyB]

I wouldn't run the Web #110 cams without shim under buckets. Spirited riding usually involves missed shifts and high revs. Even the best valve springs lose some of their control over time. Spit shims are for rookies. The .380 lift Megacycle cams seem to be the best choice if it were me. Might even consider mix and match, and use the .380 lift on the intake and the .354 on the exhaust. The megacycle 381-00 exhaust cam is slightly less duration. This will give you more punch at lower rpm's....An exhaust valve only needs to be opened so far to perform. Most cam sets are "cookie cutters", meaning they are the same except for the tach drive. Are there any other cam choices out there?????.....Billy

[Chuck78]

These are the readily available choices. There are also 2 others, the "ok with stock pistons and valve springs" base models from Web & Megacycle.

So do you think the .380" megacycle are not much of a concern with shim over bucket & accidental missed shifts?

[Chuck78]

Megacycle Grind #381-00
.354" lift
254° duration @ .040"
110° lobe centers
17 btc/57 abc 57 bbc/17 atc
.006" intake .008" exhaust running clearances

OK with stock pistons and springs in 850/1000, must check 750. Increased mid-range power.

------------------------------------------------------------

Web Cams grind #118
.365 " lift
286° duration
245°@ .050" lift

High performance street profile for stock engines. Very broad power range. Stock base circle. Price Per Set (2).

------------------------------------------------------------

This is still a big boost from stock. If I recall correctly, the stock 750 cams were around 280 degrees total duration (megacycle doesn't list that spec) and .304" valve lift, & the GS850/1000 were 276 degrees total duration and around .312" lift. So you just get more lift basically here, maybe a more aggressive ramping lobe.

[Chuck78]

The .380 lift Megacycle cams seem to be the best choice if it were me. Might even consider mix and match, and use the .380 lift on the intake and the .354 on the exhaust. The megacycle 381-00 exhaust cam is slightly less duration. This will give you more punch at lower rpm's....An exhaust valve only needs to be opened so far to perform. Most cam sets are "cookie cutters", meaning they are the same except for the tach drive.

If this is the case (I never considered the intake "sucking" vs exhaust "pumping/pushing" when looking at cams), it seems maybe that would be a good choice, or even Megacycle .380" intake and Web .365" on the exhaust for a slight bit more lift.
I do recall musclecar pushrod V8 cams typically being different exhaust profiles vs intake profiles, all ground into the same single cam, so no 2nd cam grind to cut corners on making a duplicate of...

I'm sure megacycle would tell me to stick with the .380"/.380" setup however, but I'd like some more feedback from you all first. Thanks Billy.

[BadBillyB]

Found these on GSR member "Nickp"s website. He acquired my GS1000 drag bike
http://www.suzukiperformancespares.c...amshafts/2700/

[Chuck78]

Wow. I kinda want to buy those cams if shipping wouldn't be too bad from the UK. $295 USD. Megacycle are $470 through my local vintage Japanese salvage shop the Rice Paddy (AWESOME SHOP!)

I could call megacycle & see what they say about mixing and matching their cams, but these are Yoshi, bragging rights there! Plus cheaper! Payday is tomorrow as well....

[Chuck78]

" the journals are excellent as are the lobes wear wise. no pitting. number 1 ex lobe has had a traumatic experience at some time in its life and has some cipping on the edges. the centre is perfect and this will not cause any issues whatsoever in use."

These are the Yoshi "Road & Track" cams mentioned. What do you guys think of the damage? Even at $290 USD, they are a good bargain compared to new Megacycles in nearly the same lifts. Duration is unknown on these unless I really could do some digging on the unternet.

Better to save up for new Megacycle grinds? Or have "Yoshi" bragging rights & more money to spend elsewhere on the bike? No idea yet on how much shipping from the UK to the US will run, I emailed them for a quote.

Billy I think you are 100% correct on this being the best setup, thank you!

[Chuck78]

http://www.satanicmechanic.org/yoshicam.shtml



Yoshimura Road & Track cam specs:
Int .378" 252° @ .040"
Exh .341 244° @ .040"
Int open 20°btc/close 52°abc
Exh open 46° bbc/18°atc
.004" running clearance (.006" race)

Yoshimura Isle Of Man cam specs:
Int .354" 264° @ .040"
Exh .337" 263° @ .040"
Int open 27°btc/close 57°abc
Exh open 56° bbc/27°atc
.004" running clearance (.006" race)
Must use Yoshimura valve springs

Great info to know! Actually there's a lot if insight to be gained from studying all of their various cam specs:

Durat In o/c Run-
Valve ion Lobe Ex o/c ning
Cam Lift @.04" center btc/abc clrnc
inches degr degr Description and Application bbc/atc inches
-------------------------------------------------------------------------------
Daytona Race.392 256 23/53 .004
.360 256 53/23 .004
Must use Yoshimura valve springs
-------------------------------------------------------------------------------
Road & .378 252 20/52 .004
Track .341 244 46/18 .004
-------------------------------------------------------------------------------
Stage 1 .362 253 105 21.5/51.5 .006
.330 244 105 47/17 .006
-------------------------------------------------------------------------------
Stage 2 .383 256 105 23/53 .006
.339 256 105 53/23 .006
-------------------------------------------------------------------------------
Isle Of Man Race .354 264 27/57 .004
.337 56/27 .004
Must use Yoshimura valve springs
-------------------------------------------------------------------------------
For racing applications, add .002" clearance

[nickp]

hi Chuck..post to the us would be £20 to the us. i dont see any future issues with running them. the motor they came out of was real happy. Billy...your old VHR 2vhead is back in the US at Star having a refresh and some new 80mm pistons made to match! cheers nick

[Chuck78]

Nick, can you re-measure that exhaust cam lobe height and the base circle again to re-check lift? I thought at first glance of the Yoshi specs that this was a mix&match set with one Road and Track cam and one Isle of Man Race cam, but the .354" lift is the Isle of man intake cam and wouldn't have a tach drive gear.

Are these hollow Yoshi cams by chance? I'm very seriously interested in them. If I end up building a 789cc gs550 with 650 & 750 parts, I'll run these in my 920cc gs750 & do the Megacycle Cams mix&match as Billy suggested.

[nickp]

i'll recheck when i get back in the workshop tomorrow. they are not the hollow 'works ' ones. i seem to remember back in the day there were several different road and track type yoshi cams around that we used to sell...people didnt even bother to ask about lifts or such in those days very often! just will it fit......nick

[oldgsgkd]

I've got a .380 lift intake cam, ported head to 109 cfm at .4 lift should run 140 hp