1mm os valves what kind of cams can i run?

[compression]

my engine builder is trying to say that with my 1 mm os valves i cant go to a 280* cam instead he had this cam made and didnt tell me

adv dur 259/258 dur @50 212/212 lift 411/395

instead of the 280* that i wanted

adv dur 280/280 dur @ 50 218/216 lift 422/418

heres a 272 spec

272°/272° 212°/212° .401"/.381

Stock specs 248°/248° 200°/200° .349"/.350"

what kind of disadvantage will having better lift but less duration give me? i want a nice powerband all the way to about 9-9500 rpms, i have ferrea dual spring valve springs titanium retainers and spring seat locators , i have a fully built head i just didnt want to go cheesy on the cams

even with the head shaved down to the max with 1 mm os valves ive never heard of anything like this , will somebody please clarify this for me before i go there today raising hell

 

[dsm-onster]

I've not heard of this problem before, either. . . Especially for 8.3 CR pistons, this sounds a little strange to me. BC 280s are for "built motors". Most build with oversized valves and a little higher compression.

Maybe the ramp rate of the 280 duration cams keep the oversized valves open too long for your higher compression pistons ??? . I would take less lift or ramp rate and keep the duration to fix that problem, though. . . Considering your power band choice.

 

[wortdog]

I'm running Crower 288's with 9:1 Ross pistons and 1mm os valves.

Cam choice shouldn't really be affected until you try to go 2mm os on the intake I believe.

Did the builder have to deck a lot off of the head and block?

 

[compression]

i dont know much , but i do know he did deck both i think maybe thats where the problem would lie, thats what i was thinking as well, a long duration would be a little better then a little more lift.

i just talked to my builder and he said that the advertised duration means jack shit, if thats true it looks like im ok, i dont know any specific numbers but the ramp is apparently pretty damn aggressive. so ill go ahead and use these cams and see how that work out.

 

[dsm-onster]

I guess if the block was decked enough and the head was shaved to the max. . . Do you have to run adjustable cam gears for the cams to be run "straight up"? If enough was removed from both, you should have to for your cams to be run straight up.

i just talked to my builder and he said that the advertised duration means jack shit, if thats true it looks like im ok, i dont know any specific numbers but the ramp is apparently pretty damn aggressive. so ill go ahead and use these cams and see how that work out.

Of course advertized duration means nothing. No one is talking advertized duration. Is he saying that we're tring to make some speculations based on that? Or that 280s won't perform much better than his choice of grind? The 280s have 4-6 degrees more duration at .05" lift. The cam duration he's wanting you to use is the same as fp2s or fp2Xs. The duration at .05" lift for hks 272s are even more 213, not 212. And the lift values you posted are nearly identical to fp2s. Without knowing the ramp rate, those specs look likefp2s or another similar comp variant. . . They won't do what you want at 9500rpms. Ramp rates don't help as much up top as the do down low. They do enough to help 212 duration fp2s out-perform 213 duration 272s up top. But, it won't make a cam what it's just not. Look at it this way. . . Don't you think the 280s have a much higher lift than 0.05" at 212*? So . . . (rhetorical question) What is the lift for his cam choice at 212 degrees?

Also, the cams he's wanting you to install are lower peak lift than the bc280s, BTW. All the way around you've got less than what you've asked for.

Considering the bounty of blocks out there, another used block would be worth more than having to run a duration that won't allow you to meet your goal. Why not just get another head/block (n/t engine would be fine) from the junk yard for $350 or so? You already have so much invested. . . Did he do the head work? Did he machine the head and block down without checking whether or not the larger than stock valves would clear the non-stock pistons he's installing because of the non-stock cams he's installing? . . . My point is that this is his problem. He could have told you that too much has to be removed from the head/block for the valves to clear, and asked you what you want to do: save this block/head or get another so that you can use the parts you want. You really actually NEED the oversized valves: 0.51 mach number. You have enough valvetrain for more than 9500 rpms. A 272-like cam is just not enough.

Why in the he!! would he have a custom cam grind made and not tell you ahead of time ???

 

[compression]

custom grind my ass look what i just found

COMP Cams: Mitsubishi 4G63 2.0L DOHC Performance Camshaft Set

shit can get aggravating.

it says 2400 - 7300 rpms, but the hks 272's are being run by a lot of people who take the rpms well to nearly 10k like evil eagle hes running almost in the 8's with them.

 

[dsm-onster]

272s won't do what 280s can do at 9k regardless who uses them . The 280s are just newer, so there's not many setups documented.

Did he tell you it was a custom grind? Did he lie to you or did he choose the comp 200 cam specs but had greater ramp rate cut? Why isn't he leveling with you about your investment?

Can't your clearance issue at least tolerate the fp3X grind? Much more lift and ramp rate than the comp 200s. You'll likely need to adjust the exhaust cam timing to help you 2.0L idle and your 2.0L topend. But they have the same duration as comp 200s so once centerlines are dialed in for 2.0L piston speeds, it will be like having a set of 272s on steroids.

For the price difference of fp cams (cut by comp) vs. the comp200s, you can buy an adjustable cam gear to dial them in and get the more aggressive characteristics.

 

[compression]

no he told me today he bought those, apprantly there was a problem with my cams and they couldnt be used or something so he got these cams instead

i have aem tru time adjustable cam gears so i can adjust them accordingly

i guess we are going to work something out , so im going to use these cams, worse comes to worse ill just upgrade later , couple hundred dollars and a timing job .

by the way , who does use brian crowers cams, besides wortdog so i can compare

ps this is his first 4 cylinder race engine, regardless he has built ALOT of different engines for different setups that go extremely fast with little to no problem,

 

[pinder91]

the hks 272's are being run by a lot of people who take the rpms well to nearly 10k like evil eagle hes running almost in the 8's with them.

FWIW, Jake isn't running those cams anymore. IIRC he only used them for the first half of last season. And he also using stock size valves.

 

[compression]

oh, ok what set of cams is he using, before bc cams came out iirc the hks 272's were one of the best out there besides custom grinds right?

 

[whitedawg]

He is using a custom set of FP cams which are in turn made to their specs by Comp Cams.

 

[booostedGSX]

by the way , who does use brian crowers cams, besides wortdog so i can compare

I use BC 272s and I like them. Three of my friends use the BC 280s and they work really well.

 

[compression]

how does a bc 272's compare to say an hks 272 , nearly identical ?

 

[dsm-onster]

Unless the centerlines and the ramp rate between the two are different, then the HKS 272s and the BC 272s would perform exactly the same. The duration and lift are the same between the two brands.

BC272s

 

[compression]

thats what i was thinking , but why are they so much cheaper for the set of bc's then the hks?

 

[dsm-onster]

The name.

 

[kahl23]

Also, BC's, comp, FP's are all relatively new. I remember when I was getting cams a few years back it was HKS or nothing, so they've been used to being able to charge a pretty high rate for a while.