Regrind cam question

[iTurbo]

What would happen if you were to install an aftermarket regrind camshaft that had a reduced base circle and no other changes were made to the valvetrain to account for the altered geometry? In other words, no shimed lifters or valve lash caps installed. What would be the effect on the engine running at idle or higher RPM at WOT?

[mock_glh]

It would be very noisy and the rockers would come out because there would be nothing to hold them in.:eek:

[iTurbo]

OK thanks. I was intentionally a little vague, but the engine is actually a TIII. I have some regrind cams with a reduced base circle. Lifters are new, and they seem quite. Problem I'm having is very low vacuum at idle, very little low end torque and throttle response. Runs well in the higher RPM though. Does this sound like it could have anything to do with excessive valve lash? Probably not, but I'm having a hell of a time finding anything wrong (anything obvious anyway). I have adjustable cam sprockets and have tried to advance both cams but didn't help at all. Engine also detonates audibly with any more than 7 psi.

[mock_glh]

Here's what's going on: The low vaccuum and lazy low rpm response are normal for increased duration cams, especially if the compression ratio stays the same. And I'm guessing you put in the bigger cams to get more power. That means you're letting in more air, and more air means you need more fuel. Now here's the real problem: The TIII engine uses the same size (33#) injectors to make 224 hp as the TII uses to make 174 hp. How is that? By calibrating the computer to run at 100% duty cycle instead of 85% like everything else does. What does that mean? It means you are MAXED OUT. If you add any more air (by raising the boost or installing bigger cams) you will run too lean and will detonate. Bigger injectors and a modified calibration are this doctor's orders.:nod:

[johnl]

Yes. Doc Mock.:thumb:

[turbovanman²]

If the cams were reground to much, the lifter would be noisey, as in clack clack clack.

Are these Wallaces cam's or unknown origin? if unknown, they could be really wild and thats why no power down low and of course, low idle vacuum.

Moved it to the TIII section.

[iTurbo]

Thanks for the insight! The driveability issues have been driving me nuts. The car has 3" exhaust, ported exhaust manifold, stage I cams, and a few other minor things. The SBEC and MAP sensor are stock, but the fuel system has been thouroughly modded. Walbro 255 pump, 3/8" feed/return, LWP rail, Accufab AFPR, Russel inline 6AN filter, and MP +20 injectors. Do you think all this is more than the stock SBEC can handle? I have not pushed the boost above 10 psi and I have had it set (with grainger) to 7 psi because of the audible pinging, verified with the OTC. Strangely, the SBEC is pulling timing on every cylinder by equal amounts. I have tried putting 100 octane AV gas in the tank and was able to run 10 psi all day long without a hint of detonation, but the driveability was still a little wierd.

EDIT: The cams are LWP stage 1. No excessive lifter noise that I can tell. Should I try lash caps?

[WOP'R]

anyone else noticing this with stage 1 cams? Im thinkn about getting a set but if its going to do this then there is really no point!!

[turbovanman²]

Jeremy, either you got a bad batch or you need to properly degree your cams. I haven't used any yet but all the cams he's sold, no one is having the issues you are. Based on the fact that you have low vacuum, poor bottom end, it could be that simple. Is your compression ok?

Aren't you high in elevation?

[iTurbo]

So far I seem to be the only one, so maybe not cams. Another reason my car seems 'lazy' down low is that I live at high elevation (~5000ft) and I have a lower final drive ratio (3:50 A568) than the stock R/T cars got.

Anybody else with regrind TIII cams out there? I have dialed in the cams with a dial indicator and degree wheel via the adjustable sprockets. I've tried stock centerlines, Wallace's recommended centerlines, and lots of experimentation everywhere in between. So far I like Wallace's centerlines the best, but centerlining the cams doesn't seem to be the be-all-end-all solution. Compression has ranged from 130-145 psi depending on where the cams are centerlined. The compression seems very consistent from cylinder to cylinder.

[turbovanman²]

Hmmmmmmm, I bet its because of your altitude, those cams should move the powerband up a bit and because of your altitude, your suffering. Do you have the specs, I can ask my cam grinder what he thinks.

[iTurbo]

I don't know the specs. They would be greek to me anyway so I never even bothered to ask for them. I have a bunch of stuff I'm going to try next week on my days off, including pressure testing the intake tract, installing those Aurora wires, replacing throttle body etc...I may even try the lash caps but they are about $90 a set. It was obvious the base circle on these cams was smaller because the rocker shafts installed much easier than with stock cams. They almost lay right down into the U-channel in the head without even tightening the bolts. Maybe I accidentaly got stg 2; who knows.

[turbovanman²]

I don't know the specs. They would be greek to me anyway so I never even bothered to ask for them. I have a bunch of stuff I'm going to try next week on my days off, including pressure testing the intake tract, installing those Aurora wires, replacing throttle body etc...I may even try the lash caps but they are about $90 a set. It was obvious the base circle on these cams was smaller because the rocker shafts installed much easier than with stock cams. They almost lay right down into the U-channel in the head without even tightening the bolts. Maybe I accidentaly got stg 2; who knows.

Well if your lifters are quiet, the lash caps won't help. Yes, they will be easier to install as the lifters are pumped up for stock cams, with the smaller circle, they will bolt down easier then when you start it, they pump up to the new lift.

Did you get the wires yet? should be any day now.

[iTurbo]

No wires yet. I have Mon/Tue/Wed off and will tear into the car then.

[MOPAR2YA]

Jeremy, I have sold many S1 cams and no problems from anyone. I run the S1 in my R/T and they make 18 in/vac warm. If you want PM me your number and I can call and we can go through a bunch of stuff.

[Millerman340]

I may even try the lash caps but they are about $90 a set. .
check these out, if they don't solve your problem your only out a few bucks.http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=140105358134&ssPageName=MERC_VI_RSCC_Pr4_PcY_BID_Stores_IT&refitem=140104408206&itemcount=4&refwidgetloc=active_view_item&usedrule1=StoreCatToStoreCat&usedrule2=CrossSell_LogicX&refwidgettype=cross_promot_widget

[iTurbo]

Thanks! Can't wait to try em out.

[Millerman340]

So what was the cam spec's with caliper? inquiring minds want to know,

[iTurbo]

Haven't got it yet...still need to order a digital calipers from Summit. My Omni hasn't been very cooperative lately so I've been working on that car lately. I'll reply when I know, and I have some known stock cams to compare against here.

[MOPAR2YA]

If your try lash caps, make sure they dont hold your valves open. if they are to thick they will do that.