Comp XE275HL Idle Vacuum

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AJ/FormS said:
I know you're not nm9, you're a good guy. But honestly the 235 cam is IMO just not gonna explore the limit, and the tests I outlined will prove it.
I don't do autocross, but I do do dirt rally cross whenever I can, even if just for fun. On dirt/grass the speeds are way down, and I just stuff it in second and leave it there. This puts me in the top percentile of finishers. If I can't drain my booster hard-charging and two-footing the course, how is an automatic gonna?
Nevertheless,I capitulate to your experience.
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And maybe for simple auto-x it is not really that critical... it won't get you in big trouble on such a course....just throw you off. It's just I've been there in a 'more critical' situation let's say.... when the 'oh *****!' come pretty fast, and you can see in your peripheral vision that the co-driver is hunkering down in his seat and bracing himself LOL
 
Rhoades lifter will get you a few inches at best as mentioned..... Been down this road too many times with normally aspirated and boost applications. Hydroboost will give you the pedal you are looking for. There is always a trade off with anything but it is a good option.

I personally like to see a minumum of 15" for vacuum boosters but mileage and opinions will vary....

JW
 
I took out the backseat, so no more backseat-drivers for me. Everybody wants a ride and then who gets to clean up afterwards. Sorry........, no seat/no seatbelts.

Yeah, so; in my car,tricks are in first-gear, mostly. Or maybe first-over now and then if I find a place with adequate space. Peak torque in first is about 30 mph, and with gearsplitting, I hit it again at ~40, and again at ~50 in second, and again at ~63 in 2-od....... lol; I love that lil GVOD. It's like having a CVT without a belt/chain, and, they say;with a 1200hp limit....... Looks like I got plenty of headroom.
So what I lack in finesse,I can often make up for in shear torque. I love that cam.
 
So I feel like I have good handle on the vacuum topic now. Good discussion, I learned a lot.
Can you guys running this cam or one with similar lift/duration comment on what your valve reliefs look like, if they aren't stock, especially for a 340 but I imagine 318 or 360 would be close if zero deck. I'll find out if I have stock pistons out of the hole or something else as soon as I get the car out of hibernation. If I can use this cam without having to get into the bottom end that would be perfect, but I know I'll have to do some measuring once I have the heads off. My gut tells me this thing as a fairly recent rebuild because it doesn't smoke at all and it's been painted, but I'm hoping it is still uncut.

AJ/FormS said:
Compares to my Hughes at;
276/286@.008/110+4/61overlap and 230/237@.050, w lifts of .549/.571
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duster360 said:
That's the cam I have in my 340. Has about 11" of vacuum at idle. Here is a sound clip at 900 rpm idle. But mine has manual brakes.
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mopowers said:
I've got a similar grind in my 9.6:1 340 and it pulls about 11" in gear at 750 rpm.
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autoxcuda said:
Yes. But similar to the 275HL in specs.
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gzig5 said:
So I feel like I have good handle on the vacuum topic now. Good discussion, I learned a lot.
Can you guys running this cam or one with similar lift/duration comment on what your valve reliefs look like, if they aren't stock, especially for a 340 but I imagine 318 or 360 would be close if zero deck. I'll find out if I have stock pistons out of the hole or something else as soon as I get the car out of hibernation. If I can use this cam without having to get into the bottom end that would be perfect, but I know I'll have to do some measuring once I have the heads off. My gut tells me this thing as a fairly recent rebuild because it doesn't smoke at all and it's been painted, but I'm hoping it is still uncut.
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I've just got Speed pro L2316 pistons about .015" out of the hole. With 1.6 rockers, the theoretical lift ends up at .561" (obviously actual lift is lower). When I checked piston to valve clearance, it was around .100" if I remember correctly. Plenty of room.
 
I have KB107s at plus .005 above deck. Uncut Eddies on .039 FelPros. I no longer remember the PV clearances (that was 2004) . To be safe I set my lifter preload to .020. She can't pump up to what she ain't got
She has reved to 8000 without a hitch (missed shift), and regularly goes 7000/7200.

If your engine is out and the heads are still on it, then it is easy to determine a ball-park Scr. Jut roll the engine over to get any convenient cylinder with the plug-hole as the highpoint. Then set the piston of that cylinder, to TDC compression.
Then measure out exactly 100cc of single grade oil, like 30 weight into a graduated beaker. Using no funnel, pour about 60cc in that cylinder, then slow down but continue until the oil comes close to the bottom of the plug hole. Then, very gently rotate the crank in either direction, until the fluid comes highest. Then continue filling to the bottom of the plughole, but not up the threads.
Now set your beaker down and let it sit for 10 minutes or so, until the oil has run down the sides and back into the liquid. Then take a reading and determine how much is missing.
If you think that you cannot pour the oil in there without a funnel, well then use a small funnel, and when you are done, drain the funnel back into the beaker.
If you spill some, you will have to start over using a different hole. It is better to use a funnel than spill,lol.
This missing amount will correlate pretty closely to the actual combustion chamber volume. Write it down. Using that number and a bit of math, then Bingo! ,you have the Scr of that cylinder.
Once you know that Scr number,you can figure out pretty closely how that engine is gonna run from stall to about 3200 rpm with almost any street cam. And once you know that, then you can decide on the rest of the combo.
 
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gzig5 said:
Can you guys running this cam or one with similar lift/duration comment on what your valve reliefs look like, if they aren't stock, especially for a 340 but I imagine 318 or 360 would be close if zero deck.
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Based on a recent thread, the stocker had valve reliefs right at .200" and the L2316F's are about .230". KB's are a tad deeper IIRC.

Your pistons could be lower compression 340 types; if they have 4 valve reliefs, then they are. If you happened to have a probe camera or viewer, it would be easy to see with the heads on.

FWIW: Most stock 318 types are .070 to over .100 below deck, expect for the first few years of factory 318 pistons; stock 360 are around .100 below deck.

FWIW #2: A slower ramp 268 cam with KB340 pistons at zero-deck and 1.6 ratio rockers had something like .150" clearance; it was so much I did not measure closely. But the slow ramps would make the clearance larger than your XE/HL cam.

You can do the clearance check with the heads on. Rn the engine the get the lifters pumped up. Turn off and swap in some very light springs on the #1 cylinder; the lifters ought to not pump up while you do this. Then rotate to about 20-30 degrees before top dead center on the overlap (exhaust closing). Push down the valves and measure how much further they move beyond the opening of the cam; that is the valve clearance at that crank angle. Do this every 5 degrees until you get to about 20 degrees after TDC and you will have found the minimum valve clearances.
 
Bighead440 said:
I used one in a 360 crate short block from MP and OOTB Eddy RPM heads and it was extremely streetable in a 72 Duster with a 2500 stall converter and 3.23 gears. HIGHLY recommended.
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Glad you chimed in. Man, I have tried to recommend that cam in SO many places where I KNOW it would fit right in and as always, get totally run over with "better and more modern" grinds.......enough to make me just give up around here. lol
 
Bighead440 said:
I used one in a 360 crate short block from MP and OOTB Eddy RPM heads and it was extremely streetable in a 72 Duster with a 2500 stall converter and 3.23 gears. HIGHLY recommended.
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That's awesome. I was afraid it might be a bit too much but I couldn't pass up the cam and lifter kit for $81 on Amazon. :thumbsup: As long as I don't have piston interference, I'll be golden.
 
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RustyRatRod said:
Glad you chimed in. Man, I have tried to recommend that cam in SO many places where I KNOW it would fit right in and as always, get totally run over with "better and more modern" grinds.......enough to make me just give up around here. lol[/QUOTE

What's that DCR?? HOW much quench?? LOL
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gzig5 said:
That's awesome. I was afraid it might be a bit too much but I couldn't pass up the cam and lifter kit for $81 on Amazon. :thumbsup: As long as I don't have piston interference, I'll be golden.
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It has WAY less duration to worry about piston to valve.
 
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