Low vacuum question

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fishy68

fishy68

Tyr Fryr's Inc.
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Got my Cuda together and fired up and can't seem to get to idle as good as I think it should. About 700 RPM in gear is it so I put a vacuum gauge on it and the best I can get it to pull is 8-9 inches of vacuum. Don't matter if it's in gear or neutral. I rebuilt the carb. cause it's been setting for 3 yrs. hoping to find a problem there but it really wasn't bad and didn't help much at all. Here's the rundown on the combo.

360+.030 Approx. 10.2 to 1 compression according to what KB says the pistons will be with the 68 cc heads but we didn't measure anything so that isn't verified. Note: the heads have also been shaved .020.

X heads with 5 angle valve job and minor porting and bowl relief. 2.02/1.60 Valves.

Cam is 226 deg.@ .050, 288 adv. dur., .450 lift, 72 deg. overlap, 108 LS.

Intake is an old Edelbrock Torker. Carb. is a 750 vac. sec. Holley.

Hooker 1-5/8 headers.

Mallory distributor and coil. Intial timing is 18 degrees. Total is 36 degrees.

I didn't think this cam should be so big that it wouldn't have any vacuum but what do you guys think? I degreed it in when I installed it and it came out about 1 degree advanced.
 
For 72* of overlap that vacuum is very close to what it should be for the centerline of that cam, and you said that it was 1* advanced so this makes it worse. If you cut 10-12* of overlap out which will make the cam be ground on a 112 centerline then the vacum will come back. With that cam and the valve size the bottom end power and torque will suffer some and the vacuum shows it.



BJR Racing
 
Just out of curiousity, where did you find that cam? It has some kind of odd specs there.
 
BJR and Moper Thanks for the input. I was hoping you guys would chime in cause I've seen some of your posts and you both seem to know alot about cam math which I don't.

moper said:
Just out of curiousity, where did you find that cam? It has some kind of odd specs there.
Click to expand...

Moper it is a PBM Power cam (which I'm told is ground by Wolverine) that came with the engine kit I bought at my local NAPA. I got a great deal on the kit and could upgrade most things but not the cam. Probably should've put it on e-bay and got a better one but what's done is done. Now I'm out of work and stuck with it for now.

Based on the rest of the engine combo I mentioned above what would you guys recommend for a good street/strip cam when I do change. The rest of my combo is as follows.

727 with 2500 converter. 8-3/4 has 4.10 now but will be changed to 3.55 gear with 28" tire.

68 Cuda fastback not exactly sure on weight, maybe around 3400??

I also plan on changing the intake when I change the cam. Going to either an Air Gap or M1, still looking into that one yet.

Thanks gentlemen for your time.
 
With a 3.55 ratio and tall tires?
I know I would do a (In example a) Comp cams 280* and the air-gap
 
There's the other one I was hoping to here something from. The reason I figured the 3.55's was my Dakota has them and in Drive (not OD) it turns 2500 plus at 60 mph with 28" tires. I'm plan on driving this Cuda quite a bit on cruises and am hoping to get at least a little bit of fuel economy from it. If I keep the 4.10's it has now it's turning 3100 plus at 60 mph and my guess is fuel economy is gonna suck. Pardon the Pun. 3.90's wouldn't do much for lowering the rpm's so I didn't think I had much other option. I haven't bought the new back tires yet and was tossing around 27's or 28's. Haven't figured up the RPM diff. between them yet. What are your thought's Rumble?
 
fishy68,
Wolverine makes a cam that is 107/117 centerlines and has a 112 lsa it is 222/232 @ .050 and it has a .447/.450 lift and the part # is WG1007. This cam will give you much better dirveability and pull the tires alot better.


BJR Racing
 
I have to be honest, I've only used one Wolverine Blue Racer cam in all my builds. It was customer supplied, and while it was mild, it seemed a little soft for the package it went into. (360 '71 B body with 3.23 gears) As for other choices, staying hydraulic, I'd go with one of these:
1. Crane http://cranecams.com/?show=browsePa...-360 C.I.&partNumber=693801&partType=camshaft
2. Comp XE274H
3. Comp XE275HL

I think the Crane would give the best overall performance. If you're trying to play with gearing and tires, i would run a street gear, 3.55s, and run the tallest tires you can fit. If you're going to be racing, get some sticky tires on plain wheels, and get them in a small diameter. Your effective ratio will drop to about 4.0 when you run 26" tires with 3.55s, as opposed to 28" tires.

fishy68 said:
Thanks gentlemen for your time.
Click to expand...

There's really no reason for name calling..sheesh.
 
Wolverine is Crane cams it's just on the other end of the building, it use to be Cam Dynamics but still belonged to Crane regaurdless what name you put to it.


BJR Racing
 
fishy. That could be a little tuff trying to balance power with mileage. I think you'll do OK with that. The thing is stall converter speed vs. driving RPM @ set speed.
I don't know what your stall is, but, heres why.
If your driving under the stall or where theres alot of slipage, the tranny heats up and could cause problems and possible failure.
I will have to step back here on this one a bit due to lack of automatic trans exper. and not knowing your stall. Mostly a 4spd guy.
I think it's doable and close enuff in order to be able. The car is lighter than a truck with makes it easier on the trans. and the rest of the build doesn't look like a stressful one.
Reguardless, add a tranny cooler and deep pan from MoPar and run with 27's.
Mopers and BJR's cam choices are really nice if a change comes your way.
 
Actually I'm not necesarely set on Wolverine cams. The only reason I'm running it is because it was all I could get with the engine kit. It's the first Wolverine I've ran. The first Crane you mentioned Moper is actually the one I was wanting but wasn't able to get. I've ran Cranes before and liked them but since there was no option with the kit I had no choice. For now since I'm unemployed I'm going to have to run this one until finances allow different. I know the basics about cams but since I don't know the effect cam timing has on things that well I thought maybe there was something else wrong I was missing as to why the vacuum was so low. Sounds like it is just normal for this cam. Good thing I don't have power brakes.

Rumble I know what you mean about balancing power and economy. I'm just looking to break the 12 -13 mpg. mark. The way it sounds now I'm not so sure it will even come close. I may not know cams but I am a trans. guy. I can do a 727 in my sleep. Running a 166K converter which with my combo should stall at about 2200-2300 so even with 3.55's I should be safe at cruising speeds below 50 mph and I'm running a good size cooler.

Good idea on the shorter/sticky tires for the track to bring down the effective gear also.

Thanks again guys.
 
Seeing as you cut the heads, I would investigate lifter preload if you are using non adjustable rockers. You may have to use some shim stock to get about.020" lifter preload. If this is incorrect, vacuum and low end performance will suffer.
 
sox and martin said:
Seeing as you cut the heads, I would investigate lifter preload if you are using non adjustable rockers. You may have to use some shim stock to get about.020" lifter preload. If this is incorrect, vacuum and low end performance will suffer.
Click to expand...
I am eventually going to replace the rocker arms with adjustable ones but correct me if I'm wrong right now I'd think that shouldn't be that much of a concern even though the heads were cut because the new head gaskets (Fel-pros) are .042 thick whereas the stock ones were steel shim type. I don't know the exact thickness of a stock type but I'm sure it was alot less than the Fel-pros so I'd think the .020 we shaved off the heads would be nearly compensated for by the new thicker gaskets.
 
You do make a point, but has the block been decked? I would check the lifter preload just to be sure. I had this happen to me years back... it was frustrating.
 
I concur with what the others have said..too much overlap. 72* is a bunch. It kills vacuum real fast. Yes, those Comp XE cams are good ones. That XE275HL would be wonderful in that 360 with good compression. Good luck, Terry.
 
sox and martin said:
You do make a point, but has the block been decked? I would check the lifter preload just to be sure. I had this happen to me years back... it was frustrating.
Click to expand...
I didn't deck the block but who knows what was done before me. Good point. As soon as I can I'm going to get a set of adjustable rocker arms. Thanks.
 
headsbikesmopars said:
I concur with what the others have said..too much overlap. 72* is a bunch. It kills vacuum real fast. Yes, those Comp XE cams are good ones. That XE275HL would be wonderful in that 360 with good compression. Good luck, Terry.
Click to expand...
Yeah just for grins I looked up every performance cam from every major manufacturer I could find and compared specs just to see how this one I have compared. I don't know what the deal is with this cam I got is but it has more overlap than everything I found under 240 degrees at .050 and .500 lift and its only 226 degrees at .050 and .450 lift. Really strange grind. Oh well at least I've learned something about cams through this deal.
 
I dont believe 360s ever had any steel shim. The originals are composite, and were about .035" thick if I recall right. That cam grind may be a circle track grind, like for a "claimer" or stock type engine..I had a rebuilt 440 I bought that had one similar to that grind.
 
fishy68,
The reason for the overlap being so large is the fact that the cam has a 108 lsa and is likely to be advanced 4* so the intake centerline is 104 and the exhaust is 112 with most centerlines this low the overlap increases, the further back you go the less the overlap would be on centerlines. For example a cam with 112 lsa and 112 intake centerline would have 60* of overlap. What the overlap does is give better driveability the less it is and the higher it is the racer the cam becomes and the more mods to the engine has to be done.


BJR Racing
 
moper said:
I dont believe 360s ever had any steel shim. The originals are composite, and were about .035" thick if I recall right. That cam grind may be a circle track grind, like for a "claimer" or stock type engine..I had a rebuilt 440 I bought that had one similar to that grind.
Click to expand...
Ok on the head gaskets. I thought all had steel shim types but it's been yrs. since I tore apart a stock 360 and I didn't remember. So if that's the case the Fel-pro probably isn't much thicker than the stock gasket and the lifter preload may be a little tight due to the shaved heads so Sox and Martin may have been right about that. I'll have to check into that.

Thanks Moper and BJR for the cam lesson. I think I'm starting to understand how they work now. I wish I would have known a little more about them when I put this thing together but oh well. I opened it up in the alley the other day and it actually didn't run too bad. Not a terrific 60 footer but ater the 60 foot mark it came on hard. And that is with no tuning on the carb. and a old style Torker intake which I plan on changing to a better RPM air gap which should help the 60 foot. Thanks again guys.
 
fishy68,
The overlap is partly to blame for the loss of bottom end response, this is why they the cam manufactures tell you to run a steep gear to make the cams like this work along with a loose converter. This way it over comes the lag or sag in response quicker and it's not as noticeable, a good loose converter would flash right by the trouble spot and have you moving quickly. So now you see why I said that the more over lap you have the racer that car and engine becomes.


BJR Racing
 
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