fattest cam in a 340?

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Hyperballsmcgee

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I've got a '73 340 that is, to the best of my knowledge, stock internals except the cam. it's got an eddy 4 barrel, aluminum intake, and eddy valve covers, but the cam was not installed correctly, and you can't time the motor with a light. I also don't know the specs of the cam, so I've made the decision to swap in a new bump stick.

my question here is what is the highest lift camshaft I can safely run with a stock valve train? I want a mean LOPE, I want this thing to pound the concrete, I want to be able to jump a skateboard off these lobes.
 
also don't want to hit the top of my pistons either. I really like the cam I've got, I just want to know what's in my motor. I hate when folks ask "what cam is that?" and I have no choice but to say "I dunno..."
 
I don't know if you're being serious or not...

You say you can't time it with a light, and that the cam was installed incorrectly? How do you know it was installed incorrectly? have you degreed it? And how is it you can't time it with a light? If you can't ascertain the timing with a light, then you might have it on the wrong plug wire or it might be severely retarded.

Back on the cam, even if you don't know the specs on the cam, if you degree it, you'll know...and it may be a good cam--you won't know until you put a wheel on it though...just food for thought...also, a degree kit costs less than a new cam.


You're actually leaving out a few details...

Let's assume for just a moment that all's well with your engine; good compression, free flowing exhaust, matched induction, stall, gears, etc...a good cam for lope with such low static compression ratio from a 73 340 likely will make for a soggy bottom end. The hughes whiplash cams and the Comp thumprs are supposed to give a lopey idle and decent performance, but I can't speak with any real familiarity.
 
To put some perspective on the cam install for you, I recently assembled a '73 340 with a Lunati solid cam...dot to dot on a new timing set measured 11* retarded when we degreed the cam. Just an example that until you verify the cam timing events, you won't know if it's truly right.
 
I have not done anything to this motor other than rebuilt the carb, deleted the a/c and heat, and put headers on it. what I meant was when you try to use a timing light no matter wha you can NOT see any sort of marking on the harmonic balancer. there is a notch in it, but you can't see it with the light.
 
To tune correctly any cam,you need to fix the damn timing anyway. How about a actual manifold vacuum rated vacuum reading ,to start? You need to reference the timing marks ,for the "new cam " anyway...... fix that,as well.
 
To tune correctly any cam,you need to fix the damn timing anyway. How about a actual manifold vacuum rated vacuum reading ,to start? You need to reference the timing marks ,for the "new cam " anyway...... fix that,as well.

x2 get yourself a timing tape find top dead center and start from there
 
Besides the motor details, is it an auto or stick? If auto, what converter? If you put a big lopey cam in and dont have a 3500-4000 converter its going to be a dog. Decent gears in rear will help a bunch as well. I would set your engine to top dead center on #1(buy a piston stop to do this properly), put some proper timing tape on your balancer. Also while there check your at #1 on dizzy and that the plugwires are in correct order. See if you can time it after this. Whats your plan for new bumpstick, doing it in car or pull motor?
As far as lift goes, pistons with valve relief can go pretty big, bigger then what I'm sure you'd ever consider running for a cam. I have .643 lift on my stroker with valve relieved pistons, and could have gone with more lift. Stock 1973 340 have valve reliefs? I couldnt say for sure on that one.
Good luck with figuring it all out.
 
One of the big issues with slapping a large cam in a stock 340 (other than turning it into a dog, because parts don't match up to the build), is Retainer to Guide clearance.

Around .510 - .519 lift your valve spring retainers will probably hit the stock guides & shred the valve seals. I've measured the clearance on several stock 340's and it was always in the .510-519 range max.

Any more lift beyond .500ish (give or take, varies from engine to engine) requires the guides to be cut/machined down and the use of Positive Fit Valve Seals.

I've had 2 340's and 1 318 (with J heads on it) where I could fit a Lunati .494/513 cam in, without having to machine the guides down for clearance. But that was unusual.
 
you can NOT see any sort of marking on the harmonic balancer. there is a notch in it, but you can't see it with the light.

Use a colored pencil or permanent marker and highlight the line with it. I find silver metal marking pencils work great. If the cam is large, you'll need timing tape or a dial back timing light and I second the use of a vacuum gauge as well.

I also agree with degreeing the cam as a mandatory step.
 
Like dustoff 440 said. you need to mark the balancer. Maybe it spun. Not sure, but if it's good, (balancer), and it's that far off, the thing wouldn't run. You need to find TDC first, then go from there. Read and heed, there are some very sharp peeps here, listen to them!
 
I want to be able to jump a skateboard off these lobes.

First, lets drop the 12 year old school boy routine. Statements like this only point to your immaturity and inexperience, so drop them.

Physical lobe size has zero to do with making an engine lope. It is how the air is ingested into and expelled out of the engine that does that and lobe design is what accomplishes that.

You can take a stone stock 340 cam, send it out and have it reground to a lesser lift than stock, change the duration and valve events around and have a cam that will sound like a pro stocker.

You've been given great advice so far. In general, cam lift limitations for stock heads is around .500 give or take. This is something that you really need to measure if you are going to push the envelope on stock heads with a large cam. Retainer to guide clearance is critical. If you simply stab a cam in and fire the engine off without checking, the results could be disastrous.

That .500 lift mark is not only because of the retainer to guide clearance. .500 lift or maybe a little more.......perhaps up to .550 is just about all the stock head is capable of flowing due to stock port restrictions, so anything more in cam size will be a waste.

What I would recommend would be the Comp Thumpr cam. The smallest one. You can probably do a blind man stab with that and get lucky and it will sound good. Might not pull a greasy string outta a cat's *** but it'll sound good.
 
Read the thread carefully in this link. It will show you how to accurately locate your true top dead center and timing marks using a piston stop and timing tape. It helped me a ton!
I also discovered that the vacuum advance housing on the side of my distributor had come loose right before it went into winter storage so that was flopping around and changing the timing all over the place!
Runs a helluva lot better now.

http://www.forabodiesonly.com/mopar/showthread.php?t=265983&highlight=timing+tape+piston+stop
 
Search hillbilly timing tape.

Find actual TDC, and mark away.

A 108LSA 284/484 cam will likely fit. Install it at 102-104. Plenty of chop.
 
I know you guys hate these cams, but if he is going for sound... thumpr or whiplash. Lol
 
can you see the timing mark on the damper with the timing light?
 
Rob & Rob are right. That Purple Shaft, or the Smallest Thumper will do it. Comp cams has online video clips of sound, if I recall correctly. Or use the "search" features here. Plenty of Purple shaft ,and 1 or 2 Thumper videos here.
 
I think I was misunderstood. I have a mark, as it was highlighted with orange paint and still couldn't be seen by myself or another member here with the timing light.

honestly, I like the cam I have, It just isnt degreed correctly and I want to know the specs. I just figured starting all over with a new cam would be easier.

and RustyRatRod, I've read a LOT of your posts and you clearly have a lot of mechanical knowledge and a great way of explaining things, but that comment, in my opinion, was uncalled for. I didn't join this site because I know everything and don't need anyone's advice, I joined it because I'm an 18 year old shop hand that just got into tech school who is building his first "real car". I appreciate your input, but why would you say to "drop the 12 year old schoolboy routine" and then say "pull a greasy string from a cats ***" as well as have "I like farting, it's cheap entertainment" in your bio then continue to call me immature?
I'm still learning the ropes here and all I asked was essentially how much of a lift is too much for stock valve train.

new question I guess, is there any kind of PN or serial on a cam so I can find out what I have then just degree it correctly?
 
and to the mods, so I don't get any sort of infraction or citation and get banned from this site, I've said my piece and will say no more about it. thank you.
 
I have a Comp Cams XR286HR-10 hydraulic roller cam in mine which I consider pretty "fat" (.541 lift) as you call it, however, I had my engine builder blueprint the internals to match it( springs, pushrods, pistons, etc...) If you want to hear how that thing sounds, it is in my resto forum listed in my signature link. I built my motor for performance, not sound as everyone one suggested on this forum and did a lot of research prior to the build. I ended up with a good lumpy cam as a bonus so do your research otherwise your motor will be a dog. Mine is a 340 so it is possible and she dyno'd 421hp w/408 ft lbs of torque at the flywheel.
 
Don't let some of these guys get to you. Some of them think they know more than they really do. And some are actually very knowledgeable, and willing to share their knowledge, without being condescending. I'd recommend listening to them, and blocking the rest. ;)
 
I was not being condescending. I was being truthful. I said what no one else did. What he said sounded like an inexperienced kid. If he gets out in a group of really experienced car guys and says stuff like that, he's gonna come off like a goofball. I said what I saw and then I told him how it really works. I tried to help him. Now if he will keep all this info in his mind he will understand more about it and know more how to talk about it without coming off like some tuner kid now he can sound like a real car guy. Like it or not, I helped him. If he or any of the rest of you want to dwell on me trying to be insulting or condescending, then yall are the ones fueling the fire, not me. I hate it when younguns sound like they don't know what's goin on so I try to do something about it. He's one of us. Somebody should have told him the same thing I did. It will only help in in the long run.
 
is there any kind of PN or serial on a cam so I can find out what I have then just degree it correctly

Yes, but you'll have to remove, at least, the timing cover and cam timing gear to see the end of the camshaft. There should be some numbers there...a grind number and (possibly)manufacturer...then Google that and find the cam (spec) card (hopefully)
 
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