easy way to figure cam lift on sbc in truck? worried changing heads

[knightowl73]

all i know about the motor is that its a 350 4-bolt main and it has a unknown erson cam in it. its a nice lumpity cam i know that much, makes the raggedy truck have such a cool factor as long as its running.

im switching heads this weekend on it, it has stock 350 heads on it, my buddy just upgraded heads and gave me a set of 305 heads that he had bigger valves and port n polish done to.

im replacing the lifters for the hell of it, i think they are toast and need replacing anyways since it gives lifter noise when i "launch" it too hard, but i run the *#@! outta this truck already, and this should hopefully be a real nice upgrade.

besides the higher octane fuel, what else should i be concerned about? will i need to know what cam i have, at least lift,pushrod guideplates or anything lke that? the new heads come from a motor that only had a rv cam in it, and it had almost as much nuts as this truck now. will i have to play with the timing because of the higher CR or can i just mark the distrib and stab it back in with no issues?

[LONGHAIR]

You have quite a few issues going on here. First and foremost are the 305 heads. Bigger valves are not "the answer" for these castings. Unless they were professionally reworked (and have flow numbers to back it up) there is really no benefit to using them. They will probably hurt you. The compression bump is not necessarily a good thing either. This can cause detonation problems unless the pistons are matched to them, creating the correct squish/quench area.

Replacing the lifters "because the are toast" is worse. If the lifters are indeed bad......so is the cam. It is very hard to hurt one w/o the other suffering the same damage. They wear on each other, nothing else really affects them.
If the cam is all that "lumpity", I would be sure to check the clearence of the valve springs, retainers, etc.

Timing will definately be a concern....
You can't really just "pull it out and stab it back", it's not that simple. You need a timing light to get it back in the right place. An advance curve change is probably in order too. HEI? what year? Stock?

[cableguy0]

I have to agree with everything longhair said. 305 heads are a mistake. Its likely you will end up with too much compression. 305 heads just arent capable of flowing enough air for a 350. It will come out of the hole like a rocket but will fall on its face quickly. If you do just replace lifters you HAVE to break the cam in again. I personally change them as a pair because bad lifters usually kill the cam and a cam wiping usually kills the lifters.

[knightowl73]

wow thanks for the info guys. now im completely confused of what to do. i figured this would be good upgrade based on how well his motor ran with them.

the only prob i have with my motor is the loud lifters when i get down on it. makes a horrible noise, but nothin a loud radio doesnt fix, cus despite the noise itll still smoke just about anything around my lil town. not knowing much about the motor is was goiing to build my own for it if i were to keep it, but not sure, so was trying to do the budget thing. i have 3 trucks now, so its a hard decision.

it does have hei, i had alot of trouble making it driveable , timing issues. but they cleared up alot when i put the supercoil on it and i been running the hell out the truck ever since. by now t might have a bent pushrod or valve, not sure, but it pops from time to time when im starting it and wasnt sure if its popping back thru the carb, the leaky headers, or if its the lifters cus the exhaust is so loud, its hard to tell.

im guessing 305 vortec heads are worse too, seeing the compression thing and ill have to go back with a pretty close to stock lift cam to keep from spending alot on millwork. this is what my bud is upgrading to, but with over $400 of millwork.

[PRattenbury]

If you're getting lifter noise when you rag on the engine you're probably floating the valve train. Keep your cam and your heads. Put stronger valve springs in it. Screw in studs would be a good idea, and guide plates. Then you should be able to beat on it and not float the valves.

[knightowl73]

Originally Posted by PRattenbury

If you're getting lifter noise when you rag on the engine you're probably floating the valve train. Keep your cam and your heads. Put stronger valve springs in it. Screw in studs would be a good idea, and guide plates. Then you should be able to beat on it and not float the valves.

are you serious? i thought thats why the lifters were toast? so what valve springs, like some z28 ones should work? cant i do this in the truck by putting ar in the cylinder???

[knightowl73]

im guessing as far as cheap goes, id have to replace the cam, lifters, and maybe heads in the truck. and without pulling the timiing cover first id have no clue of the cam right? id like to get another of whatever is in there. it has 350 centerbolt heads on the motor now, how do i check for a bent valve with the motor in the truck? i shouldnt have to pull them if this is not an issue. then hopefully this can be as simple as cam and lifter change and checking for bent pushrods and im back on the road.

i got 3 trucks, but this is the only one street legal and running. so i dont really want any downtime.

[knightowl73]

4.10 rear in this truck, with 31x10.50's on it, im sure i hit 5 grand daily on the highway manually shifting it. but damn now im back to a cam problem. ill pull the numbers later, i cant find where i had wrote them down at, but i looked them up on mortec.com back when it was up and it said they were 350 swirlports from a truck. does have the newer intake bolt pattern too. the heads that were given to me have the same pattern, so i thought i was doing good for lil or no money. seems like i need to try a few things, but after it all i think you guys are spelling out its just plainly the cam itself if it isnt springs or timing. i dont know with my timing light how to check like you are saying. ill have to get one that has the knob i think. but after that its most likely the cam and if so i need to pull it and have another to go back in the same day pretty much.

[cableguy0]

Theres a bunch of stuff it could be. Its really hard to diagnose over the computer without knowing anything about the engine. Can you post a video of the truck making the noise? Yes you need an advance timing light to set total timing. You can also get a timing tape and put it on the balancer instead of buying a new light.Do you know if the engine has flat tops or dish pistons?

[knightowl73]

ok id post a video if i was that advanced in doing that sorta stuff. ive had the tape come off before on previous vehicles, if one of my buddies dont have one ill just go buy one. still got projects it would come in handy on im sure. i really have no clue as to what pistons are in there and no way to really check this out without pulling heads besides look thru the spark plug hole right?? did that and i couldnt see nothing, but i assume flat tops. i stuck a screwdriver in there to make sure of tdc and it felt flat across

[cableguy0]

if the engine was on a stand you could see inside the spark plug hole and get a good look but in the truck its gonna be hard. Has this truck ever ran the way it should? Theres the possibility compression is way too high for iron heads and its pinging constantly. theres also the chance the cam is wiping out or has wiped a lobe or two. Just soo much stuff it could be. Its really hard to guess at it on here.

[knightowl73]

no ive never got the truck to run any better. ive tried lil things and some just helped a bit, thats it.. doesnt have inner fenders on it so lookin inside waasnt too hard, i just didnt see anything through the hole.

i try these few things and if that dont fix it, imma try and guess what cam it has in it somehow, and just replace it and hope its close. erson is kinda cheap on cams, and id just replace it if it wasnt such a pain to figure out what it is already. im sure id have to order the cam, and just want one for cheap thatll sound like whats in it. dont want a stock sounding cam, but dont want to spend alot of money right now either .

[jrcaprai]

you could measure the lift of the Cam by putting a magnetic Dial indicator on the head, and the tip of the dial on the tip of the rocker... then rotate the engine by hand to find the highest lift point.
other than that, take off the timing cover and write all the numbers down off the front of the Cam, and the Interweb is your Friend! =:-)

[knightowl73]

Originally Posted by jrcaprai

you could measure the lift of the Cam by putting a magnetic Dial indicator on the head, and the tip of the dial on the tip of the rocker... then rotate the engine by hand to find the highest lift point.
other than that, take off the timing cover and write all the numbers down off the front of the Cam, and the Interweb is your Friend! =:-)

ill have to find one of these magnetic dail indicators. where would i find one at? at least online so i kow what im lookn for. pulling the timing cover snt exactly easy on the truck with my jerry-rigged bracketry, so i only want to have to do that once.

[knightowl73]

anyone know of a cheaper "lumpy" cam i could get thru napa or o'reillys or something. anyone got experience with a cheaper cam they could suggest so i could just do the swap and still have a nice lumpy idle? like melling brand or something i can get from the local autoparts store rather quickly?

[PRattenbury]

You know, those 'lumpy' cams have their disadvantages, right? Your manifold vacuum will be low at idle. Your low-RPM power will be down. Those 'lumpy' cams were ground in a way that the engine doesn't really 'come alive' until 2500 or more RPM. On the street, that's not a good thing in my experience. I just put a small block together for the street in my truck and I used an Edelbrock Performer cam. Really mild, with the RPM range that's more usable at RPMs that you would normally see in street use. Just saying, 'lumpy' cams may sound cool, but they are generally dogs on the street until the RPMs get way up there. I've had my share, and learned from them.

[jrcaprai]

Originally Posted by PRattenbury

Your low-RPM power will be down. Those 'lumpy' cams were ground in a way that the engine doesn't really 'come alive' until 2500 or more RPM. On the street, that's not a good thing in my experience. I Just saying, 'lumpy' cams may sound cool, but they are generally dogs on the street until the RPMs get way up there.

My cam is pretty Snotty on the Street! 242/248 @50 .600 Lift Roller Cam.....
But I dare you to tell me this is Doggy! And does not come alive early!!!
look at my Video And Turn up the Sound!

http://www.youtube.com/watch?v=RWPfJBUI-ow

[knightowl73]

lumpy cams sell raggedy trucks.... im just kiddng. i love the sound. love it so much that i turn the radio all the way down at stop lights just to listen. and it gets so many compliments everywhere i stop. ive learned to just deal with the low rpm torque around town, can make the truck do what i want it to its all about what itll sell for in the end. down here right now if i could let someone jump in it and it do like its supposed to with no clacking or pinging, i could have taken one of them good 1500 offers like it sts and finish another one of my projects.

[knightowl73]

yeah sounds really nice man, im assuming what you are running is outta my price range. roller means higher price than a shadetree-wanna-be llke me can afford

[jrcaprai]

Not saying to go buy what I have... Just saying lumpy cams can be fine on the Street. Don't let anyone tell you it will be a Dog! I say get a Comp XE268 or XE274... I had a 383 with Stock heads and a Comp XE284 Cam and it was no slouch down low!

[joebuick]

Hey Knightowl73,, I feel for you having this prob with your truck and not being able to decide where to start. Here is where I would start. I'm not trying to be a smart a**, but can you tell if the engine is missing? If it is not missing then your camshaft is prolly OK, but here is how I would go about it. Go and buy you a dial indicator with a magnetic stand or go to a mechanic friend and borrow one. Harbor Freight has em for hardly no money, but will be cheaper than mistakenly replacing a good camshaft. Set it up on each intake rocker arm and roll the engine BY HAND one compleate revolution and log the intakes total travel. Do the same for the exhaust valves. This will either prove or disprove wheather you have a "flat" lobe on the cam. All the intakes should be within a gnats a** of each other, same for the exhausts. It will also tell you how much lift your cam has. I'm not sure what you mean by the lifters being "toast" Are these solid or hydraulic? If they are solid, they may just need adjusting. If solid lifters, Try setting them at .030 as this is a good place to start unless you know what the original Mfgr's recommendation was. If they are hydraulics, try this, If you do not have any "clips" to put on the rocker arms to kinda control the oil squirting all over,,, use some bunched up shop towels to cover the rocker arms. Remove one valve cover and start the engine ( be ready with the towels here) start at the front of engine and slowly loosen the first rocker arm till you hear it clicking, then tighten it 1/4 turn. Go down the row til you get em all. ( intakes and exhaust both) replace valve cover and go to the other side. You may have to stop and add more oil but if you lay your towels right you won't lose too much oil. What this dose is allow the hydraulic lifter to fill up to it's max potential and increase the lift of the lifter. ( old hot rod trick) Don't give up,man you'll get it.

[jrcaprai]

I was just thinking... Howards makes great Cams and are very inexpensive...

This Cam would have a Very Nice lumpy Exhaust, and comes with lifters too for $122.00

Part # CL112031 Lift: .480/.480
Adv. Duration: 288/288
Duration @ .050": 232/232
Lobe Center: 108
Broad Power Band, Works Well in Heavy Vehicles
In Stock

http://www.competitionproducts.com/H...info/CL112031/

[knightowl73]

yeah ill have to get one of them dial indicators, i dont think it is missing, and ive done the adjustment just like you said about 4x and was told that i have done it correctly and that the problem is something else. the dial should tell me what i need to know and ill have to go from there. i might mess with the advance kit after checking total timing too tommorrow once i find the correct timing gun

[knightowl73]

ok its the cam, there are 4 lobes that are off compared to all the rest according to my mechanice friend who pretty much did it the dial indicator proceedure for me. when i pulled the valve covers the real freakin loose ones were clear to tell, they were the ones that were off spec. i have also acquired a set of 350 vortec heads from him for a really fair price so i want to use them now. these are a upgrade right? can i use my current centerbolt intake or would i have to buy another one? and whats the largest lift i can run on stock vortec valve springs and rocker arms? anyone out there running a lumpy cam in a 350 with STOCK vortec heads by any chance?

[cableguy0]

The vortecs require a vortec intake as well as self aligning rocker arms. You cant run too big of a cam. Lift limit on stock vortecs is around .470 before you have to really worry about coil bind. Vortecs dont flow past .480 lift anyhow so a big lumpy cam is pointless. The comp xe268 works really well with vortec heads.