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]

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]

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???

[cableguy0]

The noise your hearing could also be pinging. Is it a sharp rattling noise? Does it go away when you let out of the throttle? Where is your timing set at? Did you set total timing and curve the distributor?

[knightowl73]

Originally Posted by cableguy0

The noise your hearing could also be pinging. Is it a sharp rattling noise? Does it go away when you let out of the throttle? Where is your timing set at? Did you set total timing and curve the distributor?

yes it goes away if i let off the throttle a bit and i thought it could be that too awhile ago, but dismissed it once i "knew" it was the lifters. timing is set at 6 or 8 degress. i think 6 because at 8 it was definately pinging alot, but the supercoil did take care of that pretty much. i never put a curve kit in the dizzy cus everyone keeps tellin me stay away, but should i really be trying the curve kit first? it runs too good for me to think t is anything major, just keep getting mixed theories of whats going on.

[cableguy0]

Theres no reason it should be pinging at 8 degrees advanced much less 6. Your going to need to verify that your timing marks are proper and the balancer hasnt slipped. have you checked the fuel filters? The quick thing to do to find out if its pinging is to just try higher octane fuel. Are you sure the heads on it now arent 305 heads? If the engine is unknown to you its hard to give you an accurate diagnosis without knowing more. Compression could be too high causing the pinging. Try 93 octane fuel and go from there. if the noise goes away you found your problem.

[knightowl73]

Originally Posted by cableguy0

Theres no reason it should be pinging at 8 degrees advanced much less 6. Your going to need to verify that your timing marks are proper and the balancer hasnt slipped. have you checked the fuel filters? The quick thing to do to find out if its pinging is to just try higher octane fuel. Are you sure the heads on it now arent 305 heads? If the engine is unknown to you its hard to give you an accurate diagnosis without knowing more. Compression could be too high causing the pinging. Try 93 octane fuel and go from there. if the noise goes away you found your problem.

ive ran the numbers, and they are 350 heads for sure. higher octane gas only makes it run better, but noise is still there. timing marks are dead on, have brought it to tdc on compression stroke and they line up perfectly. brand new fuel pump and filter. tho im running a ford 2bbl with a adapter on top of a eddybrock intake, it works way better than the 3 quadrajets ive tried. the carb that matches my intake still needs a rebuld, but im also missing some linkage off it, so the ford carb has been doing a impressive job and i didnt think right now is the time to screw with that till i rid of the noise. no matter what carb , the noise has remained.

so im back to asking should i try the advance curve kit? how do i know which springs to use, or is it trial and error on this? and timing is set right at 8 with a vac gauge to confirm its dead on.
that and some z28 valve springs , which do i try first?

[cableguy0]

What are the numbers on the heads? Your going to shoot for 36 degrees total timing @3k rpm with vac advanced disconnected.Valve float isnt noisey it will just feel like a bog and is unlikely to occur until around 5k rpm even with stock springs. Pull your valve covers and see if you have any loose rockers. The absolute most common reason for loose rockers or lifter noise at this point is a wiped out cam. If the cam wasnt properly broke in or if oil with the proper amount of zinc hasnt been used theres a good chance you have a cam problem.

[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.

[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.

[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]

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!