Question, I read on here awhile back about how press in studs can back out if a cam has too much lift. Well I would assume you mean my cam, .476/.496. It looks as if one of the studs is higher then the others (on my exhaust side).
a) How do I know if my stud is pulling out?
b) Would you think it is?
c) Sportsman IIs....... angled or straight plug.....

Matt

 

It's not the amount of llift but the amount of spring pressure. High lift cams usually need stronger springs so the 2 work together.

a) Valve lash would constantlt get loose.
b) I doubt it with that cam. What springs are you using?
c) Straight plugs are the easiest to use. Angled plugs point the plug tip towards the incoming air/fuel. They also angle the plug and plug wire towards exhaust tubes on some headers. Clearance is usually tight.

 

Steve, Thanks for the quick reply!

I'm useing stock springs, do you think it'd be a better idea to upgrade my springs? I am still flirting with the idea of new heads. How much hp can my shortblock take?

Matt

 

double post

 

WOW!! You're running almost .500" lift with stock springs? I don't know the bind height of the stock springs but that has to be close, if not over. I would definately look into some comp cam springs. You could have some serious problems if one of those springs break. Maybe someone with more expieriance with the stock springs can confirm/deny what I've posted.

I saw that you got a GM crate motor, did the cam come with it or did you swap that out? If it came with that cam, the engine was built to work with that cam and you shouldn't have a problem.

 

Nope, not the origional cam. Its a crane cam. I'm in college so the car has been sitting awhile it might have been driven 5 miles tops with the cam so I don't think anything happened yet. Yeah the guy who was giving me advice at the time said that this is the biggest cam you can use with stock springs. He turned out to be full of just about everything he said so I stopped associating with him.

Would you guys stick with my cast iron stock heads with those springs and such or would you just go out and get aftermarket heads?
If I go aftermarket and get a set up dyno'd at 420 hp by comp cams would my short block hold together?
Or should I just stop wasteing my time with that shortblock, save up and do an engine the right way? Meanwhile taking these heads off and putting some respectable springs on them.

Tell me what you think. Also does anyone know any REALLY good books that they would recommend on the topic? Thanks

 

It appears that you have a crane HMV278 cam.
the specs are 278/290 .467/.494 114 LSA
This is a good moderate street performance cam.

Your exhaust rocker stud could be moving as this is about as big
a cam as pressed in studs can handle.

I don't know exactly which "Crate motor" you have.
Some are low performance with 76 cc heads and dished piston
and 8.5 or less compression like the base replacement Good wrench 350 @205 hp. Some are 285 hp and 300 hp
These have better 64 cc heads and higher (9:1 compression)
None of these have any blueprinting.

The 64 cc late heads have potential if you are willing to but some work into them (porting etc) #217, 083 etc.

You'd want the compression ratio close to 10:1 for best street performance so the 8.5 cr motor will be a little lacking.
A set of 58cc heads would fix that up.

The stock valve springs have enough travel for the cam u have but not really enough pressure to control the valvetrain at high rpm. I'd keep it under 5300 rpm till I could replace the springs.
There are many brands of stock diameter high performace springs you could replace economically.
A new set of assembled aftermarket heads with 64 cc chambers
may be the better route in the long run as opposed to milling porting, repairing studs and guideplates etc. Just sell off your stock heads and get real high performance heads.

You could also rebuild that motor +.030" with high performance flat top pistons and proper block decking to have a real performance "0 decked block" shortblock as a base.

 

lingenfelters book on how to build small chevys is excelent. Start there That will give you a good understanding. I would be really careful with those springs. If it were me I would get a set of trick flows 23* heads and be done with it. The short block should be ok 420 is alot but I think it would hold up for awhile untill you get enough money to get a forged bottom end. Are you keeping the fuel injection or going carbed?

 

I have had pull-out studs that did their thing with considerably less lift than that.

Stock springs (like any springs) do not have a "linear" force vs. displacement curve; that is, if you push them twice as far, you don't use twice as much force. They're definitely not a perfectly ideal "high school physics class" spring. Instead, the first part of their travel is reasonably linear, then as the travel increases, the force curve heads upward, until they reach coil bind, at which time the force goes totally non-linear.

About the farthest you should try to push stock springs and still expect any kind of longevity is around .460". I'm going to guess that with your .497" theoretical lift cam and pull-out studs and stock springs, you're also running the stock stamped sheet metal rockers. These are so inconsistent in their ratio (usually around 1.43, I've seen them sometimes as low as 1.38), and flex so much, that your actual lift as measured at the valve stem is almost certainly less than .460". If you were to make no other changes and put a set of real rockers on it, I'd bet you'd pull every stud before you went 10 miles.

If you have a stud that's visibly different from the others, it's toast.

Get the right springs!!! Either get the set from Crane that they recommend for their cam, or a set of Comp 981s, or get some from Lunati or Ultradyne for a similar cam; avoid K-Motion and GM no matter what the "specs" say or how good the price is.

Without knowing which GM motor you have it's impssible to be sure how much HP it will make before it grenades. An easier way to think of it is RPMs: a stock short block will hold together almost indefinitely if it has a high-pressure, not high-volume, oil pump (M55 with Mr G 26 spring is a good way to get that); and the RPMS do not exceed 5500. With quality rod bolts, the RPMs can go higher, around 6200 or so.

 

Thanks guys thats an amazing amount of information you gave me. I'm going to copy the link for this post and when I get a chance to go home get the engine number and head numbers and see what I have exactly. Probably be seeing this post surface either tonight or tomorrow! Again... :hail:

Matt

 

Guys,
I couldn't find the block casting numbers. When the engine is in the vehicle are they easy to see? I looked exactly where www.mortech.com told me to but i really couldn't find anything. The head numbers I got tho (333882). It says that these heads are from 74 - 80 and used on 350's and 400's. Can you tell me a little bit more about these heads and/or the motor that I have and the options I have as far as the heads?

Thanks

Matt

 

Those heads are basically crap. They were extremely common on smog 350s and 400s in the 70s. They came on both 2-barrel and 4-barrel versions of 350s; what were those, 170 HP and 180 HP, something massive like that?

If your motor is the same as an actual whole motor in stock form that would have been equipped with those heads, it probably has dished pistons and would have come with the "929" cam (194° @ .050" intake, .390"/.410" lift). This would be the universal 70s 350. When it was new they would have taken that long block and would have stuck either the 2-bbl or 4-bbl manifold on top of it and slapped it off into a vehicle, which is why there isn't much HP difference between the 2. The exhaust from manifolds to street was identical between the 2- and 4-bbl versions even.

A 350 block is pretty much a 350 block, as far as being a block goes. If it's not a roller block (which that one won't be) , there's nothing else special about it either good or bad. I wouldn't get too excited about finding the casting number. I'd guess it's most likely a 3970014.

What exactly would you like to do?

 

Basically I would like to build it right, the first time. (well the second) It has the cam that I described, a 3,000 stall converter, and a Holley 650 dp. I'm planning on getting SFC's and a new rear with 3.73's this fall when coop starts as well as some new tires. Since those heads are junk i'd also like to get a set of new heads for it. I'm planning on putting about 1,000 more bucks into the engine. Since the heads are boat anchors, my plan would be to buy a nice set of Sportsman II heads with 64 cc combustion chambers, Steel Roller Rocker Arms, and hardened pushrods. I just purchased the lingenfelter book that was mentioned above because I wish I had a better understanding of how to really build a solid engine. I know my shortblock leaves something to be desired, but do you think this is the best combo for me at this time? I might also be intrested in getting a nice cam, possibly a Comp Cam Extreme Energy 284H. Let me know your opinions.

Matt

 

OK...

With the dished pistons that are in it, you have about 8½:1 CR right now. You're going to end up with about 8.8-8.9:1 CR with 64cc heads. This is really low for a performance motor. Without tearing it down and putting flat-tops in it, it would be wise not to go too far on things that the CR will affect the choice of.

I would suggest scaling the rest of the motor back a little from there, especially the cam. The one you have is already really more than optimum for such a low compression engine. That XE284 is definitely too much for that compression. I'd suggest a XE268 at most, and probably less than that.

I'm not going to guess at whether those heads would be a good thing for the short block. But, for a whole lot less money, you might want to look at the Vortecs; the heads and intake together will be less than $700. They are widely known to be a nearly ideal match with the XE268 cam. But if yo u do get those heads, get rid of the valve sorings, and put the ones that Comp will recommend on them, along with the retainers and keepers.

A 650 DP carb is a great choice for a near-stock motor, probably barely enough for this, certainly not for anything with a XE284H in it.

SFCs are good, 3000 stall is good, you will probably need some LCA lowering brackets too. You will definitely have some tire-spin and wheel-hop problems with that much power.

There are a bunch of people running well into the 12s with stock type short blocks and Vortec heads and that cam or similar, and otherwise surprisingly mild setups.

Good luck!!

 

Another thing to consider

The valve guide also limits the amount of lift a valve can have. On higher lift cams the valve spring retainer can actually come down and hit on the top of the valve guide. Since the valve can't be opened any more and the cam is still trying to push the pushrod up a number of things can happen.

Pushrods can bend or break, rockers can break, rocker studs can get pulled out, the top of the valve guides can break.

When building a set of heads for a higher lift cam, the tops of the valve guides should be machined down. At the same time they're usually cut for Positive Stop Teflon valve seals.

 

I'll second the recomendation on the Vortecs.

These are good street heads.

Here's some food for thought on an alternative
that will get you the compression ratio and the headflow (horsepower) you're looking for. Build up a set of 416 or 081 casting 305 heads with 1.94's and 1.60
valves, high performance springs and screw in studs.
Port the living **** out of them. then have them shaved a little to true the decks up and finish to 56 cc's. David Vizard's advice on porting hi performance heads is all relevent to the 416 castings too.
I just finished flowtesting a set (my second set) I ported and the flow is right there with my 2.02x1.60 Vortecs I'm working on. (2nd set.)

I got 238cfm @28 at high lift on the intake and 190 on the exhaust. I will admit these are not lightly ported but...
These heads will make power if ya don't mind porting them.
At 56cc's your new compression raio will be 10.00:1 if you re-install the 305 heads with .015"shim head gaskets. Your piston deck height is likley right around .045" down in the bores.
This is the type of gasket that comes on factory assembled motors.
I expect 420+ hp out of mine. (52cc,,,, 12.5:1 cr)

Although not as high tech as a vortec headed flat top motor,
going with the ported 305 heads on your dished pistoned
goodwrench motor will give the results you're looking for.
These heads are very common in the wreckers.

 

Hey guys, finally started my work on the engine. I got an XE274 cam and 67cc World S/R heads.. I got the heads milled to 64cc which hopefully will give me between 9.1-9.5. The cam might be a little big for the compression, but I'm saving up for a zz4 shortblock.

My question is, since it had been running so rich the pistons have a good amount of carbon built up on them. How do I go about cleaning that off?

 

A cheap way out of installing screw in studs is to use a Mr. Gasket pin kit for the studs. Basically, you make sure the stud is pressed all of the way down. Prefferably by using a drill press, but it can be done on the car, you drill the boss and the stud(easier than you think) and tap in the roll pin with a hammer. I've never had one of these fail and it beats the crap out of the costs of screw-ins.

 

I wouldn't worry about the carbon.... water-blast the motor after you get it running.

That cam should be OK with those heads. Make sure you use good springs; those cams are real demanding on them.

 

as always, you are the man. Thank you for your help. I'll post when I get this pig running!!! Desktop dyno says 365 horses.... ... almost 400ft lbs of torque. They may be off, but I don't care!!!

Matt