327 with Comp Cam Question.

Ok here is the engine:
1968 327
nothing very special about the engine. stock SBC fwiw
think the valve sizes are 1.94 and 1.60
Cam:
Comp Cam # 12-242-2

Gross Valve lift Intake .447 HYD Exhaust .480 HYD

Duration 268I 280 E

I installed the cam straight up. (Dot to Dot)

Now, Q1. woud stock valve springs live with this cam?
Problem 1. Engine seems hard to tune, Vac. "flutters" and is low and very hard to read.
2. thinking due to the fluttering low Vac. I assume this is why my Carbs 3x2 2G's are not responding well to Idle mixture tune.

(engine has done this with other intake and Carbs as well)

If i can think of more, i'll fill it in. Ok more, I was able to get 4 out of the 8 cold compression tested..125 to 135,
? is it possible for the valve spings to be too weak or bind and cause this issue?

Any one out there in HAMB land think they understand whats going on..or have had a simular issue and got it ironed out?

Thanks

 

Comp says NO to stock springs with that cam. In a 327 that's a mildly aggressive cam, tamer in a bigger motor. Definitely a noticeably lumpy idle.

 

So Don your saying I need a set of 16 springs? (will probably have the heads done too)

any particular part number?
does 981's sound like a good number?

Yeah..it does have a nice lope at idle

 

Most hot cams will cause engine vac readings to flutter and the carb/carbs to act up and send too much fuel at idle. The cam has built in overlap at the valves,so there goes your idle! Not to say somthing else could be going on too, check out some new springs. That alone could do it. You still should expect some idle problems due to the hot cam. N.N.

 

I like the Idle, it sounds nice.
but the tuneability or the lack of it, is what has me bugged..
is it possible that the "stock" SBC springs would allow the valves to act up? or maybe float?

 

I would use the 981-16 spring set

 

Thanks Don, I was probably trying to get away with something that was a No No.

any vendor here a Comp Cam or have springs in their parts line up?

 

does that 327 have a PCV in the back of the block?
if so where does it hook up?

 

Forget spring pressure, with 480 lift you're on the edge of coil bind, inspect really closely when you change the springs. You don't need fancy matched-name springs for something like that, it's gonna call for somewhere in the range of 100/300 lbs which is the proverbial Z28 spring. Spend the $40 and don't look back.

Good luck!

 

Well, in for a penny, in for a pound! While the heads are off, how about screw in studs? You have just about enough lift to justify that.Do ya think a stud may have pulled partially out? That'll really screw with the way it runs! Also 25 ish hp is what roller rockers are supposed to be good for. I've changed springs with the heads on and it's not all that bad. Let us know how you do!

 

Yes it has PCV and a breather on the opposite Valve cover too. for now..soon it will be breathing out my fill tube and a breather with PCV check valve in it

 

what should I be "inspecting for"?..or what dont i want to see?, in other words

 

Never thought about a stud pulling out

 

There ya go! She'll sound bueno!!

 

Have you talked to the folks at Comp Cams?

 

i would also put in screw in rocker studs or have them pinned. i had a 283 with a cam that that had 412 lift on the intake and when i pulled the valve covers the intake studs were pulled out 1/4 farther than the exhaust ones. With the lift and spring pressures the newr cams run today screw in studs are a must.

 

long time ago..but its on my list

 

Because of the coil bind question, lay a straightedge across the top of the rocker studs. If any one stud appears pulled out, even a little, like 1/16th inch, convert to screw-ins. Don't dick around with pinning them. It's like another $40 for the cheapo screw-ins, the kind that you can't use guideplates with. You'll spend all night tapping the holes but it's cheap and right.

Good luck!

 

I'll throw some chips on the table here !! Never install a cam without degreeing it !! I build 100s of engines a year and can't say I've seen a good pattern for guess work on cam degrees. If your going to rebuild the heads take em to a quality shop and ask for a blueprint job ,like valve heights,seat widths,spring heights,and spring pressures. Now if you up for the screw in studs have the thread work done on a machine to keep all of the studs in line !! Crooked out-of-line shit don't go fast and it'll tear the hell outta the valve guides !! And just cause it's gotta cam in it don't mean it has to idle at 2000 rpm, as the higher h-p engines I build will idle at 750 rpm. It's all about the blueprint deal. Of course this is just my opinion and I don't play well with others >>>>.

 

OK a mini thread hijack here-what do you think about hardened seats on a weekend car? Thanx

 

Here's the online "cam card", for future reference.

http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=86&sb=2

 

I'm running the same #cam, 327 .30 over,9.25 cr,1.94 valves,3 deuces.. in a model A comp cams tech said to run the "Z-28" springs.Idle @750..sounds great!! runs out good too!!

 

When all else fails ask the cam manufacturer.

 

thanks Chubbie.
New springs and some head work is my next step

 

Not to throw more at you, but how is the timing?

I just repalaced a broken valve spring, and in the process found my timing was retarded causing low vacuum, like 4-6 advanced the dizzy to 13 and backed it off to 10 and she ran fine...

big cams will have some movement but only about 1" or so on the needle.


My broken valve spring caused a bigger faster shake of the needle.

 

for all i know at this point it could be the springs, and studs, or a combination of both.
I need to find a good machine shop around here that will do my heads for me the way they need to be done. and thats getting harder to come by up here in the Motor(less) City..
shame

 

Randy, I use Cultice Racing in Adrian. Jerry does a good job for me. 517 263 6952. You might also talk to Howard at Dundee Truck and Trim to see who does his work, he had 2 cars in PINKS! when they ran Milan. 734 529 5934

Give me a shout, I have my cabs loaded up and want to hit the plasma cutter.

 

Manual? Automatic? What rpm do you have it idling at? Lippy

 

Lippy, his car is an auto. Not sure on the RPM.

 

Dans Right..350 TH auto..I got the Idle set around 600 to 700.