questions..head work, cam sizes...etc

[1low4x4]

So ive got a 350, flat top pistons, vortec heads with "Z-28" valve springs capable of .550 lift, a summit 1102 cam, a qjet thats had some work and longtube headers...etc.

Its in a 3/4 ton 85 2 wd with a 4L80e and 4.10 gears...

What im wanting to do is have some head work done, I called the machine shop who installed the cam bearings in my block for me. He said he stopped doing the full port and polish, but he wants to do some bowl work and square up the block as he calls it, or square up the intake, whatever. Basically taking out material around the intake gaskets. He said thats the most restrictive part on a vortec head...wants $250.

Should i do it, and

I think i want a bigger cam...i will link the summit 1102 cam in thr next post but i want a cam that i can hear...and something more performance based but without having to add a different converter.......any ideas

 

[1low4x4]

http://m.summitracing.com/parts/sum-1102

 

[Driver4r]

Porting and polishing kills low end power. It only gains in the high end. You will loose alot of your low end grunt.

Just gasket match your heads and intake and call it good. I highly doubt you turn your engine 6500+ to often....


I have vortecs (906's) on my 355. And they didn't need any port work. I just had them machined for lift. And cleaned with a new 3-angle grind. The way they are. They are RESPONSIVE at any rpm.

 

[cbrodine]

I have a .060 over 350 with Dart Iron Eagle Vortec heads, I'm using a Comp XE268H....just a thought.

 

[Driver4r]

I'm running a .030 over 355ci 10.5:1SCR with gm vortecs (906's) that were cut for lift. And the cam is a lunati 60103.

 

[1low4x4]

I know jack about cams. Assuming i left my heads stock, and my engine isnt bored, i have flat tops....what cam would make a big difference over the ****** summit 1102 cam. Something with some sound and performance but requiring no stall.

In other words what do yalls cams spund and perform like

 

[bucket]

I've got a mild Summit cam in a basic 350, I think it's the same one you have (I'm 500 miles from the spec card right now), and I love it. It's a very torquey sunofabitch and has a little lope to it also. It's in my big Impala with crappy 2.56 gears, it seems like it would be an awesome cam for use in a work truck.

Are you sure it's the cam you are unhappy with and not a lack of displacement?

 

[Driver4r]

Get a l79 cam. It's an old school grind. But I has nice sound. And nice throttle response.

 

[BigAl285]

I wouldn't pay for porting unless they are going to put it on a flow bench and do it correctly. Sounds like the machine shop is going to smooth out your bowls and unshroud your valves, it would help but isnt prolly needed on your build. Gasket match it yourself and save yourself decent money.

 

[1low4x4]

I've got a mild Summit cam in a basic 350, I think it's the same one you have (I'm 500 miles from the spec card right now), and I love it. It's a very torquey sunofabitch and has a little lope to it also. It's in my big Impala with crappy 2.56 gears, it seems like it would be an awesome cam for use in a work truck.

Are you sure it's the cam you are unhappy with and not a lack of displacement?

Well honestly i drove it today and the sumbitch aint lackin power...and has a great deep throaty sound...im actually really happy with it but i guess im always tryin to fix what aint broken

 

[Driver4r]

Well honestly i drove it today and the sumbitch aint lackin power...and has a great deep throaty sound...im actually really happy with it but i guess im always tryin to fix what aint broken

We share that problem haha. I just stuck my 355 in the monte late may. And now I'm looking at building a blown bigblock.

 

[1low4x4]

I have a .060 over 350 with Dart Iron Eagle Vortec heads, I'm using a Comp XE268H....just a thought.

I called comp today and they said I should use the cam below that one...my current cam is 204/214 duration @.050 and the one they spec'd is 212/212. But yours sounds Better and makes Better power probably. Did you have to use a stall converter?

 

[MikeB]

SBasically taking out material around the intake gaskets. He said thats the most restrictive part on a vortec head

Floating around on one of the Chevy truck forums is a great series of posts by a GM engineer who was on the Vortec head design team. He said the worst thing you can do to that head is open up the intake runners. They are designed for high velocity, cylinder-filling flow at low to medium valve lift -- up to .480" or so.

Now, if you want to port match, I'd start first on the intake manifold, and touch the heads as little as possible. But under no circumstances should you go any farther down the port than 1/8" or so.

Cam choice depends on your gearing, tire height, compression ratio, and at what RPM you want to make power. I'd say something around 212-218 intake duration would be good for your combo. But if you want a lopey idle, you'll probably need something with more duration and/or a tighter LSA. I can't tell you how many guys I've known over the years who got their lopey idle at the expense of manifold vacuum, throttle response, and gas mileage.

Below is a decent GM cam that's an alternative to using an L79 cam in an engine with less than 10:1 compression. And the good thing about GM cams, is they are not hard on the valve train, and are happy with modest spring rates.

24502476 Hydraulic Flat Tappet
This hydraulic flat tappet is used on the 300HP 350 and 330HP special performance engine. The duration at lash point in degrees (intake/exhaust) is 320/324; duration at .050" tappet lift (intake/exhaust) is 212/222 and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is .435"/.460". Valve lash is zero/zero and lobe centerline is 112.5 degrees.

On another note, generic "Z-28 springs" are typically good for around .510" lift if you factor in a .060" safety margin, and if they are properly installed.

 

[Joe383]

I would step up about 10* on both intake and exhaust to the summit 1103 cam. I would not bother with the head work. I have a similar cam but roller in my Camaro. The motor is about to go in my C20 soon. Here is a sound clip. The cam wont quite sound like this as it will have a little milder idle but it will be close as the duration is similar. Your exhaust might also be me quieter than mine. https://youtu.be/NWU3ZqmDS08 My cam is also on a 110 LSA which makes it a little rougher than the sum 1103. This will give you an idea though. This is about as large as I would go with a stock stall and be warned just cuz it says can use stock stall dose not mean it performs well at the bottom end if your towing. I do have good low end torque but it would be way better if I had a 2,000-2,300 RPM stall. All it means when they say largest for stock stall is it will not pull at the lights and will idle ok. Might be a good cam to try out the roads lifters on My cam pulls hard at stock stall speed but around 2,300 its like some one turned on a switch and its go time. Could be a carb tuning thing for me though or my timing not coming on fast enough cuz I still have a stock distributor.

 

[MadOgre]

Porting and polishing kills low end power. It only gains in the high end. You will loose alot of your low end grunt.

Just gasket match your heads and intake and call it good. I highly doubt you turn your engine 6500+ to often....


I have vortecs (906's) on my 355. And they didn't need any port work. I just had them machined for lift. And cleaned with a new 3-angle grind. The way they are. They are RESPONSIVE at any rpm.

I think this is what the shop guy meant. He just wants to clean up any casting debris and match the intake to the heads.

Seems a bit pricy for something you can do your self but if your not set up to do it and don't want to do it your self then I guess its an option for $250 lol