So, currently I have started a project on a L05 350. It has the swirl port heads and the Edlebrock intake manifold that converts it to a carbureted motor. I bought it with most of the front accessories, no distributor, no carb.

I plan on swapping the heads with a set of Vortec heads and running it with a carburetor. The vortec heads will retain their stock valves and springs.

Questions I have:
Will a set of block hugger headers bolt on and also fit over the spark plugs? On both the swirl port heads and vortec heads?

Will a typical HEI distributor for all the pre-86 blocks work on this set up?

What is the maximum valve lift on a stock set of vortec heads?

What are the rocker arm ratio's on vortec heads and swirl port heads? Are they both 1.5?


All this will be run on a hot stand and eventually on a water brake dyno. I will be trying to compare these two set ups with as little difference as possible aside from the change in the cylinder heads. I am going to be testing the power outputs of both set ups.


I'll have more questions later, but haven't thought of them yet.

 

I'm not sure which "block hugger" header you have however Vortecs are interchangable with any Gen 1 sbc head. "Shortie" style headers fit with no issues.
HEI will fit.
Lift on the Vortecs is typically in the .450" range. Checking is essential with the stock springs, retainers and valve stem seals.
While the heads don't come "with" rockers, 1.5 is the OEM ratio. 1.6 ratio rockers will require modifying the heads slightly.
A warning. The stock Vortec springs are terribly weak. Much beyond stock lift and you'll have trouble. That's from personal experience with Vortecs and a .454" lift cam.
I think you'll also find that the Vortecs will easily outpace your swirlport heads.

 

I already know the vortecs will provide a significant power increase, but that's not the point, per se, of the project. It's to try and get a baseline number for what the change of heads will do and only a change in heads. So, all things the same, what difference?

I do also need to figure out what cam is in this engine. I was told it was aftermarket as the engine is a remanufactured engine. I know I have to watch the lift on the vortec heads, so that's why I needs to know more stuff.

 

The Vortecs have THE BEST low lift flow of any Gen 1 head out there. At .050 - .02/.03 nothing equals them, even the aftermarket which tends to target the higher lift ranges.
Subsequently, the Vortecs produce excellent low speed torque. Combined with the right cam and compression ratio, they over achieve compared to just about any combo out there. They have their limitations of course however, for what they are, they perform like nothing else.
I have a pretty broad data base on the Vortecs. I'll post up a few links.

 

Awesome. Also, does anyone have data on incremental flow rates and on both the swirl port heads as well as the vortec heads?

 

http://www.nastyz28.com/forum/showthread.php?t=56505

http://users.erols.com/srweiss/tablehdc.htm
(Not sure if the swirl ports are in this data base)

 

Yeah, I didn't see anything for swirl ports.

Also, what would be a better idea: Attempting to accurately measure the lobe separation, durations, and lobe lift on the current cam or to just buy a new one? I'll be modeling all of this in DynoSim5 before putting it on the dyno, namely because the dyno I am using isn't operational yet. It was torn down and stored and I recently pulled it out of said storage after 7 years. So, with no manufacturer marks on it, except that of the force transducer, it will be fun to try and get this thing working again.

 

It would be a lot of work to get enough really ACCURATE data from measuring the old cam and then applying it in a simulation program. I suppose you might find that the existing cam is ideal for your application but then again.... There may be some id markings on your existing cam though.
Certainly you can get the info for any prospective cam from catalogs and plug that in.
I've recently gone through dozens and cam and head profiles (in DynoSim) trying to find a better spec cam for the Vortecs (over my XR276HR-110) or an out of the box improvement on the Vortecs (which I think I've done).

 

Well, I don't have an issue getting a new cam. You said you run .454" lift on your vortec heads? Can I get away with .460" or .462"? What is the absolute highest? Did you change the stock springs? If so, what kind of springs might you recommend I replace them with? I figure changing my valve springs would be a good idea as well, so I can keep them the same so I have equal frictional and other losses throughout the engine.

 

At the time, the Vortecs were stone stock right right down to the springs and press-in studs. One missed shift and I put a valve into a piston. That was about 7000 rpm on a hydraulic flat tappet cam.
From all the information out there, the maximum possible lift varies. At .454" I was at the practical limit but still had a few thousandths before the retainer hit the seal. Once you're at this lift (or beyond) it would be imperitive that you measure the clearences. Production tolerance stack up may work with you or against you.
There are several options available for DROP-IN replacements. What limits your choices is the diameter of the spring pocket. When I upgraded to a larger hydraulic roller, I went with Comp 26918 springs. These things are just about bullet proof but about three times the cost of a conventional spring. (I've just purchased 26918 springs, retainers, locks and spring seats for $300 USD) Other folks have been having success with running a generic tool steel spring made for an LS application. I don't have that data on hand but I'm sure it's buried in a thread here somewhere. You might get lucky and find with a search.
The springs are key to keeping the valve train under control. What you choose is also dictated by the type of lifter. Hydraulic rollers typically demand a higher spec spring.

 

So, if I don't plan on taking this engine above 7k rpm, or even 6k for that matter, should I have much to worry about?

 

It's more the profile of the cam than the rpm that will give you problems although the two obviously go hand in hand.
If you limit yourself to a mild flat tappet cam (much like what I was running which was similar in spec to Comps old 268H), my experience's say that it'll survive with stone stock Vortecs. You're at the limit though. Like I said, I missed a shift and bent a valve.