skinny z

I'm only speaking from personal experience. I purchased new Vortecs from a Chevy dealer and ran a flat tappet 218 degree/.458" lift cam for years with no trouble. I know you would be at the limit however with engine speeds below 6000rpm there was no indication of any valve float and the engine pulled strongly to the red line.
However that's just my experience.
I understand your point though. It's always good advice to upgrade the springs whenever upgrading a cam. I just suggested it's not entirely necessary.

Vortec_Formy

if I do purchase that cam and degree it and install it, will that take better advantage of the stock motor or should I just buy a set of 1.6 self aligning rr and be done with it? will the cam hurt me that bad down low even with gear? and will it make up for it between 3k and 5500?

z28freak84

That TFS cam is by far the best bang for the buck option that you right now.. will offer great power from 1500-5800rpm. buy the comp 918 springs if you can...not necessarily needed but a great idea.... car would have 12 second potential....low 13's not even trying... STock compression is supposed to be 9.3:1, but combustion chamber volume is usually smaller than the advertised 64cc. More like 63, and as low as 62cc. so closer to 9.4-9.5:1compression. That's with a .028" factory gasket. Throw in some FelPro 1094 .015" gaskets and you could be as high as 9.6 or 9.7:1.

Vortec_Formy

thx man, have you ran a similar setup?

skinny z

I copied this from an online truck forum:

L31cam 192°/197° duration at 0.050" 0.414/0.429" lift with 1.5:1 rockers. 111 LSA.

So if the truck data is accurate and we take what Z28freak84 has listed we can come up with some numbers.
Working the L31 block and using the supplied info and typical OEM specs we get:
4.00 x 3.48 bore and stroke
63cc combustion chamber volume
.028" x 4.100" head gasket
12cc piston dish
.025" piston below deck
9.3:1 static compression ratio.
To calculate the dynamic compression ratio the calculator I use requires advertised duration numbers. Since no data is available I went to the Comp catalouge and picked something close (not necessarily accurate I know). A 192/200 at .050" spec roughly translates to 240/248 adv duration.
Given those numbers you get a dynamic compression ratio of 8.1:1. with the cam installed straight up. 7.5 to 8.5 DCR is desirable. That's basically a stock L31.
That's using 1.5 rr. If you wanted to move up to 1.6rr ( see various arguements regarding stock springs ) then you will trade off a little bottom end torque for a few more HP in the upper rpm. I would think max power would be around 5000rpm+/-. I can get better data if I run it through the dyno program.
That'd what you get with the least amount of work. Stock L31 ( and stock cam ). No head removal or cam swap.
Any upgrade (aside from perhaps 1.6rr) will invlove removing /modifiying the heads and a cam swap. I would think that any increase in cam duration will benefit from increasing the static compression ratio.

86LG4Bird

iTrader: (1)

I can tell you from personal experience that you won't lose any noticeable low end torque stepping up to 1.6 rockers with the stock cam. With my ZZ3 cam, it was noticeable when I swapped to 1.6 on the intakes, but not with the stock cam.

The more I've modified and played with my truck, the more I realized that the stock cam is VERY well matched to the limitations of the stock Vortec intake manifold.
I know I'm repeating myself, but the OP would be best off with 1.6 rockers and springs and stay with the stock cam for now. For the minimal gains I've seen bumping up to the 208 deg ZZ3 cam, I honestly can say it's not worth it. And I'm one who is willing to and has the tuning knowledge to play around and try to optimize the tune for the cam change. Save the cam change for when you can pull the heads and get the CR up to where the new cam will work better.

skinny z

[QUOTE=86LG4Bird;4413701 Save the cam change for when you can pull the heads and get the CR up to where the new cam will work better.[/QUOTE]


My thinking as well.

Vortec_Formy

I'm glad I joined this forum, you guys are hellaciouslly smart. So is z28freak84 wrong with what he said, that going with that tfs cam is my best bang for the buck bet? and if i can just get a set of 1.6rr, what kind should i get so i can just throw them on? by the way, as far as my intake goes, its aftermarket and not stock.

wanab03ss

iTrader: (20)

roller tip rockers will fit under the stock valve covers and there very cheap, you can find them for $70-100 and even cheaper. Full roller rockers are better but you also pay more, especially for sa rockers @ $280 new

Vortec_Formy

i ran full 1.6rr on my 91 z28 tpi, i just clearenced the stock valve covers, are the vortec valve covers the same?

86LG4Bird

iTrader: (1)

I won't say z28freak is "wrong". If you're after a peak dyno hp number, he has a point. But if you want best street performance and 1/4 mile times, don't do it at this point.

skinny z

I think it may come down to this. How much work do you want to do?
1. Keep it all stock.
2. Add 1.6 rockers. Check for interference issues.
3. Put a cam in it. Any cam upgrade will need springs. Probably studs too. Guide plates (as opposed to self guiding rockers) are a personal choice. For the record, the TFS cam in question is a damn good choice. It provides a decent amount of duration and still stays within the lift constraints of the Vortec heads. However that being said, it would still require a set of springs. It would also benefit from an increase in compression ratio. Either way with any cam upgrade you would probably want to pull the heads.
So, how much work do you want to do?

Vortec_Formy

Yea the 1.6rr seem like the best choice since for now i just want to bolt them on and go, I liked the idea of the cam but I dont want to pull the heads off yet. What 1.6rr should I look at purchasing and right now I have the professional products cyclone intake that mimics the edelbrock performer and a 600 vacuum secondaries edelbrock carb. should i step the intake to the crosswind version which is like the rpm air gap or not and should i throw on the 600 vacuum sec. holley I have or go bigger?

Vortec_Formy

I know this is off topic but no one answered it in the cooling section but my question is.....the ac work but only blows through the defrost like the heater does, i looked under the hood and one vacuum line runs to the egr valve satelite looking thingy and theres another vacuum line just sitting there, where do I run it? to the carb?

skinny z

At this point, I'd suggest using what you have. I haven't heard great things about the Edelbrock carb however I have no experience with them personally.
Any mods you make at this point should be in the direction of what you want to achieve ultimately.
I abandoned the self guided rockers in favour of guide plates w/ screw in studs. I also upgraded to a 1.6 full roller rocker arm. If you decide on a 1.6 ratio for a little extra power (perhaps very little) then you'll have to make that choice too. Self guided or guide plates. Otherwide you'll end up buying two sets of rockers should you change your mind.
The Vortecs don't require anything more than the RPM Air Gap intake (at least on the street). At this point I think your performer will be fine. Some will argue that a 750 cfm carb is in order however I would think that would be a last step once the engine mods are completed.
Use what you have and get out and drive.
You can decide on improvements over time. Perhaps making a large purchase and building the engine in one shot. Head machining, new springs, bigger roller cam, etc.
By the way, for what it's worth, I thought there was some pretty good info tossed around this thread. I especially like real world experience. Stuff from guys who have done it and report results, either good or bad.

Vortec_Formy

Yea your right, I'll just use what I have, what 1.6rr should I purchase, I want to upgrade and dont mind the work as long as pulling the heads or motor is out of the question. Yea i too like real world experience, and that is what I want to base my modifications on. Will rocker arms like the ones that come with the lt4 hotcam kit work or do I need to purchase a certain kind of rocker arm? Should I step up the carb to a 650? keep it vacuum secondaries or mechanical secondaries? I will be doing the air gap swap cuz its not that much work.

Vortec_Formy

ttt

wanab03ss

iTrader: (20)

the lt4 style rocker arms will work, just modify the valve covers and your in good shape. search on how to modify them (real easy) and youll find all the info you need.

Vortec_Formy

Thx man, I really appreciate it, these vortec heads are good but def a pita when it comes to cam combos lol.

skinny z

I used Comp 1.6 Pro Magnum rockers. I had to modify the stock rockers along the internal brace. If you compare your stock valve covers to the attached pics, you'll see how much material needs to be removed.

Vortec_Formy

Yea I had to do something similar when I ran comp 1.6rr on my 91 z