I'm gonna be building a SBC 355 with the Stock TPI plenum, LTR's, anticipated Vortec-TPI intake and the Vortec heads.

I'm looking to get suggestions on roller cams that will give me great torque for the street and still pass NJ-DMV dyno emissions.

So far I've gotten good result in DD2000 with the ZZ3 cam and my proposed setup, 430@4k and 382hp@5500.

thanx

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Dan G.
87 Turbo Regal

 

1. DD2K is very optimistic when using street-rollers. The cure is to choose hydraulic flat-tappet lifters(vice hydraulic rollers). On your combo, this will drop your torque about 30 lbs/ft and your hp by 40 hp.

2. DD2K is not especially accurate when modelling LTR TPI engines, even more so as the cam profile gets more radical. At any rate, with the LTR's you will have trouble making hp above 5000. With the ZZ3 you will be giving away a lot of low-end torque, to a cam more suited for TPI.

3. Recommend you try modelling using one of two CompCams roller profiles: XR258HR-10 or XR264HR-10. These cams will give you great bottom-end(400+ lbs/ft from 2000 - 4000) and decent hp(320 - 335 hp @ 5000).

4. Additional advice for DD2K:
- aim for a torque peak between 3000 and 3500, and peak hp aroud 5000. this is typically the best operating range for LTR TPI's. if you exceed these values, the results will be considerably less accurate.
- keep the airflow conservative, 550 cfm for a stock MAF; 650 cfm for a gutted MAF; 700 cfm for a high-flow MAF or speed-density
- for a full exhaust, input "small-tube headers and mufflers". Choosing any of the "large-tube header" options tends to give unrealistic results, probably because it simulates true duals with no cat.
- TPI motors like a little retard on the cam timing(-1.5 to -2.0 degrees), and DD2K will usually show about a 5 - 10 hp increase if this done. this will have a small negative impact on low-end torque(1 - 3 lbs/ft). it will also move the torque peak and the hp peak a little higher.

DD2k has shown to be very accurate(when used properly) on modelling carbereted engines, but is best used only to show relative gains with a TPI intake. Camshaft and exhaust timing become much more critical on a TPI engine, perhaps in the next version of Desktop Dyno this will be reflected more accurately.

[This message has been edited by 88IROCs (edited November 01, 2000).]

 

I ran the 258, 264 and even the 270 cams.

I get the best results with the 270 numbers-wise, next up with the 264.

I plan on entering the flow data from GMHTP on the Vortec heads and seeing how much the numbers change.

Also wonder what is the best comp-ratio to run on the street...on pump gas, 89-93oct ?

any other suggestions?

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Dan G.
87 Turbo Regal

 

Random thoughts,...

-the XR270 cam would be a waste on a LTR setup. it usually works best with intake and cam able to flow to 6000 or better. not the type of level a LTR will work at.

-stick to conservative compression. 9.0:1 for iron heads, 10.0:1 for aluminum. You may have easy access to 93 octane near home. but what about when you're not at home, when a road trip finds the needle near "E", at "Billy Bob's AllNite Gas 'n Go. Noname, unmarked "premium" and a blank stare from the attendant when you ask him what octane rating it has - "Octane,.... duh what's that?".

- a single plane or dual plane manifold will always make more peak power than a LTR setup(using the same internals), but they are both very "peaky" when compared to LTR TPI. the biggest benefit to a LTR setup is big, fat torque curve. Keep Lingenfelter's word's in mind: "You sell horsepower, but you drive torque." when you're noodling around with DD2K, don't concentrate so much on peak numbers, as much as making the torque curve as flat as possible. this is especially important if you are planning to use a 700R4, with it's widely spaced ratios, coupled with the weight of a thirdgen f-body.

- unfortunately, the only cylinder head attributes DD2K takes into account are the flow numbers. in this area the Vortec heads don't shine. you can typically find Iron Eagle(180cc) for the almost same price as Vortec's, and because the Eagles have better flow number's you might think that was all there is to it. However, the Vortec's have a better combustion chamber, better spark plug location and create more swirl(none of which is modelled in DD2K), and all of these things contribute to improving efficiency and making power. so when you're swapping heads in DD2K, you are comparing only one facet of the heads potential

- i haven't had any personal experience with the Vortec head yet but, from what I've read, the intake port stalls at about 0.500" lift. Choose your cam accordingly(the XR270 is definitely to big for this head). Keep in mind too, that because the Vortec is an iron head you're choice of compression ratio is limited, which further limits your choice for cam timing.

- another idiosyncracy i've discovered with DD2K is the predicted cylinder filling efficiency(VE). DD2K always places VEmax at 500 - 1000 rpm above the torque peak. This is wrong, as VEmax always corresponds to max torque.

-remember it is only a consumer level program. it is nearly impossible to map all the effect a myriad of variables can have on an engine. there are other programs out there that do a better job, but they have three main problems that prevent their widespread usage: 1. they require more variables to be input by the user, and the variables must be accurate, 2. they require more understanding from the user(kinda like comparing KeyCad to AutoCad) and, 3. the price of acquisition is a lot higher($1000 to $5000 is typical). Just as Flight Simulator 2000 can give you a good orientation to an airplane's ****pit, it cannot simulate all the dynamics involved in an actual flight(how many times do you think you would crash into the Sears towers, on purpose, in real life?). I think DD2K's real strength is not it's realism(though it has sometimes proven to be near accurate). Rather it should be used as a tool to make relative comparison's and to better understand: which changes will have what effect(in a relative, but not necessarily realistic comparison).

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He who hesitates,... is lost!

 

The ZZ3/ZZ4 cam is a nice grind, its is however designed to run to 5300 rpm for peak HP. Make sure your runners and base will support that. Matching components is the key with TPI motors. My only issue with that cam is the Vortec heads port airflow will stall just after 0.400" of valve lift. This is well documented. The ZZ4 cam has a high lift of around .485/.510" I beleive. You will still get good area under the curve, you just wont get as much benefit as with heads that flowed strong up to 0.500 lift. I heard from 2 guys running ZZ4's w/ TPI, SLP runners and ported base when I was researching my motor and they run 13.20's to 13.40's in their camaros. They did recommend a custom chip, but said the combo idled well and was very well behaved on the street. If you look at what SLP and Lingenfelter recommend for mildly modded TPI 350's the ZZ4 cam is right in the ballpark.

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Dave Zelinka

 

88IROCs:

Could you send me your email address? I was very impressed with your response and have a question for you.
Thanks

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Dave Zelinka

 

Just to note; stock L31 Vortecs will bind above a max lift of .450", while the performance built variant #8060 has Ferra valves & better spring and handles a max lift of .550".

The #8060's are $96+ more expensive than the L31's.

Ultimately, I would like to get the motor afford me the power to goto mid-12s. This would be in a Monte Carlo SS.

I might have a deal on some SLP runners, and depending on the airflow capabilities of the Edelbrock/SDPC Vortec TPI intake, I might port it out further.

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Dan G.
87 Turbo Regal

 

Wow, that would be impressive if you go mid 12's with a long tube TPI and production heads!! Is the Monte Carlo lighter than an F-body? I really like the look of those cars. thought about buying one myself. I am in the process of porting a set of SLP siamezed runners right now for my 383 TPI. They do need some cleaning up and enlarging to get the most out of them. Contemplating extrude hone when I get the shape right. Its hard to work the inner portion of the runner with porting tools and sanding rolls. AS&M siamezed runners are clearly higher flow but I got a good deal on SLP's and anyway, I wanna see how big a pile of aluminum shavings I can get on my workbench

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Dave Zelinka

 

with the Vortec heads, if you polish the echaust ports, pocket port them and port match them to your intake (port match the intake as well)...

Then port the plenum, extrude hone the runners and base you'd prolly get enough flow for a sizeable cam.

 

Yelofvr,

The ZZ3/ZZ4 is a nice cam when used with the right combination, i.e., one using a high-rise dual plane manifold(which is what it was designed for). For a TPI intake I would choose a cam that had more intake duration and a wider seperation angle. I could see the ZZ3/ZZ4 making decent power with the SLP runners, but I think there are cams that would be better matched for this combo. The SLP runners while appearing externally stock length, would appear to the engine as shorter than stock length. This should allow you to pick a cam with increased duration for extended rpm(above 5000) power, at the expense of some low and mid-range torque.

I've got some data for CompCams TPI-specific rollers, but haven't gotten around to entering it in DD2K. It will be interesting to see if they improve on the Xtreme Energy rollers(XR series).

Both of the flow tests I've seen for the Vortec heads indicate the port stall occurs above 0.400" lift(GMHTP showed stall at around 0.450" and CHP showed stall at 0.500"). There was quite a bit of difference in methodology between these two tests but the build-up articles I've read, which used Vortec heads, seem to suggest they may well flow up to 0.500"(assuming the appropriate valvetrain components are used).

Shadowrun,

Here's one for the stupid file. About a month ago I took a look at a Monte SS 2+2. The body was perfect(albeit the paint was very faded), but the interior and engine(several oil leaks) needed a lot of attention. The owner was asking $2900(about $1900 U.S.), and owing to the general condition I told him I would get back to him. The silly thing was: I had $4500 in my wallet(purchase price + any incidentals). When I got home, I did some research on the 2+2(why didn't I do it before I looked at the car) and found out what they're worth. Needless to say I called him back, but he had already found a more informed buyer. Arghhh!

I am consoling myself by buying two 400 blocks(one is supposed to be a four-bolter) this week, at $600 for the pair . And I might check out some used complete TPI intakes while I'm at it. I'm thinking this winter I would like to replicate the "Super Chevy" 352 motor(400 block - bored 0.030" and a 327 crank), using a TPI intake. This combo can use 6.200" rods and the huge rod/stroke ratio will support very-high(11.00:1 on iron heads) compression on pump gas. Preliminary calc's seem to indicate this combo could make 390 hp at about 5200 rpm(needs a fair bit of cam though), which hopefully should net some 12.7's. We'll see!

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He who hesitates,... is lost!

 

A Monte Carlo 2+2 huh? Maybe its better off you didn't buy that car since GM never produced any such vehicle.

The only "2+2" designation was only available on the Pontiac Grand Prix of the day. It was basically a Grand Prix with the Nascar styled rear window and revised front fascia.

The Monte Carlo's were offeren in an Aerocoupe SS model which had the same rear window treatment, but they were never advertised or designated as "2+2".

Just a note, I run the g-body.org website and have been involved in the genre for about 7 years now...I'm 22 btw ;>)

In any case, as for my application, I'm trying to see what I can get with what I already have without too much additional expense.


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Dan G.
87 Turbo Regal

 

Aerocoupe or 2+2, it's kinda like splittin' hairs(to a non G-body cognescenti like me).
The whole reason I went to look in the first place was the fact I'm lookin' for something a little different. Seems like everyone and their dog 'round here has an IROC now(mine used to be the only two around, then they were the only 5.7's around, then they were the only black one's around, etc.,...).

There's lots of G-bodies 'round here, but no real nice ones(usually badly rusted ones or those sportin' multiple war wounds).

So I'm thinkin a clean one, with good paint and a little attitude would stand out 'round here,... especially if it had the big rear glass!

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He who hesitates,... is lost!