was wondering if the LT4 HOT cam will work with 1.6 roller rockers (self-alligning) without doing machine work to the vortec heads. also what kind of horsepower gains should i expect if i get the vortec heads, vortec intake, the rockers and cam, headers, slp runners and port the plenum to match, and also 52 mm throttle body? thanks

 

i have an 89 gta with a 350 right now, no cats, no smog pump, slp 3 inch exhaust. will probably get a custom chip with all the other stuff

 

make sure if you go with those heads and if you do a good port job on 'em that you get at least a little bigger cam to take advantage of the extra flow. i have no idea on numbers and figures but they'll be an improvement over stock for sure.

 

i believe you can run lt4 springs without machining them. but don't quote me on it.

With the whole heads, cam, intake setupand propper tuning, it's gonna be a good boot in the ***.

really depends on how it's tuned and such but 50+Hp is not out of the realm of possiblity

 

You have to machine down the valve guide to
ensure enough clearance between the guide seal and retainer.
Plan on it.
Ater that , what ever spring you want to use is not thaqt important. The LT4 spring would do fine.

 

yeah i agree on that.. tuning is the serious end of it. you can get so much out of it but you can probably nearly double the initial gain just by having it tuned correctly for th enew vacuum/fuel/air settings...

 

DO yourself a favor and DO NOT use the LT-4 hot cam with a LTR TPI intake. The LT-4 hot cam was designed for the LT-4 and beefed up LT-1's (which both have a "short runner" intake. If you want to go with vortec heads and the vortec TPI intake, you will want to go with a split pattern lift - split pattern duration cam. Perhaps something a little smaller than the cam that I'm running (I have alot of work done to my Vortec heads). If you want to put some money into the vortec heads, then run a cam similar to mine. Valve springs are really important, even if you dont do anything else, get valve springs that match your cam (example: order the cam from Comp cams and get the cam kit for that cam). The cam kit should come with matched valve springs, locks, retainers etc..., depending on the package you buy. Give your machinist the heads and the cam kit and have him set it up for you. You may as well have him do a little porting while he's at it, if it's in your price range. And yes, the car will need to be tuned after doing all of that (custom chip) for your ECM, unless you're like me and have decided to go DFI! Just my $.02

Mike (1bad91Z)

 

The latest camaro performers mag just did an article on the SDPC vortec inake on their heads, with all edelbrock garbage on it, i.e. 52mm TB, Runners, and Headers, with vortec heads, on the SDPC intake, with the LT4 Hot Cam and 1.6 RRs. An actual dyno.....they predict a 20% drivetrain loss with a 700R4, you will have just a tad over 280 RWHP. Not a bad advertising number. However, I feel they were real generous about the 20% loss, and 356 at the flywheel seems like a nice idea. The also say that a stck L98 would see 305hp at the motor and 244 at the wheels, using stock cam, TB, runners, ect... all tests were done using edelbrock headers.
Figure with a few changes, SLP runners and headers, stock TB, port your plenum and such, it isnt a bad way to go. I thought about it myself, except i'd use the aluminum vortec heads that Jegs has or port the he!! outta the iron nes.

 

Everything I have read said the vortecs are worse off with porting. There design is very specific, and when you port, it just messes them up. CHP did a test with someone they claimed to be the best head guy out there, he did a bunch of work to the vortecs and didn't gain much at all.

Those dyno tests were done with 1 7/8s headers and an Accell DFI, untuned. The 305 hp mark isn't hard for me to believe. I am making ~300 at the flywheel with vortecs, slp headeds, hooker cat back, 1.6 rockers. But my engine isn't brand new either.

As for the aluminium fastburns, I'm not too sure about them. People have made 440+ hp with the iron ones. The fastburns have 210cc runners, which is a bit much. I heard they are going to be redesigned soon, so I am waiting to see those.

If you want vortecs, research the hell out of them. They aren't your everyday SBC head, and there is a lot of rumors and hear-say going around about them.

 

Bitchin, everything I've read also says to leave the Vortec heads alone. Dont f*** with them. They deliver the goods out of the box, with the right combination of other components in the motor.

 

Up to about 400hp and.500" cam lift it is hard to improve on the
stock vortec ports. Beyond that you need more flow and lift
and porting will certainly help.

Having messed with them myself a bit, I recommend
trying them stock first for moderate performance. If you must mess with them, work on the exhaust port. It responds nicely to a general blending and cleanup. Nothing major needed.
Good for 20 cfm. The intakes will need a considerable
porting effort with bigger valves to see a actual performance gain.
And then only with a more radical combination. (high lift, larger intake, headers etc)

 

Vortec heads do not yeild gains from port work? Who the hell told you that? My vortec heads were pull offs from a dirt track car (circle track) that made 508 HP at the flywheel! I watched the motor being engine dyno'd. Those numbers were made with a carb though! But the numbers were also made with a cam similar to mine, just a bit bigger.

My heads have the following work done:
Stainless valves (1.94 / 1.56)
yes - stock intake valve, bigger exhaust valve
Radius cut valve job
seat work
throat work on intake and exhaust
screw in studs
valve springs good upto .560 lift

Thats all I can remember, there's probably more that's been done.
When the motor is finished being broken in, I'm taking the car to the chassis dyno. I'll post the numbers and show you how much power a worked set of vortec heads will make with a TPI intake.
Just my $.02

Mike (1bad91Z)

 

i'm not sure what i want to do yet, i know i don't want to get a blower, just about everyone i hang out with has a blower and i want to be different and still be able to run mid 12's, that's what i'm shooting for, mid to high 12's but still good driveability. any suggestions? plus i don't have a high budget that's why i was told vortecs would be good, and for around 1500 or so with all the other stuff (cam, rockers...etc) i should be close to high 12's. what do you guys think?

but then again, i can wait a few years and a friend of mine told me about a twin turbo kit for 350's, not sure if it would work with tpi but, that's definately different, and i love the sound they make.

 

NO vortec heads will only take .460 lift total on the valve guides. I found this out the hard way. I neglected to check the clearance of the guides and broke a couple.



Brian Felts

 

Vortec heads do take a porting job well AS LONG AS IT'S DONE RIGHT!!!!!!

The average shade tree mechanic doesn't have the knowledge or test equipment to make sure that what he's doing is producing good results.

Tests have shown that the Vortec heads do diddly squat when they're pocket ported. You may as well spend the time polishing your wheels to reduce drag as it will do more good.

They do well when hogged out, but that should ONLY be done by a professional with a flowbench. They aren't made to respond the same way to porting as your typical stock head.

One of the reasons they do so well is they're very efficient. If you do anything to disturb that design, it's bye bye HP.

AJ

 

It all depends on what your looking for out of the machine work.

If your looking for vast improvemnts in flow on the intake side, hoggin em out and destroying the original shape which.. is it's strength, is what you have to do.

If you wanna "straiten" the heads out, getting a better exhaust intake ratio, making them more efficient. Bowl work on the exhaust side does a bunch. Give ya more exhaust flow, better velocity and should yeild some better midrange power, with maybe a modest gain in top end power. Any timeyou can turn a 66-67% head into a 72-74% head it's a good thing, if it can be done with minor exhaust side bowl work.

 

virtually every magazine made between 400 and 450 very torque rich HP with the stock port vortec's. They need to have the guides/seats/springs upgraded for a decent camshaft. Scoggin Dickey sells them ready to run. I would think a TPIS or Lingenfelter cam in a stock type TPI would work great. Now that i'm thinking about it, CHP put together a 12 second vortec headed tpi car on a budget. the engine builder was very well versed in Building TPI cars. I would look for that article.

 

What issue was that in? Please find out, cause I would like to get a back ordered issue of it.

Thanks,

Mike

 

Car Craft did one in the Sept. issue. Although I just missed buying it. My wife works at Barnes & Noble and she just called to have them hold it since they're taking them off the shelves tonight.

IIRC, they made 406HP. I'll get you the specs tomorrow.

Other than that I have 5 issues of CHP in front of me right now that each have an engine that made over, or damn near 400HP.

In chronological order they are....

Jan. 2000... 395HP @ 5,900 RPM with Comp cams XE-268H, Edelbrock intake, 1 5/8" headers, and a slight pocket port. I know a pocket port is not stock, but all they did was clean up the bowls and back-cut the ex. valves 30* which is now the standard for the Vortec heads. Then they added 1.6:1 Comp Cams roller rockers and went to 402 HP @ 5,900 RPM. Finally they switched to 1 3/4" headers and got 409 HP @ 5,900 RPM

April 2001.... Same exact combo as mentioned above except they used a Road Demon 625 cfm carb on 87 octane gas, no pocket porting and made 390HP @ 6,000 RPM. The above combo used a 750 Holley, but on 93 octane.

Nov. 2001.... Using a Hot Cam Kit, Speed Demon 750 carb and no pocket porting, with a single plane intake made 422 HP @ 5,700 RPM. The same combo with a dual plane still made 412 HP @ 5,600 RPM

July 2002.... A GMPP 383, Hot Cam Kit, Holley 750 DP, Air Gap intake, and untouched Vortecs made 412 HP, and 416 HP @ 5,600 RPM with 1 3/4" headers.

August 2002.... Same motor as above with Comp Cams XE-282 Hyd. Roller cam, Speed Demon 750, Weiand Elec. water pump, and back to 1 5/8" headers made 449 HP @ 5,400 RPM.

That's all I could find within the 5 minutes I looked. CHP is the only magazine I subscribe to, so I'm sure many other publications have done the same but with other cams, etc.


AJ

 

To AJ - THank you!

I'm hoping to squeeze 400-450 HP at the crank with my worked Vortecs. I wonder if I'll be able to do it? They made 508 ponies on the motor they came off of, I just hope the SDPC intake wont choke to much of that away! I have port matched everything and I'm using ported SLP siameese runners. If the PROM is configed right, I may have a shot!

Mike (1bad91Z)