[leemoses]

Looking at the remote mount turbo will my vortec heads get the job done?

I am looking at the Squire Turbo Systems remote turbo kit running between 10 - 20 psi giving me b/t 650 and 800 horsepower respectfully. I have finally graduated college I am looking at a 68 thru 72 nova I am going to use the same TH350 but 3.73 gears, posi trak, i am wanting to get a little more out of the engine so a turbo is needed. I know that I will have to rebuild the bottom end forged crank, rods and pistons. Also single plane intake, a turbo spec'd cam shaft,a larger carb modified for forced induction. My question is regarding my heads... this turbo is looking at lot less appealing for the bang for the buck, if i need to spend another $1500-$2000 on a set of heads.


all right gents this is what i am starting with

A sbc 355 high tin orange block, splayed aftermarket 4-bolt caps, speed pro hyperetic pistons, steel crank, gm pink rods, 9.5 compression, comp cams xe268 kit(springs retainers dbl roller chain pushrods...the works), 1.5
rockers, stock fuel & stock oiling, vortec 64cc heads modified to
accept the .48 lift (up to .55 lift), 1 5/8 headers long tubes, edelbrock air-gap vortec intake, holley 600 carb this is in a 77 nova, 3300lbs and 2.73 gears and stock converter

LeeMoses

[worknprogress72]

Stock vortec heads flow around 230 on the intake side and around 160 on the exhaust. LS1 heads flow 233 in. The test that I saw in Chevy High Performance had the hp rating at 460 at 7psi on a pretty stock LS1. 650 hp is a tall order for 10psi. You will probably have to spend a lot of money to get the flow numbers from the Vortec heads that you need to support even close to 650hp. Might as well just buy aftermarket heads for about the same price.

[leemoses]

thanks workinprogress72... is there a formula that you know of to calculate the bench flow numbers needed for say 15 psi? your suggestions will be greatly appreciated... also do you have any suggestion on a great head to work with my turbo application?


LeeMoses

[TurboS10]

The vortec heads will support plenty of power in a boosted application, but asking for 800 is a little much. You might get there, but it will take more turbo than that squire system will put out I think, and better heads would help as well. The drawback of the smaller heads is it takes more boost to make the same power. This means more heat which causes additional problems. You really need to understand the dynamics of the system to know more.

Gotta run...maybe more later.

Chris

[NXS]

is there a formula that you know of to calculate the bench flow numbers needed for say 15 psi?

At sea level 14.7 psi would be Hp(or flow)x2xTurbo efficiency(80%). Note that this does not take into consideration Heat which is produced by boost.


Actually i don't know if there is an answer to your qeustion but if you are asking what i think you are...

[firestone]

Before you did anything, I would try some taller rear gears. I went from a 28 year old 307 to the exact same motor you have now in a 1972 ventura (same as a nova). I noticed more of a difference in performance when I switched from the stock 2.73 gears to a 3.90 and a posi than I did the swap from the 307 to the 355 in the first place. As far as a turbo goes, I think you will be hard pressed to get than thing to run on pump gas with 9.5:1 compression and 10-20 psi boost even with an intercooler. I would try 8-10 max. If you could get it to run on 8-10 lbs, I would guess your hp to be in the 550 range. I estimated this by assuming you are at 375 hp now, and that you would gain around 50% hp at 8-10 psi boost. Some other things to think about first are you rotating assembly, tranny and rear end. If these things are stock, you might blow them up with the hp you are talking about. As far as which head I would recommend, it would be the AFR 195cc head with the street CNC porting. If you got the AFR heads with the 76cc chambers, that would probably knock your compression down to around 8.5:1. That being the case, you could run an easy 15psi boost with an intercooler. That motor with a the cam you have would make around 400-420 hp with the lower compression. 15lbs boost on top of that would put you around 750-800hp if you ran an intercooler. This is also assuming you have parts that would stand up to that power.

Adam

[leemoses]

I meant to include the improvement of my rear gear ratio in my previous post. I was thinking about 3.73 locker. thanks for your recommendations Adam. NXS i was really wanting to know what cylinder head flow numbers would accommodate 15psi. I am about at 250 @.50 lift. Do i need to be at 300cfm or is 275 enough? Thanks in advance


LeeMoses

[Jared]

I would drop your compression. With that high of static compression you will be thru the roof with even 10 psi of boost. You might be able to get away with it but if you screw up on any thing say good bye to your engine. With your level of experiance I would start with low boost low compression and work up with the boost. Even with the engine you posted about it would be a decent street setup. I have a simmiler setup in my camaro and it moves. Im runing Dart pro 1 200 cc heads, 10:1 compression forged pistons all forged bottom end, air gap intake, Speed demon 650 vac sec. carb and it screams.

[57NAPCO]

someone posted this previously, and i happened to pick it up
http://www.turbofast.com.au/tfcalc.html

[leemoses]

Thanks 57Napco the link answered alot of questions...


LeeMoses

[TurboS10]

One of the main things to remember on that calculator is the VE number. That is the NA VE of the engine, which is usually lower than you realize. Peak VE which is usually less than 100% is at the peak torque output. When you use that calculator, you are estimating peak HP which is above the peak torque number. After you pass the peak torque number you are heading down hill fast. I usually plug in 80% when I use that calculator. If you have a really well matched engine with good heads, you might could use 85 or 90% VE. If you use the wrong VE, you will get inaccurate results. If you play with that number it becomes clear.

Chris

[FEDDO]

You will need forged pistons.

[Matts99Sierra]

sounds like he'd need a full forged rotating assembly, not just the pistons. right?

[martymartin04]

I have a '71 nova with an sts turbo. The motor was a 95 350 with vortec heads. I was running 10-15 psi and blew it up pretty bad. I put a 750 Mighty Dem blow through, and a wideband monitor on it. The plan was to break it and build a new short block, Now I'm looking at a new little m setup, and all forged bottom end. The attached picture shows the damage.

[turbolover]

If you want to run 800hp reliably NONE of your parts will work. Not the block, not the heads, not the cam, not the pistons, not any of it.

Now if you want to run about 550hp reliably you can use the block, the crank, the heads, and a few other odds and ends. You need better pistons no matter what though, and I would ditch the rear mount idea, the suck in every way except packaging- its the only reason to use one.


It sounds like you know just enough to blow something up and have enough budget to make a mess but not really build anything.