I have no fucking idea what I’m doing, this is my first turbo build... I am building a 415 sbc twin turbo, I’m pretty much brand new into the build, have the block/rotating assembly and heads. Block is a dart little m and eagle 4340 forged crank and rods. Weisco -20cc dish pistons. The heads are 235cc AFR heads with 70cc combustion chamber. Where I’m stumped is what I should be expecting to see in cam duration and lift..

I have a 93 camaro that I am completely stripping, plans to get the car about 3200lbs when complete, tremec 6 speed from rpm transmission, 2.94 1st gear, and 9” reared with 3.55 gear ratio. I have a Holley dominator ecu that I’ll be using since I already own it lol, wanting to achieve 1000 hp on 15 psi of boost.

I am way early into the build and figured getting on a forum before buying a bunch of shit trying to make it work would be a good idea

I had a cam recommendation from isky:
290/276 duration @.050
.790/.616 lift with 1.5 rockers
Intake closing 79 ABDC
114 LSA

To me this seems like a lot of cam, and have had many people tell me this is way too much, but the director of isky cams swears this will work..

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I would get a second recommendation, that's a very strange grind. What turbos? Cam, and turbo selection affect each other so both need to be considered when looking for a cam.

 

I thought so too, in which I’ve had 3 other places recommend something in the 250/260 duration @.050. I haven’t picked yet, but thinking somewhere around t4 72mm twins, need to figure out what a/r will be good for 3500/7500rpm.

I’m wondering if when I told isky I’m trying to make as much n/a horsepower as I can before boost is what affected the cam grind that I have.. I agree, it is very odd, but might be ok if I can get the current cam reground

 

Also wanted to throw in that I’m planning this car to be full drag race, only very seldom will it be driven on the street. Only reason it’ll ever be on the street is if I’m trying to be a show off

 

That cam is huge. I currently have a 406 10.5:1 with a 262/269 SR on a 110 LSA and it has to idle at 1100 and makes 8/9" of vacuum.
I don't know though, with the 115 LSA will idle better or not.
Probably.

 

That's a lot of duration and lift. You'd need real heavy duty springs to deal with that cam plus boost on top of that.with that one lol Lobe seperation is good.

 

shit ton of overlap in that cam too.
You really need to determine what turbos you are going to use first. Because if you where to go with smaller turbine setup for fast spool it may have more back pressure. An experienced cam designer will need to know this to make the cam work good.

Plenty of cars out there in the 1400hp range running cams in the 230s and .050 range.

 

The duration, and split is crazy, and like said, specing a cam.without turbo info makes me question Isky's process.

 

Thanks for the input! I will be calling Nolan at isky cams again today to make sure I didn’t fubar the specs I gave him of the combo when he chose that cam, but I do agree it’s huge. Although we did plan on this being a track car without much street time... it’ll live it’s life 4000, 7,500 rpm 1/4 mile at a time =D it may work great for the track but I know my idle and down low torque is going to really suck if I don’t make a change to the cam.

Are you running a turbo on your setup? I’ve heard of some people using a close lsa like that with turbos and good success, but do know with a 114-116 you’d get a lot more control of idle quality. What kind of power numbers are you getting?

 

No.
No turbo for this engine.
It's a stock 2 bolt block that's studded with all other good components.
Compression is too high to start with and I would assume with as much overlap as my cam has , a lot of boost would be going out the exhaust.
Never dyno'd it. Chassis or engine but according to some calcs from what it ran in the 1/4 it's 500+rwhp.
My goal is to be at 650+ street tune with the twins but have a much more docile idle....but when boost come in, hold on!
It might have a fuel cell too, just for race gas for the track....

 

Sounds about right, id like for it to start spoiling up to full boost around 3500 or so, not sure if I need twin 72’s or 76’s. I’ll do some research on the turbo sizing and ratios, then give the cam company a call.. if it is wrong, hopefully they can refrains what I have..

 

Sounds like a healthy setup! Again I’m brand new to the turbo world, but I plan on doing the same thing, but capability of running e85 and being able to switch to race fuel.. probably 112 or 116.. not sure though, everything is in the air right now, that’s why I’m here

 

Ok, i gathered some more information that might be pretty helpful that i forgot to mention earlier..

I originally told isky to spec a cam trying to build a lot of N/A horsepower first so to make a low boost setup, was planning on running 8-10 PSI to start off with, and then slowly step up to 15 PSI max. Cam is spec'd to pull around 1000 horsepower on 10 psi of boost. The heads i chose from AFR are good to 800 lift and will have 750 lbs open pressure, and 260 on seat i believe. I also plan on crossing the line running around 7200-7400 RPM given that i can get the weight cut down enough to get the car across the line at that rpm lol.

Im mostly guessing Isky picked that cam based off this combo setup that i gave them, plus a twin turbo setup that will run a max of 15 psi, but will probably live more in 10 psi range. Now all i have to do is figure out what size turbos, A/R ratio for the turbine side, and what flange size i need.

 

Why do you insist on talking to isky?? Call Bullet or little john performance. Two of the biggest names in designing turbo grinds!!

 

I’ve had some pretty badass n/a cams ground for me at isky, but for turbos besides the LSA, I had no idea what I was looking for. I’ll look them up and give them a call.

 

Slammed98gmc ran a 254/250 @.050 SR and did 167mph at 3200ish lbs
383 afr 195's 98mm 29ish psi. No IC E85 and some meth.
That's at least 1k to the tires.

Those Isky numbers are probably advert. duration.

And it's probably still too big imop.

Blown385 had a 235/234 HR 383 AFR 195's and did low 9's at 4500lbs S480. Close to 1k to the tires.

Guys with LS motors are doing 170+ with [email protected] HR cams.....

Something about 250 @.050 max is all you'll want.
210/520 springs and a smaller cam in the low 240's would be more in line for 1kwhp.

With your springs and say a 250ish SR you'll want a GT5594 or twin 69-72 mm turbos.

I'll be the first - you'll go faster with an automatic.....
And you won't stop at 15psi!

 

I thought they were adv numbers as well, but check out the cam card he posted, they're @ .050 numbers.

 

My cousin always told me that once you finish a build and run 10’s or 9’s, you’re never gonna stop there and be satisfied, you’ll always want more out of it!! Lol. Well he’s very right about that, although my current combination has me limited to a max of 15 psi and say about 1200 hp on the pistons & rods combo.. they are Mahle 4340’s and while Mahle says I can run them at 1000hp safely to the wheels, ima try to be as careful as I can until I get another combo put together lol. The ring lands look a little thin with 1.5x1.5x3mm rings. I’m 100% on board with you about the auto trans being faster, but I love my standards!! I like a little challenge, and if it kills a little of my et time then so be it.. lol.

I’m really questioning isky on this cam, I’ve called Nolan there and spoke to him several times about this subject now (last time I did he seemed frustrated that I was questioning him) but he swears the cam is going to work... it sounded HUGE to me too.

I gave him the following specs:
415 ci sbc, 4340 eagle crank and 6” rods
Mahle 4340 pistons, max 15 psi.
Fuel: e85/ or tune for vp112-114
Vehicle weight 3000-3200 lbs
T56 from rpm transmission 2.95 1st with 3.55 gears,

Will mostly be ran at the track, but occasional trips to a car show, so really don’t care about giving up some driveability, but hell, if I can build it to operate on the street well and still hit my 1000 @10 psi then I’m all ears!

Wanting to shoot for 1000hp at the crank with 10 psi of boost.

This is where the fun starts, he said that if I wanted to touch those numbers at that psi I would have to have my rpm range into the 7,600 range and would need a large cam like that to be able to breathe at that high rpm. I plan on shifting at 7200 and crossing the traps at about the same, give or take.. this setup has me looking at a set of 235afr’s with shaft mount rockers, and 750lb open pressure springs to fit the cam... but goddamn that’s a lot! If there’s a way that I can minimize valvetrain stress then I can make this thing last a lot longer!

 

Well. Run it and see what happens. Some engine builders wont give specs on the cams they put in a motor because its weird from the norm but it made the combo work. And they dont want to deal with people questioning it or getting their developed knowledge for free.

 

Some engine builders wont give specs on the cams they put in a motor because its weird from the norm but it made the combo work. And they dont want to deal with people questioning it or getting their developed knowledge for free.[/QUOTE]

We just went though this with my sons 600hp 406. We don't have the specs but the only thing we do know is it's a custom HR and has a 4/7 swap and uses short travel lifters.
It's good tho as it's an animal.
LOL!