hangslo

I am building a big block ... either a 454 or 502. I already have a couple of 454's, but it will most likely be a 502 since it has a larger bore and I have the heads to keep up with it. My goal is somewhere around 1200 to the ground. I have seen a 454 build with my heads and a vortech that put out over 900 HP at the crank at just under 7 lbs of boost, so airflow will not be a problem.

I plan on driving this extensively on the street, so it is not going to be a race-only truck. I am trying to figure out whether I should go with a single thumper or use a couple smaller turbo's instead. I am actually leaning towards a couple of either T-66's or T-70's. Quick spool is really not much of an issue for me, since the motor will already be making plenty of torque in the bottom end of the powerband and I will not need any more low end torque. My concern is packaging and total airflow. I have heard running one larger turbo is more efficient, but I would have to go to a large frame to get the flow and it seems that two smaller would be easier for me to fabricate the manifolds.

I know this is a traditional big block and not an LS engine, but you guys are a little more familiar with the turbo stuff, so that is why I posted this here.

Thanks

BLk01SS

iTrader: (7)

The general logic says that twins are better on the street, you can get into power much faster. But then again, you have have the motor for the low end, then get a big 88 or larger and that thing will be nasty on top!

93formto98T/A

iTrader: (28)

Street=twins all the way. I wouldn't have it any other way. Love the instant spool and broad powerband!

BLk01SS

iTrader: (7)

You might call Jose at Pro Turbo Systems. He's are resident turbo expert. He could probably give you a good recomendation for what size for the power and what would work best twins or single.

LSs1Power

iTrader: (5)

Single.... I have always noticed that a single turbo (sized to flow like Twins) will give more TQ in the midrange while retaining the same topend.

mahhddgtp

I would think an 88 would be too small for that, because they're used on 408s even.. I'd go with big twins. Lots of power, nice curve.

Dragframe

iTrader: (14)

you worried about simplicity or not??

hangslo

If it was that worried about making it ultra simple, I would just spray it ...

But, no I'm not that concerned with simple, just packaging and performance. This truck will look from the outside like every other work truck that someone is trying to lower and make fast. I do not mind the extra work of building the hot parts, but with one large frame there is the issue of down pipe size, and the two smaller DP's from the two turbos will fit more easily. Also, I dont want to get too much torque in the midrange, cause the motor already puts out over 550 ft-lbs as it is , and no less than 400 ft-lbs from 1500 rpm and up ... I would like to just extend the power band. I guess what I am saying is that I will have about the same power driving around as a mild turboed small block already ... so I dont see the need to try to get more boost as soon as possible and blow the tires away.

My goal is mid to low 9's with the ability to drive it around like normal while out and about ... no huge lumpy cam and no loud exhaust. I like clean installs, without much attention being drawn to them ... I like stealth ... that is why I am paint my aluminum heads to look like iron heads ... stealth. I also plan on running 15" rims ... because they look ordinary, and no-one wants to steal ordinary. It will just look like a normal truck, till they get blown away.

I also thought about running the turbo(s) in the rear and running the charge pipe up through where the intake tract would go so it could not be readily seen and looked like a normal setup ...

chuntington101

looks like an amazing project!

with what you are after you might want to tune the boost presure! then you could effectivly limit the torque and make it run for longer!then you would have the turbo(s) start to come in a peak torque (or just before) at low presures and then build the presure with the revs! would result in a dead flat curve that goes on for ever!

just a thought!

Chris.

hangslo

Are you referring to tuning boost with the turbine(s) and A/R on the exhaust, or is there actually a way to build boost at lower speeds (midrange), but bleed it off until you want it ... kind of like a bypass valve?

foxspy

iTrader: (1)

Hey Hangslo,

What year/model truck do you have? I have a 1990 Chevy 454ss that I'm starting a turbo build for.

Well, the truck is getting ladder bar suspension, Moser 9", cage, etc before I start the engine/turbo. My original plan was to use a PT94mm or the S95 unit from Forced Inductions. There's a guy I know in TN that has the same truck, but he's doing twin PT76GTQs and he's much further along than I am. He's using the Vortech Modno Igloo intercooler and it makes plumbing easier under the hood. After seeing his setup and how he has his plumbed, I'm thinking about doing twins as well. I know that a 5" downpipe will fit on the passenger side, w/ trimming of the "ear" on the transmission. I also thought about doing a single turbo but having the downpipe split off into two 3.5" pipes right off the turbo and run one pipe on either side of the motor. Those would fit fine.

My goals are similar to yours, streetable is key, and I also need to go 155mph in the 1/4.

Here's a pic of his setup.

hangslo

My truck is an 89 1500 with a blown (up) 350 TBI with a 5 speed. I have a 4l80E to go behind the big block and already have a PCS computer to run it. I also have a couple of 454's right now, but I am going to sell at least one of them and probably buy a crate 502 short block from GMPP ... it is one hell of a deal! I have a set of AFR 305 magnum heads with 2.3 intakes and 1.88 inconel exhausts that will put the compression right at 8.6 to 1 with the crate short block. After looking around, I am probably going to go with twins, probably the 76's like your friend did ... not for spool, but for the airflow.

You are already starting with a 454SS and I have to create one, so I have extra parts to get to get up to speed. I would love to have that 14 bolt your truck came with instead of my 10 bolt. I also have no front accesory drive for a big block, so that is another task along with the cooling system ... and of course, it must have A/C! Is your friend fabbing up his own manifolds, or is he having someone else do it for him? I had thought of making mine and making a jig for anyone else interested since it is very difficult to find anything like this for a big block. I would like some more info on your friends truck as well as yours, if you will PM me with a contact number or website, or any other info, that would be great ... thanks.

foxspy

iTrader: (1)

Hey,

I just sold my stock 14 bolt w/ Eaton posi. I also just sold my front accessory brackets w/ AC compressor. I'm doing a Moser 9" along w/ March brackets.

My old setup was a ZZ502 crate motor w/ a Comp Cam XE294HR cam, JE rings, Clevite bearings, Pro Magnum rockers w/ ported heads. I also had the block zero decked.

I'm selling the long block for $4500, so you could buy that, then sell the heads to put yours on it. It has less than 4k miles on it.

My buddy is making his headers out of mild steel, I think. I'm going to be using 304 stainless on mine.

You can check out www.454ss.com, that's where we post most of the time. You can also get a lot of info on big blocks, stuff about our body style trucks, etc.