I am planning to build a 383 for my 1988 suburban. The motor will be a roller one piece main, LT1 camshaft, shorty headers, 3 inch single exhaust, performer intake, adaptor for tbi. I use it to pull my 1991 Z28 to the track. The question I have is:
Will stock 193 heads be good for low end torque? I do not need another hotrod. If not what would work best for this combination? Do I need to do some porting? I just need this vehicle to accelerate up to 65-70 and cruise. Mostly, flat highway. Finally, will the stock tbi hold its own? Thanks, BranZ

 

Best way for you to do that is use a stock 350 TBI cam, 383 shortblock, 193 heads will work fine, 350 injectors, 350 specifics, and a 305 ECM. The 305 ECM is actually alot closer calibration wise than the 350 ECM as long as the 350 injectors are retained. For your use the TBI will hold its own.

 

Why not the LT1 camshaft? Do I stick with the 350 tbi camshaft to promote bottom end torque? Thanks, BranZ

 

Those heads are going to be a bit flow limited, especially on a 383, so it wont rev real well. An early stock LT1 cam or the stock truck cam would work. Although on a 383, it'll make the cam seem 'smaller' so an LT1 cam may have a powerband equivelent to the stock TBI cam in the 350.

If your using it for pulling, though, the tbi cam should work well for that.

 

What kind of torque numbers would I being looking at? I plan to be running down the highway between 2000 - 2500 rpm. BranZ

 

Don't worry about the 383 not reving too well. It is a long stroke motor that won't want to rev anyway. What you are after is brute low speed and mid-range torque and a little HP. I am guessing maybe 230 RWHP and 365 ft/lbs if tuned correctly.

That is why you need the TBI cam, that and the VE tables in the said 305 ecm (unless you will be tuning) is closer to the 350 TBI cam in a 383. Ever notice the 305 TBI cam is smaller than the 350 TBI cam. If you look at the stock VE tables in the BIN files it will also confirm this.

I choose the LT1 cam because I am going to 3.90 gears soon. The 3.08s just aren't helping me do what I want too.

 

Fast355,
What could I do to push it over 400 lbs of torque? Is it impossible with the swirl ports? About a different camshaft? Thanks, BranZ

 

If I were you, for a good cheap 383 that has some good grunt. I'd put some stock GM Vortec heads and a cam like the stock 350 Vortec truck cam or an LT1 cam like you said and you'd be pretty solid I think.

 

The 350 TBI got one of at least 3 cams:

A. flat tappet cam used in the LO5 TBI truck engines, up to and incl the 1995 model year

B. hyd roller cam, aka the "peanut" cam with 0.350 and 0.384" lift, as used on all passenger car 5.7 v8 TBI engines EXCEPT police versions; also used in all 305 TBI engines in B/F car line.

C. hyd roller cam with the 773 suffix, as used in the police Caprice sedan (RPO 9C1). The 773 cam was taken from the L98 parts bin; it's the same cam, confirmed by pn, P & I book verification and by micrometer measurements.

The 305 TBI cam is the same one used in the passenger car non-police TBI v8 models, i.e. as in item B above. Same specs, same lift.

The use of a different cam, either the peanut cam or the 773 cam, would alter the VE because the lift and duration of the 773 cam is higher and longer respectively. So I would expect the VE to peak at a higher rpm on the "large" cam models. But I haven't looked at the tables so I defer to you on that. FWIW.

 

Dyno Don measured 330+ rwftlbs when he used the swirl port heads and an LT1 Fcar cam. Fast355 got 335 rwftlbs @ 3200 rpm. That's 380 to 400 fw ftlbs depending on what you choose to use for a loss in the drivetrain, to convert rwhp to fwhp.

The swirl port heads can make decent power, as shown in the above highlighted thread, as well as in other threads, but only after porting. Other factory heads can also make similar numbers after porting. If you don't port the heads then you won't get the gains. Or you can spend a lot more money to get the same results with aftermarket heads.

 

I was talking the flat tappet truck cam, but all would work equally well.

As far as 400 ft/lbs, I am probably sitting at that number now with 335 ft/lbs to the ground. Your 1/4" extra stroke is definately going to put you there.

Here are the DD2000 numbers for stock heads, stock truck 350 TBI cam, cast iorn exhaust manifolds, stock intake and TBI, 383 shortblock with 9.5:1 compression. This is assuming good tuning.

RPM--------HP---------TQ
2000------151--------395
2500------187--------393
3000------221--------387
3500------239--------358
4000------243--------319
4500------230--------269
5000------202--------212
5500------161--------154

 

I agree. The vortec heads have very good flow at lower lifts and a small runner which equates to good velocity at the intake. They also have an improved chamber. My 0-60 times dropped a full second (down to 6 secs) by going from my older smog heads + open exhaust to the vortecs with an OEM 2.25" exhaust and cat. Even with the huge exhaust restriction they still made more power. If you can get them + vortec intake, theyd provide more power under the curve while still maintaining good low end torque. If not, the TBI heads will be fine for what your doing.

 

Fast355,

Do you think that exhaust manifolds would be better than headers for this application? This setup is starting to look pretty sweet. BranZ

 

Headers. Exhaust manifolds dont really scavange like headers can.

 

Dyno Don measured, on a chassis dyno, 210 rwhp and 330 rw ftlbs using stock, unported 193 heads, and Fcar LT1 cam while using a 350 cid L31 shortblock + TPI. Links to his post(s) appear in other posts of mine if you want to search them out. So long as your TBI supplies enough fuel (big block injectors at the very minimum, and probably slightly boosted fuel pressure), and you use the aftermarket intake, then your intake choice should be nearly as good as the one Dyno Don used, and your results should be the similar.

So I'd expect, assuming proper ECM/EPROM work, with your 383 vs Dyno Don's 350, that you should equal if not exceed Dyno Don's numbers. If you do the slightest amount of DIY porting to the 193 heads, especially the intake side, you'll do even better. Fast355's 5300 lb van runs the equivalent of 15.0 and that's with a 350. Your 383 in a similarly heavy 'burban should run at least as well assuming you copy what he did.

 

I want to thank everyones replies to my questions. This has been very educational. I am already getting parts together to build this animal. I will let you know how it turns out. BranZ

 

Keep in mind that the TPI will react much differently then your tbi will on a motor. The tpi is set up to resonate at around 3500 rpms so it bolsters the midrang power of anything its on. This plays well off of a poorer flowing set of heads that have smaller runners. The tbi reacts more like a carb and doesnt have as much of an effect on the torque curve that tbi has. As such, you may see less power and torque on a motor that powers to around 4500 rpms or so with tbi/carb. Conversly, carb/tbi can make more power on motors that rev above this as the tpi will become a restriction. None the less, you should be able to check in at around 240-250 FWHP with those tbi heads. Better heads would be more desirable on a 383, but youll probably be able to get by with those.