383 TBI Chevy 1

[seniorbigs]

Is it possible to stroke a 350 chevy to 383 and have it run with the TBI system? What can be done to improve prformance with this system? Thanks, Mike

 

[enginesrus]

Ah yeah it can. To improve performance, the usual things.
Improve air flow in and out of the cylinder, increase fuel delivery.
Doing the above with headers, porting, after market tbi systems etc.

 

[enginesrus]

Should have mentioned cam also.

 

[patprimmer]

If you use 350 rods and high pin height pistons, the rod in the area of the rod bolts normaly hits the cam lobe and the rod bolt nuts normally hit the gasket rail.

You will want the longer 350 rods, and a considerable increase in cam duration, exhaust and inlet gas flow if you want it to rev anywere near what the 350 did.

I personaly prefer the 350 crank in a 400 block, then every thing fits without need to grind metal of rods and bolts. piston speeds are also slower and rod angularity is still quite good

Regards
pat

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ShaunT]

The 6.00 Inch rod is the best way to go. It greatly helps the restricted induction feed the motor. You will need a reduced base circle cam with a longer push rod, and you will have to notch the bottom of the cylinders to clear the rods. Scat makes a great budget I-Beam rod for a couple of bills. There is one thing to further consider. The induction side of the TBI motors is not your best idea for HP. It is like a 2BBL carb as far as air flow is concearned. Ever thought about a 4 BBl manifold set up with an adapter to fit the TBI? What about a big block TBI? On restricted induction engines, be careful on exhaust cam timing.

Shaun TiedeULTRADYNE/LUNATI Arl,TX(stiede@ev1.net)

 

[TomOstrowski]

One of the most important areas of concern in a typical stroked 383 sbC is the camshaft. Most builders will choose a 6" rod which, due to improving dwell to an extent and optimizing the quench area(typically dished pistons are used with 6" rods), makes correct timing of exhaust gas evacuation crucial for optimum performance. Add a typical 1.6:1 rocker ratio upgrade and you've got an entirely different beast compared to the events/results you had with the standard 350 velvet. Some guys try their best with tricks such as upping the rocker ratio on the exhaust side only, adding timing to the cam, playing with ignition timing, etc. when it's much easier to get ahold of someone like, say, Comp Cams and have a grind designed for your engine. There are even plenty of good grinds available from most camshops made for most variations of the 383 sbC where specs such as optimum lobe separation, etc. are engineered into quality off-the-shelf parts- Comp's dual-pattern(designed for exhaust scavenging) Xtreme Energy series feature some killer 383 specs, for instance.

As you learn more about the 383 you'll find that tuning the exhaust is very important regarding the performance of these engines. They can produce massive amounts of torque and a lot can be gained by paying close attention to how exhaust relates to torque production. The engines really don't spin as fast as some so the amount of power to be had in rpm is limited forcing us to look at other areas. Maximize the torque potential and keep horsepower as an afterthought- a smart selection of parts(roller valvetrain, etc.) will ensure plenty of horsepower.

Adding that big arm really affects a lot of things people sometimes tend to overlook.

 

[TomOstrowski]

Here, I just ran across a link I had stored explaining a lot regarding TBI on 305cid sbCs(not quite your engine but the basics remain valid):

http://www.goingfaster.com/spo/modthel03.html

 

[seniorbigs]

Thanks for all the info. I am in the market for a Suburban 2wd. It will be a limited use vehicle, but I am after spirited performance without the gas mileage and handling penalties of a big block. I'm trying to find a 1/2 ton with a manual transmission. Main use will be vacation/ travel and family hauler. Thanks again all, Mike

 

[ShaunT]

Mike,

if I were in your position, I would very seriously look into purchasing a Whipple. Call'em at 559-442-1261. They have a fantastic piece for you.

Shaun TiedeULTRADYNE/LUNATI Austin,TX(stiede@ev1.net)