Thread: 5.7 5700 vortec power plant

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Hey guys,

First time post here. I know this is mainly for hot rods but I was hoping somebody here could give me some input on a circle track motor. I am building an enduro car for next year on a budget and hope the following year to purchase a 602 crate. I have a bone stock 5700 sb motor. I have my vortec intake and carb ready to swap on. I know about the lift issue with the vortec heads and was wondering if somebody could direct me to a camshaft with the proper lift that will give me the kick I need in the rpm range for a half mile asphalt track. Also what other easy bolt ons I can add for some extra kick such as headers. I really appreciate any help you friends could give me. Please remember this is on a cheap as possible budget. Just getting my feet wet. I don't plan on doing any work on the heads until next year. This is going into a 85 Monte Carlo with a turbo 3 speed. Thanks again.

Welcome aboard McQueenracing, good to have you here. I don't "speak" bowtie so I'll leave that for some other more knowledgeable folks, they'll be along I'm sure.. In the meantime, tell us more about this series you want to race in. Maybe once you get through the probation period, you could share a couple pics!

Originally Posted by 34_40

Welcome aboard McQueenracing, good to have you here. I don't "speak" bowtie so I'll leave that for some other more knowledgeable folks, they'll be along I'm sure.. In the meantime, tell us more about this series you want to race in. Maybe once you get through the probation period, you could share a couple pics!

https://delawarespeedway.com/wp-cont...ndurob2013.pdf

There is a copy of the rule book. Please keep in my that in racing, if you ain't cheating, you ain't trying!!!


Thanks guys.

Welcome to CHR!

We’re a pretty friendly bunch and love to hear about all kinds of racing – straight line or “go-round-and-round”.

As you may already know, the Vortec L31 engine is a 350 truck engine. It’s 5.7 liter displacement is why it is sometimes referred to as the “5700”. It was used in every Chevy/GMC/Cadillac truck platform from 1996 to 2000 and box vans from '96 to '03 (including the Isuzu cab forward popular with plumbers and electricians). There’s a zillion of these engines out there (would be more if the “cash-for-clunkers” hadn’t happened, but that’s another story!!)

In its stock form with the Vortec heads it had a 9.1:1 compression ratio and was a great un-leaded regular engine. Stock horsepower was 220-255 during its lifetime. Torque was consistently 330ft/lb. Stock cam specs were .414/428 lift and .191/.196 duration on all production L31 engines. 2002 was the final year for the L31 and the end of the “traditional small block” with its interchangeable components that dated back to 1955.

The Vortec heads are based off the second-generation of LT engines with 1.94/.150 valves a 64cc combustion chamber of. These were fantastic heads (many believe the best production cast iron heads to come out of GM) and can support over 400 horsepower and pull strong to 6000RPM out of the box.

If there is a drawback to stock Vortec heads, it’s their limited lift capabilities. The stock Vortec heads are good to .450 lift. I know of instances where people have claimed +/-.470, but I would be concerned with coil bind on anything higher than .450 lift. Your rules prohibit roller cams and rockers on carbureted engines, so your options need to focus on flat tappet. Howards makes a cam that would allow you to maximize the stock Vortec heads with .450 lift on intake and exhaust and 267 degrees of advertised duration (213/213 @ .050 lift). Summit part number: http://www.summitracing.com/parts/hr...make/chevrolet with lifters for $166 so it’s well within your low-budget concerns.

Also appears that your rules mandate stock exhaust with offset mufflers (no straight through) and no headers. Keeps the noise down for sure!!

Good Luck,
Glenn

Thanks for the awesome answer Glenn. Do you suggest I replace the rockers and push rods? Or will the stock ones be sufficient with that cam?

And do you suggest getting lifters to go with any cam I buy?

If replacing the cam, definitely replace the lifters! If it were mine (on a budget) I'd do the pushrods also and inspect the rockers for wear and damages and then decide based on results.

I was looking at this cam but from what I have read, some say there is enough clearance for the lift and some people say not. Could someone direct me to a good set of rods and rockers?

Thanks again guys....just want to have some fun....upgrading from racing my 2.4 ltr neon. The plan is to eventually move up a class in the next year or two and run a 602/604 crate

Hey McQueen!
The part number I gave you from Summit is a kit that includes the lifters. As to rockers - I believe in your class you can not go with rollers and I'd stay with the stock rocker arms - tried and true GM stamped steel. Vortec heads are good for .450 and this cam will work fine.

Installation is critical and the lifters must be properly seasoned/broken in at initial start up. Follow these instructions:
Make sure you soak the new lifters overnight in oil and then lube the new lifters with the supplied grease and slide them into the lifter bores. Next install the pushrods through the cylinder-head holes and loosely install the rocker arms with the pushrods against the cups in the rocker arms. As a part of this step you should check the pushrod length. Mark one of the valve tips with a black Sharpie before the rocker is installed and rotate the engine by hand a few times. Remove the rocker arm and examine the valve tip. If the rub point is in the center portion of the valve tip, the pushrod length is okay. If the rub mark is closer to the rocker stud, the pushrod is too short. If the rub mark is at the far side of the valve tip, the pushrod is too long.

To adjust the valves, rotate the engine by hand several times until the intake lifter of the number 1 cylinder begins to rise. When it reaches full lift, tighten the exhaust rocker until the push rod is tight as evidenced by the lifter plunger just ever-so-slightly begins to move. Slowly tighten the rocker nut 1/2-turn. You want to pre-load the lifter but not bottom it out. Continue this process across the engine, lashing the opposite rocker (same cylinder) of the one at full lift. Then you can put the manifold and valve covers on and finish the little things necessary to and start the engine – distributor, fill the radiator, etc.

Critical is that you follow the instructions that came with the cam. You must run the engine at 1500-2000RPM for 20 minutes to properly condition the cam so make sure you have enough fuel and that you have the time to do this. If you start and stop the engine multiple times, the cam may be ruined.

Have Fun,
Glenn

Thanks for the suggestions guys. My next question is, I am going to run a mechanical fuel pump, can I fit a a push rod into the hole for the fuel pump? I have read on many sites that one will not fit in the hole there and something about it not lining up with the lobe on the cam I choose? Sorry for the novice post.

You will need an electric pump. Mount it close to the tank as they "push" better than "pull". Use a regulator to keep the fuel pressure at 4-1/2 to 5psi. I like the Holley pumps but any name brand will work well. When I install electric pumps I also use a cut-off relay that shuts the pump off if the engine dies.

Look at this link:
Electric Fuel Pump - 101

Regards,
Glenn

Originally Posted by McQueenRacing

I have a bone stock 5700 sb motor. I have my vortec intake and carb ready to swap on. I know about the lift issue with the vortec heads and was wondering if somebody could direct me to a camshaft with the proper lift that will give me the kick I need in the rpm range for a half mile asphalt track

Make an appointment or drop in to the track and have a talk with the senior technical inspector. He will be the final word on whether or not you can do something to the motor or the car.
The problem with L-31 heads is the valve guide. It is too fat to run anything but a single spring without damper and too tall to allow any meaningful cam lift. The guide must be cut for smaller diameter all the way down to the spring seat to make room for a good spring with damper and it must be shortened to provide clearance between the bottom of the retainer and the valve guide seal. Most fellows will cut the top of the guide for a 0.530" I.D. seal like this one..... http://www.summitracing.com/parts/cca-503-16/overview/

The question is: Do the rules allow head work or not? If not, you are forced to use the heads as is, with the single spring with no damper spring and a camshaft that limits valve lift to around 0.420". (Remember, you must leave a safety margin of roughly 0.060", so you cannot use up all the space on a stock L31 head. You must leave a safety margin and that dictates 0.420 lift at the valve to prevent the bottom of the retainer from crashing into the stock guide seal if the motor is accidentally over-revved).

All cam grinders make 0.420" lift rule, hydraulic flat tappet cams for circle track racing. Here's a listing from Howards as an example.....
http://www.competitionproducts.com/H.../products/312/

When choosing a camshaft for any motor, the static compression ratio must be taken into consideration. Here's a list that I compiled suggesting the SCR to be used with any particular cam.....
http://www.crankshaftcoalition.com/w..._compatibility
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there are lots of issues with those heads trying to get any room for valve lift--------and---youll need to modify for different studs, valve guide plates and rocker arms---------they are good flowing heads but yuk on lots of the details-

if you want a mech fuel pump you can modify the block to accept one or change blocks

there are also 2 or 3 brands of replacement spec heads out there that are good----

The rules say no guide plates and are very restrictive.....
"OEM stock definition of engine specs are: Max compression ratio 9.0 to 1; Minimum engine vacuum 17
inches HG at 1,500 rpm or less; No grinding, porting or modifying of any component."

At 9.0:1, the camshaft 0.050" duration would have to be under about 210 degrees to produce enough cylinder pressure to move the car gingerly, plus generate 17 inches of mercury vacuum in the intake manifold.
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Glenn,

What do you think this will give me extra in the hp department?

http://www.summitracing.com/parts/hr...make/chevrolet

Also, will this cam be able to perform reaching up to 5800 rpm?

Thanks