Chevy Performance Tech Q&A - July 2014

Kevin McClelland May 9, 2014 0 Comment(s)
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Macland Speed Shop

It's been a busy month around the old homestead. Several new projects have landed squarely on the Mac house. Our good friend Jody Lang needed a place to park his motorhome and stacker trailer between races down here in Southern California. Jody lives in Seattle and towing home, one way, is about $1,200 in diesel fuel. I was more than happy to save him the money, and it gave him an opportunity to swap out the rear brakes on his Super Stock Malibu. He's only been wanting to do this for the past seven years. You wouldn't want to rush into anything!

Well, the best drag-racing brakes on the market are from Lamb Components, based right down the road in Upland, California. How tough could it be to swap over the rear discs to Roger Lamb's units? Let's just put it this way, one thing led to the next. First, there was taking apart the rear brakes and finding different offsets in the rear axles. Then Jody was bringing home the brake kit (very sweet parts) and the hats wouldn't fit over the outer flange of the Moser axles. Next, out came the axles and back over to Lamb's shop to turn down the od of the axle flange approximately 1/8 inch. They chucked them up in the lathe, and the first axle had over 0.010-inch of flange runout from a bent axle. No wonder Jody has had a long pedal all these years, as the runout pushes the pistons back into the calipers. Well, this put a stop to the quick brake upgrade while he ordered a set of Strange gun-drilled axles. Out came the housing and it's now over at Lamb getting new axle bearing retainers installed. Between the new axles and bearing retainers, this will resolve the axle offset issues we'd found at the beginning of the project. Everything should be done in the next couple of weeks and Jody will come back down for reassembly. At least this will be two weeks before the next race. Hopefully, we've found all the little issues and it will be a painless reassembly.

I'm sure, if you follow my edit very closely, you'll remember that Daniel and I dragged home a '87 RX-7 about a year and a half ago to build a track-day car to play road racer. Well, Daniel changes projects like he changes socks. He parted out all the goodies from the RX-7 and made about $1,000 profit in the process. Since we're getting our dragstrip back, he wanted to build a Sportsman/foot-brake car that we could drive back and forth to the track. Also, wanting to keep it pre-'75 and out of the Smog Police's hands here in California, we've brought home another car to build. The RX-7 left, and a '74 Vega GT wagon took its place! Over the next couple of months we're going to install the LT4 that used to power our Malibu wagon into the mid-11s, and the Stock Eliminator-prepped TH350 trans into the Vega. Our good friends at Don Hardy Race Cars still make the original Twister V-8 Vega swap kit with engine mounts and headers. We're going to upgrade the rearend with an 8.5-inch 10-bolt. It should be a fun little racer that will go way too fast for Sportsman's 12-second limit. We'll play with restrictor plates or very small carburetors.

Finally, our buddy Greg Ventura dropped off two engines that we're going to help build and teach him the finer points of engine building. We'll report on our progress over the next couple of months and fill you in on these very cool engine builds. That's all for now from Macland Speed Shop. Now you go out and find something to work on!


Squeeze Me!

Q I am working on my project '85 Camaro Sport Coupe, which currently has the original 305 small-block and a 700-R4 transmission, along with an open 3.08:1 rear and disc brakes. I have a 350 that's bored 0.060-inch over with four-valve-relief flat-top pistons that add 5 cc. The cam is an Elgin E920 with a 0.480/0.480-inch max lift, 288/288 advertised duration, 230/230 duration at 0.050-inch lift, and is ground on a 109 LSA. I'm running Edelbrock E-210 heads (PN 5085) with a 64cc combustion chamber and 0.041-inch Fel-Pro head gaskets. Right now my pistons have 0.044-inch of deck clearance, and I was looking to deck the block to try and zero the pistons out, but I still want to run pump gas. Here in Wisconsin we still have regular access to ethanol-free 91- and 93-octane gas. If I deck the block 0.035 to 0.040 inch, I should run the compression to about 10.25 to 10.40:1. Will this be an issue with my situation, or can I completely deck it to zero?

Also, I have the stock torque converter in the 700-R4. What kind of converter should I run with a budget in mind? I will mostly be driving this car on the street or autocross but occasionally to the local dragstrip.

Lastly, I found a rearend on Craigslist from an '87 F-body with an open 3.42:1 gear with drum brakes for dirt cheap. Would this be a viable option to do a low-budget swap into my '85? I'd like to ditch my 3.08 in favor of a posi and lower gearing, but the 3.42 was only available with the V-6 F-bodies. Is there any difference in the strength between the '87 V-6 rear and my '85 V-8 3.08? I also want to keep my factory disc brakes. Would it be easier to swap the 3.42 gear into my original rear or build up the '87 rear? They are both the 7.5-inch 10-bolts. I'm looking for the easiest way to do this with the least amount of downtime on the car. Thanks for your time and advice!

Kory Schultz
Via email

A Compression ratio can be a tricky thing. Too much compression with a small camshaft will rattle like a can of rocks. If the camshaft has enough overlap to bleed down some of the cylinder pressure at slower engine speeds you can get away with higher squeeze. With your camshaft selection, this will likely be the case. Let's think about this a bit.

The lobe separation angle of your Elgin cam of 109 and the advertised duration of 288 degrees will bleed down a good bit of your slow-speed cylinder pressure. Not only does the increased overlap bleed down cylinder pressure, it allows a slight amount of intake dilution, which means you have some spent exhaust gases that remain in the combustion chamber when the exhaust valve closes at slow speed. This is what we call “built-in EGR.” It not only reduces the octane requirement of the engine at slow speeds, it reduces exhaust emissions (NOx). We have been able to remove the EGR valve and have the same or better NOx emissions while designing emissions-legal performance camshafts.

With your 700-R4 and its low 3.06:1 First gear, it gives you the ability to get the car moving at the low engine speeds. Also, that you're looking to a stall converter and lowering the rear gear ratio, is all in the right direction. Finally, we reran your compression ratio calculations and came up with 10.30:1 at zero deck, and 10.0:1 with the piston 0.010 inch in the hole. Something you may not have included is the volume between the top ring of the piston and the head of the piston. Commonly, on a small-block with this bore size, you can expect that volume to be in the 1.2cc range. Also, the Fel-Pro PN 1003 with the compressed thickness of 0.041 inch displaces 9.1 cc. That said, you could live with the 10.3:1 compression of a zero-deck combination. When you put the thing together, start with a total timing of 30 degrees and work your way up from there.

Unfortunately, torque converters for the lockup 700-R4 are not budget-minded pieces. For this camshaft duration range, we would run a minimum of 2,400-stall speed. There are many aftermarket performance converters out there, and you can search easily for those. For the budget-minded swap, we'd recommend a production GM torque converter, originally used in '85-86 TPI 350 Corvettes. These converters were a 298mm diameter (11.73 inch) with a lockup clutch. They were identified on the converter with an alpha code of “DBCF”—the “B” designator called out the high stall speed. GM rates its converter stall in what's called a K factor. The factory rating of a 140K converter is 2,025 rpm with a specific amount of torque applied. In an '86 TPI Vette, this converter stalled to 2,800 rpm. (We raced one for several years.) The Vette converter is a re-man, sold under PN 24201203. Next, look into the H.O. 4.3L (L35) V-6 converter used in '95-and-up S-10 trucks. The alpha code for the L35 V-6 converter is “DBLF.” It's the same core and K factor as the earlier Corvette. Also a re-man, it's sold under PN 24202310. You can try and find one running around a junkyard, but it's probably already baked and the lockup clutch is worn out. We also understand that you can pick up one of the GM converters in the $250 price range with a $35 core charge. Give Ken Casey a call at Elway Chevy (800.345.5744) to give you the straight scoop, and he may even be able to find one of the gems for you.

The '87 V-6 rearend is as strong as the original '85 diff that's in your Camaro. The disc brakes will swap right over onto the '87 rearend. This would be the shortest downtime for your ride. When you upgrade to a posi differential you'll want to get a '90-and-up 7.5/7.625-inch differential, as it will upgrade your axles from the '89-and-earlier 26-spline to the '90-and-later 28-spline. Yes, you will have to buy new axles with your diff change, but this will give you the strongest posi and axle package.

Sometimes we don't have an unlimited budget to build our toys. It's nice to know there are parts combinations out there that can give you bang for your bucks. Good luck with your budget blaster.

Sources: elwaychevrolet.com, felpro-only.com


Positive Stop!

Q I just got my '78 Chevy small-block 327 and there is no timing mark on flywheel. How can I time my car?

Jeff Ison
Via email

A We know of very few engines that ever used the timing marks on the flywheel. There were a couple of imports, and '50s and '60s domestic models, but no GM engines that we can remember. We assume you're referring to the fact that you have no marks on the harmonic damper on the front of the engine. Or, better yet, you don't have a timing pointer on the front cover. Either way, we'll explain the method of finding top dead center (TDC) with the cylinder head in place—surely, many folks out there either doubt their timing mark accuracy, or have the incorrect pointer for their damper. GM, on the small-block alone, has had at least three different-diameter dampers, and three different timing pointer locations over the long history of the small-block. Let's see if we can break this down to an easy way to get accurate timing.

First, you're going to need a couple of special tools. You will need a degree wheel that can be mounted to the harmonic damper and then fabricate a pointer out of a coat hanger or welding rod. Next, you will need a positive stop to screw into the spark plug hole of the No. 1 cylinder. You can pick these parts up from any of the mail-order speed shops. Summit Racing offers these tools; the 11-inch degree wheel, and a set of three bendable bolt-on pointers. Proform offers a TDC locator (positive stop) under PN 778-66792. With these tools you can accurately find TDC of any engine.

To prep the engine, you'll want to remove all spark plugs, the driver-side valve cover, and all the belts and pulleys from the harmonic damper. Install the degree wheel to the face of the damper. With the valve cover removed, rotate the engine slowly and watch the rocker arms on No. 1 cylinder. What you'll want to do is rotate the engine clockwise from the front of the engine. First, you will see that the exhaust rocker arm will open the exhaust valve and, as the exhaust rocker is closing, the intake will begin to open. As the exhaust is closing, and the intake starts to open—stop turning the engine when the rocker arms are equal. This is where the intake and the exhaust valves are open the same amount, or what is called overlap. This will be within a couple of degrees of TDC. Once you have found this location, fabricate a timing pointer that aligns with TDC on your degree wheel. Once you have done this, rotate the engine one full revolution, which will put the No. 1 cylinder at TDC on the compression/power stroke.

Once you have your degree wheel and pointer set up, you'll move onto using the positive stop. First, rotate the engine clockwise 100 degrees. Now you can install the positive stop into the spark plug hole without hitting the top of the piston. With the positive stop installed, very slowly rotate the engine counterclockwise until the piston comes in contact with the positive stop. Again, slowly—if you get after the crankshaft and turn it quickly, you can bend the stop in the spark plug hole and dent the piston. When you have found the stop and the crankshaft has positively stopped, record the degree location on the degree wheel. Depending on how far the positive stop is inserted into the cylinder, this could be anywhere from 20 to 50 degrees before top dead center (BTDC). Now turn the crankshaft clockwise one full revolution and slowly come up on TDC until you hit the positive stop again. Record the location on timing pointer and see where you have stopped. What you are going to do here is see the difference and adjust your fabricated timing pointer until you have equal degrees of rotation when you repeat back and forth from the positive stop. For instance, if the first timing mark you recorded was 20 degrees BTDC, and when you rotated the engine around to the other side it was 25 degrees BTDC, you would take these two numbers and add them together and divide them by 2. This would leave you with 22.5 degrees. While the piston is still against the stop, and at 25 degrees BTDC, bend the timing pointer until it lines up with 22.5 degrees on your degree wheel. Next, rotate the engine counter clockwise until you're coming up on 22.5 degrees BTDC and slowly rotate until the crankshaft stops. If it lines up squarely with 22.5 degrees, you have found TDC with your degree wheel and fabricated pointer. Once you have achieved the same degree readings on both sides of the positive stop rotation, you can remove the positive stop tool from the spark plug hole. Then rotate the engine until your fabricated pointer lines up with TDC on the degree wheel. This will be true TDC on your engine.

In your case, if you don't have a factory pointer on the front of the engine, pick up an adjustable Spectre timing pointer PN 865-4237, which will fit 6-, 7-, and 8-inch GM dampers. It is held in place by two of the front cover bolts. Adjust the timing pointer until it is aligned with the timing mark on the factory damper. If there is no timing mark in that location, then scribe and mark a new timing mark on the damper as you have found TDC on your engine combination.

We know this sounds like a difficult process, but it's really easy if you follow the step-by-step instructions. This is how you can find TDC on a fully assembled engine. You can find many examples online on how to find TDC and degreeing camshafts on short-blocks, which make the job much easier with a dial indicator. Hopefully, you'll be able to set up an accurate pointer, and this has given the masses the ability to check out their timing. Good luck, and be patient!

Source: summitracing.com


Budget S-10

Q I am currently working on my '82 S-10 shortbed pickup. The engine I currently have between my framerails is an old 350 block out of an '89 Camaro IROC. The bottom end is completely stock. I'm working with a limited budget. The top end consists of a set of double-hump heads with 2.02 valves, double springs, screw-in 7/16-inch screw-in studs COMP Cams 1.6-ratio roller rockers, a COMP Cams hydraulic flat-tappet nitrous cam that specs out at 0.487/0.501-inch max lift, 274/292 advertised duration, and with 113 degrees of lobe separation. For the intake I'm running an Edelbrock Performer with a 750 Holley double-pumper carb, and a 150-shot nitrous plate on it. The trans is a TH350 with a mild shift kit and a 3,000-stall converter. The ignition system is nothing special, as it sports an old-school HEI distributor and top-mount coil. I'm curious to know an estimated horsepower number for this setup. I am told it should be around 385 naturally aspirated, but I'm a bit skeptical. The truck is about as light as I can get it while retaining mostly stock body panels and suspension. I'm hoping this engine on spray is enough to power my S-10 into the mid-11s this season. The rear will remain stock for now, with just a mini-spool to get me through this season until I can put a better one together. Is this doable, or am I still dreaming?

S-10 Racer
Via email

A Whoever gave you the 385 hp estimate was pretty darn close. We'd peg it in the 350-360 hp range. The Performer intake is probably one of the first upgrades you should look at. Any of the Performer RPM intake line will give you at least an extra 10 hp in your application, and we like it better for the nitrous application, as the plenum of the manifold is larger and you should have better distribution with the RPM.

Getting into the 11s is going to be all about traction. The trans/converter is there to support what you're trying to do. You didn't mention gearing, but you did say you're going to install a mini-spool. This will give you both tires to work with, but unless they have some grip, it's all going to be for naught. Next, the stock 7.5-inch rearend with 26-spline axles is going to give up under nitrous hits. Make sure that if you get the truck to stick, wait until at least the 60-foot clocks before engaging the nitrous. Hitting the diff with all that torque on the launch will certainly spell disaster for the stock diff. Keep your eye out for an 8.5-inch S-10 rearend, which is a direct bolt-in to your truck from the 4.3L H.O. L35-powered S-10s and most of the late-model 4x4 S-10s. They are getting really hard to find, as we've been on the hunt for another swap.

Good luck with your truck, and have a blast. Working with what you have and seeing how quick you can run is a ton of fun. Doing it on a budget can be very rewarding.


Chevy Vortec L31 Motor

Q I have access to a '98 Vortec 350 L31 small-block out of a Chevy Tahoe. I'm wondering if this is a good base engine to start with. I'm basically going to leave the bottom end stock, but will be adding a cam, intake, headers, and such. Should I stick with the stock Vortec heads or go with an aftermarket setup? Money is pretty tight right now but the engine is free, and I do have most of the parts mentioned above sitting at home. I had planned to put the engine into a '67 Chevy C10 pickup. Thanks.

Jaime Castellanos
Pacifica, CA

A The Vortec small-block is a perfect building block to create a really nice street cruiser. The stock iron Vortecs are the last iteration of the iron LT1 cylinder heads. First, GM designed the aluminum LT1s, which debuted on the '92 Corvettes on the Gen II small-block. Then, a year later, the iron headed LT1 was released in the F-cars. The iron LT1 heads flowed better and performed better than their aluminum counterparts. Finally, in '96, the Vortec small-block came along. Everything GM learned in the previous two versions of cylinder heads was incorporated into the iron Vortecs. These heads are the best production small-block head ever produced. They will give you outstanding performance for the money.

Adding a dual-plane performance intake manifold, a mild hydraulic roller, headers, and free-flowing dual exhaust will produce well over 400 hp, and as much as 430 lb-ft of torque to pull around your '67. The only thing you will need to do is upgrade the valvespring package to accept the lift range of your performance camshaft selection. We really prefer the GM Hot Cam package (PN 12480002) to throw into these engines. It will give you over 410 hp and the 430 lb-ft quoted above. This cam specs out at 218/228 degrees duration at 0.050-inch tappet lift, 0.525/0.525-inch max lift with the 1.6 roller rockers, and is ground on 112 centers. This package gives you outstanding idle vacuum and a mild performance idle. It comes with camshaft, LT4 valvesprings, retainers, spring seats, keepers, and 1.6 roller rockers. Again, you will need to do a little machine work to install this spring package, but it's well worth the upgrade.

Hopefully we've convinced you to use this core engine to build your budget swap. There are many money saving ideas out there if you have the right components. You've got them right in your garage.

Source: chevrolet.com/performance

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