Chevy Performance Tech Q&A - August 2014

Kevin McClelland Jun 26, 2014 0 Comment(s)
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Big Al

Last month I left you guys with a teaser that we would be building a couple of engines with our good friend Greg Ventura. I believe I wrote a couple of years ago that we lost Greg’s dad, Big Al Ventura, to cancer. I met Al Ventura back in the early ’80s, racing at Orange County Raceway in my Project Pro-Gas ’57 Chevy that I built. Al had a show-car-quality ’55 Chevy with a nasty big-block running in Super Gas. I was the punk kid rolling into OCIR, and Al was the cagey veteran holding down his turf. Greg was in his early years, riding around on his BMX bicycle and causing trouble for his dad. Al and I hit it off, since we were into Shoeboxes and mine was blue, as was his.

Al retired as a mechanic, taking care of heavy equipment. On the side for many years he had Ventura Racing Engines building any type of engine from street performance variants to Pro Mod nitrous-fed big-block Chevys. Over the years, Al passed the driving duties to Greg and we faced off many times. Al and I always respected each other’s talents and I looked up to him, as—I’d learn later—he did I.

In the last year we had Al around, he was collecting parts to build a really nasty big-block for their ’66 Nova to run Top Sportsman. He had acquired a tall-deck aluminum Brodix block with a raised camshaft tunnel. This block and rotating assembly came from a Top Dragster racer who decided to get out of the expensive game—he’d had very limited runs on the block and rotating assembly. As Al was collecting parts for his dream engine, we learned of the Big C, and we lost him within eight months. Awhile after Al’s passing, Greg came to me as he wanted to build this engine in his dad’s honor. We’ve lovingly named the engine Big Al, and we will try to do the name justice.

Greg’s plan was to complete the engine with a set of Big Duke cylinder heads that they’d run on various combinations over the years. These heads are related to a Pro Stock design from about 10-15 years ago. They used shaft rockers with large exhaust rockers and large offsets to get around the intake ports. Well, cylinder head technology has moved miles in the past several years and the latest conventional-style big-block cylinder heads flow serious air, and use conventional valvetrain components common to big-blocks for the past 50 years. We landed on a set of the new Brodix SR-20s and the matching single-plane racing manifold. The “20” in the name refers to the intake valve being rolled to a 20-degree angle. The intake sports a 2.400-inch valve with a 440cc inlet runner. This CNC port, out of the box, flow’s an outstanding 507 cfm. The exhaust port squeezes in a 1.800-inch valve and flows 335 cfm! Now, they consider this configuration a conventional head, but it requires a specific dome to mate to the 95cc, specific shaft rockers for this valve angle, and valve covers. Brodix did stick with the GM design on the valvetrain and made subtle changes for the valve angles.

In the coming months I’ll report in on various other trick components on this 601ci behemoth that I’m having a ton of fun building. Our main goal is to make Al proud. We want to get their ’66 Nova into the 7s without any power-adders, and enter one Top Sportsman race and have Al ride along while Greg turns on win lights. Stay tuned.

Edelbrock Pro-Flo XT

Q I have a ’69 Chevelle SS with a ZZ502 crate engine from Chevrolet Performance. It used to have a carb, but I’ve installed an Edelbrock Pro-Flo XT EFI.

The car has 17-inch wheels, a Hotchkis suspension, Wilwood 13-inch front discs, and Stainless Steel Brake Corp 11-inch rear discs. Power runs through a five-speed Tremec and a 3.73 12-bolt GM rear.

I’m in the process of installing an EFI gas tank from Tanks. I’m hoping this will solve my fuel starvation problem when I hit the gas. The new tank will have a reservoir for the fuel pump. Right now my fuel pump is on the framerail. I’m hoping putting it in the tank will take care of my bog.

Is there anything I’m missing? Thanks!

Nick Moscato
Rockville Centre, NY

A Sounds like you’ve got a really nice build on your hands. We’ve always had a very soft spot for ’69 Chevelles. Big-block Chevelles are hard to beat on the smiles per mile!

The way you have described your problem, it sounds like the engine bogs or starves for fuel when you hit the throttle. We assume you’ve checked the fuel pressure with a gauge to verify that you are truly losing pressure at the hit of the throttle. With a full tank of fuel, there should be no way the pickup in the tank could be uncovered and suck air. After reviewing the Pro-Flo XT system, we believe the big-block, PN 3567, comes with a baseline calibration for a 502-cid big-block with a 236-degree duration at 0.050 inch tappet lift camshaft grind. The separation angle falls right in Edelbrock’s recommendation of 112. What they are trying to say in a nice way is that you need to limit the overlap of the cam to make the EFI happy. Your ZZ502 camshaft is a mild street grind, coming in at 224/234 degrees of duration at 0.050 inch tappet lift, but is ground on 110 centers. This camshaft profile gives you a nice chop at idle, but really has less overlap than the camshaft Edelbrock did its calibration on. The ZZ502 camshaft should have no problem interfacing with the Edelbrock system. Also, the coolant temperature is very critical so you pull from the proper fuel tables in the EFI calibration. Edelbrock clearly states that you must have an engine coolant temp of at least 175 degrees F or the engine controller will constantly run in an enriched warm-up mode. If you’ve been trying to adjust the fuel tables for your possible lean bog, you could be chasing your tail unless the engine is up to operating temp.

We gave Clayton a call on the EFI Tech line at Edelbrock, and he recommended you start by downloading the Quick Start Guide for the Pro-Flo EFI systems. This explains the basic calibration methodology you should use. After discussing your issue, we came to the same conclusion: You may need to add what is referred to as “transient fuel.” Adding fuel to this table is just like adding a larger accelerator pump shot nozzle on a Holley carburetor. Larger-duration camshafts, and large plenum inlet manifolds, require adding transient fuel to prevent bogs. The Pro-Flo XT inlet manifold is as close as you will come to a tunnel-ram design in an EFI format. We believe this is where you are going to find your sag or bog on transition. If you have any other issues Clayton recommended that you call in directly at 800.416.8628.

Adding your Tanks fuel system is nothing but a good thing, as you will have a production-like fuel tank with a controlled reservoir around the pump and pickup. Also, upgrading your system with a wideband O2 sensor will give you much better information for your air/fuel tuning decisions. The production narrow-band O2 gives you little information as it only lets you know when you switch from rich/lean at 14.7:1 AFR. The wideband O2 system is sold under PN 3532.


Get Some Flow

Q I didn’t see any flow number listed for the Chevrolet Performance aluminum cylinder heads, PN 12363390, with 2.19-inch intake valves. These seem to be a popular head for Chevy crate engines now. It is on the anniversary ZL1 427. Thank you for any info.

Dan Howie
Chicago Heights, IL

A We just received, fresh off the press, the new Chevrolet Performance catalog, which lists the cylinder head for the ZL1 427 as PN 12363392, and it’s a fully dressed cylinder head with the 2.19/1.88-inch valve package. The 12363390 cylinder head is the same casting machined for the 2.25/1.88 valve package. This head is used on the larger ZZ502 engine that can utilize the larger valve package. Below are the flow bench numbers for the 2.19/1.88-valve-package 12363392 cylinder head flowed on a SuperFlow SF-1020 flow bench at 28 inches of water:

Lift in inches Intake flow/CFM Exhaust flow/CFM
0.100 74 71
0.200 143 128
0.300 207 153
0.400 250 178
0.500 284 200
0.600 309 218

These are decent flow numbers for a street-performance cylinder head—much better than the original iron oval-ports from the late ’70s they were fashioned after. You can pick up an easy 25-30 cfm on both the intake and exhaust with bowl work and minor porting. From experience with these cylinder heads, you will see the matching 25- to 30hp gain with the flow increases.

Hope you get a chance to score a limited-edition ZL1 427. Rat motors are very cool when they are fully dressed in aluminum.


E85 Big-Block

Q I am rebuilding a 454 and would like to run it on E85. What internal stuff has to change? Do I have to run EFI or can I run a carb? What about fuel lines, do they have to be stainless? What kind of fuel tank? What about mechanical fuel pump? Does the timing have to be different and can I run an MSD box? Thanks for your time!

Jim Sherman
Via email

A Converting a vehicle over to an E85 happy fuel system will take a few bucks. Yes, to truly make an E85-compatible fuel system, you should replace the fuel lines with stainless steel. The 85 percent ethanol that is mixed with the 15 percent gasoline is hygroscopic, meaning it attracts and absorbs moisture. This moisture suspended in the ethanol will accelerate the oxidation (rust) in the fuel system. As you mentioned, a stainless fuel tank would also be preferred. If not, you can seal your existing tank with a specific alcohol/ethanol-resistant sealer. Bill Hirsch offers a specific sealer just for this application. One pint will coat a 10- to 12-gallon metal or fiberglass tank. You can pick up what you need from Aircraft Spruce by ordering online, or calling 877.477.7823. A quart is sold under PN 09-03477. This will take care of just about any tank you have.

You can convert over to EFI, as most of the EFI injectors will support the use of blended gasoline with various loads of ethanol. The main issue you will have is if you allow the fuel to sit for long periods of time and absorb humidity out of the atmosphere, or purchase either fuel from bad tanks or old fuel. It can have high moisture levels, which will give your injectors or carburetor fits. Yes, we said “carburetor.” You can run E85-specific carburetors. This would be a carburetor that has been calibrated for the increased fuel flow and the appropriate needle and seats, accelerator pump, and gaskets to live with ethanol. Most performance carburetor builders offer E85-specific carbs. Check out Quick Fuel Technologies’ Q-750 series carb, which is E85 calibrated and specifically engineered for the use of E85 pump fuel. The main body and fuel bowls are aluminum with QuickSet sight windows on both sides that make for easy float adjustment. Billet metering blocks and throttle plate ensure leak and porosity-free sealing between circuits with unmatched adjustability. Each carburetor is hand-assembled and engine tested before it goes out on E85. Look into PN Q-750-E85 online and give them a call for more information at 270.793.0900.

Now, to feed this monster you will need an E85/alcohol-specific fuel pump. There are mechanical pumps on the market, but one of the nicest is from Holley, under the Ultra HP line. These billet aluminum pumps are constructed from CNC machined 6061–T6 aluminum to provide the utmost in strength, with a black anodized finish. The pumps were put through extensive durability testing before they were released for production. The pump comes standard with AN –10 inlet and AN –8 outlet fittings. This Ultra HP pump is rated at a max flow of 225 gph. The bases are independently rotatable from the top to fit most all applications. The pump is internally regulated to 15-17 psi, which will require the use of a Holley fuel pressure regulator, PN 12-704. Check with Holley for any question about these components at 866.464.6553. With these components your fuel system will be bulletproof.

Finally, stepping up with an MSD ignition system will help burn the high volume of fuel. With the increased octane levels of the E85, you should be able to run more spark advance over standard pump gas. Usually with street pump gas, we’re running right up against the knock limit of the fuel. With E85 we would start with 36-38 degrees of total timing. From there you may be able to squeeze in a couple more degrees if the engine performs. You will need to do some type of performance testing to land on your best spark advance.

Good luck with your conversion to E85. You’ll want to pick up an Echecker E85 fuel test tube (PN 36-E85) from Quick Fuel. With this tool you can accurately check the percentage of ethanol content in your E85 pump gas. The amount of ethanol in the fuel can vary greatly from gas station to gas station. We’ve heard of some fuel as low as 70 and some as high as 90 percent. This greatly affects your tune-up from spark timing to jet sizes. Have fun!


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