RHS® Top 10 Tech FAQs

[jjamros]

This FAQ contains general information about RHS® products. If you have a specific question that you cannot find an answer to, please call RHS® directly at 877-776-4323, or visit the RHS® Tech Center.


1. What is intake runner size, how can it affect performance and why is biggest not automatically the best?

Runner size is the volume of the port from the intake flange to the valve. It is measured in cubic centimeters (cc). There are many considerations that need to be taken into account before choosing a runner size including, but not limited to, CID, fuel, application (drag race, circle track, street), rpm band, vehicle weight and transmission type. The theory bigger is always better does not apply to runner size. A larger runner moves more air, however on a small CID engine, it will not have the velocity of a smaller port. Consequently, this will have an adverse effect on the torque. An alcohol engine can utilize a larger runner volume. Because the fuel ratio is almost 2:1 compared to gas, a significant amount of the port is being used to accommodate the additional fuel. This is why it is best to talk to our tech department (877-776-4323) to work through the entire engine combination in order to determine the proper runner volume.


2. How much is the raised runner head raised?

The raised runner head has the intake port raised .500”, compared to the stock head. This means the port floor is .500” higher from the head gasket service. The raised port provides a straighter line of site to the back of the valve, which significantly increases the airflow potential. In addition, this head has the valve angle rolled 2 degrees to a total of 21 degrees.


3. Where can you get an intake for the 14 degree and raised runner head?

The raised runner head can use any aftermarket 23 raised runner manifold. The most popular part is the Edelbrock 2945, which is a thick flange version of their 2926 manifold. The 14 degree head design originated from the GM 18 degree heads, so any 18 degree manifold can be made to fit. RHS® is currently working on our own one piece manifold for this head, to be released later in the year. As always, we recommend the intake manifold to be port matched to the cylinder heads, and note that with all aftermarket heads, it is not uncommon to have to slot the bolt holes to assure proper alignment.


4. How much is the exhaust port on the BBC raised?

The exhaust port is raised .500”. This is the norm in the aftermarket. The exhaust port has always been the most restrictive part of the BBC design. It was common to open up the exhaust valve size on the OE heads to increase the air flow on the exhaust side. However this limited intake valve size and reduce air speed. Therefore the aftermarket adopted the raised exhaust port to alleviate this problem.


5. Which company's headers normally work with our heads?

Header fitment is always an issue when using aftermarket heads that have been optimized for performance. Spark plug entry angle is an area where we have found additional power. However it can cause interference with some headers. Most header manufactures have made specific parts to fit our heads. The problem typically is limited to some of the street applications where packaging headers is an issue, regardless of the manufacture of the heads. Shoenfeld, Headmen, Dynatech and Mac have always been good choices. In some of the problem prone applications, we have had success with Sanderson headers.


6. Do you have a list of basic engine formulas?

   Click on the formula list below to enlarge.



7. Do you have a spark plug application chart with brand, heat range and plug size listed?

This is a very common question. It is not possible to provide the exact heat range for every application, but we think it is important to provide a base line and the configuration for the heads. The iron heads use a .708” reach tapered seat plug, while the alum heads use a .750” reach gasketed plug. The instruction sheet for each head indicates the recommended part number.


8. How much can the head be milled, and how thick is the deck?

This will vary by part and can be found on the tech sheets.


9. How long of pushrods will I need for my RHS® heads?

Due to the amount of variables involved, we recommend utilizing an adjustable pushrod to determine the length required to achieve the best geometry. Valve length, head milling, block deck milling, base circle diameter, lifter type and rocker arm design all effect the length. It is highly recommended that you mock up the valve train for proper geometry to determine the length.


10. Do my heads require an offset rocker arm?

All Pro Torker™ and Pro Action™ cylinder heads are designed to utilize the factory valve train components, with the exception of longer valves. OE and after market rocker arms with the standard pushrod locations will work. The Pro Elite™ series heads begin to push the envelope, and some require an offset rocker arm. At RHS®, we highly recommend going to a shaft mount rocker system when utilizing an offset rocker to maintain proper alignment.