New Combo
 

Wondering what you guys think about the following combination for an upgrade to one of my 1978 S/E T/A’s. I will be using Items I have instead of going out to purchase new aftermarket parts.

Current combo – 406 CID W72 block, Edelbrock performer intake, XE 274H-10 cam, Forged pistons, forged Eagle H-beam rods, Stock crank, 6X#4heads with port match and cleanup of bowls, 9.45 to 1 compression, D port Doug’s headers. Horsepower is 370 -380.

New combo – same 406 CID W72 block, 234 factory intake manifold, Butler RA IV roller cam. Same rods, pistons & crank. RAII heads, round port Doug’s headers, 10.25 to 1 compression.

Cam specs – https://butlerperformance.com/i-3164...tegory:1234841

Estimated HP 450.

Let’s hear it.

Thanks in advance.

With what I have seen from having the RAII heads on the flow bench they flow like most any stock D port at lifts above .450” and flow really well on the exh side, in fact so much so that since your running headers I don’t think you want to run a cam with more exh duration then intake duration, since the headers themselves will pick up 4 to 5% more exh flow at lifts above .250”.

Note also that the stock tulip RAII intake valves are not the way to go.
The normal replacement nail head types flow better with that intake port.


Also on the subject of cams you did not mention what you have for rear gears?

That RA4 roller cam is going to act a good amount bigger then that 274 cam.

3.73 gear.

Is there a reason an Edelbrock performer rpm head isn't be considered? Or just want the cool factor of having the RAII heads?

I like this build either way. Should be kinda rowdy.

Want to use parts I already have.

Had a feeling you probably already had a set, that makes sense.

Should run very well. I run a 10:1 428 with 614's and a 236/244 hydraulic flat tappet camshaft, Doug's headers, factory IV intake and a Quadrajet. It is plenty streetable, never overheats and will turn the tires into smoke with a 3:23 rear gear and a 4 speed.

Stock exh flow comparison @ 28” casting #62 and RAII.

.100”////43.4//// 35

.200”////82.2//// 84.7

.300”////120.2//// 122.6

.400”////139.7//// 161.6

.450”////149.3//// 174.4

.500”////155.6//// 190

.550”////159.1//// 201.2

.600”////162//// 206.3

.650”////165.6//// 210.3

Steve25
what flows better in 6X heads Ferrea 12 *undercut or their 9* flow dish?
2.11 intakes

While I do have two stock 6X-4 heads on hand I do not have either of those valves

RAIIs are worth a lot of money to the right person. You could just about get any aluminum head you want with the cash.

Steve25,

It seems the solution to the flow of the intake and exhaust of the heads is to port the intake and leave the exhaust side alone. When it gets to a proper increase on the intake side it will allow the dual pattern cam to run with no problem.

You could...but everyone has a set of aluminum heads. I personally like opening my hood and showing off a set of factory round ports in a sea of aftermarket heads, even if very few people notice.

What carburation?

Holley Brawler 750 CFM Double Pumper