Head confusion

[Chumley]

I've been looking at Edelbrock intake manifolds, and most of the recommended ones for my engine(402 big block) specify oval port heads. I know from installing headers that the exhaust ports are rectangular. Can I assume that the intakes are as well? Some of the rectangular port models are for EGR which my engine does not have. I'm also assuming that the port design should match, although my header ports are round at the flange and fit inside the rectangle on the head. Any input on this? Thanks................Ron

[PICK-M-UP]

Most BB have oval intake ports & square exhaust. The high performance 375hp & 425hp had square intake & round exhaust...really big holes!!!
Call Edelbrock before you buy...they will be glad to explain & recommend options for you.

[Chumley]

Thanks for the info, my engine is stock and I don't think is considered high performance. 210 HP factory spec. I'll give them a call.

[Dewayne]

I might be wrong...Wouldn't be the first time...But my 70 402BB has a factory rating of 310 HP http://classicheartbeat.com.westserver.net/ubb/smile.gif...I Think?....Feedback?
Regards,
Dewayne 70cst

[Chumley]

You're right DeWayne, but it dropped to 210 by 1972. Not sure why, unless pollution control related. All my truck had was thermostatic controlled air cleaner and TCS.

[70GMC_BOB]

what is the hp for a 71 402bb?

[Sams_71]

What was the year that they changed the way they computed HP? Whenever it was they either started showing a net HP after all the power equipment or changed from HP at the flywheel to HP at the rear wheels. Maybe that might be the 100 horse difference.



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Sam

http://home.att.net/~tmj39/wsb/html/view.cgi-home.html-.html
tmj39@att.net

[cheyenne10]

I fairly certain sams_71 is correct. The horespower ratings dropped significantly due to the method and location of measurement. The earlier 396 motors may have been a little higher but not nearly 100hp. With emissions on the later motors and maybe slightly lower compression ratios the early 70's motors HPs were reduced in general over their earlier predecessors. When rebuilding I doubt you would get a difference using same components. Dynos are the true tests. manufacurers really play this off unsuspecting shoppers, look at new truck specs today. A given torque at a certain RPM can be a better indicator.

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Bob
Founding Member
cheyenne10@msn.com

[longhorn man]

Originaly opsted by Sams_71What was the year that they changed the way they computed HP? Whenever it was they either started showing a net HP after all the power equipment or changed from HP at the flywheel to HP at the rear wheels. Maybe that might be the 100 horse difference.
They starting dynoing the engines with everything mounted and running...alt, water pump, smog pump, full exhaust system....ect. Even today, they do not do 'at the wheel' readings for advertising.

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'69 G.M.C. (http://geocities.com/andys_69_gmc/) 350/350 and a heluva cam. Still trying to clean up the left over damage from the Dope-Smokin-Old-Man.
The 1970 One ton Longhorn (one of only 1404 built) with only a TH350...soon to be CADDY powered and a TH350. Check out The Longhorn Webite. (http://www.longhorntrucks.freeservers.com/) Andy, in Columbus Ohio...Home of JEGS

[D J Derringer]

Regarding the horsepower drop for the emissions years...the cc's were also raised in the heads, reducing compression and HP.

DJ