Rhoads Variable Lifters. . .Auto-X/Road Racing???

[Ron Sutton]

Originally Posted by atomicjoe23

OK, I was finally able to read the casting numbers. . .the passenger side was basically illegible no matter what, but the driver's side was easy to read with just a quick shot of engine de-greaser.

061. . .should be 1967 400 2BBL/4BBL heads with 72cc (or 75cc depending on what site you look at) chambers, press-in studs, and 2.11"/1.77" I/E valves if online sources are correct.

I also finally found the part number on the carb 1850-4 with 3145 below it. . .should be a Holley 4160 600 cfm with vacuum secondaries and a mechanical choke. Should be a good starting point for a relatively stock engine I would think.

Joe, those are the basic D-port headd. If you plan to pull the heads off (or are rebuilding the whole engine) ... I suggest you have a knowledgeable person remove any dimples from the port floor & rework the bowls under both valves ... then do a quality multi-angle valve job where they lap the valve in a final step & install 7/16" screw in rocker studs. This will not hurt any responsiveness nor torque. It will just help these heads build more power from 2500 rpm up to 5500.

The cam I'd recommend is based on your goals & usage. If this is a frequent "driver" ... and/or you want a very mild performance set-up ... I'd recommend this package HERE with 1.5 ratio rockers. This will be a good, all around, easy to drive package with power right off idle all the way to 4800-5200 rpm. (Shift at 5000)

If you're looking for a higher level of power ... have a manual trans with at least 3.73 or lower rear gears ... consider this cam package HERE. The engine will lope, have less vacuum & not be as smooth taking off from idle. It will run stronger from 2000 rpm & up ... to 5500 +/-.

Pick your poison & Best wishes !

[GregWeld]

Good choices!

Cams are so hard to decide on -- we all want the bad ass sound of a big cam - but few of us want the drivability issues they bring.... And frankly NOTHING is worse than a motor that's a dog, torque wise, were we drive "normally". I always liked an engine that pulled with just barely any throttle. That way you FEEL the power without having to have the speed that goes with the big bad boys. To each his own..... some guys love a car that barely runs. Nothing worse than a "lazy" bottom end to me.

Can't tell you how many hot rod buddies that buy a crate motor - low compression - and choose the wrong cam (bigger is ALWAYS BETTER - BS!!) and have an exhaust sound that's just wuss all the way... the cam bleeds off what little compression the motor did make... and the throttle feels like the car is out of gas. HORRIBLE. LOL

[atomicjoe23]

Thanks Ron. . .I'll check those out.

I'll probably go with the milder cam because I don't want a lazy bottom end as Greg-Weld mentioned.

Hoping to have this thing up and running for the first auto-x of the season in March.

Thanks again.

[GregWeld]

Originally Posted by atomicjoe23

Thanks Ron. . .I'll check those out.

I'll probably go with the milder cam because I don't want a lazy bottom end as Greg-Weld mentioned.

Hoping to have this thing up and running for the first auto-x of the season in March.

Thanks again.

I didn't look at either of the cam choices before making my comments about lazy bottom ends.... My comments were more GENERAL about cam choices, and people tendencies to use the "if a little is good - more is better". It's pretty much the way we all think.

[Ron Sutton]

Originally Posted by GregWeld

I didn't look at either of the cam choices before making my comments about lazy bottom ends.... My comments were more GENERAL about cam choices, and people tendencies to use the "if a little is good - more is better". It's pretty much the way we all think.

I agree Greg. Most people pick way too large of duration for street cams & the overall power is poor ... especially in the range we drive them on the street ... from idle to 3000. I was always amazed at how many "hot rod guys" would pick a race style cam with a powerband of 3500-7000 rpm .... then drive it on the street 90% of the time below 3500 rpm.

Joe, I was a Pontiac guy as a youngster and these 400" engines make good power from idle to 5000 ... as long as we don't mess it up with cam selection. If was driving the car myself ... often ... on the street. I personally would pick the smaller of the 2 also. The larger one will make the car faster, but the side effect will be the idle to 1800-2000 rpm range will not be as strong, nor as smooth.

With the smaller cam, I think you'll need to keep the compression around 10-1 to avoid detonation. Any higher & you'll probably have detonation issues. Any lower & you'll give up power & efficiency.

If you ever desire to build a more racy Pontiac ... you'll need different heads.

Best wishes.

[atomicjoe23]

Thanks Ron. . .the car will primarily see street & local auto-X (once a month) use for at least the next year so I will probably stick with the smaller cam.

A racier motor may be in the cards, but not until I've improved my driving and the engine starts to hold me back. . .might be a while.

[atomicjoe23]

Ron & Greg. . .this thread has morphed into a cam discussion, but that's fine with me. . .

. . .how would you guys compare this Edelbrock cam ( http://www.edelbrock.com/automotive/...2157&submit=go ) with the smaller Comp camshaft ( http://www.compcams.com/Company/CC/c...csid=1215&sb=2 )???

On paper they are VERY similar, but I don't have enough experience to know how much difference the small differences on paper between the two would make?

I'm looking at exhaust systems right now as well. . .at the moment I'm looking at a Magnaflow system and I have a choice of 2.5" or 3" systems. . .would selecting the 3" exhaust have a negative effect if I have a relatively stock engine (with one of the two cams above; the car already has headers on it. . .I think they are Hooker headers, but I'm not positive because they came already installed on the car and they are wrapped)? I'm just thinking that I would eventually want/need the 3" system when the engine gets modified if it wouldn't adversely affect the engine now.

Thanks again for the help!

[GregWeld]

Just at first glance the Edelbrock cam is rated at 500 RPM higher than the Comp cam -- but otherwise they're pretty similar.

Cams also depend on SO MANY OTHER factors -- head flow etc. A lot of times people get a cam that will flow more air than their heads can handle!! LOL


As far as the exhaust system goes --- A 2 1/2" systems is generally rated to handle LESS than 500 HP.....

A 3" exhaust system is rated at 700HP plus.

The Edelbrock cam says that using their matched parts will create 387HP.... and a Torque number of 439 Ft lbs.... nice and torquey that's for sure.