[Tony Goat]

Hey Fellas, I need some help. I have a line on a set of RA IV heads and exhaust manifolds from a coworker. He is getting me the casting numbers for further identification, but in the mean time here is what I need to know;

What drive-ability issues will I have if I swap the stock heads from my WT engine to the RA IV, am I going to increase the compression too much to run pump gas?

What other changes will I have to make for the installation?

What should I look at paying for the set of heads and pair of manifolds?


Thanks,

Tony

[U47]

I hope you live near a race track so you can get the fuel you will need. I can't even use the RA111 48's on pump gas. If those heads are in good shape they should be expensive so what I would do is buy a set of Edelbrock aluminum heads that can take this wizz bang gas of ours without detonation and use those. Now if you want to be authentic you'll have to use the iron heads and remember you can't hammer it!

Don

[Half-Inch Stud]

Could go with E85 (high Octane & cheaper than 87 Octane gasoline) by buying the Carb Conversion kit for a Holley.

[Tony Goat]

Don,

What is it about the RA heads that is causing the higher compression and thus the need for super high octane? From what I have gathered, they have the same 72CC chamber volume as my stock heads. I'm I mistaken about this similarity, or is it something else causing the difference?

Tony

[U47]

Tony, well it's only 1cc difference but even the 96's - 48's - 16's @ 72cc on a 400" detonate on hard acceleration or when pulling a long hill when it's above 85 degrees. Even 7K3's in my 455 detonate under the above conditions. For now I've got to baby it, and that's not what I built it for. When time permits I will put the "E" heads on. BTY the highest pump gas we can get is 91 and that has 10% ethanol. That 10% was just mandated a few months back... now all my vehicles are getting from 2-4 MPG less..Thank you California.

Don

[johnta1]

The RA IV heads will give you the same CR as your heads now, unless the RA IV's have been milled.

The exhaust if using the manifolds may have the outlets in a different spot than what you have now.

With the IV heads it would need some good breathing (camshaft).
With the right camshaft, you could be better on the detonation issue and also make a ton more power.

[LATRLL1]

If your running RA3 exh manifolds already - the RA4 manifolds will bolt right up ( check the flanges for the correct # of holes)...if your currently using the stock exh manifolds - you will have to change the head pipes and flanges
Unless its a RA4 car, you willl prob get a better bang for the buck going with edelbrocks
Cam change with either heads and good exhaust system
- My RA4 had 3:90s and and an M21 - was soft until it got up around 3000 rpm - very ill tempered in the lower rpms ( mid 1980s cam technology )
Id definitley have a good mach shop check the heads before laying out any cash

[U47]

[QUOTE=LATRLL1;4057673]If your running RA3 exh manifolds already - the RA4 manifolds will bolt right up ( check the flanges for the correct # of holes)...if your currently using the stock exh manifolds - you will have to change the head pipes and flanges
Are you really saying that RA3 D port manifold/ head is the same as RA4 exhaust manifolds/ Head round port & will bolt up. Look again LATRILL1.

Don

[2manyponchos]

[QUOTE=U47;4058048]

Originally Posted by LATRLL1

If your running RA3 exh manifolds already - the RA4 manifolds will bolt right up ( check the flanges for the correct # of holes)...if your currently using the stock exh manifolds - you will have to change the head pipes and flanges
Are you really saying that RA3 D port manifold/ head is the same as RA4 exhaust manifolds/ Head round port & will bolt up. Look again LATRILL1.

Don

I think he is saying that if you currently have a car equipped with RAIII manifolds, the head pipes will work when switching to RAIV manifolds. He never said that RAIII manifolds will bolt to RAIV heads. He's been around the block before and has owned cars with SD heads, RA heads, etc. Probably just needed a little clarity.

For what it's worth, I know that a properly tuned 68-72cc head 400 cubic inch engine will run fine on pump gas with no sign of detontation with proper cam selection, timing curve, and an effective cooling system. I've got 2 running around (one of which went on a 1600 mile round trip to Wichita) personally and can point to about 2 dozen within 30 miles of my house. All about tuning and the proper selection of parts.

[Tony Goat]

Thanks for the info guys. To clarify what has been stated;

- Swapping stock exhaust for the RA 4 will require modification of existing down pipes

- RA IV has minimal combustion chamber difference between stock heads

- RA IV heads will run fine with stock cam with out detonation issues or racing gas



The questions still remaining;

- Will my stock intake bolt up to the RA IV heads?

- Are there any other items of concern I've overlooked?

- What is the going rate for RA IV heads?

- What is the going rate for RA IV exhaust manifolds?


Thanks again,

Tony

[LATRLL1]

Hey Tony
Heads are in the $1500 - $ 4000 range ( depending on condition )
Exh Manifolds - $ 400 for repros
The intake bolt pattern is the same for 68-71 - aluminum or cast

To clarify the dport vs round port - dport man will not fit a round port head and vice versa
the head pipes are the same length and opening for a RA3 and RA4 ( 69-70 A-body)
This applies to factory produced pieces
I melted a RA4 manifold in the 80s , had to get the car back up , so put a set of 48s on it with the RA3 manifolds...exhaust bolted right up....back then, it was all used factory pieces - no repro manifolds available ........Today, you can get the RA manifolds all day long and different outlet sizes are available

[Tony Goat]

Hey guys,

I appreciate all of the input. I have gotten some more info on the casting numbers and my coworker was mistaken..... Not RA at all. The two sets he has are casting number 670 and 13. I was able to locate the flow numbers for both of those sets and the RA III, RA IV, RA V, Edelbrock, and what I think are my stock "16" heads (Still need to verify). Neither the 670's or the 13's flow any better than my 16's and all three of the RA heads pale in comparison to the Edelbrocks. I may still pick up the exhaust manifolds since they are for D port heads and will fit my 16's. I'll hold of on the heads until I decide to drop the coin for the Edelbrock set up.

Thanks for your help.

Tony

[Tony Goat]

Last question for you guys. What issues will I have with the RA III exhaust manifolds bolting them up to my existing system? As far as I know, I shouldn't have any problems matching them up to my heads since they are both D port, but my concern is the conection at the down pipe. Am I going to have to modify it and if so, by how much?

Thanks fella's,

Tony

[428RA4]

Food for thought.

The main difference between a RA III and RA IV head swap is the 1.5 vs. 1.65 rocker arm. Either way, you will be running into valve train geometry issues that you HAVE to check and verify. You could screw up your engine and wind up doing a bottom end as well as wasting the heads.

Think about it...