400 rebuild help-advise

Hi all, newbie here looking for advise. Looking to do a somewhat mild rebuild on my stock '68 400 with #15 heads, Edelbrock Performer Pontiac intake, and Holly 670 street avenger vac sec. carb.  She's getting a little tired and I'm ready to upgrade the front suspension, brakes, and steering so why not pull the motor and clean up the entire front. So She's a '67 Firebird with a stage 2 - 200R4 by Bowtie Overdrives and 373's in the rear, 4 wheel Wilwood discs are whats going in. I'm looking for a street performance build as I also cruise in town and long distances at high speed (hense the 200r4) this ain't a drag car.I don't need 500 hp, but love to make this poncho quite a bit meaner. I also have a set of 670 heads but really don't know what route to go........budget is an issue and will need to stay in the $2-3k range if possible and I will be limited to 91 octane fuel as well. Let me know what ya think! Thanks.  

welcome to the forum Code!..
Both of those heads will give you @ least 10:1 CR which is too much for a poncho on todays gas without added octane booster all the time which raises other concerns in itself. The 670's are a closed chamber design but have the larger valves. The 15's are the open chamber design but have the smaller valves. If you're going into the motor, I'd look into dished pistons to lowerr the CRF to 9.5:1 or a little less and go with the open chamberr heads. TO help it breath a bit better, I'd port match the intake to the heads and consider the RA reproduction manifolds. A change in camshaft will help you also. Lunati and Comp cams are some of the favorites here but either way you go, I'd get a dual pattern cam with a little more duration and lift on the exhaust side, especially if you use the #15 heads. My own personal choice in Camshafts is Crower.
I wouldn't go to big on the cam since the 200r4 (assuming it has OD) should keep your RPM's down on the highway. The Holley 670 might be on the edge of being a bit small. Pontiac put 750 CFM carbs on just about all 400's if it was equiped with a 4bbl. Exception to that is the RA IV which they used an 800 CFM. I'd have the rotating elements balanced also.
Just my 2 cents here.. I am sure others will have input..  
Jim,

Welcome to HPP code.

+1 My71
You don't want to build that 400 too much or you'll be rebuilding that BTO-200R4.
It's only good for about 400'lbs of TQ. You'll be shelling out $4k for an Art Carr 200R4 to take the TQ if you have a lead foot like me. The closer you get to 9.1:1 or 9.3:1 on the CR the better. You'll have to carry a bottle or two of 108+ for the crummy 91 octane you'll run into on the highway if you get it up to 9.5:1CR.

BTW what is the date code on the #15 heads?
1968 #15 400 cu.in. 290/340hp Big Car D-PORT
1.96 1.66 92 CC = 8.7:1 w/400 @+0.030 over  
or
1970 #15 455 cu.in. 360 hp D-PORT
2.11 1.77 87 CC = 9.1:1 w/400 @+0.030 over


There are ALOT of assumptions with those #s so verify what you have before you start. (flat top pistons, fel pro gaskets, 0 deck Htg., yadda yadda...)

Good choice on the 200R4! I have one too. 2500 RPM & 82MPH right on the TQ curve. The need for speed! On the track of course    
I know, it's not red
~~
How may I serve you?
Boiled, Deep Fried, or Flambe'?

Date code is JO77, Oct. 7 1967. The other head's date code is sort of hard to read. It doesn't really make sense but looks to me as O238? In my research I did find them to be the big car D port but I got 2.11/1.77 72CC not the 1.96/1.66 92cc in my code hunting, anyone else chime in and verify??
Yah I like the 200R4, might go with the stage 3 if I need too because now is my last chance to do a build before I get shut down by my significant other for a long while, we don't mention the W word on this site.....right? Thanks for the help Guys I'm really enjoying learning the tech side of these motors!

I thought I knew a bit but I really don't know Sh@*!  

An Art Carr 200R4 is going to cost you $4200 with a trans brake.
2 weeks to make it but it won't come unglued

Year  Engine HP Engine code Trans CR Cam Head Code BBL Carb No. Misc
1968 400 290 HP WA M 10.5 066 (2)15 1-2 7028066 Block Casting # 9790071
1968 400 290 HP WB M 10.5 066 (2)15 1-2 7028066 Block Casting # 9790071
1968 400 290 HP YC A 10.5 254 (2)15 1-2 7028060/70 Block Casting # 9790071
1968 400 290 HP ZR A 10.5 254 (2)15 1-2 7028060/70 Block Casting # 9790071
1968 400 340 HP YE A 10.5 537441 15 1-4 7028262 Late year change. Block Casting # 9790071
1968 400 340 HP YF A 10.5 066 15 1-4 7028264 Block Casting # 9790071

Somebody could have put 2.11 and 1.77 valves in the earler heads

just be sure of what you have

Put a set of dished forged pistons and a good stick say
Pontiac - 287, 301, 316, 341, 350, 370, 389, 400, 421 & 455
Performance level 3 - Hi-Draulic Hauler - Lope at idle. Hot street/strip cam with strong mid-range power.
INT/EXH - Dur @ .050” Lift: 229°/239° RR: 1.5/1.5 Gross Lift: .480”/.501” LSA: 108° RPM: 2500 to 6500 Redline: 6500 Won't need any hotter.
Icon IC 890 pistons.4.5cc dish 8.4:1 CR with 98 cc heads. 9.2:1 with 87cc heads.
Tomahawk Connecting Rods (A-beam) Pontiac 6.625 SAE 4340 steel with ARP 8740 bolt. Bronze bushing. Maxx Lite A-beam design. Average Weight is 690-710 grams Price $399.95

Balance it and it will rip!

 

It's all fun till someone loses the race  
I know, it's not red
~~
How may I serve you?
Boiled, Deep Fried, or Flambe'?

my book shows the 68 #15 heads to be 72cc 2bbl and most likly pressed studs. what kind of studs do you have? the o maybe a (D)april 23 68 still 6 month apart

i wonder if the 670s have enough meat to open them up to 80cc. they where still rated at 360hp with the closed chambers.  
76 455/4spd TRANS AM
69 GRAND PRIX 406/5SPD

Hello

Welcome to the site, your  info is xlnt and helps greatly.

My suggestions will focus on building your motor as inexpensive as I can think of.

Do you currently have a cam in it and if so what is it? Do you want something more?

CURRENT COMPRESSION – There is a major discrepancy or misunderstanding in what the actual cc of your combustion chamber is. Having decent compression is very important when doing any perf type builds that is why this is an important topic. Ken’s machine says your factory #15 heads are 92 cc not 72 which gives you 8.37 static compression with a .030 over motor. This is a bit low for your app. Kens machine has measured most if not all of the heads he has listed. The heads that give you 10.5 compression are listed as 15/215. I have no clue what the 215 means, maybe someone here does.

I personally believe Ken’s is correct because simple logic tells me that Pontiac would not give a base model 2 or 4 barrel 400 engine the same extremely high compression that is used in all 400’s from HO’s to the RA IV however, what I think doesn’t matter because you should absolutely have your heads cc’d to see exactly what they are anyway.


Ken's performance site

http://www.angelfire.com/fl4/pontiacdude428/HeadID.html

1968   15  400 cu.in. 290/340hp Big Car  D-PORT 1.96   1.66   92 C



CYLINDER HEADS – If yours are 92 cc them mill .025 only off from original height to increase comp slightly.

CAM – summit 2800 minimum size or summit 2801 max size. $58.00 May need new high springs.

VALVE SPRINGS – Buy anyone’s $60.00 springs on summit that meet your cam requirements.

PISTONS – Flat top keith black silv-o-lite. $250.00 or just an oem set of “badger brand” pistons possibly $160.00 a set but they may not be flat too so your compression may be too low. Don’t use the cheaper sealed power pistons summit has.
Keith black .030 over size.


RINGS – cast iron sealed power $36.00 Or upgrade to their molly fill [not plasma] $57.00


Sealed power nice cast pistons $220.00 a set no rings or maybe oem “badger brand” pistons possibly $160.00 a set but they may not be flat too so your compression may be too low. Don’t use the cheaper sealed power pistons summit has.


GASKETS -  FEL PRO

EX GASKETS - use rimflex or soft aluminum only with headers.

BALANCE MOTOR  

Code,
Based on what the guys are saying regarding various info on the #15 heads, I've checked 3 web sites this morning and came away with 3 different sets of data for those heads. Some say 72 CC 1.96/1.66, so say 72 CC, 2.11/1.77 some say 87cc (for the 455HO in 1970). Best thing to do is have them CC'd and have the valves measured. Once you know that, you can determine the pistons you need shooting for 9:1-9.5:1 CR.  
Jim,

One site has #15s listed @ 92cc small valve for the '68s and 87cc large valve for the '70s

Break out the plexiglass plate and cc them - then you'll know.
"And knowing is half the battle - G.I. Joe"

The "W" is the other half of the battle  

On the "Stage 3" note:
Take a close look @ extremeautomatics.com/eavscomp/th2004r.html for a comparison of a BTO and Monster trans and an EA trans. Then go buy a 12019 with whatever bells and whistles you want from Art Carr at cpttransmissions.com. EA & Art Carr have very similar engineering on their work. Art just has 40 years of experience. EA Trans has delivery issues, long waits, etc. BTO has less service and warrantee issues but more 200R4 failures with high TQ. Art has only one or two complaints that I can find on the entire web and he answered them personally. Heck flip a coin but without all the hardened parts, pump, boost valve, and VB work the 200R4 will fry the clutches faster than two 16 year olds at a drive in movie in the back seat of mom & dad's '72 Olds 98
 
I know, it's not red
~~
How may I serve you?
Boiled, Deep Fried, or Flambe'?

Great info! Yah now that I'm really thinking about it most my research shows the #15's a big valve 72cc but Ken's machine might be right because I have never had a ping even running 89 oct. when 91 wasn't available. As far as the 200r4 I will look into it. $4k + is a little outa my budget right now. I'll pull the motor soon and post an update, thanks!  

their must be 2 versions of 15 heads. i see a 340hp 400 in 68 with 15s. i don't think 8.2 will get you there with a 066 cam.

i have a set of 061 heads claimed 72cc but cc at 80.  
76 455/4spd TRANS AM
69 GRAND PRIX 406/5SPD

Hello


Xlnt observation on the no ping thing. lol.  Wish i would have thought of that, guess I still cant see the forest for the trees sometimes. lol                    I personally think that confirms they are indeed 92cc just like ken's said. I  also think ken's is right about the 70 being 87 cc's for a 360 hp 455. Sounds about right. I actually have no idea who ken's is i just lucked across them a while back. lol