which heads to use?
 

my build is a mild 400 street only build with a .010 cylinder bore. my goal is low end torque with very little highway driving. i have a set of 5c, 7J2, and 6X heads. i think the 6X are 6X-4 but must check. which should i use? very mild cam is the plan.

6x. Even though the 5c is basically the same head. They have a 4 and 8 version like the 6x.

6X-4 definitely.

5C are next in line if there’s something wrong with the 6X-4 set, but only if they’re 5C-4.

7J2 to the scrap man or donate to a friend who probably should scrap them as well.

7J2, is that a 72 2 Bbl 455 head?

The 7L4 is the 455 2-barrel head.

The 7J2 is the 400 2-barrel head.

Both have pressed-in rocker studs, expensive to ‘make right’. Also missing the end bolt holes for headers or exhaust manifolds, yuk.

It’s getting harder every year to justify putting money into rebuilding iron heads. Definitely choose the ones with the best features, screw-in rocker studs being the first consideration for street performance or just simply reliability.

The only press-in stud castings worth working on are the early high-compression GTO 389 (716, 77 and 093) and big Pontiac 421 heads, most of which are the same as the GTO heads. Because they look right and belong on a period correct engine they’re worth putting some coin into.

In my opinion putting money into essentially worthless castings like the 7J2 would be a mistake, unless you live outside the continental USA and had nothing else available to work with.

The 5c or the 6X if they are -4 castings are are nearly identical, but for the 5 series heads having a bit less Intake port volume which is not a bad thing if your stuck running 3.08 rear gears or less.

If I am not mistaken that 7J2 head had no center Exh port divider extending out from the head bolt to the flange.

Thanks for all the responses. i brought the 400 YX block and heads to the machine shop today. heads are 6X-8's going in my 66 GTO. i want a good drivable torquey street driver i will be running a holley sniper EFI, so next question is suggestions on the right pistons and camshaft to match this setup.
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You’ll have a hard time making that 400 a torquey street driver with the size of the chambers in those-8 heads, as they are more suited for a 455 then a 400!

What is the dash mark on those 5C heads that you have?

they are 5C-8's and based on research they are same as the 6X-8's, 101cc-2.02/1.66. at this point i don't have a better option with what i have on hand. at this point i'm open to head suggestion within budget reason. i'm open to head swapping.

Sell or trade the heads you have for some 6X-4 heads would be the best solution.

Find some 13s or 62s, 6X4s. 64 heads work great on 400s too.
13s and 62s are not 72 cc like the manuals say. More like 77. They will get you 9.4-9.6 CR if they have not been milled.

Where are you getting .010" over Pistons from?

13s, 62's, 62s would be best as 6x4s will have compression too low on a 400, around 8.5

The -8 heads are not the end of the world. My TA had 7.6:1 compression ratio, 2.41 gear, and with the stock automatic, ran nicely. Cliff uses a couple of Crower grinds that help these engines.

If you were to find some 6X-4's at a machine shop, ask them if they'd take the 7J2's as cores. Doesn't hurt to ask...

With only something similar to a 7.6:1 compression ratio for the most part the Crower camshafts would have too much seat duration and /or a wide LSA

Do the homework...

Get the intake closing numbers on different cams.

http://www.wallaceracing.com/cam-deg-calc.php

NOT that it means a whole heck of a lot but look for interest how it affects the DCR

http://www.wallaceracing.com/dynamic-cr.php

Jay S can chime in here with more helpful information.


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Example. The popular Crower 60916 hyd flat tappet cam for a 400......

278 / 289
221 / 229 at .050"
112 LSA
.455 /.470 lift w/ 1.5

Now run the numbers using a custom Bullet Racing Cams with lobe H270/306 on the intake side as an example:

270
222 at .050"
0.459 lift

Then combine it with a exhaust lobe duration that suits the cylinder heads and the cars exhaust system in use. Then consider the LSA.

Then consider the low compression ratio.

Or do we want to throw darts at the catalog for a cam choice ?

Call Tim Goolsby at Bullet Racing Cams

https://www.bulletcams.com/

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My 78 with 97.5 cc(never milled) 6X-8s ran high 14s with 2.56 gears and decent power. Not the end of the word for just a cruiser.

If your tossing around getting the heads milled then look into a set of custom pistons with a like a 8 to 10 CC dome.
The cost of milling the heads a minimum.045” and a custom piston may just be real close to a wash, and going to a standard normal .030” overbore would help out nicely also !

What is your reasoning for going only .010” over?

I think the Crower 60240 was the low compression cam I had in mind.

IRC a guy can cut .070 off pretty easy on those 6x-8. I think the chamber is a little narrower than some other heads, makes them a little more friendly to mill some extra off, .070 would be removing almost 14 cc’s. I think .040” off gets it down into 6x-4 range, if you were going to bother having them machined I would at least go .050”, that would get the compression into the mid 8s.

If you pick a good cam, the upper 7 SCR can be workable, certainly would rather be higher, I think upper 7s would ok for a cruiser though. Steve C mentioned I use dynamic compression designing cams, which is correct. On something really low compression I would suggest working backwards and pick a profile from intake closing targets. I also would not suggest starting with DCR first, I would look at V/P index’s first then work your way to DCR. The DCR on that low of compression will give you a false reading compared to what most people try to run. The compression is so low, if your not careful you will end up with a very tiny cam, likely to small for the head flow you have.. Go to big and it will be a gas guzzling slug. For that upper 7s static compression I would try to get the V/P (using that Wallace DCR calculator) around 120 from as correct as possible .006” tappet intake closings, that should end up in the upper 50s lower 60s for the intake closing. I also recall that the Crower cam Cliff R likes with lower compression is the 60240. It is 270* and has a intake closing of about 67. The Lunati Voodoos are more aggressive, dealing with something really low compression I would rather use something like them. The way those lunati’s are ground the little Lunati 262 voodoo (702) actually has nearly the identical intake closing as the 60240. With the lower compression I would rather run the smaller 701 (255 adv duration) than the 702 (262) or the Crower (270). But both the 702 or the 60240 cams are about as big as you would want to use. Bigger than those the engine will start acting sluggish. Bullet has a Ultradyne grind that is listed as a H00 that would be inbetween the 701 and 702 lunati’s , probably be my first pick, and on a 110 LSA instead of the 112s. I think it would build some more compression and might get better milage

Might be difficult to actually find a cam right now, may have to have to use a common generic grind like a 204/214 white box grind(summit 2800, jegs, melling, Elgin….) I have ran it in the 7s compression with ok results on various engines. Not my first choice anymore.

The smaller voodoo the 701 (256/262) is unavailable, no idea when it will be avaialable.

The crower 60240 doesn’t appear to be a available until November or December unless you can find someone that has one on the self. On a 110 ICL it’s intake closing is 65* abdc. I must have used a different centerline when I came up with 67* in the earlier post.

The Bullet I was thinking of (H00 int, H28 exh) is 260 intake to 270 exhuast [email protected] and [email protected], .440, .443” lift.. On a 110 LSA with a 106 ICL it’s actual intake closing is close to 59*, would be 56* if you just used a event calculator. Tim could tell you for sure. That is why I suggested it, it will build more compression than the other shelf cams I mentioned, and still be easy on valve terrain parts. Could even get by with pressed in rockers if you had too. The voodoos are ground a little different irc the 701 would have an actual intake closing of 62-63* and the 702 is close 65-66* on 108 ICL.

I think the 204 int / 214 exh (2800 summit) would have an intake closing of 63*. Rough number off the top of my head.

They are all in that range that would work for the 8ish compression.

Here is a Howard’s also, going to take a broad search to find something right now, even Howard’s is back ordered for more than a month if shipped direct. Might have a decent chance of finding it on someones shelf though.

How about just a copy of the factory 066 Cam.

066 copy would be a melling spc-4. Looks like it is available. 066 pretty small, leaving a decent amount of performance untapped with it, the summit 2800 is a decent step over it in lift and duration. But going to have to use what can be found.

Looks like there are some small XE cams available at the big warehouses yet. Xe262 and the 268 both work good for very low compression, especially if your car has loud exhaust and your kind of deaf, valve terrain noise won’t be a issue then. :). Suggest using a hylift Johnson lifters though, and not the hi energy that come with their cam kit. Better odds of getting a semi quiet combo. Performance wise that 268 can run pretty good yet even with 8.0 compression, even into the 7s.

What transmission and rear gears this car have?

What intake/carburetor set up do you plan to run?

Exhaust system being used is also important.. Very important!

Exactly what RPM range do you call low end torque?

Clay

The 2800 is an available camshaft having run one in a mid compression 350 it's no where near to big of a camshaft for any 400 as it's like a typical 60's/70's 4bbl camshaft in a 350

The 2801 Summit works good in the low compression 400 in my 81. 93.5cc 6X-4 milled 0.050 but "ridge" in chamber smoothed so got it back to the starting 93cc.

to answer the .010 question, that is merely a reference to clean up mild pitting in the cylinder walls. waiting on machine shop to give me an update on that. i also have a set of 350 4X-4H heads, are these any better for the 400? 1.96/1.66 -98cc. this is by no means a hotrod, more like a family jewel (66 GTO Convertible) that i would like to have a little more torque that will be running a holley sniper EFI. i've owned it for 35 years, and was bought new by my dad in 66 when he worked at a Pontiac dealership. i repeat, i don't need a hotrod, and will race no-one so please keep that in mind. i would love to have the original 389, but Dad "blew it up" in the early 70's when i was around 10 years old, as he raced "everybody" that would take him on. it was his daily driver. the biggest resistance i have to date is an LS Swap. i also have a 72 Blazer and a 72 Firebird that are running LSX's, i wanna keep this one true Pontiac.

Some food for thought, a low-compression 400 that had my friend questioning if it really was only a 400 when I took him for a ride:

https://forums.maxperformanceinc.com...1&postcount=22

Keep it simple. Running less than 9:1 compression doesn’t make it a dog.

Ok, I will ask of the OP for a third time I guess, where are you getting these needed .010” over pistons from?

B-Man, I am not saying that your 400 you referring to was not a strong motor, but you buddys Frame of reference might be coming from a sick or poorly tuned motor, and yes maybe of even more CID then your 400.

I have witnessed a built 74 455 ( non SD ) yanked from a guys 1978 GP and put right on a dyno.
The motor made a pitiful 270 hp .
The timing was found to be 39 degrees ( with iron heads ) and the jetting very lean and it was running hot even on the dyno, ( partial jammed T stat as we later found out ) how it did not blow up is a mysterious!

When the timing was reset to 34 and the jetting of the Q-jet got into the ball park the motor gained 40 hp!

My point is if OP has to get a different set of heads anyway may as well aim for something that will make 9:0- 9:5 compression. If OP already has the heads it skews things a little bit but I would argue he is still ahead to get the better heads.

Ok, so your going to go to a common ,030” overbore then, if you can make every effort to get pistons that use 1/16” compression rings, not 5/64”.

I would use those 4X - 4 heads if they are not cracked and convert them to screw in studs if need be.

The 78 NHRA stockers can run 87cc chambers but still a low compression 400 and are deep n the 11s. My wimpy 180 HP stock 78 motor pushed my 3900lb TA to 130mph+ in the straights at Texas World Speedway. So they can be a decent street performer.
Heck if you are getting new pistons then get a mini dome to bump it to 9.5:1!

Your with me I guess Skip, still wondering what pistons will be used because like you said a custom one with a small dome will bring everything in line .

My point of view on using 6X-8 heads, as is.....My 77 TA (180HP) may have had a different cam from what Skip's came with, not sure, BUT it was a teenie weenie bumpstick. I've never gotten an exact idea of what my cam part number was, BUT several of the articles and mayber a Motor Manual, list the lift below .400". Likely they were going for max port velocity at driving RPM's. My TA ran well!!! Never drag raced it, to have an exact idea, but was fun to drive!!!
My thought being that a 066 (Sealed Power CS641) cam would be a considerable step up from the stock cam that was in my 400.

I'm Thinking the OP'er will not spring for $500-600.00 custom Pistons. Just looked some L2262F pistons, $429.00 for the set.

62 heads are not hard to find complete and ready to bolt on

FWIW, I think the 180 HP engines that had the 6x-8s used a single pattern cam from the factory. [email protected]” on both the intake and exhaust. 107.5 LSA, 105 intake and 110 exhaust, .365” lift. Introduced in 77 and used in all the 6x-8 engines through the end of the production run. For certain, was engineered for brute low end torque to pull those highway gears, plus fuel economy. The 066 cam was pretty close to the original cam in my higher hp 77 400 with 6x-4s. But the higher hp engines had the cam retarded about 5 degrees from the factory for top end power for 20 hp difference between the 6x-8 engines and the 6x-4.

Lol, if Pontiac would have did a cam like a summit 2800 in the 6x-8 engine with full dual exh and 3.42s they would have had no trouble outrunning the 6x-4 w72 engines. 77s we’re really held back by their crappy single car though. I lost count of all the engines I have used that 204,214 cam grind in. Still have multiple engines with them, no Pontiacs. 300 Ford, 397 cid Windsor 351 stroker, 360 dodge, and a 440 dodge. Have the bigger 214/224 in a 455 yet. I loved my high school ride and the 214/224 in a little 318 mopar with headers, 8.5 compression,2200 stall and 3.23s. Ran Low to mid 15s, shifted at 5500 in a 3800 lb car. Even turbo charge on 318 and dropped the compression down into the 7s, it pulled the car fine when not on boost. It isn’t a big cam either. I agree with Skip, if my little low compression 318 can absorb that 2801 grind cam, 7s compression 400 won’t have any issue either. Just to be honest though, it really wasn’t a up grade e.t wise from the smaller 204/214 on any of the low compression engine I did and took to the track. Big enough cam it like headers.

Sounds to me for what the car is used for the 2800 cam and the 6x-8s would be just fine. I know of someone looking to sell their fresh 66 tripower 4 speed coded 389 though if you want to go back to stock looking coolness. :). That era engine just has date codes and engine ID stamps, I don’t think it had vin stamping as for original cars, not until 67 anyway.

I will add this for Steve C to read, cause it is kind of fun to use calculators, he knows enjoy playing with them. :) I brought up that v/p index sizing cams to intake closings, I will add one more dynamic too that. If you know your compression that your going to have, if your plotted the V/P index against the intake closing event on a graph there will be an area on the graph that is linear, then logarithmic (downward curve) and then will go back to linear again. Best results seem to be keeping the closing event in the logarithmic part of the graph, same way with compression for a given intake closing. If you get the compression to high for the intake closing and it is where the graph goes linear, you need a bigger cam, same deal on the bottom of the scale, if you have low compression and you plug the closing event in and the the V/P ends up down on the linear scale on the bottom side, the engine has to late of an intake closing for the static compression. I have played with intake closing and had v/p index from the 60s into the mid to upper 200s . The higher the compression is, that logarithic part of the curve trends up, or lower the SCR, it will move down. On a 400 with 8 ish compression I would guess the V/P logarithmic range will be 90 to about 140. 90 it turns into a pig, above 140 and the it start to hit a wall on the top side. That range is just off the top of my head guess, but if you don’t mind playing with calculators you can use that info and find the range that the DCR should end up and a starting place for your cam design, and work on the opening rates and E/I ratios from there. Most people just talk about DCR, but to really properly use it, the V/P index is actually pretty important. It is an indicator of the pressure waves that build the cylinder pressure. V/P index on the low compression late seventies 6x-8 was usually 120-140 depending on the altitude, kind of right at the top of where they could have good bottom end and still have good power, the Pontiac engineers did a lot of neat interesting stuff with cams.

So would you recommend the summit 2800 cam with my setup? I have been juggling all suggestions.

-Running 3:42’s 400 trans
-Holley sniper EFI (planned)
-2-1/2” full exhaust w/ magnaflows
-power in the idle to 3000rpm range

With a 350, 389 or 400 motor If the compression ratio and can pick does not make for at least 160 psi then the motor will be a lame Dog !

With the 6x-8s and an off the shelf cam I would either look for the summit 2800 or the Howard’s cam I shot a screen shot of in one of the earlier posts. I would have suggested that Lunati 256 if it were available, but I know it will be impossible to find. Better shot finding the Howard’s, but I think it is a long shot also. So IMHO… Best cam that is available off the self at the moment is the 2800. Would work good degreed in at 108 ICL. If it was my engine I would have a shop cut .040-.050” off the 6x-8s to get the compression up a little, I think it would be close to that 160 cranking pressure that was mentioned.

With only a cut of .040” the intake flange should get cut also so the intake manifold bolts up and plays nice!

Once your paying for both of those machine milling jobs removing a cut of that amount, a custom small dome piston is within the money ball park, and plus your not then jerking around with the need for different length push rods to get the geometry back while having adjustment range left in your lifters!

FWIW, we usually find that after a valve job seats the valves in a little further, and swapping in a higher lift cam that uses a smaller base circle the stock pushrods are closer to the correct length with some taken off the heads.

I have some .005” over 400 domes on the shelf. The last set of 400 pistons I bought were IC890 Icons. They gain some compression over a stock 2262 speed pro or a cast piston, don’t quite get the SCR as high as a dome though, and the min size is probably .030” over on the ic890s. For the money they are nice pistons.

Barnett performance might be a good shop to check out for cams, I think they are in Alabama. I have bought parts from them that they stocked that were hard to find otherwise. Would be worth looking into, I would rather run this cam than a 2800 summit.

https://barnettperformance.com/6014....p&VIP=02019002

I chose the 6x-4 for my mild 400 build a few years back and was happy with the outcome. Had a little clean up done in the ports. Brian

true story there...both sets i have are in the 76 cc area. Had my (now dead) set decked to bring into 74 after I did some chamber work 30 yrs ago.

Thanks for the advice, I found a pair of 62’s. The 6X-8,s had one crack and the 4x-4s were both cracked. The 4X-4s were in a running car with not known issues, go figure. Now I just need to match a cam for the 62’s.

Last time I visited Barnett's shop they were in Atlanta, GA. Very nice folks, good recommendation Jay.

Things just took another turn for the better . :)
It hurts to see smog-era parts under the hood of a 66 GTO

Complete yes....ready to bolt on...unlikely. There is no way I am bolting on a set of heads with 50 yr old valves. Just went threw this. Actually am using some #62's on my 455 build ONLY because I MUST buy pistons....so -18cc dish it is. #62's on my old 400 (trw slugs -7 cc reliefs) netted a 10.2:1 compression as they were .028 in the hole (trw's way of lower the compression for you on OLD high compression motors) Yeah i didn't know they needed to be zero decked to help with squish and detonation ...this was almost 30 yrs ago..

+1 on 6Xs for street - have all the manifold bolts and hardened seats.