Hey all, I am new here just wanted to see if anyone could tell me what I have, and how to get the most out of it.... Casting 447344 YX block, 7j2 heads. I was playing this weekend, and I couldn't get any rubber, just took off then around 50 she kicks in, anvanced timing a bit, now getting about 100'of smoke i guess that helped. What are the specs for this engine and heads???? What should i do to make it better???? Oh yea its in a 69 coupe with a th400
Seems you have the excact engine I do....Mine came from a `72 model car (prev owner installed it in my 69 convert.). the YX is a factory 400 ci V8 2bbl rated 200 hp automatic engine....mine was installed w a th350 though, I also have a 4 bbl 650 holley on it...the 7J2 heads are what I removed , got some help/input from a couple of sources here and on PY board...I bought a set of 5C heads on EBay for $150...lesser known but good flowing heads w the bigger valves (most people use the more known 4X, but they usually sell for more), had them checked out for cracks,checked the CC`s on them ,they were at 95 cc, had them milled to 88CC , and should now give approx. 9.2-9.3 CR...runs good on "plus" gas ,no need for premium , and I also went to 1.65 rockers from the 1.5 ,and kept the orig cam...car runs great now... You may also check your rear axle, mine is set up for cruising rather than racing and I have the least "rubber burning" ratio....but still squeels out...I have the 2.56 rear and like it since I mostly drive on hwy.I also added a B&M shift kit for better shifting. Now it gives me 14 mpg on hwy at 70 , about 9 in town. No idea on my hp now but should be around 270-280 ,my best guess
Your on the right track! Start off by working with what you have, make sure all your components are in good shape (plugs, points/Dist. wires, carb exhaust etc...) then tune it to get the best performance. Then from there it will start getting a little more expensive.
The right combination of Carb/Intake/heads/cam/Exhaust will hold the key to the major performance you will get out of the motor. Then botom end if in good shape will be good, but the variables will be the heads/cam for the most part, and then the rest will follow...
So eventually changing the heads will be the biggest factor and one of the most costly... Maybe pict up the new book by Jim Hand Building Max Perfomance from a Pontiac Motor (something like that?) as he explains in detail much of this information, along with proven combinations. $14 on Amazon.com
Thanks guys, so am i right in guessing that these heads really can't be expected to do much???? The short block is pretty much the same on all 400's or no?? I also found out this week that the rear shocks on the car are there but but the only thing holding the car up is the springs, shock=junk, what would you all recomend for rear shocks???? Thanks again!!!
You are right , those 7J2 heads are small valve heads...thats why I went to better flow, larger valve heads( 7K3 are larger valves ,but not as good flow as 5C`s I`m told , 5C`s are also not well known so its easier to get a good 'deal')....and milled down for better compression....fairly inexpensive , comparatively... I bought the heads for $150, shipping was $45 ea to Houston from NY, had them checked for cc, a valve job and milled for $450 (also drilled larger push rod holes for the new rockers),added the 1.65 rockers I bought new off EBay for about $75, installed all by professional, another $400...Approx. $1100 total...
My shocks were also shot,I bought Delco shocks from Year One , to be similar to the originals...think they were +_$20 ea.
I also recently bought a set of unused older ( I think Monroe) shocks off EBay so I could offer to the guys in town , but nobody needed any....I can check and see which brand,take pics, if you are interested I can sell those to you for $20 for both,plus shipping
Yeah if you could get the information about those shocks that would be great.... Looks like i will have to talk to the wife about new heads too, better start saving my pennies though!!!!!!!
Yes, short blocks for the most part are the same... the real power will be in the heads/cam combo and then how you get the air/fuel in, and exhaust out.
Take your time, study up on what heads you'll want/need, and or bouce some ideas off of the group (i.e. Q and Banshee) and then you'll know what to look for and get the best deal on a set of heads.
I've sworn by KYB Gas-Adjust shocks... best bang for the buck. Some think they are a little stiff for the ride, but I feel they give greater control.
But Bjorn has a good solution for even cheaper!
Brett - 67 Drop Top 455! (originally from Hibbing, then Bloomington/Burnsville, then Cali, now Seattle!)
Most 400 blocks are the same ... for the most part. There are differences in motor mount bolt holes, but some blocks have them all drilled and tapped. But the short blocks are as different as the heads (from motor to motor). In fact, each motor/head combination also had a specific cam. If the same size motor had adifferent set of heads, it almost always had a different cam, too.
The cam in the '72 YX is pretty lame from a performance stand point. Bjorn was able to improve his '72 400 with better breathing heads and higher ratio rocker arms. The change in rocker arms adds lift at the valves. The biggest difference is the larger intake valves to add flow into the cylinders.
The best improvements in performance will come from matching the carb, intake, cam, heads and exhaust together - and at the same time - as Brett pointed out.
When i bought the car he told me a different cam was installed, i have no idea what it is though. How could i find out what is in there????? The engine was rebuilt just before i got it so i really have no idea on the internals of any of it? There is an edelbrok intake and a holly on top i suppose that opens it up a bit..
The best advice I can give you is to get a degree wheel and a dial indicator. That's the only way to accurately check out a cam while it's still in the motor.
Those heads will negate virtually any added benefit from a 4-Bbl manifiold and carb, and will even put you into an "over carbureted" condition.
overcarburated=too much fuel not enough air????? also if new cam was put in what if the heads were reworkd? Bigger valves would help that right? or would they have to be milled and planed as well? i am not a guru (as some on this site appear to be) on engines actually just starting to learn, so any help is greatly appreciated......
What size Holley on there? I also had a Edelbrock intake plus a 650 holley......you really dont want too big a carb. it just blows fuel thru it..(on one of my earlier cars I changed down on carb size , got more power and better mileage..) the 7J2 heads are very unlikely fitted w larger valves, but you never know... they could be milled some , but if money was spent on them , they prob. should have done that on larger valve heads....maybe they also put other rockers in? to really know it seems you`d have to take heads off... But my guess is that they may just have put another cam in....can you ask former owner? then when you know, use that info to go forward w as you look at bigger valve heads...etc.
I think that is a good idea i will try to contact the guy that built the engine, guess i might learn something that way. i think it is a 750 not for sure but i think that is what i was told...
The heads, if reworked, were probably not treated to a set of larger valves and the full-scale milling that would have been required to give markedly better performance. Those heads are not worth the effort. For a 400, there are a dozen better places to start.
The myriad of possible head choices are as varied as the opinions about which is best.
What you should be after (IMHO) is a reliable, streetable, torquey motor that runs all day long on pump gas and still reminds you that you are dirving a V-8 on street tires whenever you need to be reminded.
To get there from here, you will have to go after other heads. There's almost no two ways about it. What you are looking for is a set of heads that can be finished out to about 88-90cc combustion chambers, have large valves (2.11/1.77) and screw-in studs. There are many casting numbers that can be worked to achieve that, but only one set that actually came that way from the factory. (#64)
Here is a short list in the order that I like them. (We all have our biased opinions.)
#13 (Open up chambers) #62 (Open up chambers) #6x-4 (Mill) #96 (Mill) #4x-7H (Mill) #5C* (Mill)
There are others, but because of ambiguity in casting numbers (multiple years or multiple applications) I should't list them.
The #13 and #62 have superior ports, though the 6X are also good. To use these two heads the combustion chambers can be opened up by blending the corners and unshrouding the valves. This will increase the detonation resistance and promote better flow.
* #5C use a small exhaust valve. It's been shown to improve EGR which helps increase gas mileage with almost no compromise in performance. Edelbrock aluminum heads also use this same combination of small exhaust valve with large intake valve.
Q, what do you think of just throwing on a couple of Edelbrock 87 cc aluminum heads? How does $850/each compare to what it would cost to pick up some used heads and do all the work on them?
My opinion...Edelbrock are factory assembly line built heads. They don't receive the care in preparation and assembly that heads crafted by someone like Banshee does. Also, rebuilt heads are already heat cycled and will stay stable, can be tailored for your needs and budget, and all the parts are especially selected for your application. Plus the price is more economical, and you can keep stock looking heads on the car. Only you need to know they've been ported and chambers reworked.
Q- don't the #16s have characteristics similar to the #62s?
Vikki 1969 Goldenrod Yellow / black 400 convertible numbers matching
Bob , w/o the installation cost I had about $700 in my heads , $150 for two 5C`s,( $90 for shipping ,but you prob. will need that for edelbrock heads too??)$80 for 1.65 rockers, for valve job, milling etc add`l $450. thats about $700 for both (or $800)=+- 2 to 2.5 times less.....but yes w the alum. heads you`ll get some less weight.... but as Q states you`ll need to buy more stuff too...like round port headers..
As Bjorn suggested, I would try to find out from the last owner what the specs were, and or who built the motor and contact them for further information.
Then you'll have a better idea of what direction to go, and or maybe a better idea of which heads will work better with your cam/intake and carb combo. But any of the heads Q mentioned would get you much closer to a match I would think than what you have at this point.
But your going about it right... asking the questions, learning, and then you can make an educated decision and know your spending your money wisely!
And it's nothing you have to do right now... you can work at it slowly. Find the heads... then in a few months have them built... a few more months tear it down and install them just in time for spring etc...
lol That is exactly what I am doing, looking at a set of cores on e-bay right now. This board is great in the short time i have been on i have gotten tons of great info, with this thread and all of the old ones. I really didnt think there were that many first gen birds out there. Since I have had mine have seen only 1 68 and 2 69 guess they must not like the cold weather we have for half the year....
As far as finding a set... I'd watch, and get a good feel for what they go for... start checking places like the for sale/wanted sections on this site, Performance Years http://forums.performanceyears.com/6/ubb.x message boards and http://www.classicalpontiac.com/ (classifieds at the bottom of the page) as well as ebay to get a good feel before you buy anything.
(I'm sure this is what your doing.. but just in case)
Half of the year? More like 3/4's of the year! Lol... As a kid, Minn. was great... But I'd hate to have to work on my bird over the winter unless it was in my basement now as (a so called grown up!)
It will all come together soon enough... then you'll have to look for other things to work on with the car! Lol...
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