Engine Compatability Problems

I'm new to this forum and I am in dire need of some answers for my 68 Firebird. I'm having problems getting this motor tuned and i was wondering if any of your pontiac engine geniuses would know if my parts are even close to compatable. The engine will run good for a day or so...and then the next ay it wont want to even idle. It's like it goes back and forth and i think im just chasing it around. The Block is a 1973 400 Y4. Heads are from a 69 GTO Judge Ram AirIII #16 from a YZ motor. Cam is a Ram Air IV spec with 1.5 rocker ratio. The 73 motor had 8:1 compression and the Judge motor had 10.75:1 compression. Im running timing at 13 degrees. I have no clue if any of this will work when put together. As for the pistons, i think they were with the 73 block. My dad built this motor and something is obviously not right. The carburetor is brand new and the fuel system is too. I'm clueless to what the problem is. I really want to get this car going soon...I'm 17 and i need a car bad... so if any of you have answers please let me know. THanks.

what kind of carb is it?

make sure the cam isnt to big

I'm new to this forum and I am in dire need of some answers for my 68 Firebird. I'm having problems getting this motor tuned and i was wondering if any of your pontiac engine geniuses would know if my parts are even close to compatable. The engine will run good for a day or so...and then the next ay it wont want to even idle. It's like it goes back and forth and i think im just chasing it around. The Block is a 1973 400 Y4. Heads are from a 69 GTO Judge Ram AirIII #16 from a YZ motor. Cam is a Ram Air IV spec with 1.5 rocker ratio. The 73 motor had 8:1 compression and the Judge motor had 10.75:1 compression. Im running timing at 13 degrees. I have no clue if any of this will work when put together. As for the pistons, i think they were with the 73 block. My dad built this motor and something is obviously not right. The carburetor is brand new and the fuel system is too. I'm clueless to what the problem is. I really want to get this car going soon...I'm 17 and i need a car bad... so if any of you have answers please let me know. THanks.


All those parts will work. Ram Air IV cam will work fine also, as it is rather mild. Cranes Fireball cams are close to the specs of your cam. Question is what Carb are you using, how much cfm ? You need at least a 750. What type of intake are you using? and what exactly do you mean by the car will run good for a day or so and then the next day it won't even idle? What are the real symptoms?
Besides you need to go with the timing for the Ram Air cam/engine which is 15 degrees before at 750 rpm with automatic transmission. And 15 Before at 1000 rpm with a manual transmission.
let me know more.

the carb is a 650 cfm...does that not have enough flow?

volkerc...what i mean by saying that the car will run good and then wont even idle...is that for instance...i drove the car last weekend with no problems at all...none...and then one day later i went to start it and it wont even idle at a stop sign...the car will just die. i dont understand.

volkerc...what i mean by saying that the car will run good and then wont even idle...is that for instance...i drove the car last weekend with no problems at all...none...and then one day later i went to start it and it wont even idle at a stop sign...the car will just die. i dont understand.


Hello,
well it is a little more info. First off your carb is to small. The 650 you got would work well on a 350 not a 400. So this carb is actually restricting the output and performance of your engine. Switching to a 750 is the right thing to do. For performance use a double pumper, for daily driving, economy and acceptable performance use a vacuum secondary. With that type of cam and engine combo you should also use headers. Now, none of the above relates to your problem though. At current your car will just be slower and run a bit on the lean side.
Your real problem can be in two areas. Area one would be your choke. I assume that you run an electric choke. If that is the case, you might have an improperly adjusted electric choke. Noticeable when the car is cold, sat for a while, starts but dies if you don't give it gas. The other problem could be a distributor that has been installed wrong. I would check the choke first.
A bit more advice, if you don't have it already use a decent aftermarket intake, Edelbrocks Performer will work well and they are not that expensive. You can find them used also...
Let me know if that fixed your problem and if I can be of more help.

thanks for the help, but i dont think it is an intake manifold or carb issue. It has to be somewhere in the ignition setup. Im wondering if im running to much compression for the street. Does any one know the compression ratio of stock 400 pistons in 73...Y4 block. the motor had 8:1 from factory.

also i run the stock choke...should i upgrade to electric

sounds alot like a cam thats to big, bought an engine one time and went to a smaller cam , and
fixed the problem

the carb shouldnt be to small

how can you install a distributor wrong,
all that matters is your engine is set to tdc,(most engines), with # one up on compression stroke
wherever you set that button is where the # 1 will
go
lets not confuse him, if its not backfiring sputtering and popping the dist is prob ok

now the 400 is i think set like13 degrees off, but Im not sure, never could hold to that when i ran a 400
but mine was modified

also i run the stock choke...should i upgrade to electric


here we go again, don't listen to this thumprkil or whatever.
Pontiac says to set timing at the numbers I gave you before.
This guy always comes up with the arguments that peoples cams are to big which is absolute nonsense. compression has somewhat to do with the pistons you run, but also with the ccm of the heads, as well as the head gaskets and if the heads had been milled. Compression also determines which gas you should run, I would use 93 octane cause you stepped up in performance.Your RamAir Cam is a street cam. And compared to the manufacturers of racing cams it is a mild pattern, so it is not anywhere to big. It gives you great driveability with enhanced performance. I can even name the specs for you, which I'm sure thumpwhatever can't. Your carb is to small for the cam and that is a fact, check high and low for answers and everybody will tell you that, with the exception of this whatever. he just likes to start arguments and waste peoples time. would just like to see one time that he really helped somebody.
Also I did not say that the carb and intake are related to your problem, I just noted room for improvement. Now if you do have a manual choke than the choke is not the cause. I would check next if the distributor is installed wrong, and yes you can install a distributor wrong, 180 degrees off and the car will fire, but run and idle like s***. Eventually causing damage to bearings etc. Bring the engines #1 cylinder up to TDC and see at what spark plug wire the rotor points to. It must be cylinder 1. Then check if you have the wires in correct firing order. Let me know the result.Also make sure your vacuum advance is hooked up and working.

yep your right, volk guy
hey didnt you used to be on the underdog show
segment
Mr Know it all
stop bad mouthing me have already asked for action against you
sometimes a cam can be a lil to big for some setups, this can cause a car to idle sometimes and sometimes not, as also a big cam can rob you of vac and also effect power brakes
and if the car runs an doesnt backfire sputter and spit, why would you worry about the dist?
you dont always have to go bigger to get results with a carb, if this is a cam problem (i could be wrong) the a bigger carb isnt gonna solve its
if you dont undestand this logic
then im sorry for you
would you want someone to steer you wrong if you needed help,
wake up , grow up and think before you answer

yep your right, volk guy
hey didnt you used to be on the underdog show
segment
Mr Know it all
stop bad mouthing me have already asked for action against you
sometimes a cam can be a lil to big for some setups, this can cause a car to idle sometimes and sometimes not, as also a big cam can rob you of vac and also effect power brakes
and if the car runs an doesnt backfire sputter and spit, why would you worry about the dist?
you dont always have to go bigger to get results with a carb, if this is a cam problem (i could be wrong) the a bigger carb isnt gonna solve its
if you dont undestand this logic
then im sorry for you
would you want someone to steer you wrong if you needed help,
wake up , grow up and think before you answer






Foul language, improper english, insults,threats and bad advice to other members. I just feel sorry for you.I do not have to badmouth you, you are doing a much better job yourself.And as far as the last passage is concerned the same goes for you, little man.

okay...well we should all settle our differences. im going to check the distributor for improper install, and i just bought a cam from summit racing, with a small amount of lift...it is less radical.

okay...well we should all settle our differences. im going to check the distributor for improper install, and i just bought a cam from summit racing, with a small amount of lift...it is less radical.


and what I may ask do you think you are going to achieve with this? you are running high compression cylinder heads 72 cc volume and you are decreasing your lift? you run to small a carb, use high compression heads and now want to go with a weak cam...

the cam never was your problem, but good luck and please complain to whoever you listened to.thankfully it ain't my time and money.

good luck!

well I do rmember I did gradyeate, but, I dont worry much bout english on here, Im sertian poeples
kin get me here, but volly guy , u, u, mestbe from
that kountry that makes them there france fries,
you know the one with the tower
do your wife shave her armpits
sheeze

I think the cam could cause this problem, thump never said a thing about compression
if the car runs there must be compression
dont just replace the carb without troubleshooting
first