Please see my post on the intro board (new member and I put my post in the wrong place) Got a question on my 65 vintage 327 vette engine performance after a valve adjustment.
Hi jeffer47, welcome to the HAMB. You can reply to your own posts to ask the question or you can edit your original post. Anyway, I went to the intro board and read the question. Here it is so maybe we can get some answers. Got a newly acquired 32 Ford running a 65 Corvette 327 fuelie block, 30 over, camel hump 2.02 heads, solid cam of unknown specs, roller rockers, single plane intake and a 670 Street Avenger, hooked to a TH-350 and a 9". Runs great after 2800 rpm but will shut off if you give it any gas from a stop. Have to really pedel it to get it going. Fuel pressure is 7 psig and the accelerator pump is adjusted properly. This all staerted after I adjusted the valves to eliminate the old electric typewriter sound it came with. Would really like to be able to get off the line without loosening up the valves and beating up the works. Suggestions welcomed
If it did it after you lashed it and you don't know the cam specs...I would loosen up the lash. What did you lash it to? Hot or Colt?
If you have a cam of unknown specs, how did you arrive at the valve lash or clearance? Typical lash or clearance for solid SBC cams is either .012 to .018, or .030 depending upon grind. Does this occur when the car is cold, hot or both??
First question I have is, What distributor are you running, is it a vacuum or mechanical advance? I did a google search and found some interesting reading on setting valve lash with a solid lifter cam. Now if I was only smart enough to understand it!! Check it out here.. http://www.lbfun.com/warehouse/tech_info/valvetrain/SBvlvadj.pdf
Setting the valve lash too tight will result in a crappy bottom end, as you are effectivley increasing the duration of the cam. The article posted by 327/365 alludes to this.....as you decrease the lash or clearance, the lifter is hitting the ramp on the cam sooner, effectively increasing the advertised duration of the cam itself. Bigger than that of course is the possibility of burning the valves.....as the car heats up, the clearance decreases especially on the exhaust side...Open valves during combustion = burned valves and seats. Not good.
If you adjusted the valves and got rid of the electric typo sound you have made a boo boo. That is the much desired sound of a trad hot-rod that is music to a gear-heads ears !! What lash did you give the valves and how did you go about setting them ??
there it is: solid lifters making mucic. i have a duntov 30/30 you can hear the lifters a block away. i think.... a 30/30 got its name from settin the valves at .030 intake .030 exhaust. otherwise 22 intake & 26 exhaust is the solid lifter settings i believe.
If loosening up the valve setting does not make you happy, you could try one other thing. Single plane intakes are not responsive at low RPM's. That can be remedied by putting a divider in the open plenum. I did that on a street driven big cammed, automatic trans, sluggish small block. Engine really gained a lot of bottom end after the divider was added.
Or,,,,,,,,,,,,,,, you could pull the cam out and verify what it is. Be SURE to keep the lifters in order if you do this!!!! Alternative, replace cam with hydraulic cam and lifters. Zero noise and probably good enough for a street only engine. You can get some pretty good performance with a hydraulic cam.
I bet he wishes the electric typewriter sound was back. Anyway, unless you knocked something else loose while adjusting the valves, simply readjust them. I'll assume they're tighter NOW, as you didn't like the clatter? So, try and remember approxiamately how much you tightened the valves on the average. Also, try and remember if you went more or less on intake Vs exhaust, or the same on each. What are they set at now? I know that block's over forty years old, but if for some reason it's got the right "fuelie" cam in it, the lash should be .030-.030
what size stall are you running? is it to tight. also is it geared correctly but this probably isnt your cause if it ran well before im no help
HMMM. I'm gonna guess here. You say some were fine at .018? I'll guess those were the intakes (on split lash, the intakes are tighter). So, i'll guess again that the lash was supposed to be .018 on the intakes and .024-.030 on the exhaust, and now they're ALL at .018. Readjust just the exhaust valves to, let's say .025 and tell us what happens
Adjusting the valve lash should help but..... Adding a divider to an open plenum is not that hard. Have the divider welded to a spacer plate. Grind the divider to fit the intake when the spacer is placed under the carb. The bottom of the divider does not have to be sealed fully to the floor of the intake plenum but it does need to be a close fit. Bottom end response will be greatly improved without that much loss on top end.
basicly it comes down to how long you want cam to live in a sbc, the lifter rides on the cam theres no bearing it wears constantly those particules will pass through a main or rod bearing but wear a cam like fine sand paper the duntov ran 30 thou for a reason to wear only the lobes an live long enough to sell, a racer could adjust them to maybe 8 on intake 10 12 exshaust for a night then put them back to drive home up to you something in 20 ish is best never under 12 for intake 16 /18 ex for street an on a trip open it up much as you can bear wouldnt go over 30 i think thats what factory thought was limit but thats a guess also thats for an unknown cam you didnt have specs, the cam will live with those numbers IMHO o the ex is normaly 4 thou more for heat if your up in the 20 thou mark dont think would matter much the reason for the big lash is to keep cam in oil bath long as possible !!!
if you have the motor out an degree the cam and watch where its hitting the ramps an how peaky the lobe is just figure it out how to make it comfortable as possible an keep it together
Oh man! I just liked a bunch of 9 year old posts thanks to this thread resurrection. That's like Marty kissing his mother back in 1955! Heavy.
Typical FNG thing, give a bit answer to a post that you found on Google that has been dead for nine years and joined so you could show your knowledge.
I don't mind the reply, just wanted him to understand that it's an old thread. I've joined places and forget to look at the dates because of enthusiasm. Better than trying to bend HAMB rules to allow your '86 Camaro with lS motor and 26" wheels
Your OK, I just checked and the guys you "liked" have not been on here in years but I bet they are smiling now and can't figure out why.
I didn't even look at the dates either! but good read!! Sent from my Z981 using The H.A.M.B. mobile app
I do get a little entertainment value out of some these threads, some I also learn from and some I contribute to. Many thread questions remind me of how people used to write in to the Popular Mechanics type magazines with a mechanical issue, what do they do; wait till the next issue arrives to (maybe) get their question answered. I always got a laugh out of a guy I used to work with, he had an interest in cars but it seemed like anything he knew hot rod related was from Popular Mechanics magazine.
Yes I read all the GUS's model Garage. Say smokey and Tom McCawhill ect when I was a kid. actually I learned a lot from reading. I always liked John Diania's articles in hot rod also.
The Jalopy Journal
