hey hey y’all! Happy new year to you, and thanks in advance for any experience you may be able to share ! I have a 64 Pontiac bonneville with a bone stock 389 .. 4 barrel with secondary vac ... and I need to spice things up a touch ! I’m looking for some advice on a recommended camshaft for my ride to let it rev some more and bulk up the midrange .. Thanks for your help In advance guys Cheers Griff
Auto? How about gears, exhaust? What cam is in it...Lots of unknowns. An 068 should do the trick, keep it simple & hope the press-in studs stay pressed in.
Auto ... th400 tranny Stock exhaust for now ... but will be changing at the same time ! No kinks or dents ... I did check this for sure ! I’m pretty confident it’s a stock cam ... the history on the motor was pretty clear according to the paperwork I have ... An 068 ?? Sorry I’ve heard of it but know no more details ... could you expand on it ?? Was this the stock cam for the TRI power GTO? Or am I mistaken? And proper thanks for your input
You can't beat 5 spokes can you. That's a really nice Poncho. Wouldn't mind seeing more of it even if it's bone stock.
I have a few more questions: what heads are on it now? I’m guessing 1.92 / 1.66 stock heads since you say it’s bone stock. I’m also assuming a carter AFB like a 3649 or similar. What’s your “exhaust change” coming soon mean? Headers or larger primary pipes? Making too many changes at once isn’t good imo unless there is a game plan already set in place (doesn’t sound like there is). I’d agree with Bird man that an 068 cam would certainly help but again a set of 1.65 roller tip rockers, a new roller chain with a 2 degree adv key would help your stock cam with mid range as well but I’d like to know what you are going to do with the exhaust and what the end goal really is and can it even be met with those stock heads. Recurving the distributor (assuming it is still points equipped?) would help too. How many miles is on the engine? Is it in good shape, have you pulled the valve covers recently to see if it’s full of sludge? Do the plugs show any signs of oil usage? Lot of questions need answers imo....Randy Sent from my iPhone using The H.A.M.B. mobile app
You can gain a lot by using later 400 heads and the 400 intake and improving the exhaust. A HEI will also fit your early engine. Unless you engine is in top condition adding compression, cam lift & duration and CFM flow will soon lead to engine failure. If you want reliable power. Swap in a 455. There is no substitute for cubic inches. Adding a bigger cam will make it use more fuel and have less torque. A big car needs torque more than HP or RPM.
Thanks for getting back to me man .. I appreciate it !! Bone stock heads ... and your right with the valves ... the head code were corroded amd an exhaust stud was broken so I pulled a head to fix it ... the motor look to have been refreshed by an engine shop (according to paperwork) around 15,000 miles ago and I’ve no reason to disbelieve this ... the motor didn’t seem to burn any oil and the bores don’t look worn at all (suggesting it probably went one size over but no documentation to prove) the plugs dont oil and the engine doesn’t seem to be breathing heavily at all , compression check revealed a healthy motor on that side of things on my inspection. No sludge at all just some crappy surface rust on the outside suggesting it had been sitting for a while ..The primary chain is good .. very little sag there .. again backing up the paperwork .. The passenger side exhaust had been crimped but this looked like a loading dent ... sorted that no worries .. The dizzy has been replaced with a GM HEI ..and timing set stock . Runs and starts wonderfully ... idle CO levels set at 3.5 % on base idle .. honestly it runs flawlessly upto around 3600 ... then just won’t rev any more .. I’ll go an exhaust ifnthat what it take to open it up a touch no probs ... I just don’t get the impression it’s exhaust that’s causing this issue... I’m convinced this is cam .. I’m a motorcycle builder by trade and build a lot of race bike engines for your equivalent of the AMA .. and my instinct are screaming this is valve /cam issues ..but I’ve much less experience with v8 motors ... and every day is a school day for sure !! My research has shown that the heads on these so have their limitations but a fatter cam should give some healthy gains ... Gents ... I’m in awe of your experience here ... and I’m learning good ... thankyou kindly always !!
Thanks for getting back to me dude ... I appreciate !! If you can see my reply below it’ll kinda make sense what I’ve done checked .... but briefly .. HEI is there ..check hehehe Motor does look like it’s beem refreshed lately and the compression is real good on all cylinders and even .. I hear your words in the heads ... maybe some fresh aluminium heads would be a feasible option ?? It’s kinda tricky to get a 455 here in the U.K. ... them bad boys are rare !! I love the analogy that bhp is barstool and torque does it all !! I hear you sir !! Cheers Griff
We reckon on 6 adults if you cut them up But that just between you and me! Heheh And thankyou very much sir !
Your 389 has 10.5 compression cam choice might depend on detonation or not with the fuel you want to run.
When you say it doesn't rev past 3600, do you mean it won't make power over that RPM or it won't rev higher? If you hold it in low gear and mash the throttle what happens? Pontiacs are unlike all other engines in some ways, but exactly alike in others. Do the easy stuff first, true dual exhaust with free flowing mufflers, headers if you are adventurous enough, a nice 4bbl intake and 600 cfm carb of your choice. Also, figure out what rear gear you have, it may be super tall which will kill acceleration. Nice little car, by the way. You probably won't park next to another one at the grocery store. -Abone.
95 and 97 is very common here in the U.K. ... so I’ll hopefully be ok on a 10.5 ... my SBC ... seems to be ok ...hope this makes sense ?
Hahahah thankyou sir !! It’s a rare thing around this town that for sure , makes the locals smile ... This is exactly how I tested it ... low gear and floored it it was pulling strong and seeemed to flatten off quite quickly ...3600-4000 .. it’s nkt a dead stop run flat or even a misfire like it’sbad Timing .... it’s just feels like its tuned to do this ...like a small capacity Honda motorcycle is, excuse my swearing here but it’s the best example I can give .. those little engines are designed to rin at 65 all day long And with out cam heads and ign it never will .. they’re just built that way ! Boring bloody things !!
A cam with more overlap can actually reduce compression. Im here to tell you it isn't the camshaft that's keeping the engine from turning more than 3600 RPM. Check the easy stuff first. without the engine running . Have someone mash the gas pedal to the floor. Remove the air cleaner and look down the carb and check to be certain all four throttle plates are vertical. A friend had a worn out 389 with stock AFB in a 64 bonnieville and was clocked on Radar at 130 MPH and slowing down. He was a Marine just out of the service . was in Nam a few days before. The cop let him off with a warning.
The fastest thing to do is what Wolf said, make sure all 4 throttle blades are fully vertical. Next on the easy/cheap list is see what is going on with the timing. You have to know FOR SURE where your timing numbers are. Get a decent dial back timing light and set your total timing at 34-38 degrees while holding the throttle steady at 3000 rpm. Next, see where that leaves your idle timing with the vacuum advance plugged. 12-16 degrees should be about right. Once you know your numbers, we can move forward. -Abone.
Secondary’s are opening sir no probs ... I checked .... and that engine is showing no signs of being worn ... compressions are good .. leak down test positive on all cylinders ... cross hatching is clear and visible on all cylinders and valves are seated without question... the ignition advances as it should .... and paperwork backs all this up from a refresh recently ... like o said it doesn’t run flat and stop at 3600 it just feels like it fails off and all the power has run out at 3600-4000 ... the small block In my g20 felt the same until I rebuilt it into a 383.. heads and cams it’s revs strong and pulls like a train now ... Im unsure hence asking the advice .. it all points at this stock cam and head set up hence asking for the recommendations but happy to be proven wrong .. once again sir ... thankyou
I think you have a problem and not design issue like the others have said. My 389 pulls fine to 5200 rpm. I believe the others here are pointing you in the right direction. Good luck. Randy Sent from my iPhone using The H.A.M.B. mobile app
If it has the early lifters, they could be pumping up and holding the valves off the seats. A set of poly-locks and a slight preload would cure that. The carb bowls could be running low in fuel too.
Thankyou .... I’ll reconfirm the timing .... i now have a little doubt ....I was certainly in the ball park on the advance .. the figures escape me now but I’m convinced it was around 30 ... the lack of advance would be consistent wouldn’t it !
Yes check to be certain you have WOT first. Them make certain the vacuum and mechanical advance are working. And after that suspect a worn loose timing chain & gears. Those cheep imported so called roller chains will stretch and get loose real fast. the stock link belt is much better and will last longer.
Beautiful car!!!!! It won't Rev above 3600 RPM??? In order, check: (1) Throttle linkage (footfeed on the floor should translate into throttle wide open, maybe it isn't. (2) Tachometer accuracy (3) Choke adjustment (if the choke butterfly is not vertical, the secondary lockout prevents the secondaries from opening). The original 4-barrel is 610 CFM; replacing with a 600 is going the wrong way. There is an excellent, inexpensive reference book available. Don't remember exact title, but something like "Pontiac Performance 1955-1979" by Pete McCarthy. Get the second (or later) printing. First printing had binding issues, and rapidly becomes loose-leaf in a notebook. Jon.
Cheers for getting back to me man .... forgive Me ... could you explain ? I don’t understand your terminaology ... I’m sorry ... I’m a limey ... it’s kinda different here !! Heheheeh
If the carb was running low you would have a lean condition and it would backfire thru the carb. Just reaching a certain RPM and setting at that and running perfectly. sounds like a governor or restrictor plate like they use in NASCAR?
Hey hey . Forgive me ... the car kinda runs flat around that rpm ... rather hits a hard rev ceiling .. the secondary’s are open and full throttle is accurate .. this was one of the first thing I’ve chexked for sure ... tach accuracy ..... holy crap .... I’ll do that as well ... I have a spare I’m my goodie box in the mancave !! I’ll look up the book to man thankyou ... To be honest the more I sit here and think about it the more I reckon a dyno run with an A/f trace wouldn’t be a bad idea ..... Thanks man !! Griff
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