Im in trouble now for sure! I have changed camshaft in my -68 350-4 (PP) engine! Before this, with the stock type camshaft, I had enough torque to spin the tires from standing still just by flooring it, at least 10-15 feet minimum. Now I cant even do that, unless the road is wet or something else makes it easier. I gained some mid /high end power, but it vas not supposed to end up like this when I ordered the camshaft! The camshaft is a Crane part no: 710571 Cam timing @ .050 lift : Opens Closes Max Lift Duration Intake 2*BTDC 36*ABDC 107*ATDC 218* Exhaust 20*BBDC ( 4 ) BTDC 117*BTDC 226* Recommended rpm range Minimum 2000rpm Max 4500rpm Float 6500rpm The car is a -71 skylark convertible whit a TH350 and 2200-2300 rpm stall speed. Manifold vacuum at idle in park (1000-1100rpm) 16 inch hg 3, 08 posi rear. 235/60-14 rear tires, stock heads, and stock intake manifold with a 4-hole 2 high spacer and a Holley 650 spread bore with vacuum secondary on top with a 50cc accelerator pump. Dual 2 1/4 exhaust with an H pipe. To day I modifying my distributor with the Crane advance kit, Earlier I tried a MrG kit, no good will not give all in below 3000rpm I tried all combos of springs even the lightest (2 X yellow) springs without getting any pinging! Then I went back to 2 X medium (silver) springs, anything lighter springs gave a feeling of less power!? I am running 98 octane (the only benefit of live in Sweden) Initial timing is ~ 16-18* (estimated, as you all know there are no marks that high) total timing ~32-34* without the vacuum advance connected (it is connected to ported vacuum when I am driving). Before swapping camshaft it could not handle more than 12-13* initial without pinging. BTW I did not degree it, just went by the marks with a new chain. I just remembered that on previous chain swaps with the old camshaft I did not get all the OOmp until I had driven it 80-100 miles, can this be the reason, the chain needs some stretching to get things right? It feels like I am WEARY close to get things right, but I am totally lost now! Where to lock now? Can it be the secondary opening to late? Is the way out to buy Rhoads or Cranes bleed down lifters? (This feels wrong, to much vacuum at idle!?) Or is there anything else I have forgotten? o No: Lars
Seems to me Hot Rod or Car Craft magazine put out info a few years ago that all available aftermarket Buick 350 Cams were missmarked and installing them on centerline would really be a few degrees retarded. This was in a article titled something like "The other 350s". I don't know how they came to that conclusion. Seems there is a lot of Cam manufacturers for all of them to be wrong. Don't ask me, I just remember reading something like that. Picking up top end and losing bottom end will result if a Cam is retarded.
The time is 23:29 where Im at so I am a little to tired to be thinking straight! Retarded, will that be the result of a stretched (worn) chain? How much is one toot on the camshaft sprocket worth in* I know I did the marking/alignment ok, just wondering if it can bee fixed easy, if this really is the reason why.. Lars
I think one tooth is like four degrees or something like that. This would be the time for some engine builders to chime in.
Is my camshaft to big for my application? And how about this? What one is retarded and advanced? BCDE I hope you can se the picture! I am no computer wizard I confused, that is an understatement!:error: But I do understand that I have to use a degree wheel to know how many degrees it is off (if it is) and after reading on all day I also understand that the markings on the sprockets is just a starting point. To often are they not where they is supposed to end up. I will never ever again, put an engine together without degreeing it. uzzled: Just to let you know how stupid I was when changing cams I tell you this: I got a Crane degree wheel on a hock I my garage, but did not use it. (I use it when I check port timing on two-strokers). Please dont tell anyone.:stmad: Retarded will that give more power low or high end power? The feeling in the car is that the power its coming just a tiny bit too late. Lars
First things first.. Degree the Cam! Search the board, there's a thread lurking around that gives detailed instructions on degreeing the cam correctly. Next thing, ditch the "ported" vacuum source for the advance can, use a manifold port. And the clarrification: Retarded Timing = Your car runs like it's a retard. Advanced Timing = Your car runs in the advanced math class.. :grin: Degree the cam, shove the two medium springs in the advance and set the initial with the vac can disabled to 12*, the top marker. Check the total advance and see where your at, if it doesn't all come in soon enough, replace one spring with a light one and retest. Once you've got full advance under 3k, reset the initial timing to yeild a total of 32-36* @ 2600-2800rpm. Plug the vac can back up and go around the block.. No pinging? Have fun roasting the tires!
Please explain way the manifold vacuum is better (the effect of the change from ported to manifold vacuum) As for the rest off the ign.timing i am already there, (and a little bit more) 16-18*initial and 32-34*total all in at 2600-2800. Forgive me if i lead you wrong, I was referring to camshaft degreeing when i wonder about the retard/advance thing. that's why i added the picture. I will order a offset crankshaft gear (if i can find it in sweden) before i start checking the camshaft. It just most be off in one direction or the other!? Lars
