What's acceptable using roller cam? Checking things out with the new build. Crank hits cam lobe big time! IIRC Mike at TA recommended at least .020.
No on the molnars, not to that point yet. Degreeing cam, & crank throw hits lobe. Did the same only with different throw on last build too. Crank needs to clear roller cam lobes. This is a blue motor crank with a 68 block. What is, or is there a standard clearance spec? It clears after some surgical grinding, but only have .020 and think I should go with at least .035
I would think you would want to go. 035 also. Maybe give Derek a call. He might have some thoughts there
Mart, I have heard the later capscrew rod crank has larger counter weights. If your cam has super high lift and is advanced or retarded you may be even closer. I hope your timing chain never breaks.
Lol, don't want timing chain to let loose, that's for certain. Yes, that's the whole purpose using the blue crank. Internal balance should use no or minimum mallory metal. And yup, it's all in the degreeing. Trying to have 4* retarded to 6* advance range with plenty of clearance. This is not my numbers matching motor, so I'm pushing some limits. Rod clearance is up next!
Here's 71, & blue motor cranks side by side....yellow area's are missing on the 71 crank, and other spots, So yes, the blue cranks have heavier throws.
Gee wizz, NEVER considered any differences in cranks My other crank ( the one with #3 rod journal ground down) was a ‘78 crank. The crank I’m running now I bought from TA many years ago, don’t know what year it is. Didn’t have any issues tho with the crank itself hitting the cam......... interesting
Well rods hit too, I'll take care of that. Meanwhile, crank/cam clearance is now .050 Front throw and second to last throw were hitting/tight/ marginal, at best.
Mart, Are you just going to angle the area where rod bolts stick through on cam side? What lift is your cam and what stroke is your motor? You are pushing the limits! On Chris's 300 Stroker (Late 350 crank and 350 capscrew rods) had no clearance issues in those areas. Just had to use washers under the windage tray and a little ball peen work on the bottom front shallow area of the oil pan.
Yes Jim, rods will get chamfered/angle ground to clear. Lift is .584, stroke is slightly over 3.990, maybe 3.992 Roller cam running solids. Advertised duration is 306/ 318, 107 lsa, 35 * overlap. Should wind up nicely..... Got the iron heads in for additional porting, trying to max out this N/A iron head build.
Yes Ivan, thanks. Great pics. Looks like a lot of "meat " needs to be removed to get .060 clearance. If that's what it takes, that's going to get done...... You only advanced Haydn's cam +2? Did you still have additional room if degreed -4* and up to +6*?
Mart, Piston to valve clearance gets closer too. Advancing, the intake valve gets closer. Retarding, the exhaust valve gets closer. +4 degrees is usually safe, +6 is probably pushing your luck with high compression.
Jim, Degreed cam at +5-1/2* last time it was together. Had .100 piston to valve clearance on both Int & Exh. Don't worry, I model clay all the potential tight spots. So far, this blue crank and my gearset line up perfectly square to this 68 block, go figure.....
Yes, we only went +2. Straight up, the cam was hitting the rods. We clearanced the #1 rod until we had about 0.070", and clearanced them all the same, checking all the while. I don't even wanna think about how many times we installed, and pulled each piston/rod. But, without doing that....it isn't gonna run at all before destroying itself. Way too much money into it to just call it "good enough", or "close enough".
And people wonder why I’m not super eager to encourage others to stroke a 350... we pretty much see all the challenges here in this thread and I know full well the car would run super hard with a few less cubes... especially once boost is added.
not a fan of stroking a 350 buick. too many compact areas for hitting each other. couple of things to consider stroking the 350. didn't some people worry about the bottom end and want to add a plate for block strength. has anybody taken in the issues of thermal expansion. has anybody taken in the issues of centrifugal forces by high rpm's. look at how the block was made. lastly, will it do 7500rpm all the time with a s/charger on it.....
Yes, but same issues with Molnar rods using roller cam, same crank closeness also. TA even advocates checking crank clearances, so roller cams without a small base circle seem to be the factor. I don't know about your Hersch rods, but I would think if the strength/ size is configured like Molnars or Carrillos, you may have the same issues. You can't have strong rods that are dinky.
