348 Tri-Power Build gone wrong / Follow New Rebuild

1964SuperStocker

Well Known Member
Supporting Member 3
I've taken many blocks in the back of a pick up to the"quarter in the slot"car wash.Usually came back as wet as the block was but the block was clean.
I set blocks in the sun and spray oven cleaner all over (Lemon scent Easy OFF). Let them bake in the sun for about an hour or so depending on how dirty it is and the garden hose will wash it all away. Paint, grease and anything not attached to the block down to bare metal. Did the car wash once, never again. :D
 

Don Jacks

Well Seasoned Member
Supporting Member 3
While they're machining the block have them deepen the valve relief in the block for the exhaust valves by .075-.100[simple procedure].Reason;The cam that I've recommended has a lift spec.with 1.7 rockers of .550 which is right at the limit without notching.If your rockers are 1.75 he max.lift would end up at .565 and the valves and block will clash.The Comp Cam part number is 48-801-11 .The series number is XE272HR-10.
 
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1964SuperStocker

Well Known Member
Supporting Member 3
While they're machining the block have them deepen the valve relief in the block for the exhaust valves by .075-.100[simple procedure].Reason;The cam that I've recommended has a lift spec.with 1.7 rockers of .550 which is right at the limit without notching.If your rockers are 1.75 he max.lift would end up at .565 and the valves and block will clash.The Comp Cam part number is 48-801-11 .The series number is XE272HR-10.
Pretty aggressive cam. Did you check for piston to valve clearance? Certainly the cylinder wall is important too but just wondering how you know the valve will clear in this case.
 

Don Jacks

Well Seasoned Member
Supporting Member 3
At 218-224 @.050 it's not what I'd call aggressive at all.This cam is very strong torque wise,right in the rpm band where he runs that engine.Comp says max.revs are 5800.With his set up,I'd set the rev limiter at 5600.
 

'37-4D

Well Known Member
Those bearings were from dirt from improper cleaning methods being used.The piston failure was from the over rev and valve contact.It didn't help anything by having those cheap cast pistons in there.While your replacing parts,scrap those weak stock rods as well.Let's build it to last this time.A truck as beautiful as yours deserves nothing less.
Noted! Thx
 

'37-4D

Well Known Member
While they're machining the block have them deepen the valve relief in the block for the exhaust valves by .075-.100[simple procedure].Reason;The cam that I've recommended has a lift spec.with 1.7 rockers of .550 which is right at the limit without notching.If your rockers are 1.75 he max.lift would end up at .565 and the valves and block will clash.The Comp Cam part number is 48-801-11 .The series number is XE272HR-10.
Will pass info along, thank you Don
 

1964SuperStocker

Well Known Member
Supporting Member 3
At 218-224 @.050 it's not what I'd call aggressive at all.This cam is very strong torque wise,right in the rpm band where he runs that engine.Comp says max.revs are 5800.With his set up,I'd set the rev limiter at 5600.
It was my understanding that anything around 6000rpm was aggressive considering what the stock motor was doing before. 7000rpm plus is extreme which I know some of you do spin them up to. :burnoutBut something I can't find the information for anywhere on here or the previous build thread is what Camshaft specifically was in the motor when it let go? Valves slapping pistons isn't normal or advised.
 

Don Jacks

Well Seasoned Member
Supporting Member 3
If memory serves me correctly,Show Cars 0950.218-224@.050,110 lobe seperation,106 centerline,right at .500 lift.The largest cam that can be used in a 348 with 9.5-1 pistons is 220@.050 without notching.The lift doesn't matter,it's the duration at .050[overlap] that'll get you. Lot's of people have used this little cam with exellent results.It's close but fine as long as you don't "float' the valves.
 

1964SuperStocker

Well Known Member
Supporting Member 3
If memory serves me correctly,Show Cars 0950.218-224@.050,110 lobe seperation,106 centerline,right at .500 lift.The largest cam that can be used in a 348 with 9.5-1 pistons is 220@.050 without notching.The lift doesn't matter,it's the duration at .050[overlap] that'll get you. Lot's of people have used this little cam with exellent results.It's close but fine as long as you don't "float' the valves.
I may have to install that camshaft in my wagon motor if it stays in. Looks like the 0950 Comp is 1300-5600 power range. That is a pretty good jump over the factory camshaft I'm rocking now. The motor has everything going for it but the camshaft at this point. Thanks again for the information Don!
 

427John

Well Known Member
It was my understanding that anything around 6000rpm was aggressive considering what the stock motor was doing before. 7000rpm plus is extreme which I know some of you do spin them up to. :burnoutBut something I can't find the information for anywhere on here or the previous build thread is what Camshaft specifically was in the motor when it let go? Valves slapping pistons isn't normal or advised.
I agree that a cam that can pull hard to nearly 6000 rpm is definitely a performance type grind,the problem is there were a lot of muscle car era engines that came stock with a cam that fell into that category,so then do you consider that as the staring point or do you step back to the milquetoast base version cam.Some guys would consider upgrade cams to be the next step above what the top factory option was,this illustrates why it is so important to view cams based on their @.050 values so you can compare apples to apples,also make sure to include factory offerings sometimes you will find one that closely matches your needs and even though they will typically have slightly less aggressive ramps and will have a little less room under the curve,they will also be easier on your valve train so if thats really important to you it may be a better choice.When researching a cam choice it is important to make comparisons based on builds that most closely approximates your own,because as the amount of deviation increases the comparison rapidly becomes less relevant.
 

fourzeronine

Well Known Member
That Z-shaped line in the block next to the cylinder bore is most definitely a casting line from where two cores met.

While they're machining the block have them deepen the valve relief in the block for the exhaust valves by .075-.100[simple procedure].Reason;The cam that I've recommended has a lift spec.with 1.7 rockers of .550 which is right at the limit without notching.If your rockers are 1.75 he max.lift would end up at .565 and the valves and block will clash.The Comp Cam part number is 48-801-11 .The series number is XE272HR-10.

The engine I'm slowly putting together is also a 872 block, with .060" overbore and using 333 heads with 1.77" exhaust valves. I'm pretty sure that when I put some valves in to get a quick idea of possible cam lift it measured out to have more than .600" of valve lift before hitting the block.
 

1964SuperStocker

Well Known Member
Supporting Member 3
I agree that a cam that can pull hard to nearly 6000 rpm is definitely a performance type grind,the problem is there were a lot of muscle car era engines that came stock with a cam that fell into that category,so then do you consider that as the staring point or do you step back to the milquetoast base version cam.Some guys would consider upgrade cams to be the next step above what the top factory option was,this illustrates why it is so important to view cams based on their @.050 values so you can compare apples to apples,also make sure to include factory offerings sometimes you will find one that closely matches your needs and even though they will typically have slightly less aggressive ramps and will have a little less room under the curve,they will also be easier on your valve train so if thats really important to you it may be a better choice.When researching a cam choice it is important to make comparisons based on builds that most closely approximates your own,because as the amount of deviation increases the comparison rapidly becomes less relevant.
I agree about the @.050 value but no matter how many cars in any era they made in the 6000rpm they made hundreds of thousands more that never came close to that. My concern with any cam upgrade is can the parts already in there (in this case stock parts) handle what the Cam is asking them to do. At 25% more RPMS than factory, that is a considerable chunk (aggressive) more rpm's for anyone to ask of their factory low performance 348. The factory parts for a 348 were designed back in the late 50's and what we now know is those designs, tolerances and materials weren't very good. You have to start with what was factory low performance as a base because that is the base, then move up the performance ladder from there. I get chills just looking at a standard 348 rod vs. any BBC rod made after that. BBC Truck rods can take 500hp easy but don't ask factory 348 car/truck rods to do the same. I wouldn't have factory 348 rods in my wagon engine if I would have known better before. If you use the words "performance type grind" then we both agree in the idea just not the descriptive word given. :D
 

'37-4D

Well Known Member
Don, post a list of parts for us please! Trying to soak all of this in and make sure the next guy to follow this can get answers too.
I would post but I better let @Don Jacks do it. they are mentioned in a long private conversation.
But basically, I will be using 333 heads instead of my current 971s on my 872 block and upgrading to Hydraulic roller lifter's combo'ed with Comp Cam Extreme Energy line that they've come out with recently that comes in at 218 in. , 224 exhaust @.050
Will have to get new everything I assume for the heads. And do a little bowl work as Don mentioned. :good
 
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