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all big block z owners please report to the dance floor.


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In terms of what? If you mean drag racing you are wrong. Any drag racing car will do better with the higher horsepower/torque engine, regardless of big or small block.

 

I didn't mean only drag racing. however while we are on the subject, much hard to hook up a BBC in a stock bodied Z car than a SBC.

 

 

Geez, you must really believe everything you read. While it is true that BBC require a bit more spring pressure to maintain valve control, its nothing crazy.

 

Same goes for the cam and lifters, unless you are speaking of solid roller which all high rev, high horsepower engines will kill with time, regardless of BBC or SBC.

 

Valve guides? Are you serious? BBC's have huge valve guides in both diameter and length. Even in stock form BBC valve guides last light years longer than SBC's.

 

Bottom line, if you have the correct quality parts on a properly built street/strip BBC, they will last every bit as long as a SBC, if not longer because a BBC doesn't have to work as hard if they are making the same power (hence easier on parts).

 

ANY SBC or BBC revving to 7000 needs more than just a solid flat tappet cam and decent spring pressure to live.

 

Again, if both are built with same quality of parts like forged crank, decent rods, and forged pistons, etc...either with happily rev to 7000.

 

No, I don't believe everything I read. Thanks for asking. I have my own set of valve floating cam eating big blocks for that (no reading required). However, my experiences seems to match the published BBC tech articles.

 

And I also have a 7200 rpm sbc with just a stock set of dart 200cc heads and a compcam 292H. Hyper pistons, 2 bolt block, and a factory steel crank. Needs a rebuild now but lived for 8 years with red line drives every time I got in the car. So, I disagree than a sbc needs more that a flat tappent cam and good valve springs to live.

 

As long as you mean the LS series of engines, I will agree for the most part.

 

Although it takes more than a cam and a head porter to get 500+ ponies from an otherwise stock 5.7 litre LS1. Think about it, a stock LS7 with 7.0 litres is making 500+ and it has way better heads stock than the best ported factory LS1 heads. Even the magazine built-ups with their inflated numbers need a 6.0 block and HUGE heads to breech 500 HP.

 

While it is true you can get better DYNO numbers with a carb on a LS series engine, I seriously doubt in the real world that the properly tuned and sized EFI will be bested by the intake/carb combo.

 

Chevy high performance used a little 5.7 ls1 engine with a set of 210rhs heads and a tiny xr265hr (212/218 with 0.520") and made 529hp and 488 ftlbs. There are many other examples of the 5.7 making over 500 with bigger cams and ported stock heads. The 6.0 are getting closer to 600hp with heads and cams.

 

Real world performance. Check out some LS1 sites and notice the carb guys a more often than not beating the efi guys on the drags.

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It seems strange to have a BBC vs. SBC debate on a Datsun site! That said, let’s clear up some misnomers…

 

- all pushrod engine families are having problems these days wiping lobes on flat-tappet cams. There is anecdotal evidence that big blocks are more prone to this than small blocks. My single data point is a 1978 Mark IV BBC into which I installed a Comp 262 Xtreme (or whatever it was called) hydraulic flat-tappet cam, together with their matching springs - back in 2000. Wiped the cam after 20 miles, despite by-the-book break-in. Now I run a mechanical roller.

 

- It is true that the BBC valvetrain is heavier than that of the SBC, but a matched set of lifters-cam-pushrods-valves-springs-retainers, set up with correct clearances and installed-height, will even the playing field.

 

- If you do buy good aftermarket valvetrain parts, prices for SBC vs. BBC are not much different. The notable exception is heads: BBC heads are around $2000 assembled, while comparable SBC heads run $1000-$1200.

 

- The BBC family has no equivalent to the LSx; a more proper BBC vs. SBC comparison would be Mark IV BBC vs. Gen I SBC.

 

- 500 hp is about the break-even point, beyond which a BBC build becomes comparable in cost to a SBC build. Head north from that, and the BBC becomes cheaper.

 

- There is no JTR-type kit for BBC installation in a S30 Z. Some people have however successfully used a very similar approach, while others have used firewall setback (me) and still others have gone the full tube chassis route (Ron Jones, Brad Barkley)

 

- The BBC remains an engine for specialists, who grew up using them or who just prefer their layout over the LSx engines. As I’ve been saying for many years, the “best†engine to swap is the engine with which you personally happen to be most familiar. That may not be the most elegant, or most economical, or most advanced engine - but if that’s the engine with which you have the most experience, that is the best swap candidate for you.

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all pushrod engine families are having problems these days wiping lobes on flat-tappet cams. There is anecdotal evidence that big blocks are more prone to this than small blocks. My single data point is a 1978 Mark IV BBC into which I installed a Comp 262 Xtreme (or whatever it was called) hydraulic flat-tappet cam, together with their matching springs - back in 2000. Wiped the cam after 20 miles, despite by-the-book break-in. Now I run a mechanical roller.

 

What size solid roller cam did you use?

how do those solid rollers sound?

How often do you adjust and what size lash?

I went with hyd roller lifters on my 454 but those make the float problem even worst. however, they cured the flat lobe issues.

 

A flat tapent BBC cam of the same duration of a SBC typically has more lift which causes more cam issues because the lifters are the same diameter. Then there is the new formulated engine oil which also eats lobes.

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  • 13 years later...
On 10/26/2007 at 6:28 AM, Pyro said:

 

What size solid roller cam did you use?

how do those solid rollers sound?

How often do you adjust and what size lash?

I went with hyd roller lifters on my 454 but those make the float problem even worst. however, they cured the flat lobe issues.

 

A flat tapent BBC cam of the same duration of a SBC typically has more lift which causes more cam issues because the lifters are the same diameter. Then there is the new formulated engine oil which also eats lobes.

 

It occurred to me, that after thirteen and a half years, a reply might be judicious.  Or at least amusing....

 

The vendor is/was called "Cam Motion", from their "low lash mechanical roller" line.  A modern internet search reveals this: https://cammotion.com/low-lash-solid-roller ... but that's for LS-series engines, and not for Mark-IV big blocks.   I can't find anything about big-blocks on their current web site.

 

Back in the day (winter of 2006-2007), the part number was L2402-2501-12+4.  That's 239/249 deg @0.050”.  Lift is 0.642”/0.646”, 112 LSA, installed +4 deg.  Springs are Comp Cams PN # 933: 185@ 1.920" (valves closed) and 490-500 over the nose.

 

Valve float was, if memory serves, nonexistent.  The real rpm limit was piston speed, or in other words the structural integrity of the rods and rod-bolts.... 3/8" ARP bolts, but stock (resized) GM rods.  In hindsight I ought to have redone the bottom end... maybe even gone with a stroker crank and 6.385" rods

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