496 or 511 or ???

[dualquad]

I'm planning a BBC for my dads chevelle that he drives 1000 to 1500 miles a year. Its a street car with a four speed and 3.55 rear. It will be a stock block, pump gas motor with a 6500 rpm max. I was figuring on building the popular 496. But if I'm buying a rotating assembly, why not go 4.375" or even 4.5" stroke? I know that 4.5" is tight, but possible and 4.375 doesn't sound bad at all, for clearance, that is. Regardless, I can handle any clearance issues, so for this discussion it is not an issue. The thing is, my dad is a torque fanatic. He loves it. So........ Is there any downside to going larger than a 4.25 stroke? As I type this, the 4.375 stroke with .100 overbore for 520 cubes is on my mind! How far would you go?


Thanks, Kenny

[Racerrick]

tall deck with 4.5 stroke or short with 4.25

[dualquad]

tall deck with 4.5 stroke or short with 4.25

Short deck. 454 block.

[Keith Morganstein]

I'm planning a BBC for my dads chevelle that he drives 1000 to 1500 miles a year. Its a street car with a four speed and 3.55 rear. It will be a stock block, pump gas motor with a 6500 rpm max. I was figuring on building the popular 496. But if I'm buying a rotating assembly, why not go 4.375" or even 4.5" stroke? I know that 4.5" is tight, but possible and 4.375 doesn't sound bad at all, for clearance, that is. Regardless, I can handle any clearance issues, so for this discussion it is not an issue. The thing is, my dad is a torque fanatic. He loves it. So........ Is there any downside to going larger than a 4.25 stroke? As I type this, the 4.375 stroke with .100 overbore for 520 cubes is on my mind! How far would you go?


Thanks, Kenny

I'd go easy. 4.25" stroke and wherever the bore cleans up. .030" to .060" whatever. More than enough and will never notice or need the difference. Easier build and thicker cylinder walls.

[GuysMonteSS]

My 513 is 0.070 over with a 4.375 stroke crankshaft in a low deck stock Mark IV 454 block.
It needed clearancing for the rod bolts,not too big of a deal.
The big thing to watch for is oil level.I'm using a Moroso # 20403 pan and app 5 1/2 quarts seems to be what it likes.
Nice torque and it makes for a great driver.
Guy

[Frankshaft]

A 496 is more than enough. If you want the 4.375 stroke for the cool factor, I guess it would be fine. THe problem with the 4.5 stroke in the short deck, is the rod length. It will pull the piston out of the bottom of the cylinder a long way at bdc, and will reduce skirt and ring life. Its a bad idea. I know guys are doing it, but if you see how far the piston comes out of the bottom of the cylinder, its like, wow.

[mag2555]

It's good that he will only drive the car a Little because nether a super T10 or a Muncy will statand up to either of those cid motors for long , even in the face of having no traction!

Ask me how I know, lol!

[rfoll]

What is in the car now?
Going from a 454 to a 496 is a significant increase in torque.

[SupStk]

Just go with 4.250" stroke if you want to keep it easy and afordable.
Going over 4.375 in a mklV is gonna get close to breaking into the side oil gallery, depend on the rods. Bet 4.5 would get really dicey.

[pdq67]

For either size engine, might want to go with no more than a good old CC 282S Magnum solid lifter cam and have, "T", a-plenty! Or onna UDHarold's solid lifter cams that the guys like over at Team Chevelle like.

Imho.. Talk about, "GRUNT"....

Build it for like 5500+ rpm here and go have more fun than John Law will allow!!

I miss Harold.....

pdq67

[mark_follweiler]

Just go with 4.250" stroke if you want to keep it easy and afordable.
Going over 4.375 in a mklV is gonna get close to breaking into the side oil gallery, depend on the rods. Bet 4.5 would get really dicey.

this. will be plenty.

[DaveMcLain]

The Big Block Chevy is an engine that really gains in the breathing department from having a larger bore so going to a 4.350 bore is definitely going to help and if your block can do that(most can) that'll be the way to go irregardless of the stroke.

About 10 years or so ago I did a 505 build for a guy with a big heavy 1 ton four wheel drive truck. I built it low compression with a flat tappet hydraulic cam, oval port heads and a dual plane intake. I didn't have it on the dyno but it was a blast to drive in the truck. It made it feel like it was light and agile running around. One time I told another customer about the build and he said that he saw it doing a burnout in four wheel drive, anything is possible.

[Racerrick]

tall deck with 4.5 stroke or short with 4.25

Short deck. 454 block.

easiest short deck combo is 4.25 stroke and 6.385 rod 1.28 piston.

[JES]

4.250 stroke and shoot for 10.25 comp cam 260/268 @.050 Promaxx 317 heads. Relieve block on intake side by the valve. Have fun. Great street engine. 10.15 at 131mph 3500lb

[David Vizard]

Maybe I am more adventurous than most because I can do more than just one build of anything so if it fails I still learn from it. But more to the point here is my advice on the subject.

If you are starting with a 454 and it is all going back with all 'as new' then it only bumps up the budget a small amount to go to a Scat 9000 series 4.25 strocker and a set of 1/4 long Scast stroker rods. With 496 cubes now on hand this configuration can actually deliver more than the 9.25% displacement would suggest. Part of this seems to be that for any given CR the piston dome is less. BTW there is a quick piston crown mod that will bump up torque right from the get go as well as boosting hp. This is good because it will allow a cam of less duration to be used thus enhancing the torque potential even further.

If the budget is there then one of Scats entry level forged cranks should be considered. I have built 4.375 and 4.5 strokers for 511 and 525 cubes. Have done four 525's and they all have shown outstanding torque as well as hp capability. I ran one of my 525's on one of UNO's dynos (the same dyno used for many of the EMC contestants). If 739 lbs-ft with a truly streetable cam and on 87 octane appeals to you then here is some pointers that should help you get the outstanding torque these builds are capable of regardless of 496, 511 or 525.

#1 make sure you use a set of heads with the 2.3 valves in not the 2.25.
#2 excessively oversize ports cost torque and power. For what you are looking to achieve a 496 should have about a 300 cc port max and a 525 about 320.
#3 be aware that to get the best from these builds you need to avoid the typically used wide LCA cams that most cam companies pedal. Assuming a 10.5/1 CR your 496 will need, at the widest, a 107 LCA, for the 511 a 106, and for a 525 a 105. Follow these guidelines and a nicely done build will produce right around 1.4 lbs-ft per cube.

Be aware that this data is not an opinion it is the result of a very substantial number of dyno tests.

If you have never built a real performance BBC you might want to consider buying a copy of my best selling book on the subject (Amazon stocks it)
DV