[Skippy597]

Planning out my engine build and I really want to go with a 4" stroker 400 (433ci) with the molnar crank and their own pontiac rods with a bbc rod end. Sounds like it will be a great combo and meet my power desires, plus I plan on running a 150 shot also. But the 461 stroker combo that everyone has done seems to be the same price so its hard to justify getting less for the same.

The 461 combos I've seen typically use a 6.8 rod which I'm not crazy about running that short of a piston but enough people run them I guess its not an issue.

The 433 would use a 4 inch stroke, 6.625 rod and 421 style pistons.

Seems the 433 with the shorter rod (still pretty long) will have better wear characteristics and wont have any piston rocking issues. But I'm still learning so could be wrong.

I really hope you guys can give me something to commit to the 433 because I like things that are less common but at the same time dont want to build it and wish I've gone my other way.

Build is going in a 66 lemans street machine build, lots of driving and roadtrips planned. Will be backed by a tkx and a ford 9" with 3.89 gears.

[Skip Fix]

Being a stick I'd go with the 433-my plan for my stick 65 GTO project. I have a 4" Ohio billet when Ken Keefer had some made before forged cranks came out. Not as much drivetrain breaking torque and can rev some.

[JLMounce]

Steep gears with a TKX, I'd build the 433 personally. It'll be a bit more high strung than the 461 with greater RPM potential if the valvetrain can keep up.

If that's not your driving style and you prefer to lumber around more, I'd probably opt for the 461, but I'd target a different rear end gear with that deal myself. Something like a 3.42 depending on which gearset you choose in the TKX.

[25stevem]

What level of hp are you looking to make without the shot?

Looking at things in a Apples to Apples way the cid difference between the two motors will have a 7% effect on whatever heads you bolt on this motor.

In terms of running heads that are the choke limit to making a given level of HP the 433 motors peak HP curve will nose over 7% slower , the 461 will be 7% faster, in terms of the torque these changes will be the reverse.
This is where your transmission choice can level the playing field in the difference in the torque output of both motors while giving the smaller motor the fuel usage advantage over the larger motor when just cruising around.

[Skippy597]

Honestly this is enough to convince me. Because I really want to build the 433. Really trying to shoot for 550 but I'm fine if I come up short a little. Planning ported edelbrock round port heads and a offy dual quad setup that I know will get plenty of opinions as to it killing power, but I'm gonna port match it and do what I can with it. The rear gear doesnt seem too steep but could step down to 3.70s just fine. Planning a solid roller or maybe even a solid flat tappet. Something like the lunati 40510511 solid roller with 242/249 at 50 and .556 lift and run 1.65 rockers.

[mgarblik]

Originally Posted by 25stevem

What level of hp are you looking to make without the shot?

Looking at things in a Apples to Apples way the cid difference between the two motors will have a 7% effect on whatever heads you bolt on this motor.

In terms of running heads that are the choke limit to making a given level of HP the 433 motors peak HP curve will nose over 7% slower , the 461 will be 7% faster, in terms of the torque these changes will be the reverse.
This is where your transmission choice can level the playing field in the difference in the torque output of both motors while giving the smaller motor the fuel usage advantage over the larger motor when just cruising around.

I think this very well sums up your choice. I just finished a 468 and have it back in the car. 4.181x4.25. I already had a billet crank left over from the Boss Bird funny car so that made the decision for me. I wanted the engine to really "zing", so I used a solid flat tappet cam and light rotating assembly. Didn't really matter, it's done making power at 5900 RPM. I had anticipated it zipping right to 6300-6400 RPM. Has a nice, broad torque curve. Just depends on what you want. I would tend to favor the shorter stroke with the stick trans and the desire to spray in the near future.

[77 TRASHCAN]

The 461 has tons of builds, for years, nothing to worry about. Of course machine work on any build is paramount!!!

I ve about many folks here, that REALLY like their 4 inch stroke engines, even some that have had good running 4.25 stroke engines!!!

Carry On!!!

[PAUL K]

I always steer folks with a manual transmission to build a 4" stroke combo. Never had a complaint when they went in that direction. They are more fun to drive and easier on parts... Win x 2

[Skippy597]

Awesome, really appreciate the input guys. Love this forum. I'll build the 433, its gonna be a bit since cranks wont be done until about august but ive got a spare engine for the meantime.

[Dragncar]

My buddy has had very good luck with a 433 and 6.7 rods.

[Formulas]

the difference wont be a night and day thing there is no compromise

i like a 400 because i like the top end, i like the 455 because of the electric motor like torque the 428 sits right in between with a bit of both

[mgarblik]

Originally Posted by Formulas

the difference wont be a night and day thing there is no compromise

i like a 400 because i like the top end, i like the 455 because of the electric motor like torque the 428 sits right in between with a bit of both

Among the various stock Pontiac engine sizes, I agree with this. The 428 is a wonderful size for a Pontiac engine given the heads that were available from the factory. Great torque and they had better high RPM power than the typical 455. (not talking round port here). At a factory rating of 390 HP in HO form, they were a powerhouse.

[Skippy597]

So if you guys were building an ideal 433 would you use a aftermarket factory length rod 6.625 or a bbc style 6.8 rod?

I was leaning towards the 6.625 but inhave read a lot about the "ideal rod ratio" being 1.7 which on a 4"stroke is 6.8 for the rods.

Seems the differences are minimal at best but since im buying everything anyways might as well get every bit I can.

[Formula8]

I went with a 6.8 in mine. Really for no other reason than ease of parts availability. I doubt that the rod ratio is that critical in a street engines RPM range, particularly with the shorter stroke.

[mgarblik]

In the post COVID age, I would go with the rods that have the quality you desire, the matching piston pin height that is correct and the crankpin diameter you can get. Getting the three parts, all matched is a challenge right now, unless you want to wait a long time. I don't think the rod length is a factor for most builds with the small difference. Current personal favorites: Ross Pistons, Molnar rods and crankshaft, Chevy rod bearing size, (for much better bearing size availability) Good luck with the build.

[Formulajones]

Rod length has been a very long ongoing discussion among engine builders for years.

You hear all kinds of pros and cons, but it does seem that most of the high end engine builders that are good at making HP and longevity will favor a longer rod combo more so than a short rod. Some will argue more dwell time with the longer rod is more beneficial, especially with a good cylinder head, then there is the less side loading or stroke vs rod length scenario, and other points to be made. It's probably the reason why you see more long rod rotating assemblies available.

For me, I'd go the long rod route and not give it a second thought. If it's piston pin location vs ring lands you're worried about, I wouldn't. Stroker engines have been built with the pin in the oil ring lands for decades, it's fine. Shorter pistons and small ring packages have been the way to go for years now as well and have proven to be durable. In fact some builders will tell you the smaller ring packages will actually seal better than the old giant 5/64 stuff. Honing procedures have improved drastically and come a long way in the last 50 years. No need for the giant ring packages anymore. Some HP to be found in the piston/ring package too.

As far as engine size, I like bang for my buck so I generally go bigger if I can because in many cases, the rotating assemblies cost the same.

[Skip Fix]

I think a 6.625 vs a 6.8 is not even going to measurable on the dyno nor at the track all things else the same.

[adamo]

With the new molnar 4” stroke 3” main Pontiac rod journal I can finally build my 440 with my max a lite a beams that I have been sitting on for a while.

[blueghoast]

I love my 440 CI.
Did drag week two years in my 62-Tempest.

GT

[Skippy597]

Just called molnar and put my info on the list for the 4" crank with bbc rod journals. Gonna go with 6.8 rods.

Really shooting for 500 hp, I'm pretty sure I can get there with a street 433 and then spray a 150 shot on the strip.

Thanks guys.