I dont think i will go over 6000 rpm and the lift on my cam is substantially lower than .600 at the moment. And on top of that, the car will most likely be driven less than 300 miles per summer. I barely get time to drive it. I am really interested now in the idea of finding a nice bare 400 block and building it up and then using my current top end on that block. How much power do you reckon it would yield compared to if i had gone with a 383 kit on my current setup?

 

The rule of thumb states that if everything is the same. Intake, cam, heads..... and all you change is the ci. The larger the ci will increase the TQ, but the HP will be nearly the same at a corrospondingly lower rpm equal to the amount of ci increase.

I have not built a 383 in probably 20 years is how much I'm against them. The cost is the same for forged crank rotating assemblies, so it is foolish to build a 3.750 stroke 383. The other thing is everybody has a 383

bigger cc heads get you down to 11 or less C/R. so my 396 with 64 cc heads at @ 11.2 C/R just uses bigger duration roller cams of 236 and above get the dynamic C/R down to 91 unleaded friendly. My 434 is @ 11.7 and runs on the local 91. But it takes cams larger than 242 duration to get the DCR down. I actually drive all over the place fine.

https://www.usaperform.com/rotating-...sh-11-8-1.html

 

How is the CR of your 434 higher than the 396 but it can run on 91? is it due to the roller cam? i thought once CR gets over 11 you would have to go beyond 91 octane fuel? If i were to build the 421, would i have to upgrade to a roller cam or could i get away with a flat tappet and still use regular pump gas?

 

I have two motors for my vette so I can change it out in a day if I have to. 434 11.7 and 396 11.2 Dynamic compression ratio is probably about the same to run fine on 91 california max unleaded. You can use a flat tappet cam with bigger duration to lower the dynamic c/r....... I just don't own or work on very many non roller cam motors in the last 25 years. So I don't even claim to be an expert on flat tappet. roller cams are a nobrainer if you are trying to make power or even a good running street motor.

 

Problem with FT cams is finding a decent lifter that wont self destruct. I happen to love the simplicity of them...if you got a 421 and a decent head youre leaving a TON on the table not using roller. But...which brand to get.
your drivebility and tq will really improve. Popular stuff out there that is really junk thats the problem.
Try Straub Technologies talk to Chris either way he can get you straight. Really knows his stuff.
https://straubtechnologies.com/

 

If i were to make the switch from flat tappet to roller, aside from the cam itself what other components would need to be changed? I dont think i will do anything to this motor at the moment, but if i find a nice 400 block to build, I'd like to know which of my existing components i could use and what would have to be ditched to go roller on the new build.

 

Thank you for that. So i gather to make the switch i would be buying a roller cam and roller lifters? is there more to the puzzle?>

 

Pushrods, cam button. Or machine the block to take a retainer like late model blocks do.
Nothing wrong with a cam button easy to set up.

 

Valve springs are required to match the cam also. I swapped my ft for a retro hyd roller. It's the only way to go these days if you have a few extra bucks to do it.

 

Just walked into this but just a point, with a 400 don't use that crappy 5.6 rod.ive always liked the 5.85 rod over the 6" but I believe the 6" rods run cheaper. Don't know what you guys think but this seems like a good discussion . Hopefully good data in the future for future projects.

 

Longer rod ➤ piston's shorter compression distance aka pin height ➤ lighter piston ➤ lighter bob weight.

*typically, increased mass of a longer rod is < less than mass decrease of shorter piston ➤ net weight reduction

Additionally
*typically, longer rod Improves Rod / Stroke ratio

 

I get that, but the longer rod shoved the Piston pin higher getting into the oil ring area which depending on the application can be less desirable. I think you reach a limit of how long a rod to use.

 

Of course there's a practical limit

 

I am slowly learning.

 

GKULL
Not meaning to hi-jack OP’s thread, but I have a Bow Tie block 434 waiting in the wings to go into the 72. What oil pan do you use in your 434 that allows crank clearance and fits in the Vette?
Thanks much

 

Ya know, if it's your first build it's too easy to get into it over your head. Before you make a $5000 mistake just build your 355 and use it as a learning tool. 355 with good heads and cam should be close to 400hp and fun to drive. When you know you need big displacement and power you can spend your money on that knowing what you are doing.

Just my two cents.

 

This is to everyone wanting to build big inch stroker SBC's. If you flip a stock 2-4 bolt block over you will see that the pan rails narrow towards the front. So when you are clearancing the pan rails for a 3,75 - 4 inch crank, (Yes you can make 408 ci stock blocks with a 4.030 bore.) You only have to actually clearance the most on the front cylinders and a lesser amount on the next 2 or 3 cylinders and mainly only on one side of the block because of the way the rods swing around on the crank. The type of block determines which high capacity aftermarket pans. Just ensure you get the correct for your dip stick (driver side or passenger)

I'm just going to say this and it is just my personal experience. People that build using bowtie blocks have a 40 year old mindset and are foolish. They are against learning anything new. They have several problems. the greatest is the max bore of 4.155. So in you case your 434 ci is at the max bore. So you are kinda screwed as the bore wares out because you can't over bore it. The other problem is that even with the splayed main caps it is only rated at something like 700 hp. the casting is weak compared to the more robust and 35 pound heavier Motown and higher end Dart blocks (not SHP) . which is kinda limited to 3.750/3.875 Which function very well in 1200 hp twin turbo motors. You are not saving any money buying a crap bowtie block and it has no future rebuilds unless you sleeve the block. I think that my Motown has a max bore of 4.200.

Dart and Motown blocks have straight pan rails. so you have to get pans specific to those blocks. I ordered my Motown racing with an 8 quart deep pan made for Vettes with a shallow front for up to 4.125 stroker cranks. On my stock block 396 I have a Morroso 8 quart drag and road racing pan made for up to 4 inch stroke but I had to mod the front to clear the cross steering arm. I've also seen another person here on the forum that ground away the top of the steering arm for the same Morroso racing pan.

I don't know much about bowtie blocks because nobody in the know would even use one. But someone like the tech guys at Summit racing could point you in the right direction in a racing side pan Canton or Morroso. You really want to have volume along with baffles and windage. Then you have to get pan specific oil pump pickups. I try to stay within about a 1/4 inch of the bottom for the pickup screen

 

My former 427 abc used a Bow Tie block. The pan I used was a Milodon Stroker Low Profile, # 30908. 6 qt. capacity, and fit perfectly in my '69. https://www.summitracing.com/parts/mil-30908

Pics.....427 pan.....







My current 440 sbc (Dart block) uses a Milodon # 31505 low profile 7 qt. pan.
This one.....https://www.jegs.com/i/Milodon/697/31505/10002/-1
Either pan will accomodate a 4" stroke and fit in your Vette.

 

Thanks for the info. My Bowtie 434 was built before the Dart and Motown blocks were available, but I agree totally. The options to go fast these days are growing while at the same time the cost per HP is dropping. What a great time to be a gear head!
Appreciate the pan info.
Thanks. Dave

 

thats exactly what I’m going to do. I clearly don’t know as much as I should and as much as I’d like to have a big 500-600hp motor, I don’t want to end up wasting money or build something that could’ve had more potential. My motor still needs more fine tuning to get to its full potential I think. But I’m glad I started this thread, so much valuable info from all you guys.