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Discussion Starter · #1 ·
First time posting to this forum,
I have a 1976 triumph tr7 (not a hot rod ik) that has had a 350 sbc squeezed into it (so a big block is out of the question for my hp goals). I was going to build that up for some extra horsepower but i was told not to waste my time or money but to instead build up a 400 sbc. Same size, 50 extra cubes, totally makes sense. So i went to ye old facebook marketplace and found a 4 bolt main 400 sbc (511 nickel) for $200 and scooped it up. I have now come to find out that a 2 bolt main would've been better. So now im wondering if with after market main caps (any recommendations pleasantly welcomed), some ARP hardware and maybe a main cap girdle? if itd be able to handle 600hp. Or should i just bite the bullet and drop way too much for my taste on a dart block for the piece of mind that i wont hit the throttle and saw several thousand in half.
 

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I would not lean on a stock 400 block without Sonic checking the cylinder walls.
For 600hp I would be buying a aftermarket block
 

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Agree ^^^

450-480 HP in a stock 4 bolt block is about it, and even then you will have a 1 in 10 failure rate for a thin cylinder wall that cracks in less than 5000 miles.

Anything above that is juat a gamble, some guys will push a 2-bolt with aftermarket splayed main caps to 600 HP but you better definately have it sonic checker or it is a massive roll of the dice.

Problem with factory 400 4-bolt caps is the location of those outer bolts....the bigger main bearing daimeter pushed the bolt pattern outboard, and put those 2 outer bolts drilled right into the weakest area of the main bulkhead/crankase, thus actually makng it weaker than a stock 2-bolt block.

600 HP reliably, you need an aftermarket block.

For what it is worth, I know of someone putting somewhere in the neighbor hood of 24 psi turbo'd 1200 HP through a Speedmaster block, and 850-900 HP nitroused HP though a second one.

Pricing isn't bad, actually has me thinking of it too instead of my 2-bolt block.
 

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Discussion Starter · #4 ·
Agree ^^^

450-480 HP in a stock 4 bolt block is about it, and even then you will have a 1 in 10 failure rate for a thin cylinder wall that cracks in less than 5000 miles.

Anything above that is juat a gamble, some guys will push a 2-bolt with aftermarket splayed main caps to 600 HP but you better definately have it sonic checker or it is a massive roll of the dice.

Problem with factory 400 4-bolt caps is the location of those outer bolts....the bigger main bearing daimeter pushed the bolt pattern outboard, and put those 2 outer bolts drilled right into the weakest area of the main bulkhead/crankase, thus actually makng it weaker than a stock 2-bolt block.

600 HP reliably, you need an aftermarket block.

For what it is worth, I know of someone putting somewhere in the neighbor hood of 24 psi turbo'd 1200 HP through a Speedmaster block, and 850-900 HP nitroused HP though a second one.

Pricing isn't bad, actually has me thinking of it too instead of my 2-bolt block.
Wow those are some impressive numbers! Yeah im starting to lean back towards resale of the 400 i just picked up and then saving up for an aftermarket block.. now i just need to see what combination of parts should help me make some power on pump gas.. but ig octane booster is an option instead of buying actual race gas.
 

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Why are you playing with a old v8.


Many 4 cylinders that can make some nice numbers with a bit of boost
Having only 450hp with a powertrain that is 3 to 500lbs lighter will give similar acelleration and better handling.

If your stuck on a v8 a 5.3 LS with a bit of boost can do 600hp easily.

Do not get hung up on a horsepower number.

You should focus on a acceleration number from say 0 to 120mph or whatever your goals are and look at what it will take to make that goal without having excessive weight or the crazy expensive maintance cost of say a $800 clutch.
 

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If you're stuck on a v8 a 5.3 LS with a bit of boost can do 600hp easily.
One question would be, is there room for a turbo?
It seems like the turbo and plumbing would be really tough to work out.

But I'd agree that this is a situation where it seems like a junkyard LS swap makes alot of sense.
It's already non-original, so really no reason to require an sbc.

Without a turbo, what would the options be to make sufficient HP (what size LS, price, etc.)?
I assume all except the truck motors are aluminum blocks...?
That would save a decent amount of weight, which I'm sure that little car would appreciate.
 

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I don’t know if the 2 bolt main block is better than the factory 4 bolt. The problem is the factory bolts all the bolts directly into the main bearing web. So the web carries all the loads imposed by the cap. The aftermarket 4 bolt caps angle the outboard bolts into the pan rail so all the loads are not so much concentrated into the bearing web.

On stock 4 bolt blocks that are developing over 450 into 500 hp and are also circle or road track racing, so they are taking a beating, we have cracked a few main webs over the years. For just putting around and showing off now and then even at these power levels the blocks should be OK. But if you have the money an aftermarket block brings a lot to the game.

For stuffing foreign car engine compartments which tend to have more length than width, the Ford Windsor 302 block is an easier fit because it is pretty narrow, this an attribute of the 221, 260, 289, and 302. The 351 is taller thus the heads spread out more as the SBC does. Plus the 221-302 is about 60 pounds lighter than Gen I, SBC before you put aluminum heads and intake on it.

Bogie
 

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One question would be, is there room for a turbo?
It seems like the turbo and plumbing would be really tough to work out.

But I'd agree that this is a situation where it seems like a junkyard LS swap makes alot of sense.
It's already non-original, so really no reason to require an sbc.

Without a turbo, what would the options be to make sufficient HP (what size LS, price, etc.)?
I assume all except the truck motors are aluminum blocks...?
That would save a decent amount of weight, which I'm sure that little car would appreciate.
 

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I will offer this, and it's simply my opinion. If you want to just go nuts with a 400 in a Triumph, go for it. If you want it to actually be fun to drive, pause and consider.

There are four basic things to consider here: HP, torque, RPM range, vehicle weight.

When you're talking about a heavy vehicle like a truck used for towing, a full-size car you want to move fast, etc.... the answer is big cubic inches. You already have a heavy vehicle, so the weight of a big iron V8 won't make much difference. Cubes make torque, and they make their HP with a lower peak torque RPM.

When you're talking about a light vehicle, the weight of a big-cube iron V8 makes a huge difference in overall weight. You also don't need the mountains of torque to overcome inertia in a lighter car.

Think of it like a diesel in a truck that redlines at 3500 but can pull 15,000 lbs without working hard vs a 500-lb sport bike with a 600cc engine that revs to 13,000 rpm. Now imagine putting that big diesel engine in the sport bike. It's no fun. Heavy, sluggish, and not well matched to the application.

I would argue that you need power density. A high rate of hp per pound of engine. 2JZ, EJ20, VG30DETT.... something you can max out some power and keep it light weight.
 

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If you have the slant 4 that engine has potential.
I am a fan of old overhead engines. But never came across one of those to play with it. Still the design seems rubust and able to run 110 or even 120 hp with basic maintance/tooling/tuning.


If you do not want to run it because of say a cracked head then a miata engine makes similar power with about the same weight. They have potential to make 200 to 250hp and still be driveable.

Weight and hp is a fun thing. The less weight you have the less hosepower you need. Also light weight parts can be used in a low hp application that would need to be heavier or much more expensive in a higher horsepower application.

You can make 600lb but you may add 1000lbs or more to keep from rebuilding/replacing something every weekend. .
 
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