Thread: 350 vs 400 vs 383 what to do?

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I know I'll get a lot of different opinions but here goes.

We race a 88 caprice in a factory stock circle track division. We just blew our 350 and we have to build up a new engine for next year. I have 2-400's and 2-350's. We have to remain mostly stock (we've gotten away with running a bigger cam, a racing HEI ignition, and might get away with running a 383). We have to run q-jet 4 barrel.

What would be our best engine for this car? We run around 2800 rpms in the turns up to 5300 rpms in the straights.

I know the 400 would have more torque but would it take longer to get up the rpms? We need to accelerate quickly out of the turns.

An engine builder told me he would put a 307 crank in a 350 block to get a 327 displacement (I think I have that right). He said it would have good accell.

What do you all think? I need experienced help.

A 307 crank in a 350 makes a 350....both have 3.48 inch strokes

If you use a 400 block and it is against the rules.. it is really easy to spot due to the number of core plugs on the sides.

Use the biggest engine that you can.....you want torque off the corners.

An opinion and costs nothing.....

"A 307 crank in a 350 makes a 350....both have 3.48 inch strokes"

robot, I think you'll find that a 307 crank in a 350 block will make a 327. A 307 was a 283 block and 327 crank (3.250" stroke). You may be thinking of a 305, which uses a 3.480" stroke.

Tech....duh, I had my brain out of gear. I was thinking of a 305 since all the posts are usually 305 questions. You are absolutely right abotu the 307 crank.

I need to get 20 lashes with a worn timing belt for that blunder. Thanks for the correction... will try not to do that again (my personal policy is to make new mistakes each time)

We can run a 400 without problems. I have one block that has 3 frost plugs on one side and another block that has 2 and it looks just like a 350. But either way, we don't have a size restiction.

So just plain old torque... does rotating mass figure into how fast
you can accelerate?

What does a 383 do for you? It would have more torque than
the 350, but a 400 would have even more. Why don't people just go to a 400? On the bigger engines, isn't the torque more in the low rpms?

Tech should be able to give his now-famous web link that compares about two zillion engine combinations (Chevy) so you can get an idea of the effect of cubic inches on the torque.

If Tech sees this message, that is.

Use the 400 block, 350 rods, 5.7 inch, or 6 inch rods and a 350 crank to make torquey 377. There is less expenisive machine work involved than a 383. No block clearancing necessary. KB sells pistons to do a 6 inch rod in a 400 with a 3.48 inch stroke for $261 a set which is only $25 more than their standard 350 pistons. Aim for a static compression ratio of 10.5:1, put some AFR 190cc heads on top of a zero decked block and a Comp Xtreme Energy cam inside. Top it all off with a high rise dual plane like the Edelbrock Performer RPM and a 750-850 cfm carb and you'll be set to make some serious midrange power on pump gas.

The rules in our class require factory components so I'm limited to stock intakes, and stock heads. I can get away with somewhat of a performance cam as long as the tech crew can't detect it with a vacuum test. Right now I'm stuck with 1.94" intake valves on stock heads (hope to get 2.02" soon). 10.5 compression might be pushing it as they check that ocassionally.

I have a Comp # 12-211-2 cam that I hope to use. The rules limit the cam to .410 lift, but I think we can get away with the .470 since everyone else is running bigger cams.

So within these limitations, would the 377 be the way to go? What is it about this arrangement that gives me the midrange torque? larger bore with smaller stroke? so would low range power be large bore large stroke, and top end power be small bore small stroke?

http://www.ryanscarpage.50megs.com/combos1.html

On paper a 383 looks the best.The 400 blocks run hot and are very prone to cracks.I would try and run a 383.With the bore of a 350 and the stroke of the 400 you should have plenty of torque.I would try and run a 6 inch rod.The piston will dwell longer at T.D.C. and you will have better piston skirt life and the rings will last longer.There is also more metal between the bores and you are less likley to blow head gaskets with the 383.As far as the cam try Isky or Howards the both have cams for the lift rule.

Comp's Xtreme Energy 250H makes 19.5 inHg at an idle of 800 rpm, stock is 20. You could pass that as worn rings. It makes power from 600-4600 rpm and over 400 ft lbs of torque. This is all in a 350. Since you're limited to stock vacuum, a bigger motor will pull more vacuum on a bigger cam. I say build that 400 and run the biggest cam you can still get stock vacuum with. Any cam that pulls 20 inHg at idle will run out of power way early, so run the biggest motor with the bigger cam and you'll be able to make more power as you approach your 5300 rpm top speed. The 4-bolt 400's are crack prone, but the 2-bolts are not. Most claim the overheating issues have to do with the 400's siamesed bores, the bores actually touch between cylinders in the water jacket and there is no coolant flow between. I don't necessarily believe this to be true. Most racing engines use siamesed bores. GM's new LS2 and LS7 engines both use siamesed bores. I believe the overheating issues to be caused by the fact that a 400 is a big block in a small block package and retains the small block cooling system. Just make sure your cooling system is sufficient and you'll be set.

[i] The 4-bolt 400's are crack prone, but the 2-bolts are not. Most claim the overheating issues have to do with the 400's siamesed bores, the bores actually touch between cylinders in the water jacket and there is no coolant flow between. I don't necessarily believe this to be true. Most racing engines use siamesed bores. GM's new LS2 and LS7 engines both use siamesed bores. I believe the overheating issues to be caused by the fact that a 400 is a big block in a small block package and retains the small block cooling system. Just make sure your cooling system is sufficient and you'll be set. [/B]

I have both 400 2-bolts and 4- bolts sitting on the flooor of my shop with 3-4 inch cracks in them.Some in the lifter valley and some between the freeze plugs.Of the 400 2-bolts the 817 blocks are the strongest.I have weighed both the 509 bare 2-bolt and the 817 bare 2-bolt blocks.On the ones I weighed the 817 block weighed 11 lbs. more.Was it just those blocks?I don't know but the 817 did look like there was more metal in the main web area.

Just an opinion:

I just read David Vizard's "How to build maximum perfromance chevy small blocks on a budget". The thing which might interest you is this: One of his main criteria in this book is cost and you can keep cost down by using second hand stock Chevy parts and modifying them. Like for example grind the crank down to create less windage loss. Use 6 inch rods for more torque. Give the valves a 30 degree instead of a 45 degree seat to increase flow at low-lift. Pocket port your heads (if you're allowed to do so in your class) to get more swirl and thus better burn... There are a great many cool things you can do with cheap second hand STOCK Chevy parts and a carbide grinder.
There are also good books on tuning Q-jets, which aren't that bad once you get the hang of them. Edelbrock and Holley beat the Q-Jet hands down when it comes to ease of use, but if you toy around a bit the performance will be the same. That's Vizard's opinions and he's been in the racing and building business for over 40 years. At the end of the book there are some nice engine combos which would maybe suit you very well, based on 350s, 383s and 400s.

I liked the book very much, gives you a bit of a technical view on things, the bigger isn't always the better...

Just my two cents worth...

Mad

Originally posted by erik erikson
The 400 blocks run hot and are very prone to cracks.

Not true, but this rumor along with "all 400's have 3 freeze plugs" seems to never die, the biggest cause of the overheating was using NON 400 head gaskets which did not have openings for the steam holes.

We prised the 2 freeze plug 400 blocks which most believed to be 350's and won lots of street races with chevys top torque mouse motor.



dcoffield, run the 400, enjoy the extra torque.

Don't forget non-400 heads to go with their non-400 head gaskets. Any non-400 head will work, though. You just have to drill your own holes. You'll know you did it right if you hit a water passage in the cylinder head.