Engine choices, 331 or 347??

HiFlow5 0 · Nov 26, 2005

I'm going to be building a new short block over winter and I can't decide which to go with, a 331 or 347. Also am not sure on compression, was thinking of 10.5:1 NA or keeping it a little lower like 9.5:1 and squirting a little juice. Either kit will be ordered from CHP, I know that, but just hit this little road block before I move forward and I just want some opinions.

Also, I'll be running Edelbrock Performer heads with 1.6 rockers, Trick Flow intake which I already have, and I'm looking into Comp extreme energy cams.

Grn92LX · Nov 26, 2005

Build a 10.5-11:1 compression 347. Nitrous works with high compression, do not sacrifice compression. Are you ordering a CHP assembly or having them build the engine?

89white50 · Nov 26, 2005

with your heads, i would say 331. I do njot think they flow enough for a 347, unless you have them ported. IMO.

5spd GT · Nov 26, 2005

My preference ='s

331 for daily driver

347 for weekend warrior

Thomas302 · Nov 26, 2005

I would say 347. Why sacrifice the 16ci for the same money. I wish I would have gone 347, but at the time I built mine, there was still a big stink about the 347 and oil problems so I went 331.

5spd GT · Nov 26, 2005

Thomas302 said:
Why sacrifice the 16ci for the same money.

I so want to address this...

Grn92LX · Nov 26, 2005

Thomas302 said:
I would say 347. Why sacrifice the 16ci for the same money.

Well said and the fact that you have a 331 is the nail in the coffin.

How is the car running? What was the set up again? I remember you used the TFS R manifold but I forget what else.

5spd GT · Nov 26, 2005

Grn92LX said:
Well said and the fact that you have a 331 is the nail in the coffin.

Lol...no that doesn't mean anything. He hasn't had a 347. He hasn't had more sideloading, more wear, more piston speed for that "more power".

That's like me saying I want a Performer RPM over my Performer and saying the Performer is because I would rather get a "less streetable" RPM for a touch more power. Horrible argument.

Thomas302 · Nov 26, 2005

The cars is apart right now, changing a few things, but the tfs-r intake was a good change from the gt-40. I know I have never had a 347, but when I was at the track, there was a guy with almost the same setup as me but on a 347, and he was running 11.5's to my 12.1's. He had no problems at all driving it all the time. But I am no expert by any means. I really enjoy my 331, it runs great. I just have the go faster bug, and 16ci more would be nice for the same money if I was to do it all over again.

69Rcode_Mach1 · Nov 26, 2005

The performer heads will not breathe enough to extract full power from a 347. Keep your compression high especially if you are planning on the juice. I would just go 347 personally, it can cause more wear, but I think 60,000 miles is plenty of time, then again my car is a weekend warrior. For a daily driver just go with the 331.

WarPig53J · Nov 26, 2005

I'd go 331 and a 125 hit of spray. Nitrous loves high compression, but be aware that detonation may come into play with pump gas. I'd stick with your 10.5:1 idea and remember back out 4 degrees of timing for every 100 hp of nitous.

Rick 91GT · Nov 26, 2005

I'd go 347, you can go with a 5.315" or 5.4" rod combo and with a 4cc flat top you can get about 10.5:1 with a 58cc chamber.

Go custom cam and get the best bang for your buck.

fivespeedsteed · Nov 26, 2005

408 windsor

89white50 · Nov 26, 2005

he only has Edlebrock Performer heads...you guys really think those will flow enough for a 347?
rick, i would really like to know, not trying to be a prick or anything.

69Rcode_Mach1 · Nov 26, 2005

That is what I said too, the heads will not be a good match.

NKau · Nov 26, 2005

69Rcode_Mach1 said:
That is what I said too, the heads will not be a good match.

Depends what you are after. Will they be optimal? Maybe not on something that's being built exclusively for the track and is being spun past 6500 rpm often, but for a street car I don't see why they wouldn't work. I'm putting together a 347 this winter that will have the 1.90/1.60 rpm heads and rpm intake. Should put down an easy 300+ rwhp go easy 12's in my notch; will find out this spring.

Grn92LX · Nov 26, 2005

Rick 91GT said:
I'd go 347, you can go with a 5.315" or 5.4" rod combo and with a 4cc flat top you can get about 10.5:1 with a 58cc chamber.

Go custom cam and get the best bang for your buck.

:Teh-Win:

Nuff said. Next thread

The 2.02 rpm heads will be ok for a mild 347. They will make for a nice mild street car. I'd do something like a holley/rpm II/tfs R manifold, 75mm tb, custom cam with valve springs and longtube headers. Go 28oz balance with an aluminum flywheel and a light weight balancer too. I'd also suggest you talk to Rick about building it, he know's his shiit

HiFlow5 0 · Nov 26, 2005

I don't think the Performer heads will limit me too badly, they flow nicely out of the box and were enough to put me into the 12's on a stock bottom end. Of course a nice cam will be used to get as much out of them as I can, without going over board. This is not going to be a high rpm track car, but a decent pavement pounder with more low rpm torque then high rpm power.

I'm not trying to break the bank on this build and am doing this on a budget, so that is why I'm reusing my current heads and intake, but may opt to go with a different intake in the future, just not right away.

I'll be ordering the rotating assembly from CHP and building it myself with a friend over winter. That's where my lack of experence in stroker motors starts to show, as I was just looking for opinions on what would be best for my desired goal, 331 or 347?

But another question which I have not thought to much about yet is 28oz or 50oz balance? Any pro or cons of the two?

gaslight · Nov 26, 2005

HiFlow5 0 said:
But another question which I have not thought to much about yet is 28oz or 50oz balance? Any pro or cons of the two?

28 or zero if you can. the closer to zero you can get the better at least that is what I have read. IF its internally balanced to zero it puts alot less stress on the whole assembly especially as RPM rises. The 50oz was done to save money along with a lot of other thing on the car.

Rick 91GT · Nov 26, 2005

Like mentioned above it depends what you are after. Those heads are not ideal for a race tye motor but for a healthy street car they will be fine, and it will make a ton of TQ and good hp with the right cam.

If you go with a cast crank go 28oz, if you go forged and Eagle internal balance cranks are available go with that.

I did a 347 with 9.5:1 for another SN guy who put on a GT40- cast iron head and it runs great, it's a tq monster not a high hp dyno queen but it is very nice on the street.

Engine choices, 331 or 347??

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