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Best intake runner size for sbc 350

28K views 28 replies 10 participants last post by  levisnteeshirt 
#1 ·
Whats the best Intake runner size for a 350 sbc that will see about 6500-6800- rpm at the most(Iron and Aluminum)? Whose head would u recommend?
 
#4 ·
whats it used for? cam? head? stall? compression? When picking anything for your engine you dont just pick it for "your engine", you need to pick it for the whole system and its application.
 
#6 ·
you lacking lots of info here like Pwrtrip asked for....

but based on you 350 and only turning 6800 tops... 180 cc runner, edelbrock RPM 650 holley, a 270+ but not over 276 duration cam @ .050.... with a min 3000 stall...

you compression is critical, as is squish/quench... gears, converter, cam, etc....
 
#7 ·
double hump,,

I think the 461 or 462 chevy heads are still tough to beat for the RPM range your talking about and on a 355. Yes they are getting old but yes they didn't get their reputation for not being good. MY engine builder friend just built a 355 with 462's and a hydraulic cam ( Lunati ) that ran a 6.90 in an S10 on pump gas.
 
#13 · (Edited)
I think the 461 or 462 chevy heads are still tough to beat for the RPM range your talking about and on a 355. Yes they are getting old but yes they didn't get their reputation for not being good. MY engine builder friend just built a 355 with 462's and a hydraulic cam ( Lunati ) that ran a 6.90 in an S10 on pump gas.
They got their reputation because they were all that was available at the time and they were on the "corvette" engines which were big and bad back then. Im guessing what your engine builder did with those 462s was at least some work which is time and money. You can take a set of todays heads out of the box and run circles around those worked over heads....at a fraction of the price it costs to work them over.
So "tough to beat"..... not in the least bit.

How is that so new heads unoported beat old ported ones? Intake runner volume, bowl volume and design, chamber design. The old heads were made for a 327ci engine, not anything bigger.
 
#9 ·
Very true.. Vortec heads are even a BIG step up from the old "Camel Humps"..

It's all in the combination of parts chosen and making sure they all work together. I've seen a lot of 10 and 11 second street cars built (as Judson Massingil once said) "That's a great combination of $@#%^ parts!"...
 
#12 ·
It can get extremely complicated especially when you start trying to look at ported heads. Who ported them? Were they "Really hogged out"? Is the throat size vs. average runner CSA vs. valve diameter all proportionate and correct. There's a hell-of-a-lot more to it than 90% of the people out there know or could even comprehend.
Then comes camshaft timing. There's some real wizardry going on there as well. Start the intake charge a little too soon and you could loose the ram-fill effect, disrupt the intake charge with reversion, etc.... Start the exhaust event a bit too soon and you give up power. Start it too late and the piston will see too much heat and pressure spikes, it will be inefficient at expelling the exhaust (disrupt in the intake charge), and will totally kill any chance of using the exhaust to scavenge--or help start the intake charge.

As far as matching the components together for a good combination......that can be fairly simple. You just have to be completely honest as to where the engine is going to spend the majority of it's time (RPM range) and shoot for the fattest torque curve and peak power.
The torque converter should "Stall" just a little below your peak torque and the rear end gearing should put you right at your red line as you cross the finish line.
Now, If it's more of a street car, then there's a long list of compromises that will hurt a little performance but make it more "Streetable" but that's completely relative!!:devil::yes:

First, decide what the car's primary role is going to be.
Second, list out the parts you've already got.
Then you will get a lot of usable feed-back on your parts selection process.
 
#14 ·
The car is 85% strip- 15% street!!! I already have 3.73 gears in the rear. Im looking forward to build a 350. I guess the motor will spend most of its time above 3k. Whats a good rpm range for 3.73 gears as far as 1/8th mile and 1/4 mile go?
 
#15 ·
Don't waste your money on "Camel Hump" heads...Pretty much any aftermarket cylinder head is better than those fossils.

Now, you can't expect accurate answers when you ask such vague questions. Is this 350 standard bore/stroke? Trans type/converter? Gears? Tire size/type? Suspension type? The list goes on...What do you have???:rolleyes:
 
#18 ·
How's the engine built?
What pistons were used?
Deck height?
What all are you looking to change? Heads, cam (lifters and pushrods also), intake and carb?

Everything has to be considered in the total package in order to get the combination to work together properly.

Is the engine tore down now? If you don't have the part numbers for the pistons, can you get it from your rebuild shop or possibly have a picture of the tops during the initial build? There's some pretty sharp folks around here so someone might very well recognize them.

What all tools do you have or have access to? Depth gauge, dial indicator, degree wheel, feeler gauges, micrometers, snap gauges, valve spring pressure tester, calipers, etc...

We need to know what you've got to work with and what you're capable of doing. We're willing to walk you through the entire process but just keep in mind, there is no such thing as "Knowing too much". Every little detail MATTERS!!
 
#20 · (Edited)
Then the absolute FIRST thing you should do is work out a realistic budget for the build!!! Be sure to make clear goals and expectations. Then start making out a parts list including anything you'll have to farm out (ie: machine work, transmission work, rear end set up, etc.) because of not having the proper tools/equipment or know-how to tackle on your own. Then add another 40-50% for miscellaneous expenses like gaskets, fasteners, cleaners, lubes, filters, plumbing, electrical, etc..that always seem to throw a serious monkey wrench in the tighter budgets!! :yes:
Also remember to include the cooling system, fuel system, ignition system, brakes and suspension, etc...

Once all of that is known, the discussion as to what would best suit YOUR build and YOUR budget can ensue..
 
#22 ·
on a 355 , 65-6800

Eh , say what ya want about those old heads, on a 355 in a 73 model , I think they're about 3500# aren't they ? only a 373 gear. Hmm ,, recalling my friends 66 chevy II, 355, roller , ported 186 double hump heads with 2.05 valve, 750 annular booster carb , 456 gear with a 26 inch tire , ran 7.15's . He bought a set of Track 1's and slowed down .15.

Maybe in this 355 you put a small hydraulic roller like the 604 crate engine has with a 210 cc head like the 604 crate engine it might do good. The 604 puts out about 400ft lbs of torque , that combo might get a 3500 # car moving with a 373 gear
 
#23 ·
Eh , say what ya want about those old heads, on a 355 in a 73 model , I think they're about 3500# aren't they ? only a 373 gear. Hmm ,, recalling my friends 66 chevy II, 355, roller , ported 186 double hump heads with 2.05 valve, 750 annular booster carb , 456 gear with a 26 inch tire , ran 7.15's . He bought a set of Track 1's and slowed down .15.

Maybe in this 355 you put a small hydraulic roller like the 604 crate engine has with a 210 cc head like the 604 crate engine it might do good. The 604 puts out about 400ft lbs of torque , that combo might get a 3500 # car moving with a 373 gear

I went from fully ported, bowls blended, 5 angle valve job, 2.02/1.60 double humps to mildly ported Brodic track 1's and picked up .6 in my heavy 76. Now thats a HUGE power increase to pick up over a half a second.
 
#26 ·
Sounds like you are just starting out, which is great. We all started somewhere, and I know from my own experience, that what you first build will eventually morph into something completely different as time goes on.

I started drag racing with my stock headed 355. I upgraded to the Edelbrock RPM package using the same 4 eyebrow cast pistons that came in my original NAPA engine rebuild kit, some Eagle SIR rods, and a turned GM steel crank. I ran that package until I built my current 383. So, depending on your budget, you may have to "piece" together your first build just to get started so to speak. Parts may not match up perfectly, but as long as they are close enough, you shouldn't have any problems, and can upgrade or make changes as your budget allows.

If you have the money, then the best way to do it is as has been suggested in previous posts here. Do some research, and match your parts/pieces to make the most powerful, efficient engine you can.

You can also do a build around a proven engine combination. There are many out there to choose from.

How fast do you want to go? What will the foundation of the engine be (stock or after market block)? If you shop around carefully, you can find excellent deals that can save you a lot of money in the long run.
 
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