Ported Chevy 081 heads 305 version

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Ported Chevy 081 heads 305 version

Post by Carnut1 »

0216161247.jpg
I found these in storage and I knew there were a few guys who had questions on large valves jammed into 305 heads. I know these were 305 castings. They have been plunge cut to 350 gasket size. I did these for a mild roller setup using Comp conical springs. It was before I had my spring perch tooling. It has been said these castings are useless, I disagree I know they run well for what they are. This is 90's porting with lots of mistakes. Wide valve seats and a horrible ssr radius. I will do some work on them with my newfound flowbench knowledge and probably find water! All in the name of horsepower.
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Re: Ported Chevy 081 heads 305 version

Post by Carnut1 »

0216161248.jpg
laugh at that port all you want.
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Re: Ported Chevy 081 heads 305 version

Post by Carnut1 »

0216161340.jpg
They flow worse down low than I expected and a bit better up top than I expected. I think the swirl reversal is interesting but probably a waste of energy.
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Re: Ported Chevy 081 heads 305 version

Post by pdq67 »

Thanks for the info.

I've asked many times, but does anybody have any info on reworking the old 305HO, -601 heads.

The ones with the 1.84"/1.5" valves and 53 cc chambers. Does it help them to install at least 1.94"/1.60" valves in them? I want to keep the small chambers if possible.

How about 2.02"/1.60" valves??

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Re: Ported Chevy 081 heads 305 version

Post by Carnut1 »

pdq67 wrote:Thanks for the info.

I've asked many times, but does anybody have any info on reworking the old 305HO, -601 heads.

The ones with the 1.84"/1.5" valves and 53 cc chambers. Does it help them to install at least 1.94"/1.60" valves in them? I want to keep the small chambers if possible.

How about 2.02"/1.60" valves??

pdq67
I know you have been asking about them. I do not have any 601's to test. I bet 1.94/1.6 could net 234cfm with a tight chamber and some good porting.
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Re: Ported Chevy 081 heads 305 version

Post by Carnut1 »

0216161556.jpg
before ssr huge, high, protruding.
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Re: Ported Chevy 081 heads 305 version

Post by Carnut1 »

0216161610.jpg
After ssr lower and a bit more flow.
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Re: Ported Chevy 081 heads 305 version

Post by Carnut1 »

0216161629.jpg
Ssr reshape a few cfm increase.
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Re: Ported Chevy 081 heads 305 version

Post by F-BIRD'88 »

Good Thread.
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Re: Ported Chevy 081 heads 305 version

Post by Carnut1 »

F-BIRD'88 wrote:Good Thread.
Thanks! Keeps me out of trouble. Almost.
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Re: Ported Chevy 081 heads 305 version

Post by rfoll »

One of the cool things about these is the huge boos in compression they give to typical 70s and 80s smog motors. Even with the chambers worked and the addition of a composition head gasket,(as opposed to the .0.15" shim), compression will be well into the 9s. The first time I did this I picked up over 4 MPG.
So much to do, so little time...
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Re: Ported Chevy 081 heads 305 version

Post by Carnut1 »

Interesting about the swirl. I have always been a swirl fan and one of the reasons for the shrouded large valve was I thought that would really kick the swirl up like the 84 Mustang head. Seems it doesn't work that way at all.
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Re: Ported Chevy 081 heads 305 version

Post by Adger Smith »

I always like a certain amount of swirl to help fill the cylinder, but too much and all the air does is swirl around and stop the filling.
As you can see in his 487X the swirl slowed and stopped the flow when things were wrong in the port/ VJ combination & it ran out of port volume.
I've done the 614 and 601 heads , but it has been so long ago that I can't remember the results. I do remember using the 614 heads on a stroker 305.. Put a 3.75 stroke crank in it with 5.7 rods. It made killer TQ in a pickup and got outstanding MPG. We had a problem way back then getting pistons so we took a dished 305 + .030 piston and cut the dish out. We also had problems with the 2 aftermarket cranks counterweights hitting the piston along the side/pin area. Instead of turning the counter weights down I ended up cutting down the mains on a stock 400 crank and it cleared much, much better. That was a long, long time ago. I was talking to the customer about 6 months ago and he still uses the truck on his farm. He told me it had nearly 300,000 miles on the engine. Back then I wanted to market an engine combination like that as Tq and mileage, but when you tell a customer that you are going to make a 334 cu in engine out perform a 350 you loose them pretty quick. They just don't understand a 3.766 bore and a 3.75 stroke is almost a square engine and can make good Torque. It had A lot more usable Tq curve than a 350 engine. It took less air to make the Tq and TQ not HP pushes you down the road. I only built 2 of them and both customers loved them. about the same time I had a customer doing a restoration on a '66 El Camino he wanted to keep it numbers matching, but hated the power level of the 283. Being an old fart and knowing some guys cheated with 283's and 4" stroke way back in the day. I turned down the mains on a 350 crank & put it in the 283. I used a 400 rod and a 307 piston. It sat the piston down in the hole (no block decking, had to keep the numbers) and kept the compression ratio in the 9's. I was lucky the customer had a late model 66 block that had the cut outs machined from the factory for the bigger 327 counter weights. I think they did that toward the end of the 283 block runs because all machine work for the 283 and 327 were on the same line. I used the 283 numbers matching heads and put 1.94 x 1.55 valves(turned down 1.60) in them.
It made a sweet running engine and looked and matched all the 66 El Camino casting numbers & date codes.
So much for my trip down memory lane.
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Re: Ported Chevy 081 heads 305 version

Post by Carnut1 »

For the real question, when in rpm/lift is too much swirl?
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Re: Ported Chevy 081 heads 305 version

Post by mag2555 »

Swirl consumes port energy and at some rpm point in every NA motor under the Sun there will be a point where that energy is better put to use in restarting the mass of the intake flow again on the next intake cycle rather then helping the burn rate.
This is what my thoughts are on it and for many years now I have been trying to put together the collective math to pin down that rpm change over point!
And in terms of your flow regression at .650" lift, if you layback the last 1/4" lenght of the crown of the short turn by some 1/32" of a inch your flow drop of will go away!

Actually the first thing you might try is to make / tare off along strip of 80 or 120 grit floor type belt sander and loop it around the short turn to polish the whole width of the turn into a more gentle arc.
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