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Old 08-06-2012, 04:32 PM
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305 heads on 350 short block, snap crakale pop

I built one once, the plan was a high efficiency 350 in my Blazer.
My first mistake was putting it in a 4500 pound vehicle.
My second was running it hard before i had the timing dialed in.
I had a roller cam setup, i used the Chevy 4 banger (shorty) roller lifters and Ford 351 push rods, a LT-1 cam, ported heads. ground and filed the valley to make the lifers fit, modified the lifter alignment bars, used d-dish GM pistons, compression was 10 to 1, i spent hours building this thing.
She ran pretty dare good, pretty peppy. i was merging on to the hi-way one day and liad into the throttle pretty hard, she pinged real hard and that was the end of it, i cracked both heads through the seats, when i got home she was steaming out the pipes like a choo choo train. that motor today is a 357 vortec with comp high energy cam with 9.8 to 1 compression. Would i ever build another one? nope...save up your denaries, new far supirior heads are so cheap now there like they woulda been next to free 15 years ago.

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Old 08-06-2012, 06:13 PM
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The 305 heads on your 350 w a .480" cam will work fine.
Get a 3000+stall converter for the cam and recurve the distributor.
The cam will want gears too.

May need more than 87 octane.

Exactly which 305 heads do you got? casting number...
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Old 08-06-2012, 06:14 PM
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When you port a 305 heads you get a lot more power.
If stock heads keep your expectations modest.
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Old 08-06-2012, 07:41 PM
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Generally the whole idea of swapping a small combustion chamber 305HO head onto a 350 is to raise the compression ratio, easily at low cost.
On the stock 350 short block by replaceing the large chamber 76cc heads.

Putting a 58cc combustion chamber on a 350 does not result in excessive compression ratio. But such an engine generally will need better than 87 octane gas.
Stock 305HO heads ( the 4416 and 081 castings) flow just a bit less than a typical 350 stock head. The valves are smaller. (1.84x 1.50 typical)
The idea being to home port them to increase flow and increase the valve size to 1.94x 1.60. This also increases the chamber volume a bit (62ish cc) when the chamber walls are relieved to fit the larger valves.
You end up with a high compression high perf motor with much more flow than stock
that will now work with a typical high perf cam etc for increased horsepower output.
Do all the porting yourself. This keeps the cost down.

The cr will be right around 10:1 (with flat top pistons) which is right were you want to be for a high perf street motor. 92 octane.

When the heads are fully home/self ported with the large valves the engine will rev right up and make good power well in excess of 6000rpm with the right cam etc. increased port flow is the key.

using 2.02" valves is a bad idea in these heads.
Its is not cost effective to pay someone else to port these heads.
DIY.
some of the #601 305 head castings have very small 53cc chambers.
Ends up "deshrouded" larger once larger valves are installed.

There is a "624" head that is essentualy a #4416 head.
Do not confuse with the crappy 462624 casting.

The other 305 heads are not the same beast 450-434-801 187 181 castings etc)

The 305 Vortec heads (059) have some potential with mods and porting
they require using a vortec intake.
When generously home ported with larger 1.94x 1.60 valves the 305ho heads flow well in excess of 230cfm in and 180ex with excellent port velocity. just right for typical high perf street cams.
400+hp capable with correct supporting parts combo.

Some other good diamond in the rough stock heads to look for a the 083 cast L98 and the 113 L98 aluminum castings from TPI motors.

All these are modest in stock form but get real good with generous porting.
Use a felpro 1205 gasket as a guide. Don't be shy with the die grinder.
Its real hard to port too big on these heads. Flow is power.
you want to end up with a 175 to 180cc port volume when all done.
you want to remove about 10cc of metal overall , from each port.
They need a good bit of opening up, contouring deep in the port.
Blocking the heat riser passages in the ex ports is a good option.
Really improves the two center ex ports and header scaveging.

Last edited by F-BIRD'88; 08-06-2012 at 08:09 PM.
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Old 08-06-2012, 07:59 PM
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If you want to get your port work flow tested ,keep it simple quick and low cost.
You don;t need to know flow on every port at every .050" of valve lift.
A quick and simple bench test at .400" lift and peak flow lift. (usually around .550") tells the story. They either flow, now or they don't.
Don;t get all wrapped up in ultimate flow numbers either. You either improved the head or you didn't. You're not building a NHRA Superstocker.
The real test comes when you put the petal to the metal.
Every thing in the many David Vizard books on SBC engines and head preparation (amazon/local library) is all relevant to the job.
perf cams with 106 to 110 LSA , up to 510" lift work very well with these heads.
pick the duration @.050" based on desired rpm range.
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Old 08-06-2012, 08:58 PM
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Keep the valvetrain simple and low cost.
I like to drill and roll pin the rocker studs and shorten the guide boss
for aftermarket seals and valve lift.
if you want to use 1.6 ratio rockers, lengthen the push rod slot in the head
with a 5/16" rat tail file in a drill.
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Old 09-11-2012, 05:03 PM
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So i followed every friggen post you have on porting the 416 heads lol, I have likely around 40+ hours in the friggen things..! I dropped them off yesterday at my machine shop and he called me back quickly. Turns out he is an older hotrod guy and loves these heads, he has been porting them and using them for years and absolutely loved the work I put into them and thinks they will work really well! He says they already had new bronze guides installed so he offered to install 194's at no additional charge as they hadntonbe re- seated anyways due to a couple slips with the die grinder. They are getting hot tanked, new valves, new seals, minor de- shouding due to the bigger valves, and assembled with my comp springs and appropriate shims.....out the door for 300$.....seems fair to me? I'm wondering, if anyone actually read this novel, if they could sim this combo to give me a rough idea of what to expect HP wise?
Heavily worked 416 heads
Perfomer intake port matched to 1205
1" Carb spacer
350 with flat tops using shim head gasket
Lunati bare bones cam pn# 10001k.
Duration 280/290, Lift .443/.465,*
Shorty headers
750 quad on top.
Thanks!
And p.s thanks a million f- bird for all your posts lol.
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  #23 (permalink)  
Old 09-12-2012, 04:38 AM
How fast is fast enough?
 
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Quote:
Originally Posted by 66GMC View Post
If you're planning to do 75 to 85 mph on the highway ... don't do it near Spruce Grove, Alberta. Right Harry? (Inside joke)

OK, seriously now ...
IMO Cylinder heads and camshaft selection won't have a dramatic effect on your car's ability to drive at consistant highway speeds, as I am sure that your engine RPM will be within that range.

With 3.73's and 15" tires, I would guess-timate about 3000 to 3200 RPM in 3rd gear at 65-70 MPH, right? (less with an overdrive trans)

If that is correct, then a stall convertor isn't going to hurt you much either.
If you're just worried about cruising at around 3,000 RPM then the cam and the heads are probably a bad idea!

The cam affects a lot at steady cruising, especially mileage and passing power. For a street only vehicle focused on cruising I would get your compression at about 9.5:1 with a cam about 205/210 duration and all the lift you can get. It won't lope and it'll have no balls past 5,000 RPM, BUT it is what you need for the best highway cruiser.

To really make the most of it bowl port the heads, consider going to a 30 seat angle (at least a 3 angle seat is a must, as is back cut valves), 1 1/2" long rube headers, a performer manifold and a good vacuum secondary carb. If well done you can get an easy 300hp at a low RPM.

The cam will definitely not work, the heads may work well depending on how much work you put into them, a 1.84" valve is more than adequate for this combo but the castings need cleaning up and compression should not exceed 9.5:1 if you want to run 87 octane.
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  #24 (permalink)  
Old 09-12-2012, 04:45 AM
How fast is fast enough?
 
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Quote:
Originally Posted by bygddy View Post
So i followed every friggen post you have on porting the 416 heads lol, I have likely around 40+ hours in the friggen things..! I dropped them off yesterday at my machine shop and he called me back quickly. Turns out he is an older hotrod guy and loves these heads, he has been porting them and using them for years and absolutely loved the work I put into them and thinks they will work really well! He says they already had new bronze guides installed so he offered to install 194's at no additional charge as they hadntonbe re- seated anyways due to a couple slips with the die grinder. They are getting hot tanked, new valves, new seals, minor de- shouding due to the bigger valves, and assembled with my comp springs and appropriate shims.....out the door for 300$.....seems fair to me? I'm wondering, if anyone actually read this novel, if they could sim this combo to give me a rough idea of what to expect HP wise?
Heavily worked 416 heads
Perfomer intake port matched to 1205
1" Carb spacer
350 with flat tops using shim head gasket
Lunati bare bones cam pn# 10001k.
Duration 280/290, Lift .443/.465,*
Shorty headers
750 quad on top.
Thanks!
And p.s thanks a million f- bird for all your posts lol.

If you really opened them up a lot then a 1.94" valve can fit them well, BUT for a given flow using the smallest valve possible will result in more hp. Your parts are a bit mismatched, if you haven't ordered the cam yet I would go a little smaller- assuming your compression isn't too high, which it may be depending on the pistons.

A better matched engine will make the same power but at lower RPM. It won't sound as nasty or use as much fuel. Easier on parts too.
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Old 09-12-2012, 02:51 PM
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345 to 360hp. The shorty headers are going to cost you 10 to 15hp and some torque.
Long tubes are way better. The cam you got is a good match to the shorty headers. Needs a good exhaust system.

A drag strip test (MPH and known car weight w driver) will tell you how much HP you are really making.

Last edited by F-BIRD'88; 09-12-2012 at 03:01 PM.
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Old 09-12-2012, 05:09 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
345 to 360hp. The shorty headers are going to cost you 10 to 15hp and some torque.
Long tubes are way better. The cam you got is a good match to the shorty headers. Needs a good exhaust system.

A drag strip test (MPH and known car weight w driver) will tell you how much HP you are really making.
I'm sightly concerned with the previous post saying my parts are " mismatched"? I selected a small cam, and that's actually the only part I "bought" lol...... everything else I had....but I figured the performer and these heads would work well with this cam? Hmmmmmmmm

F- bird, hey thanks for getting back to me, yah, for exhaust I'm running the Shortys straight down to "3 diameter, 6" dynomax bullits and to 3" side pipes, nothing else lol....so I suspect breathing won't be an issue? Although volume might be! It will hit the strip hopefully next weekend when I get it all back together.....Its in a 77 Vette, TH350, I believe a small converter, and 411 gear.....I will be happy as pie if it runs a low 14 or high 13.....
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Old 09-13-2012, 12:55 PM
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Drag strip traction with street tires is going to be the limiting factor to a quick ET.
If you can get and use some sticky tires it will make a huge difference.

As I said the MPH tells the tale of horsepower produced.
You have only just started the tuning process to getting
to a decent ET/MPH. But its a good start.

Post your track results when you get them. (1/8th mile track data is fine)
Good luck
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Old 09-13-2012, 05:36 PM
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Originally Posted by F-BIRD'88 View Post
Drag strip traction with street tires is going to be the limiting factor to a quick ET.
If you can get and use some sticky tires it will make a huge difference.

As I said the MPH tells the tale of horsepower produced.
You have only just started the tuning process to getting
to a decent ET/MPH. But its a good start.

Post your track results when you get them. (1/8th mile track data is fine)
Good luck
I do have access to the drag radials on my buddy's blown SBC vette so i may borrow those, my biggest concern right now in the Carb, I know zip about quads, I know its on the car now and works flawlessly, no bog, no stumble, no anything weird other then it seems slightly rich (smell and plug color) ....that being said I have a virtually new edel 1405 on the bench so i may try that......heads are being dropped off in the am so sat I will take it apart and should have it ready to run at the track next weekend.....
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Old 09-13-2012, 06:20 PM
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You are not going to go faster by putting a tiny carb on it
The rich smell is cureable. (heat, primary metering rod, timing curve, fuel pressure)

Performer manifolds always run too hot(smell rich) unless you get the heat riser flow corrected.
(especially with a AFB carb)
Block it off, or block one side and restrict the other side. (winter driving)

Get a wood carb spacer too. Heat isolation. I recomend a divided type wooden spacer for that manifold, for your car.

The RPM intake manifold is way better in every respect. It does everthing better than the performer manifold.

That and long tube headers should be on your wish list.

sell the performer and the tiny carb to someone that wants to run 14's.
To fund a RPM intake and corvette long tubes.
Now the cool low buck ported 305HO heads will suddenly be all they can be.
(and make a lot more power and torque)

Last edited by F-BIRD'88; 09-13-2012 at 06:45 PM.
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Old 09-13-2012, 06:21 PM
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You cannot smell a "rich" mixture. You are smelling incomplete combustion in the ex and overheated carb/intake manifold temperature
that is hot soaking.

The 750 is the right carb. You just need to dial it in.

Last edited by F-BIRD'88; 09-13-2012 at 06:46 PM.
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