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  #16 (permalink)  
Old 09-30-2013, 12:59 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
Adding a 76cc head in place of the 58cc 60cc 4416 head yess will drop the compression ratio a lot.
But by doing that you can hit it with a LOT of boost on (92) pump gas with out
detonation.
you want to port the ehad too to improve port flow.
Don;t be shy with the porting.

Some 76cc heads are crappy. not worth it. avoid 882-462624 etc.
What is the head casting numbers you got there.

Flat top pistons? dished pistons?

You want to get the cr to 8.5:1 or a bit less.
They're the 333882 castings. I haven't opened up the motor yet.

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  #17 (permalink)  
Old 09-30-2013, 01:01 PM
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Quote:
Originally Posted by robyyo View Post
is a 76 cc combustion chamber too much? Will such a low comp ratio kill power? Or will the turbo make up for it?
The lower the static compression ratio, the more boost you can shove into the motor. Use 76cc heads with these forged 24cc pistons to generate a 7.5:1 static compression ratio, then tailor your turbo for 10 lbs of boost on pump gas. Don't worry too much about squish on a blown motor, the blower/turbo will homogenize the mixture on the way in. Also, don't spend time and money on porting heads. I can guarantee you that with 10 psi pushing the mixture into the motor, you'll make plenty of power with stock port and valve sizes. Also, turbo lag can be overcome with a small shot of N2O. You'll learn all this stuff if you read the book I linked for you.
http://www.summitracing.com/parts/srp-139632
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.

Last edited by techinspector1; 09-30-2013 at 01:07 PM.
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Old 09-30-2013, 01:07 PM
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Originally Posted by techinspector1 View Post
The lower the static compression ratio, the more boost you can shove into the motor. Use 76cc heads with these forged 24cc pistons to generate a 7.5:1 static compression ratio, then tailor your turbo for 10 lbs of boost on pump gas. Don't worry too much about squish on a blown motor, the blower/turbo will homogenize the mixture on the way in. Also, don't spend time and money on porting heads. I can guarantee you that with 10 psi pushing the mixture into the motor, you'll make plenty of power with stock port and valve sizes. Also, turbo lag can be overcome with a small shot of N2O. You'll learn all this stuff if you read the book I linked for you.
http://www.summitracing.com/parts/srp-139632
.
.
I'll get that book. Those pistons in the link are for a 350.
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  #19 (permalink)  
Old 09-30-2013, 01:08 PM
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It is possible to use the 4416 305HO heads on a thrbo 305 ( especially if the 305 has dished pistons)
if you home port then, add 1.94" valves and "deshroud" the chamber for the new valve, generously
to increase chamber volume. A 64cc to 66cc finished volume would be good.
Porting adds power. Then the boost actually does something.
What are the head castings on your 305?
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Old 09-30-2013, 01:11 PM
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The 882 heads stink. Don;t bother with these.
What is the head on the motor? a 920 head is a lot better start point.
The ports are better to start with . and end up better with porting and it does not have
the doubled heat riser passage.
Give the 882 heads to someone you don't like.

A "turbo Cam" comp cams # 12-400-4 268-262 218-212 115LSA .454 .440

Last edited by F-BIRD'88; 09-30-2013 at 01:23 PM.
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Old 09-30-2013, 01:19 PM
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In the meantime, read through this article and pay attention to the LSA as explained by Kenny Duttweiler....
Turbo Camshaft Guide - How to Select the Right Cam for Your Turbocharged Engine - Car Craft Magazine

The rest of you guys on this forum should read through Duttweiler's take on LSA and overlap and stop automatically suggesting a "114 cam".

"Duttweiler also mentioned that attempting to build a turbocharged engine with a set LSA (such as 112 or 114 degrees) can lead you astray. He mentioned some work he did way back in the early Buick Turbo V6 days while racing these engines in NHRA Stock Eliminator. Stock class rules required the intake and exhaust lift and duration specs to remain stock, so to improve power, he tightened the LSA on these engines to 109 degrees to help the Buick’s really small cam improve power. The engine responded by building boost much quicker. “When you spread the lobe-separation angle way out, the engine gets lazy,” Duttweiler says. As an example of a good V6 engine, Duttweiler says he built a V6 turbo Buick with a 215-degree-at-0.050 intake lobe camshaft that made 900 lb-ft of torque and 580 hp and idled at 16 inches of manifold vacuum."

Last edited by techinspector1; 09-30-2013 at 01:26 PM.
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Old 09-30-2013, 01:23 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
It is possible to use the 4416 305HO heads on a thrbo 305 ( especially if the 305 has dished pistons)
if you home port then, add 1.94" valves and "deshroud" the chamber for the new valve, generously
to increase chamber volume. A 64cc to 66cc finished volume would be good.
Porting adds power. Then the boost actually does something.
What are the head castings on your 305?
the castings on the 305 are 14014416
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  #23 (permalink)  
Old 09-30-2013, 01:31 PM
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Quote:
Originally Posted by robyyo View Post
the castings on the 305 are 14014416
You are better off using these as a start point than using 882's

Port them,, deshroud for larger 1.94" intake valves. Generously, to get the chamber volume up.
Don;t fall for the "you don;t need to port the heads with a turbo.
It is a myth. All engines need improved port flow to become a high perf engine.
Don;t shoot your self in the foot by just bolting a turbo to a very restricted motor.
You got to let the air get in and get out of the motor to make power
even with a turbo.

Generous porting to a felpro 1205 gasket +1.94 valves + deshrouding the chamber for them + a suitable turbo friendly cam + shorty headers
will GLH.
Ditch the stock exhaust manifolds. they really kill power. expecially with a turbo.
Heads can be shorty type. ESpecially for a single turbo.

Mount the turbo at the back of the car. TONS of advantages.
Replaces the muffler on a 69 Firebird.
2.5" in to 1 3" exhaust (flowmaster Y250300 Y pipe)

Lots of room on this chassis for the turbo air pipe. Can be single turbo or twin turbos.
the single 3" exhaust runs down the passenger side. The turbo air pipe runs up the drivers side to the air inlet.

Could be two JY turbos from a 2.5 L to 3.8 L OEM motor.

Do this right and you will have a very cool turboed 305 TPI.

Last edited by F-BIRD'88; 09-30-2013 at 01:38 PM.
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  #24 (permalink)  
Old 09-30-2013, 01:33 PM
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lda?

Quote:
Originally Posted by techinspector1 View Post
In the meantime, read through this article and pay attention to the LSA as explained by Kenny Duttweiler....
Turbo Camshaft Guide - How to Select the Right Cam for Your Turbocharged Engine - Car Craft Magazine

The rest of you guys on this forum should read through Duttweiler's take on LSA and overlap and stop automatically suggesting a "114 cam".
John Lingenfelter liked very wide LDAs in some applications both turbo and N.A.
I use wider LDAs as the engines get bigger.for lower rpm or smaller engines I "prefer" tighter LDAs.if you do the math,quite often similar results can be obtained with totally different cams.Its tough to get a perfect choice,because,,,whats perfect for you might not be what is perfect for me. application of power plant might change many variables,IE; I like road race type power delivery which is different than drag race type of power delivery.
generally speaking we should have similar choices except where very specific needs are required.
I always recommend a roller cam,,,they make more power and do not usually have lobe problems.
the grinding is higher standards on race type cams too.
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  #25 (permalink)  
Old 09-30-2013, 01:39 PM
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Quote:
Originally Posted by robyyo View Post
Those pistons in the link are for a 350.
Awww crap. I don't mess with those fosdick 305's and automatically think 350. Sorry for the wrong link. Here's an upgrade....
http://www.summitracing.com/parts/jep-170771-8
I don't think you'll find a deep dish 305 forged piston.
The SRP 170771 will make about 8.6:1 with a 76cc head and you can make about 6 lbs of boost on pump gas without detonation with that SCR.
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Old 09-30-2013, 01:42 PM
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Trade the 882's for a set of 920's. port and mill to 70cc.
(For a flat top piston)

Or use a factory like cast dished piston and use the 4416 heads with porting and the larger valves. (62-64cc finished)

You do not need a forged piston. When it is engineered correctly the turboed engine does not detonate
ping or knock. no severe piston stress. A cast piston is plenty strong.
Most all OEM turbo cars use Cast pistons.

The key is to get the engine compression ratio correct for turbocharging.
Build a turbo motor that does not knock under boost and you will never have piston problems.

Last edited by F-BIRD'88; 09-30-2013 at 01:52 PM.
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  #27 (permalink)  
Old 09-30-2013, 01:52 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
Trade the 882's for a set of 920's. port and mill to 70cc.
(For a flat top piston)

Or use a factory like cast dished piston and use the 4416 heads with porting and the larger valves. (62-64cc finished)

You do not need a forged piston. When it is engineered correctly the turboed engine does not detonate
ping or knock. no severe piston stress. A cast piston is plenty strong.
Most all OEM turbo cars use Cast pistons.

The key is to get the engine compression ratio correct for turbocharging.
Ha Ha, looks like you and I are destined to bump heads for the rest of our natural lives. Using cast or cast hyper pistons in a blower motor is just silly. Forged pistons and a set of Scat Pro Stock rods will do the job and allow you to sleep well at night.
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Old 09-30-2013, 01:56 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
Trade the 882's for a set of 920's. port and mill to 70cc.
(For a flat top piston)

Or use a factory like cast dished piston and use the 4416 heads with porting and the larger valves. (62-64cc finished)

You do not need a forged piston. When it is engineered correctly the turboed engine does not detonate
ping or knock. no severe piston stress. A cast piston is plenty strong.
Most all OEM turbo cars use Cast pistons.

The key is to get the engine compression ratio correct for turbocharging.
Build a turbo motor that does not knock under boost and you will never have piston problems.
Ok, that's what I'm thinking. However I do want to keep the turbo in the engine compartment. I've been doing some research and found this comp cam 12-253-4, which should be correct. So I think I've got the framework for the engine figured out. I found this turbo kit on ebay http://http://www.ebay.com/itm/27109...84.m1438.l2649 what do you guys think about this kit?
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  #29 (permalink)  
Old 09-30-2013, 01:56 PM
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Ha Ha, looks like you and I are destined to bump heads for the rest of our natural lives. Using cast or cast hyper pistons in a blower motor is just silly.
ALL OEM turbo motors use cast pistons. They don't fail.

its detonation that kills pistons, not boost.
Boost is not hard on pistons at all.
A cast piston will take 20psi turbo boost.
its a matter of correct engineering to avoid engine knock.
If it knocks the forged piston will fail too. It just fails differently and costs more to replace.
Spend your money on correct engineering.

Anybody can turn this into a $10,000 build.
Its a friggin 305. Get the compression ratio down to between 8:1 and 8.5:1 and you are good to go.

Last edited by F-BIRD'88; 09-30-2013 at 02:02 PM.
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Old 09-30-2013, 01:59 PM
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You don;t need a E bay turbo kit.
Buy a good turbo from Turbo City or same...
Most of the stuff on E bay is crap.

In a single pattern cam Comp cam 12-252-4 XT256H is a better choice.
Keep the cam mild. This is plenty cam for a turboed 305 TPI motor.
it is easy to over cam it.
Port the heads for power. Do not over cam. If you want more valve lift use a 1.6 or 1.65 rocker arm.
Keep the duration mild-moderate and the overlap low.

Last edited by F-BIRD'88; 09-30-2013 at 02:14 PM.
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