Thread: advice on twin turbo heads?

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so just like the title states, I'm building a twin turbo 350 and I am having issues with heads. right now I have the stock 1975 3986339 heads and want to upgrade but I'm unsure what to upgrade too, plus I'm trying to avoid breaking my wallet.. so any advice will be appreciated. thanks.

OK, here's my take on it.....
If I wanted to build a budget twin-turbo street motor, I would build it low compression, like somewhere between 8.0:1 and 9.0:1 static compression ratio. Using these KB forged pistons will allow you to use anywhere between 68cc chambers and 76cc chambers when used with a 0.005" piston deck height and a 0.028" compressed head gasket.
https://www.uempistons.com/index.php...roducts_id=165

76cc heads would yield a 8.16:1 static compression ratio
72cc heads would yield a 8.46:1 static compression ratio
68cc heads would yield a 8.77:1 static compression ratio
I wouldn't use 64cc heads because they would yield a static compression ratio over 9.0:1. I'm sure you'll find plenty of folks who will tell you that you can run over 9.0:1 with twin turbos on pump gas, but I'm not one of them.

I would be looking for a set of heads that would flow really well on the EXHAUST side, like 200 CFM or more @ 0.400" valve lift. The heads will have no trouble feeding the motor on the intake side, because the intake will be under pressure, but the exhaust side is still going to have to depend on the piston pushing out the burned exhaust gases just like a naturally aspirated motor. If I had a set of heads that flowed 200 on both the intake and exhaust at 0.400" valve lift, I think I'd be satisfied that I could make good power. Of course, there is nothing wrong with a set of heads that will flow 230 or 240 or 250 or more on the intake side, I'm just thinking that a set of heads that flowed less on the intake side and had been ported on the exhaust side to flow 200 @ 0.400" valve lift would be cheaper. Maybe not, you'll need to talk with the providers and take their pulse on this.

I think I would begin by calling some of these racing head providers and asking if they had such a set of heads on hand that would qualify. I'd tell them that this is a budget build and that if they had a set of Gen I production iron heads that had been ported on the exhaust side but not on the intake side, I would be interested in talking about them. Call these guys on the phone and talk with them.....
"Hello, this is J Scott from Klamath Falls, Oregon. I'm interested in speaking with someone about a set of Generation 1 small block Chevy cylinder heads, probably production cast iron, although i would be interested in hearing about alternatives if the price was affordable". Have pen and paper handy and take good notes so that you can make sense of them later.

TriMark Performance - Performance Cylinder Heads

Weingartner Racing

Texas Speed and Performance

SPEIER RACING HEADS - SRH INFO

Slawko Racing Heads

JONES ENGINES DEVELOPMENT - RACING ENGINES AND DYNO SERVICE - LANCASTER, CA - PHONE 661.942.3364

https://www.cityfos.com/company/Ron-...MO-2134691.htm

Total Flow Products - Cylinder Head Repair, Race Engine Cylinder Head Porting, Race Engine Cylinder Head Repair

MadCap Racing Engines: Rocky Mountain Horsepower

RHS - Racing Head Service

HRD Racing Heads - Cylinder Heads, Ford Racing Engine, Ford Cylinder Head, Racing Heads, Chevy Racing Engine

West Coast Cylinder Heads - Home

https://mikesracingheads.com/

https://www.headsupcylinderheads.com/

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Welcome to CHR!
Great advice from Tech (as usual). Central Cylinder Head Services are in Portland and have been in business since 1969. They perform soup-to-nuts and and they know heads.

Services

Phone number for the machine shop is: (503) 233-8262

I like Tech's approach - call them and let them know what you're up to and they probably have exactly what you are looking for. The shipping from Portland to K-Falls wold not be too bad and you'd have your heads in a couple days.

Let us know what you decide.

Regards,
Glenn

awesome! I appreciate the response tech and glen, I will give the Portland company and others a call and see what they can offer. I was considering using the factory head but the studs are pressed in for the rocker arms, and if I'm gonna spend the money to have those pressed out and tapped I might as well look for some upgraded ones.

I'm not suggesting that you do this, but just adding to your knowledge. It is not always necessary to pull the studs, mill the pads and tap for screw-in studs. Assuming the threads of the studs are in good shape, Mr. Gasket makes a kit for pinning the studs to prevent pull-out.
https://www.summitracing.com/parts/mrg-806g

I don't know if this link works for you, but when I click it, it goes to a Viglink Shopping site. I tried to re-post it, with no luck. The kit I am talking about is Mr Gasket, number 806G.

yes the link did work thank you!

Originally Posted by jscott36

yes the link did work thank you!

OK good, like I said, just making you aware of some alternate ways of doing things.
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Any and all help gratefully accepted Denny, thanks buddy.
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My Dad showed me how to do this on my first truck and he somehow knew what happened that helped cause it. It surely wasn't my right foot. Ok, it was.