Slant Six Forum :: Lobsters Build?

Slant six heads have a flow ratio that is biased towards high exhaust flow so they make good power, more efficiently with shorter exhaust duration.

If this were my build I'd use Oregon Cam grinding lobe 819 on the intake and 818 on the exhaust. That gives 219/212Â° at .050" lift on the intake and exhaust. Lift is only .437.431", but that won't hurt power too much and it will be nice to drive. They are tight lash profiles so they should run quiet. If the exhaust turbine is a little bit on the small side to bring the boost on more quickly the 112Â° lobe separation will work well, but slightly narrower, say 110Â°, will make more mid-range torque. In theory at least.

Quote:

That's BIG cam for turbo engine. Even stock cam should get you to 13s.
Why is shorter duration to exhaust side better?

Author:	Lobster1 [ Wed Jan 25, 2012 8:56 am ]
Post subject:	Lobsters Build?
Hello there, Iâ€™m putting together a turbo 62 Signet 225, and I wanted to post the proposed build, and listen to any suggestionsâ€¦ I want a minimum of 400 ft pounds torque at the wheels, 13â€™s and streetability. Working top down; Projection3, hurricane, peanut head shaved .050 1.70/1.44, Venolia forged pistons with recessed rings, bored .030 over. Double roller timing chain, Dual Dutra Duals, Turbonetics T04B H trim comp wheel, 54 mm turbine wheel .47 ar, intercooler, HEI, 2800 stall/904, Tranny cooler, how big? Oil cooler? Cam specs from Comp; For your engine setup it would have to be a custom grind camshaft. I would use some of our High torque solid lobes as they have a better ramp rate and profile for a turbo engine. The specs of the cam would be 235 /235 lift .495 /.495 112 deg. LSA This is the suggestion from Comp Cams, is it good? Thanks Slanters!

Author:	Joshie225 [ Wed Jan 25, 2012 9:25 am ]
Post subject:
That all looks pretty good, but I hope Holley has improved their technical support for their injection systems. I've heard bad reports from users. If they have not improved their support you might as well use MegaSquirt and get help from the guys who run it. The cam is probably a bit long in duration and should be shorter duration on the exhaust side than intake. With a compression ratio suitable for turbocharging you're not going to have much low speed torque with 235Â° duration at .050" lift. For a street car I would run about 224Â° duration at .050" lift on the intake side and 218Â° on the exhaust or even less. The fast turbo cars here run pretty mild cams.

Author:	MJF [ Wed Jan 25, 2012 11:54 am ]
Post subject:
That's BIG cam for turbo engine. Even stock cam should get you to 13s. Why is shorter duration to exhaust side better?

Author:	Dart270 [ Wed Jan 25, 2012 1:10 pm ]
Post subject:
I agree completely with Josh's recommendation. 235 is way too big and will shift your RPM range too high for a 225 engine. The Drakes and Cameron Tilley played with cams and found 215-225 deg is good. I have basically a stock cam in my '68 turbo Dart (MP 244/0.436" cam) and I am quite confident it will do 13s this year on 11 psi (3400 lbs racewt). Runs like a stocker until you get into boost. It is almost not worth your time/money to get a bigger cam, for those goals. Every cam company will try to sell you a cam, even if they don't know squat. Focus more on head flow... Lou

Author:	Joshie225 [ Wed Jan 25, 2012 2:52 pm ]
Post subject:
Slant six heads have a flow ratio that is biased towards high exhaust flow so they make good power, more efficiently with shorter exhaust duration. If this were my build I'd use Oregon Cam grinding lobe 819 on the intake and 818 on the exhaust. That gives 219/212Â° at .050" lift on the intake and exhaust. Lift is only .437.431", but that won't hurt power too much and it will be nice to drive. They are tight lash profiles so they should run quiet. If the exhaust turbine is a little bit on the small side to bring the boost on more quickly the 112Â° lobe separation will work well, but slightly narrower, say 110Â°, will make more mid-range torque. In theory at least. Quote: That's BIG cam for turbo engine. Even stock cam should get you to 13s. Why is shorter duration to exhaust side better?

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Author:	Lobster1 [ Wed Jan 25, 2012 5:28 pm ]
Post subject:
Thanks, I will not use that grind. I filled out the comp cam form, I'm a little disappointed in them. I gave very specific information about the build and goals. Maybe I'll go with the Oregon Cam? Also running a 3.21:1 sure grip, and Powerjection not projection, my bad... Cheers!

Author:	emsvitil [ Wed Jan 25, 2012 5:43 pm ]
Post subject:
Comp Cams always thinks in terms of a Chevy V8......

Author:	MJF [ Wed Jan 25, 2012 8:05 pm ]
Post subject:
Quote: Slant six heads have a flow ratio that is biased towards high exhaust flow so they make good power, more efficiently with shorter exhaust duration. If this were my build I'd use Oregon Cam grinding lobe 819 on the intake and 818 on the exhaust. That gives 219/212Â° at .050" lift on the intake and exhaust. Lift is only .437.431", but that won't hurt power too much and it will be nice to drive. They are tight lash profiles so they should run quiet. If the exhaust turbine is a little bit on the small side to bring the boost on more quickly the 112Â° lobe separation will work well, but slightly narrower, say 110Â°, will make more mid-range torque. In theory at least. Quote: That's BIG cam for turbo engine. Even stock cam should get you to 13s. Why is shorter duration to exhaust side better? Is the flow ratio all from head only, does manifolds affect it? I almost ordered Comp 264 cam, but I'm thinking if longer intake duration would be better. I'll run individual throttle bodies and megasquirt if that matters.

Author:	Dart270 [ Thu Jan 26, 2012 5:29 am ]
Post subject:
I think the head is the main flow ratio factor. I have never heard a good piece of advice on a Slant 6 cam from a commercial cam manufacturer/grinder. Best to use our community. I hear that more int duration is also good for a turbo motor, but I've not heard a convincing argument as to why. So, this would make you want to have even more int/exh duration ratio than a NA 225... Lou

Author:	MJF [ Fri Jan 27, 2012 2:04 pm ]
Post subject:
Thanks Joshua and Lou. I'll have to call local cam grinder what cam profiles they have. Something 230/225 at .050 in my mind.

Author:	Lobster1 [ Fri Jan 27, 2012 5:00 pm ]
Post subject:
Thanks Guys, I will go with Oregon Cam Grinders.

Author:	Shaker223 [ Fri Jan 27, 2012 5:48 pm ]
Post subject:
I have a comp cams: 229I, 225E @ .050 .326I, .319E lobe lift.

Author:	Lobster1 [ Sun Jan 29, 2012 10:25 pm ]
Post subject:
I appreciate all the input and I will call Oregon Cam tomorrow. I have been scouring the web and reading all that I can on turbo cams, for every assertion, I will find the opposite also documented and well thought out. shorter intake and longer exhaust is better, or longer intake and shorter exhaust... most seem to favor more LSA, but I also find opposition as in this article: http://www.carcraft.com/techarticles/ct ... ewall.html It seems to be majority opinion that shorter exhaust duration is the way to go with the slant six. Even with 3.21 gears and 2800 stall I don't afford to lose low end torque. Cheers!

Author:	Lobster1 [ Wed Apr 03, 2013 6:13 pm ]
Post subject:
A quick update; The engine is done and the OCG cam is installed. 226 intake @50 and 219 exhaust @50 and lift 440/436 and 114 LSA. I hope to have the car on the dyno soon. I am not turbo-ed yet. Barnaby

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Author:	robertob [ Thu Apr 04, 2013 8:03 am ]
Post subject:
Cool, what CR did you end up with?