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 Need Help 1970 360 hp with #15 heads
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jd63
Tribal Scout

Canada
4 Posts

Posted - 28 Jul 2017 :  09:29:15 AM  Show Profile  Reply with Quote
Hi everyone
I have a long story for you.I have a 1981 trans am auto t roof car that yrs ago I stuffed a 455 olds into,but the trans just went so I want to put it back to all Pontiac so I bought a 1970 Bonneville with the 360 hp engine which I was just going to drop in but then I started thinking I should modernize it.
My goal is to have a hot trans am that I can drive and get decent gas millage and have a occasional street race
I am going to put a auto overdrive in it and I was thinking 323 or so gears.
Now are these 15 heads good heads or should I sell them and get a different set and then what are they worth and the cam is a 067 from what I read, is that good or what should I replace it with.
what carb and intake is a good choice for this engine
Thanks jd63

cortcomp
Coyote

USA
5335 Posts

Posted - 28 Jul 2017 :  09:58:47 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
If you're going overdrive, i'd consider more like 3.42 gears. You don't want to be cruising around at 1500rpms lugging it.

One, it will be kind of soggy vs a numerically bigger gear, so you'll use your fuel savings putting more pedal into it. Also, like 2k rpm+ is better for oiling and the engine is just humming along without a lot of resistance but still not wound up and beating on valvetrain. If I was going to setup an engine as a generator or some other fixed load use, it'd be like 2k-2500 rpms.

Two, as CobraBill like's to point out, your timing isn't all in yet so you're likely not being that efficient. I build only OD projects, and have played with 2.56, 3.42, 3.73, and 3.91. With the torque of a pontiac, you can do whatever and it will move. Stick OD is more forgiving obviously. I currently DD a 56 chevy with a very low end 280hp 327, and 3.70s and sometimes it feels like i'm working it. For a pontiac that'd be perfect, or again, even the 3.42 which is my favorite for the pontiac motor.

Those heads show as small valve, 87cc heads. If it's std bore, .039 gasket thickness, 6cc dish pistons, .0-15 deck height at like 10.6 compression? That seems high for iron heads even with a complementary cam. Someone here will have better advice for that. But be warned, if you go with a cam that's lumpy on the low end to handle the compression, and you gear it so you're in low rpms a lot with a 200-4r or a 700-r4, it won't be that enjoyable of a driver.
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Blued and Painted
Chief PONTIAC

USA
3406 Posts

Posted - 28 Jul 2017 :  10:20:31 AM  Show Profile  Reply with Quote
Welcome jd63
Looks like the #15's are 87 cc heads with the smaller valves. 87cc's is a bit small for the 455. Some light contouring of the chamber could get you to 9.5 to 1. IIRC Mr Cliff said he only lost two tenths in the quarter when a set of small valve heads were substituted on his race combo.
Large valves can be installed but labor for re-sizing/installing seats then blending for flow is expensive. A set of aftermarket heads then becomes cost effective. Eldebrock or KRE aluminum heads out of the box will out flow most any iron head.

The 067 is too small for a 400 or 455 in my opinion. The 068 or an aftermarket cam will let the big engine breath.

Many guys are running 3.55 or 3.73 gears with the OD Trans




Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 28 Jul 2017 10:25:11 AM
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Steve C.
Crazy Horse

1675 Posts

Posted - 28 Jul 2017 :  11:10:12 AM  Show Profile  Reply with Quote
Use of a lock up converter or non-lock up converter can factor into the cruise rpm. Personally I prefer a non-lock up converter with my 200-4R transmission with 3.73 gears and 27.76" tires. About 2300 rpm at a steady state 70 mph or so.


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cortcomp
Coyote

USA
5335 Posts

Posted - 28 Jul 2017 :  11:35:24 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
That's about where i am with my 700r/327, although i have a lockup converter. Knocks a couple hundred RPMs off when you're doing 70-75. Took me a bit to get the vacuum switch dialed in just right. You could also wire it so that you're just always locked up when in 4th, but that's not for me.
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jd63
Tribal Scout

Canada
4 Posts

Posted - 28 Jul 2017 :  5:36:50 PM  Show Profile  Reply with Quote
thanks for the input I will go with 342 0r 373 gears I just wasn't sure. how do I know what cam is in it is there a way to tell
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