Got a car, is my planned motor build too radical? - Team Camaro Tech
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post #1 of 3 (permalink) Old Jul 8th, 09, 07:34 PM Thread Starter
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Got a car, is my planned motor build too radical?

About a month ago I bought a 69 Z with about a 10 year old resto, NOM 350, X33 coded, M21, 12 bolt with stock 4.11's, nothing to indicate that it was not a real Z. The guy had been showing the car, the 350 that was in it has a lot of chrome, it was painted to match the rest of the car and engine compartment in blue, looked great but it was really nothing special and sounded like a stock p/u motor (cam was maybe 1 size bigger, vortecs that are on it have not been modded for lift) and didn't run hard at all.

Today I got around to calling the guy that had done the resto on it and ask him what happened to the original 302 inch motor. I was betting that it had been run hard and somehow damaged the block or something that would excuse throwing such a thing away, but what the guy told me really shocked me.

He said that it was running and had about 100k when he got the car, but he pulled it and scrapped it in favor of the 350 when he did the resto. I was shocked and asked him why, he started telling me about how small cubes can't make respectable power and nobody can tell the difference by looking at the motor, that the small mill was a waste of a 4 speed and 12 bolt setup, etc. I asked him why he didn't save the original block at least, telling him he could have made a 350 or 383 and still preserve the matching numbers, he responded telling me that I was wrong, it was too small a bore to make a 350 or a 383. Basically, I think he thought it was a 305. I thanked him and hung up.

Right now I'm having the tranny worked over by a friend that has been working on 4 and 5 speeds for a long time and I'm going to put it back together with a new motor: my 350 is a 2 bolt, 80 over, stock cast rotating assembly job from a high volume rebuilder and I don't really trust it to hold together being run in a performance application. My machine shop told me that they'd done some 80 over motors for some cheap asses that ran a fleet once but they agreed that expecting any sort of lifespan out of one was just not possible and that the previous owners of my car were lucky to have gotten the 10k and 10 years out of it that they did.

I'm going to use a SJ 327 block and forged 283 crank, aftermarket splayed 4 bolt main caps, some dart aluminum heads that I bought used(i had them rebuilt), 10.5:1 compression, 300-36 intake, and a solid roller valvetrain. I've never built anything this radical (mostly high torque stuff for mud trucks) but am hoping that all this stuff runs good. A guy I know that has a SBC swapped into a datsun Z car said that this will definately scream, but doesn't know whether a first gen camaro is light enough to work with that type of motor and a nova or a vega might work better with my combo.

I was tired of running out of breath at 45 mi/hr with that 350, but i'm hoping now that I didn't go too far in the other direction. So my question is really aimed at people that have experience with short stroke SBC's because there aren't many people that I know that do- am I going to regret building something with no manners, yet still get my *** whipped by 355s and 383s as the people running those motors claim, or am I running a good enough combo to go hunting for big engines? I have no idea and would hate to have pissed away money on something that just sucks. I guess i can still cam up my 350 (364 lmao) and mill the heads for CR if that is the case.
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post #2 of 3 (permalink) Old Jul 8th, 09, 08:13 PM
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Re: Got a car, is my planned motor build too radical?

There is nothing wrong with your idea. You have an X33 car and it needs a 302 in it!!!. Now, since a 302 has such high rpm capability, you can run a decent sized solid roller cam, with large runner heads and higher compression as well. I would consider bumping the compession up to at least 11:1, maybe 12:1 if the cam is large enough. See, the dynamic compression is what really matters with pump gas fuel today and as long as that is around 8-8.25:1 you should be fine on 93 octane pump gas. You could probably squeeze 8.4-8.5:1 dynamic compression out of it, but you'll have to have a really good cooling system, and you may have to pull a little timing out of it in the summer months to prevent detonation. Now, with a motor like this, I wouldn't really expect it to start making power until 3500-4000 rpm. However, if all of the valvetrain is setup correctly, and you have a balanced bottom end, 8-9000 rpm shouldn't be a problem.

AFR 195s, Brodix IK 200s or some dart pro 1s would be good a good head choice along with a single plane intake and a 750-800 cfm mechanical secondary carb.

1967 Camaro SS: 406 sbc, 522hp/514 ft lbs, Doug's 1 3/4" headers, M20, posi, 3.73's, vintage air gen IV, IROC steering box, Comp Eng. weld-in sfc's & traction bars, chrome US Mags

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post #3 of 3 (permalink) Old Jul 8th, 09, 09:04 PM Thread Starter
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Re: Got a car, is my planned motor build too radical?

I just looked up the casting numbers on the heads I've got and they come up as dart pro 1 platinum heads, 200cc runners, 64cc chambers. Judging from my experience building mud motors they are WAY too big for a 306" engine, but they were cheap and should flow really nice for their runner sizes according to the published numbers.

I actaully have a comp XR280R cam right now that I got from someone that ended up not using it (he wanted to stick it in a k5 with 35" tires and a roller block 350, i talked him out of it and offered to buy it from him to soften his mistake). It's a 280/286, 242/248 at .05", .570/.576. Comp claims that it's good to 6500 in a 350, but putting it into Desktop Dyno with the dart aluminum heads and "high flow dual plane" gives me more than 300 lbs-ft of torque from 2000-9000, with peak power at 7500. Nice smooth curve too. I'm getting it balanced, so I hope to get a decent life out of the motor presuming that the lifters can survive street driving.

10.5:1 static compression puts my DCR right at 8.3 with that cam, so I'm thinking that this should work using pump gas and not kill the bottom end. I'd love to build something with 11:1 or 12:1 but honestly I was thinking that a pump gas motor with either of those static ratio's would be better suited to 4:56 or lower gears, or maybe an M-20 with 4:11's. I really dont know though, because this Z is the first thing I've tried to hop up that weighs less than 5000lbs.

As far as a carb, I have a 750 edelbrock that I've had for awhile sitting around but I think it's more suited to a 454 in a truck than this application. I'm planning to run it for a short time then put a 700/750/780/800 holley on it once I can find a good deal on one.

And to be honest, while I have no doubt that i could go to 8000/9000 a few times with a balanced soild roller 3" stroke SBC, I don't think I can afford a new one every 6-8 months. That's why I'm leaning towards a mid/top end combo as opposed to one that strictly emphasizes top end. I just think I may be an idiot for trying that sort of combo with a 302.
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