Overbuilt 383? - Chevelle Tech
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post #1 of 69 (permalink) Old Sep 1st, 19, 9:23 PM Thread Starter
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Overbuilt 383?

Wondering if I overbuilt my last motor. Was intended to be a street/strip car and now is entirely a street car. Its a 67 Chevelle with a 383/4 speed/3:55 rear gear. Was going to be a 4:10 rear gear, but changed it to a 3:55 when it became a street car. We are running 15 x 7 with 235 60's on the front and 15 x 8 with 255 60's on the rear.

The bottom end is good until about 500 horse. It has a cast Eagle crank with something like SIR rods I think with -12 dished hyper pistons in it. Compression came out around 10 to 1, maybe a slush under it at 9:9 to 1. It has 195 cranking compression. The cam is very mild...its a UDHarold design at 280/288 and 226/234 @ .050 with .536/.536 lift on a set of 1.52 roller rockers. The cam is installed at 109 ICL and is on a 112 lsa. Not sure why the builder chose that as the cam card called for 106 ICL. The heads is where I think its overbuilt...for the street...we had a set 200 Dart Conquest ported and flow very well for what they are....they flow at .500 270 and at .600 they flow 285. We used a second hand Edelbrock RPM intake with a Holley 3310 on it. Motor runs fine with the exception of a rocker getting loose from time to time. Our timing is at 18* initial with a 16* mechanical curve for a total all in of 34* around 2100. The can adds another 12* for a total of 48* at cruise.

The car has a 160 thermostat in it here in Florida and runs about 180 to 190 in the Florida summer heat. Fans come on to keep it in this this area, but then go off. Really pleased with the cooling.

I feel the cam would run better on a 108 lsa there is no doubt about that, but I also feel that we should of left the heads alone and run them unported and run a 2.05 valve for the street to keep up velocity. However, Eric Weingartner did the work on them thinking it would be a strip/strip motor. The motor is a little sluggish to me down low for a mild cam, but really seems to run really well at above 3000 to 6500. Seems to pull very nice up there. We want more bottom end with a shift point of around 5800 to 6000 to make it more like a strong street motor....but its all good in that it runs good for a cruiser.

Anyone want to add there opinions to the discussion?

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #2 of 69 (permalink) Old Sep 1st, 19, 9:36 PM
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Re: Overbuilt 383?

Take Eric's word for it on the heads. Not many better than him available.

sounds like the ignition is set up pretty good.

where does it feel sluggish? off the line? how does it run at WOT in the mid-range?

Have you tried giving it a little more advance? 2-3 degrees?

Have you tried giving it a little more pump shot? like going from a 28 to a 31. quick, easy and cheap. Pump adjusted correctly? no slop in the linkage at closed throttle.

Seems like that would be a pretty hard running combo.

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post #3 of 69 (permalink) Old Sep 1st, 19, 9:43 PM Thread Starter
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Re: Overbuilt 383?

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Originally Posted by Tom Mobley View Post
Take Eric's word for it on the heads. Not many better than him available.

sounds like the ignition is set up pretty good.

where does it feel sluggish? off the line? how does it run at WOT in the mid-range?

Have you tried giving it a little more advance? 2-3 degrees?

Have you tried giving it a little more pump shot? like going from a 28 to a 31. quick, easy and cheap. Pump adjusted correctly? no slop in the linkage at closed throttle.

Seems like that would be a pretty hard running combo.
Yeah, Tom...I really like Erics work. He has has done a lot of good work for me. He has done my heads on my track s10.

Yes, pleased with the ignition.

It feels a little sluggish off idle and off the line...with the 255's on the back it doesn't really just bust the tires loose....it just seems to go....but if you push the clutch in and bring it up to around 2200 to 2500 it will spin the tires. .

Runs very strong at WOT in the mid range...nothing to complain about.

I haven't done anything to the 3310. I just told a local racer who rebuilt the 3310 what the motor had and he jetted and tuned it according....we have not had it on a dyno yet or at the track...never checked the plugs. I do think it has a yellow spring in it.

It does run very well...just thought that a 383 with that small of a tire would break the tires loose off idle with easy.

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #4 of 69 (permalink) Old Sep 1st, 19, 9:53 PM
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I have a similar cam, 221/235 .544/.544 lift with 1.6 rockers. 108LSA. Brodix IK180 heads, Holley single plane that I’m going to switch back to my air gap. Four speed with 3.73s. 357 with 10:1 compression. Fun motor pulls great form down low easily to 6000

1974 chevelle with 73 laguna nose sbc 357 Brodix IK180 heads Comp Cams XE274H Edelbrock RPM airgap 650 AED double pumper, M20 muncie, Truetrac with 3.73s
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post #5 of 69 (permalink) Old Sep 1st, 19, 9:56 PM Thread Starter
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Re: Overbuilt 383?

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Originally Posted by JF74chevelle View Post
I have a similar cam, 221/235 .544/.544 lift with 1.6 rockers. 108LSA. Brodix IK180 heads, Holley single plane that Im going to switch back to my air gap. Four speed with 3.73s. 357 with 10:1 compression. Fun motor pulls great form down low easily to 6000
Justin, I have a 350 with a similar combo as yours. It runs great. I run the same cam in 350 as the 383. It is cut on a 108 lsa and installed at 104 ICL. Everything else is the same as yours....Brodix Iron Killer 180s and a RPM Air Gap with 10.3 compression....this motor ran 12:50's in my 67 Chevelle with a 4 speed and 4:10 gears.
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67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #6 of 69 (permalink) Old Sep 2nd, 19, 1:21 AM
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Quote:
Originally Posted by Aaron View Post
Quote:
Originally Posted by JF74chevelle View Post
I have a similar cam, 221/235 .544/.544 lift with 1.6 rockers. 108LSA. Brodix IK180 heads, Holley single plane that I’m going to switch back to my air gap. Four speed with 3.73s. 357 with 10:1 compression. Fun motor pulls great form down low easily to 6000
Justin, I have a 350 with a similar combo as yours. It runs great. I run the same cam in 350 as the 383. It is cut on a 108 lsa and installed at 104 ICL. Everything else is the same as yours....Brodix Iron Killer 180s and a RPM Air Gap with 10.3 compression....this motor ran 12:50's in my 67 Chevelle with a 4 speed and 4:10 gears.
These are great budget heads. And this cam seems to match them very well.

1974 chevelle with 73 laguna nose sbc 357 Brodix IK180 heads Comp Cams XE274H Edelbrock RPM airgap 650 AED double pumper, M20 muncie, Truetrac with 3.73s
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post #7 of 69 (permalink) Old Sep 2nd, 19, 1:30 AM
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Re: Overbuilt 383?

Id spend some time at the track dialing in you ignition and carb before swapping cam. Seat of the pants is often inaccurate and shouldnt by itself be the basis for expensive changes. If you live fairly close to s track there is no reason not to go. Since its a 4 speed, dont necessarily judge your car by its 60ft, pay attention to the time between each incremental on the time slip and the mph at the 1/8th and 1/4 mile.

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Last edited by Steve R; Sep 2nd, 19 at 1:33 AM. Reason: X
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post #8 of 69 (permalink) Old Sep 2nd, 19, 8:22 AM
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Re: Overbuilt 383?

I was a little confused by the cam talk there, but if I read that the cam is in "straight up", and Harold's cams "always" run better advance 4 or so. I'd rephase the cam to +4 or and feel the bottom come back in. 105-106 ICL. Heck even 104. This will increase the intake" ram" effect and "shrink" them heads a freckle.

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post #9 of 69 (permalink) Old Sep 2nd, 19, 8:47 AM Thread Starter
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Re: Overbuilt 383?

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Originally Posted by 427L88 View Post
I was a little confused by the cam talk there, but if I read that the cam is in "straight up", and Harold's cams "always" run better advance 4 or so. I'd rephase the cam to +4 or and feel the bottom come back in. 105-106 ICL. Heck even 104. This will increase the intake" ram" effect and "shrink" them heads a freckle.
Gene..Harolds cam card calls for the 112 lsa cam to be installed at a 106 ICL. Its installed at 109 ICL...only three degrees advance. Do, a 106 would be 6* of advance. I think, if Im right.
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67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #10 of 69 (permalink) Old Sep 2nd, 19, 8:52 AM
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Re: Overbuilt 383?

Which 4 speed are you using? If its a Muncie with a 2.20 first gear, and coupled with a 3.55 gear it may feel a little lacking down low.
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post #11 of 69 (permalink) Old Sep 2nd, 19, 9:40 AM
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Re: Overbuilt 383?

I gave up years ago trying to tune drag motors for street use. Today I just use big cubes with stock heads and low compression but run high initial (22-26) with 10 to 14 mechanical in late like 2800.. Starts without issue, idles nice and smooth, power brakes work great.. I'm into suspensions now, making them handle well.. 9 out of 10 old cars out there have suspensions that cant handle the power trains they carry... Frankly on the street, the stock big cube motors feel much faster then the small drag motors I used to slave over, probably just my imagination but I enjoy this much more..
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post #12 of 69 (permalink) Old Sep 2nd, 19, 11:28 AM
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I would advance the cam to what it is supposed to be.
Change the timing curve to get the initial at 25-26, with 10 in the centrifugal curve.
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post #13 of 69 (permalink) Old Sep 2nd, 19, 12:01 PM
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Re: Overbuilt 383?

Aaron, I agree with your thoughts that the heads are a mismatch for the combination. Its causing you a loss of port velocity which translates in to a little laziness until you get the engine well up in the RPM range. Id be looking for another set of heads first. (My opinion is they need more cubes, cam and compression.)

Id be afraid to advance the cam which might make you a noticeable change on the bottom but is likely to take the heads out of their operating realm.
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post #14 of 69 (permalink) Old Sep 2nd, 19, 12:25 PM
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Re: Overbuilt 383?

I would try a couple more degrees of timing. If it has the yellow spring, try the brown one. My 355 ran quicker with the brown over the yellow.

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post #15 of 69 (permalink) Old Sep 2nd, 19, 2:55 PM
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Re: Overbuilt 383?

All my SBC from 355 on up have gone quicker and faster with a 106 but if you are going to run a lot on the street the 112-114 cams idle better and are much more driveable. On a BBC it seems to be different as one does not need as much low end tq. so a wider LCA seems to broaden out the tq. curve and help out top end.
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