Cheepy Three-Sixty build

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mario03srt said:
RAMM,

I noticed the lean AFR condition up to 4500 rpm. Was that only part throttle up to then? I would not think so. The #'s could be off, why so lean?

Marion
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I usually test at a fairly quick accel rate (400 rpm/sec) and the fuel turbines lag behind somewhat. While they seem to be accurate they may not correlate to exactly what's happening at that exact RPM. Still this is fairly lean which indicates the carb is too large for this little lung , which it is. Wish I had a 650 on hand. J.Rob
 
Ok so there's been a new development. Installed the Magnum hall effect distributor and MSD 6530, drilled a hole next to #1 terminal in cap checked rotor phasing which was actually quite good and set timing to 40 total. Loaded a retard curve into the 6530 and did two pulls. It really must not have liked the locked out distributor I was using prior. J.Rob

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Hah! Now you're talking. It gives me hope for the stroker. The 6530 is what we bought for the next dyno runs.
 
IQ52 said:
Hah! Now you're talking. It gives me hope for the stroker. The 6530 is what we bought for the next dyno runs.
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The 6530 takes a little getting used to but it really makes quick work of timing changes. So I'm stuck @ 396 currently, hopefully the rockers fit and let more power find its way to the crank. J.Rob

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I must have missed the "locked distributor" mention. I have to be honest and say I'm a little surprised that the small cam is doing this well. I wouldn't have guessed this high.
 
RAMM said:
Still this is fairly lean which indicates the carb is too large for this little lung , which it is. Wish I had a 650 on hand. J.Rob
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what size carb is on it now?
i went back and did a quick look, didn't see what carb for sure, think i might remember you said it's a 950hp...
 
rumblefish360 said:
I must have missed the "locked distributor" mention. I have to be honest and say I'm a little surprised that the small cam is doing this well. I wouldn't have guessed this high.
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I don't think I mentioned it--Its just a LeanBurn unit that I always use, that is my GO-TO dyno distributor, it never lets me down. I give plenty of credit to the manifold which is 100% OOTB. J.Rob
 
cookietruck said:
what size carb is on it now?
i went back and did a quick look, didn't see what carb for sure, think i might remember you said it's a 950hp...
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Sorry some times I get mixed up between my own notes and what I've posted online. It's a very nice 750 XP which is no doubt helping the output. J.Rob
 
MOPEkidD-3 said:
I just read through this start-to-finish and it was great... I want to take the Magnum top end from my busted 360 and build basically the same as you did but on a 318 instead. Same kind of bottom end, zero-deck flat tops etc. but with something like this cam Voodoo Hydraulic Flat Tappet Cam - Chrysler 273-360 268/276 - Lunati Power; the lift with 1.6 rockers would be like .527/.547" though, you think that would be excessive for how these tend to stall past .500"?

I was thinking about just leaving the heads alone, they're untouched iron Magnums but this thread convinced me to get a good valve job done. I'm OK with reusing the factory Magnum valves and Hughes springs/retainers though no G3 Hemi valves lol.

What do you think the HP/Tq curves would be like in comparison to your 360? I'd guess around 40-50 less lb-ft, and mayyybe 20 HP less if I'm lucky?
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I've used that cam in a 360 LA head and it made 425 HP or so with stock stamped shaft rockers. Ignore stall with true street oriented RPM's and Power levels. Re-use the 1.92/1.625 valves it will probably be better than what I did. You will likely make 345-360 hp and 370-380 tq with relative accuracy. J.Rob
 
great info! can you tell us more about the mods needed on the distrib. etc. would not both setups have the same amount of advance at peak horse rpm? you can borrow my 625 AVS but I do not think a smaller carb will help peak horse. maybe a thinner oil and HP1 filter, what u running? maybe that small cam will like 1.6 rockers, but we have never gained much going up on ratio when the cam is "right"
 
stixx said:
Very solid numbers for such a small cam, showing that you used the given parts to their best!

Looking at the cam specs I have got a question (kinda stabbing in the dark): isn’t is usually said that the Magnums have a good exhaust port that doesn’t need a lot more duration, if any, than the intake?

I noticed that your other 360 you showed recently (?) had like 224/224° duration and made very good numbers (with different cylinder heads, I admit). So does the Cheepy really need the split on intake/exhaust … or was the cam just one you had on the shelf, or could it have made even better numbers with a ‘square’ cam?
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If you look at the flow #'s I posted you can see that the exhaust does flow somewhere around 72-73% of the intake. This usually works well as a "rule of thumb". I am a big fan of single pattern cams and there is no telling what one would do in this case. J.Rob
 
woods said:
Now I'm curious to see how it does with the new rockers.
My build is close to yours. same pistons. a little less compression. a little more lift and EQ heads with 1.6 roller rockers.
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Yours will perform very very well--better than this one, the EQ heads are that good. J.Rob
 
IQ52 said:
We'll test anyone's engine for $550/day. But in a town where the sign reads "Population 1081" before the big mine layoff, it's mostly our own stuff.

I have a 350 core with some Vortec heads sitting out back. Never tested them though.

A while back I alluded to a 383 Chevy we built. Local customer requested 450 HP for his show truck because he could get that on a budget of X$ from an outfit advertising on the internet.

Ah, well, we kept to the budget, and.............with a carburetor he got 392 LB-FT @ 3,000 rpm, 484 LB-FT @ 5,000 rpm and 518 HP @ 5,800-6,000 rpm

With the Holley Terminator FI not fully through it's learning curve, 399 LB-FT @ 3,000 rpm, 472 LB-FT @ 4,900 rpm and 511 HP @ 5,800 RPM.

10.1:1 compression, Pump gas, Victor Jr intake, AFR 1034 heads, custom street solid roller 236/242 .564/.570 113 LSA 109 ICL, 1.5 Scorpion roller rockers, and using the long tube headers for his truck.

I'm still a 383 Chevy novice because that is the sum total of my 383 experience.
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I hear ya on the small town reality. I've tested more than a few 383's and every time they have any kind of AFR head they go well over 500 HP. Love Scorpion rockers for value. Youre results from carb to EFI mimic my own. Check the averages--carb was WAY better in my case even thought the peaks were very close with EFI.

I would love to see an AFR SBM head someday but I doubt it will happen. If I had some serious funds I would handle the pattern making and cover the cost of a run at a foundry and then handle the final machining--but alas this is one of my better dreams. J.Rob
 
Marcohotrod said:
great info! can you tell us more about the mods needed on the distrib. etc. would not both setups have the same amount of advance at peak horse rpm? you can borrow my 625 AVS but I do not think a smaller carb will help peak horse. maybe a thinner oil and HP1 filter, what u running? maybe that small cam will like 1.6 rockers, but we have never gained much going up on ratio when the cam is "right"
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Basically I removed the "shutter wheel" from the Mag distributor and machined up a new 8 window shutter and epoxied it back where the old one was. Then I looked up a schematic to find the ground/+8V reference/trigger inputs and wired them into the 6530. Both setups should have the same amount of advance at X rpm but that is not all there is to it.
You want to give any engine enough spark lead to light the charge at JUST the right time. Too early(advance) and you are performing negative work (reduced power) too late (retarded) and the charge doesn't get a chance to burn long enough and gets exhausted before it has consumed all there is in the chamber (again reduced power). Providing an engine with just the right ignition curve allows better/optimum transfer of power to the crankshaft. J.Rob
 
Just a screenshot of the engine idling with the MAP sensor hooked up for the first time. Atmospheric pressure was 14.5 psi and in this shot 7.75 psi was idle so the difference is 6.75 psi which is 13.75" vacuum give or take a bit. J.Rob

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RAMM said:
I hear ya on the small town reality. I've tested more than a few 383's and every time they have any kind of AFR head they go well over 500 HP. Love Scorpion rockers for value. Youre results from carb to EFI mimic my own. Check the averages--carb was WAY better in my case even thought the peaks were very close with EFI.

I would love to see an AFR SBM head someday but I doubt it will happen. If I had some serious funds I would handle the pattern making and cover the cost of a run at a foundry and then handle the final machining--but alas this is one of my better dreams. J.Rob
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Might have a new head on the market in another year...won't be AFR though.
 
Ok so I put these on in about 30mins. Fired it up and it idled beautiful @ 800 rpm with a whisper quiet valvetrain. It was a little "clicky" before. Very happy with these.
Any guesses as to the outcome? I already know, lol. J.Rob

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