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Old 04-20-2018, 04:14 PM   #1  
Knerf
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Ok ladies and fellas, i have a good one here.

when i got my 68 it had no engine in it, it just so happened that my brother had a 383 built that he was no longer in need of, maybe 300 miles total on it, fairly well built all around, here are the specs

220 afr heads
crower street roller 383 cam 288R 112 advertised288 290 at .050 250 252 lift .570" .584"
new crank and rods (engle i think)
forged pistons +7cc
victor jr intake
qft 850

he figured he would be at around 11.2:1 for compression, but this thing is kind of gutless for how it is built, kind of why he got rid of it.

and here is where i came in to it, i tuned it up a bit and and squeezed a bit more out if it than where he was at, so now im making 380hp at the wheels, this is where i started sctratchin my head too, because this should easily be obver 400hp at the rears EASILY, then i saw it...

he ordered +7 cc pistons, not -7 cc pistons... i had asked him if he ran a compression check on all the cylinders when he was having problems with it and he said they were all within a couple psi of one another and i never asked what the psi was i guess, so i checked for myself and they are all in the 130psi range... lol. so i went and plugged my numbers into a compression calculator and it says im at 8.3:1 with what i have in there.

so now im at a crossroads here, and am looking for some opinions, i got this engine for a song so im not too heartbroke about this but what would you all do, swap the pistons out?

no machine shop within 100+ miles of me to balance it so would you just go for making them weigh the same as what you took out of each hole? pull the whole rotating assembly and send it off with said new pistons for balancing? say screw it and drive it like it is and enjoy using 87 octane fuel?

im open to suggestions.
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Old 04-20-2018, 04:28 PM   #2  
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A bad-*** supercharger?
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Old 04-20-2018, 04:35 PM   #3  
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A bad-*** supercharger?
i have kicked around throwing a pro charger at it, i would like to keep everything under the hood that is on there so a roots is out of the question, but i have had 0 experience with prochargers and i fear the unknown
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Old 04-20-2018, 06:17 PM   #4  
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Take the heads off and get them milled to a smaller chamber size. Angle milled if you want smallest chamber size.
of course check to see what the min size is and where that would put you before committing to it.
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Old 04-20-2018, 06:30 PM   #5  
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Not an expert but 220 AFR's on a 383? 383's should have 195's not 220's. Also, 250/252 duration? With those heads and that duration the engine is going to be a dog at anything less than 4000 RPM not to mention the compression. Holy smokes............

Sounds like that 383 needs compression (10:1), correct runner heads (195 CC), and a much lower duration roller cam (225/230) for good mid range street torque.........

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Old 04-20-2018, 07:04 PM   #6  
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Not an expert but 220 AFR's on a 383? 383's should have 195's not 220's. Also, 250/252 duration? With those heads and that duration the engine is going to be a dog at anything less than 4000 RPM not to mention the compression. Holy smokes............

Sounds like that 383 needs compression (10:1), correct runner heads (195 CC), and a much lower duration roller cam (225/230) for good mid range street torque.........
it was built to live up high, and i agree, could use a bit smaller head and cam to improve torque, but if i was going to go that far with it i would just start all over.
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Old 04-20-2018, 07:11 PM   #7  
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ok, i was off on the power number, 380hp was stuck in my head for some reason it was 380ft/lb torque, max HP was only 358

here is the dyno sheet, never took it over 6 grand on these runs as it was for more of a baseline after i got it in and tuned up a bit, it was loading up really bad still so there was a big dip when stomped it down as you can see in the graphs.


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Old 04-20-2018, 07:19 PM   #8  
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I'm going to go with ReelaV8r on the smaller combustion chambers. AFR heads are pretty much reported to breathe well, so bumping the compression should help. Personally, I'd drop the carb down to a 750 too. But that kind of depends on what you're looking for. I'd suspect the whole thing is lazy until you start getting the RPM built up. Smaller carb will improve the bottom end.

IMHO, not much challenge in just yanking it out and starting over. For me, it would be fun to play with the little stuff, (carb, ignition) and see if I could get it where I was happy before starting over. Especially if I was not heavily invested in what I had.

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Old 04-20-2018, 07:24 PM   #9  
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That's just a really bad combination. Too much cam, too little compression, too much head. Best solution? Slip a 427 short block under those heads & put in a cam with about 230 degrees of intake duration. Or, get some 180 heads, install them with the thinnest head gasket you can find, and put in a cam with about 220 duration.

Even if you change the pistons, you've still got too much head, and the thing will be a bear to drive on the street. And you better not have an automatic.
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Old 04-20-2018, 07:24 PM   #10  
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The heads and cam are fine, but you need compression....if it really measures out to 8.3-1, the whole combo is off... You can't mill the heads enough to get you much of anything...and doing that will kill the flow if you angle mill them. 220 cc heads are perfect for a 383.... Don't believe the hype... You just need to spin the motor to make use of them, and you have enough cam for that...You just need compression. A 195 head is great for a 6000 rpm 383..... but a 220 head will work great on a 6500-7000 rpm 383...

The only real resolution is to put the correct pistons in it, rebalance it and reassemble it. I'd also touch up the valve job and make sure the heads are sealed well.

Bump that compression up 3 pts and it'll gain a bunch of power.... Probably 60-70hp at least I'd guess, and a TON of power down low, and across the whole range.

All that being said, 360 rwhp ain't no slouch...

You didn't say if its auto or stick but...that makes a huge difference on the dyno.

Last edited by ajrothm; 04-20-2018 at 07:29 PM.
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Old 04-20-2018, 07:28 PM   #11  
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yeah, sorry, its got a manual in it.
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Old 04-20-2018, 08:16 PM   #12  
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The heads and cam are fine, but you need compression....if it really measures out to 8.3-1, the whole combo is off... You can't mill the heads enough to get you much of anything...and doing that will kill the flow if you angle mill them. 220 cc heads are perfect for a 383.... Don't believe the hype... You just need to spin the motor to make use of them, and you have enough cam for that...You just need compression. A 195 head is great for a 6000 rpm 383..... but a 220 head will work great on a 6500-7000 rpm 383...

The only real resolution is to put the correct pistons in it, rebalance it and reassemble it. I'd also touch up the valve job and make sure the heads are sealed well.

Bump that compression up 3 pts and it'll gain a bunch of power.... Probably 60-70hp at least I'd guess, and a TON of power down low, and across the whole range.

All that being said, 360 rwhp ain't no slouch...

You didn't say if its auto or stick but...that makes a huge difference on the dyno.
My comment about the 195's versus the AFR was based partly on this thought process on a 210 not 220 AFR:

"Re: AFR 195 Eliminators vs AFR 210's


I have done that very test several times now. At 6500 RPM, the bigger head is little or NO better than the 195. At 7000, the bigger head will be about 15 to 20 better, but below 6500, the 195 is better. My testing was on a 383 making 570 at 6500 with the 210 heads


JOE SHERMAN RACING"
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Old 04-20-2018, 09:31 PM   #13  
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That's just a really bad combination. Too much cam, too little compression, too much head. Best solution? Slip a 427 short block under those heads & put in a cam with about 230 degrees of intake duration. Or, get some 180 heads, install them with the thinnest head gasket you can find, and put in a cam with about 220 duration.

Even if you change the pistons, you've still got too much head, and the thing will be a bear to drive on the street. And you better not have an automatic.
right now im seriously considering the 427 short block option.
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Old 04-20-2018, 10:44 PM   #14  
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Originally Posted by jb78L-82 View Post
My comment about the 195's versus the AFR was based partly on this thought process on a 210 not 220 AFR:

"Re: AFR 195 Eliminators vs AFR 210's


I have done that very test several times now. At 6500 RPM, the bigger head is little or NO better than the 195. At 7000, the bigger head will be about 15 to 20 better, but below 6500, the 195 is better. My testing was on a 383 making 570 at 6500 with the 210 heads


JOE SHERMAN RACING"
Yeah the 195s are great all around heads for sure...And if I was looking to build a 500hp 383, I'd probably go that route. BUT, to say that a 220 head is "too big" for a 383 and the reason its missing power is just ridiculous. I know you weren't the one posting that, I'm just loosely quoting someone else's post.

I think most people WAY under size the heads they need to make the most power, and they put WAY too much emphasis on intake port CC size, and not enough on cross sectional area and port design, valve size, throat size etc.

Look at LS motors, the smallest cathedral port on a factory head is 200cc.... And that is on a 327" 5.3l LS. Most of the opinions here would say that head is WAY too big... yet we port them another 15cc and gain 40hp....


Back to SBC examples, on my buddy's home built 383, he started with some old Dart 215cc castings, home ported them himself. Afterwards, they poured 230cc... and with a little 224 hyd roller, the engine made 495 hp with an RPM air gap....That was as basic of a combo as you can get.... big heads, small cam, still made great power and drove awesome. It was his daily driver for years. The engine runs 10.90s in a 62 Nova with a 200R4 and full weight.
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Old 04-20-2018, 10:55 PM   #15  
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right now im seriously considering the 427 short block option.

While I'm all for going big....you are gonna spend a fortune, and basically not use much of anything you have there other then the heads.

The cam will be wrong, the intake will be too small, and none of the short block stuff will cross over...

So you are talking about dumping another $7-8k in a short block minimum.... vs. spending $2k to freshen up your 383 and put the correct pistons in it... Gain 50-60hp for $2-3k...... or gain 100hp for $7-8k+....

"Speed costs $$$, how fast do you want to go?"


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Old 04-20-2018, 11:36 PM   #16  
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thats where i was at, 2k ish to freshen up this one or get something like this

427 short block

at that price it would almost be silly to not go that route, throw a set of smaller heads on the 383 and sell it off for what that cost me.

i dont know yet, thats why im here, you guys always have some good ideas
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Old 04-21-2018, 02:38 AM   #17  
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Pull it out and start over. Build the motor into something you want. Save your money and do it right.
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Old 04-21-2018, 03:58 AM   #18  
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thats where i was at, 2k ish to freshen up this one or get something like this

427 short block

at that price it would almost be silly to not go that route, throw a set of smaller heads on the 383 and sell it off for what that cost me.

i dont know yet, thats why im here, you guys always have some good ideas
Yeah its $4100 for the short block...(with ching ching no name parts in it)

Plus $400 or so to go through the heads, springs, setup for hyd roller etc.

Another couple hundred for a good intake, gaskets etc...

Another hundred for good pushrods in the correct length

Another couple hundred for a GOOD oil pan to help with windage from that 4" crank.

So on, so forth....it'll add up quick. $5k+ for a long block full of no name Chinese stuff in it...No telling if it will actually make power...(since they already have a cam in it, without knowing what heads/induction you'll be running )....

At this point, you may as well start over and build a GOOD 427 from scratch.... spend the $10k-12k, make 600hp and call it good. At least then you know what you are getting...

Or spend $3k on the 383, make 500hp+ and reuse 90% of what you already have sitting there...


Its your money......
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Old 04-21-2018, 08:26 AM   #19  
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I trust that you are not using cranking compression PSI for any calculations right?
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Old 04-21-2018, 08:36 AM   #20  
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I'm with ajrothm. Sounds like a great engine with nowhere near enough compression. Give it a hone and put the right pistons and rings in it for at least 11:1 compression (I'd be shooting for high 11s provided you have good tight quench), you have plenty of cam to make that work on pump gas, and it will be an absolute killer engine. The heads aren't too big, I've got some afr 227s to go on my 388 when I get around to it (and spend up for the offset rockers).

Having said that, having bolted all those expensive parts together without measuring the compression ratio...? I think I'd be checking and measuring everything closely while you have it pulled down to swap the pistons.
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