Quazz

iTrader: (1)

Just curious:

383 Stroker motor, 10.5:1 compression

How much of a gain HP and torque am I going to see just from the swap/retune? Car currently has lightly ported stock castings with stock size valves. GM847 cam as well. Paccesetter longtubes, and a full catback with a

No comments on how "shitty" the CR is or how "old" the camshaft tech is, just straight answers please.

Stroked96Bowtie

iTrader: (22)

Assuming the intake is ported to match the heads, larger TB, I think you can assume a 'signifcant' increase. Putting a number against would be a guess for me. Not just the valve size increase but the intake runners also.

Quazz

iTrader: (1)

I figured as much. Just trying to nail down a ballpark number though LOL

Thanks for the response!

joelster

So many factors come into play, it's hard to say. What cc are the chambers in the heads you currently have? Who ported them? That cam is not real big for 383 cubes to feed.

97Z28SS

iTrader: (5)

Which AFR 210s the Race Ready or the Competition series, anyway for the competition ported I'd say 60-80 hp at the flywheel wouldn't be unreasonable. However as others have stated it would depend on what the old heads were flowing, how much hp did the old combo put down?

Quazz

iTrader: (1)

Old combo was 55CC heads not much work done to them...stock castings. They were home ported by a member here, but judging by some of the other work on the motor probably not well. Stock valve size too.

The AFR's are the newer AFR eliminators, milled to 57CCs, Full CNC. These are the race ready heads. The larger "race" valves that AFR offers. I'll be running the same 1.6 RRs that I have on my current heads


The car put down 334whp and 344flbs through a 4L60E and a 10" PTC 3600 stall.

This was on a dynojet.

joelster

What rpm did it peak at?

I'm guessing that it will pick up a minimum of 60hp. To only put down 334 beforehand tells me the current heads are a mess.

bufmatmuslepants

iTrader: (3)

I'm guessing that was with your 10.7:1 and 847 cam? Goes to show how your compression is killing you.

Quazz

iTrader: (1)

bufmatt: Yeah, that was with the GM847 and the compression ratio at 10.5:1

joelster: I think it was in the neighborhood of 48-4900rpms? I'd have to dig out the dyno sheet to be sure. I agree with you, the heads are likely a mess. I know the valvetrain is good, but the home porting..... well, it didnt look like much was touched, but it could have screwed them up pretty good.

The motor will still be at 10.5:1 after the head swap though. This is with slightly larger chambers in the AFRs and a thinner head gasket. We've already discussed the cam in another thread, and i'll likely be going with something different soon.

96capricemgr

iTrader: (1)

If peak HP was that low an rpm the valvetrain was a mess. Be it wildly poorly adjusted or completely wrong springs or something, even with poorly ported heads choking it the peak HP should have been more than 1000rpm higher

Puck

iTrader: (17)

Wow something was terribly, for lack of a better word, fucked.

Stock cam will peak after 4900 RPM. 847 even with shitty heads will want a lot more. Pic of the graph by any chance? Do you know what springs were in it?

That wreaks of valve float.

bufmatmuslepants

iTrader: (3)

I really don't think you'll get 60 just by swapping the heads, what were the old springs and are you reusing them on the new heads? Post pics of the old heads' port job, and of the graph. An 847 in a stock longblock should peak around 6600 at around 360rwhp, the fact you were 1500rpm low and 30hp shows more issues than a bad port job. I still say **** or get off the pot with the fi option, either add boost now or change pistons to up that compression ratio while you have it apart. That 847 is fine for a 383 with good heads, but maybe go to a 1.7in/1.6 ex rocker ratio.

Quazz

iTrader: (1)

I'm going off of memory here, just to clarify. I'm not sure it peaked at 4900..... I remember the HP and torque specs. If I remember correctly, the springs were specc'd to the cam, and at the installed height, they had something a bit over 400lbs open pressure, and had room to play with coil bind. I DO know that the valvetrain was correctly set up. A 5 angle valve job was also done at the time. I don't have pics of the graph... I MIGHT have a pic of the previous dyno session somewhere, before the rebuild and converter. We moved recently, and I was lucky to find my build paperwork from the motor lol.

Oh, and I do have decent 1.6 RR on the car already. The new springs in the AFR heads are trickflow...... I can't remember the specs offhand. I'll post them tonite when I get back home. So to answer the question, no I'm not using the same springs in the AFR heads. Just the roller rockers. The same person who built my motor milled an assemble'd the heads. He's mostly a ford guy, but has a lot of experience with LT and LS motors as well.

NewOrleansLT1

The tune could be off... Or the heads... Or the valve springs... Or all three...

1toofastlt1

iTrader: (4)

Does any one offer a big head that has a 48cc combustion chamber? If so that would help a lot.