One more about 383 build, but I need a final check
10-23-2017, 06:43 PM
#1
One more about 383 build, but I need a final check
Hi, there are many 383 related threads, but I don`t want to hijack somebody`s with my questions.
I have working 1980 stock C3, and initially wanted just a small/light refresh of the engine, but as it usually goes, I realized that only complete rebuild does make sense. And if complete rebuild than 383 is a logical option. Long tube Hooker headers are already mounted.
I am from Europe and in my region there are people who can build the engines but not SBC 383. So I have to prepare the configuration myself, provide the parts and tell them what to do.
I have no experience with this, so I have read D.Vizards book and the most of the related threads here in the forum, I have tried to do my homework and still have some questions.
I would be grateful if you can help with the final check before I start shopping.
I would like to have street performance engine, no strip, that will never see 6000 rpm, focusing on low to mid range torque. The target would be in the range of 450-500 HP/lbs. Hydraulic roller cam.
Bottom end:
- I would go for Scat rotating assembly, 6" rods, hyper eutectic flat top pistons (7cc), internally balanced, deck clearance 0.02
Question: can this balanced rotating assembly be used out-of-the box as is, without checking balance? The difference between balanced and unbalanced is ~300$ (200 + 100 for shipment, duties,..). If it needs to be checked than it would make more sense to buy unbalanced.
Top end:
- Cam
I would like to use stock converter (recently rebuilt 350). According to the cam vendors info appropriate cam would be i.e. Lunati voodoo 270/278 (219/227 @0.5, 112/106) or Compcam XR270HR (218/224 @0.5 110/106) or maybe XR276HR (224/230 @0.5 110/106)
Question 1: Are these cams ok for my config?
Question 2: What about i.e. marine cams XM270HR (218/224 @0.5 112/110) and XM276HR (224/230 @0.5 112/110). They have the same duration but bigger LSA, so less overlap, but closing later what lowers dynamic compression and moves power/torque band to higher rpms.
- Heads
With 0.02 deck clearance I will need ~0.02 gaskets. I will go for some aftermarket heads i.e. Profiler/Jegs (it seems Jegs is discontinuing them) or Promaxx. When I put all the info in the CR calculators, using small of the above mentioned cams, with 64cc heads I got SCR 10.86 and DCR 8.92. With 72cc heads they are SCR 9.96 and DCR 8.2. I understand that the heads size is not the only parameter that influences detonations but still need some indication. Here we have 95 and 100 RON gas (equivalent to 91 and 95+ in USA).
Question 1: What would be the safe head size for my config, 64 or 72 /70, with an option that I use only 100 RON (95.75 USA) gas? I would not like to go with the bigger cam, since it would not fit with my stock converter. Is it better to go with the marine cams since closing later (i.e. 64cc heads with XM276HR closing at 68 deg, the DCR is 8.45)?
Question 2: I am looking into 195cc intake heads. But if I get a good deal on 180-185 or even 200, would it be also ok? I plan to have 1.6 rockers.
- Intake manifold
I am going to keep my Q-jet. I will take one of the Edelbrocks - either 2601 Performer Air Gap or 7104 Performer RPM QJET - still to be decided. Please recommend.
Thank you in advance.
Corto
I have working 1980 stock C3, and initially wanted just a small/light refresh of the engine, but as it usually goes, I realized that only complete rebuild does make sense. And if complete rebuild than 383 is a logical option. Long tube Hooker headers are already mounted.
I am from Europe and in my region there are people who can build the engines but not SBC 383. So I have to prepare the configuration myself, provide the parts and tell them what to do.
I have no experience with this, so I have read D.Vizards book and the most of the related threads here in the forum, I have tried to do my homework and still have some questions.
I would be grateful if you can help with the final check before I start shopping.
I would like to have street performance engine, no strip, that will never see 6000 rpm, focusing on low to mid range torque. The target would be in the range of 450-500 HP/lbs. Hydraulic roller cam.
Bottom end:
- I would go for Scat rotating assembly, 6" rods, hyper eutectic flat top pistons (7cc), internally balanced, deck clearance 0.02
Question: can this balanced rotating assembly be used out-of-the box as is, without checking balance? The difference between balanced and unbalanced is ~300$ (200 + 100 for shipment, duties,..). If it needs to be checked than it would make more sense to buy unbalanced.
Top end:
- Cam
I would like to use stock converter (recently rebuilt 350). According to the cam vendors info appropriate cam would be i.e. Lunati voodoo 270/278 (219/227 @0.5, 112/106) or Compcam XR270HR (218/224 @0.5 110/106) or maybe XR276HR (224/230 @0.5 110/106)
Question 1: Are these cams ok for my config?
Question 2: What about i.e. marine cams XM270HR (218/224 @0.5 112/110) and XM276HR (224/230 @0.5 112/110). They have the same duration but bigger LSA, so less overlap, but closing later what lowers dynamic compression and moves power/torque band to higher rpms.
- Heads
With 0.02 deck clearance I will need ~0.02 gaskets. I will go for some aftermarket heads i.e. Profiler/Jegs (it seems Jegs is discontinuing them) or Promaxx. When I put all the info in the CR calculators, using small of the above mentioned cams, with 64cc heads I got SCR 10.86 and DCR 8.92. With 72cc heads they are SCR 9.96 and DCR 8.2. I understand that the heads size is not the only parameter that influences detonations but still need some indication. Here we have 95 and 100 RON gas (equivalent to 91 and 95+ in USA).
Question 1: What would be the safe head size for my config, 64 or 72 /70, with an option that I use only 100 RON (95.75 USA) gas? I would not like to go with the bigger cam, since it would not fit with my stock converter. Is it better to go with the marine cams since closing later (i.e. 64cc heads with XM276HR closing at 68 deg, the DCR is 8.45)?
Question 2: I am looking into 195cc intake heads. But if I get a good deal on 180-185 or even 200, would it be also ok? I plan to have 1.6 rockers.
- Intake manifold
I am going to keep my Q-jet. I will take one of the Edelbrocks - either 2601 Performer Air Gap or 7104 Performer RPM QJET - still to be decided. Please recommend.
Thank you in advance.
Corto
Last edited by Corto; 10-23-2017 at 06:48 PM.
10-23-2017, 08:09 PM
#2
Pro
I ran a similar 383 a while back - some things I would do a little different now, but here is what I had:
[LIST][*]Gen 1 4-bolt main block[*]Scat internally balanced rotating assembly w/6" rods. [*]I also used Hyper pistons - My view is that these are OK at your proposed power level, but I personally wouldn't go any higher or do any power adders with them.[*]Heads - I used AFR 195 Eliminators out of the box. I love these heads, and IMO are perfect for a 383.[*] Cam - I ran a Comp XR270HR[*]Intake - Ran both Edelbrock 7501 air gap and a 7401: both worked well. [LIST]
To (partially) respond to some of your questions, have your machine shop check/adjust balance. Don't assume its right, best to have it checked (assuming its in the budget).
Heads - Get the best heads you can afford. Profilers are good, but also look around for used Dart, AFR, etc. They come up now and then on the forum or craigslist. Even smaller heads like AFR 180s would make a torquey and IMO a fun to drive 383.
Intake - I think the smaller Air gap you suggest would be OK with smaller heads. larger heads like AFR 195s can also work with a single plane, but my power range suited the 2 duel planes I mentioned earlier.
Cam selection - I tend to prefer milder cams for drivability. My cam was relatively mild cam even for a 383 with AFR heads; If I did this again, I would probably go a little bigger and look for something around at least 225 to 230 degrees at .050. The smallest I would go with is the Comp 276 cam. Also - Choose your heads first, then look for a cam profile that works best with the heads (For instance, AFR heads tend to like single-pattern cams; other heads will like a split. Talk to a cam specialist like Chris Straub to get more info on that).
You will get different opinions - Take your time and do research on what you see on here. Hope this helps.
[LIST][*]Gen 1 4-bolt main block[*]Scat internally balanced rotating assembly w/6" rods. [*]I also used Hyper pistons - My view is that these are OK at your proposed power level, but I personally wouldn't go any higher or do any power adders with them.[*]Heads - I used AFR 195 Eliminators out of the box. I love these heads, and IMO are perfect for a 383.[*] Cam - I ran a Comp XR270HR[*]Intake - Ran both Edelbrock 7501 air gap and a 7401: both worked well. [LIST]
To (partially) respond to some of your questions, have your machine shop check/adjust balance. Don't assume its right, best to have it checked (assuming its in the budget).
Heads - Get the best heads you can afford. Profilers are good, but also look around for used Dart, AFR, etc. They come up now and then on the forum or craigslist. Even smaller heads like AFR 180s would make a torquey and IMO a fun to drive 383.
Intake - I think the smaller Air gap you suggest would be OK with smaller heads. larger heads like AFR 195s can also work with a single plane, but my power range suited the 2 duel planes I mentioned earlier.
Cam selection - I tend to prefer milder cams for drivability. My cam was relatively mild cam even for a 383 with AFR heads; If I did this again, I would probably go a little bigger and look for something around at least 225 to 230 degrees at .050. The smallest I would go with is the Comp 276 cam. Also - Choose your heads first, then look for a cam profile that works best with the heads (For instance, AFR heads tend to like single-pattern cams; other heads will like a split. Talk to a cam specialist like Chris Straub to get more info on that).
You will get different opinions - Take your time and do research on what you see on here. Hope this helps.
Last edited by cooper9811; 10-24-2017 at 01:28 PM.
10-24-2017, 01:25 PM
#4
Drifting
You say you want to use the stock converter and I am guessing stock gear of 308? That will load up the engine at low speed wont this increase the chance of knock with the compression looking to be around 10+:1? Forged get my vote as they can handle any knock better than hypers (broken piston skirt caused my engine to lose oil pressure). If keeping the stock converter for sure the smaller cam would work better.
10-24-2017, 01:28 PM
#5
Pro
I used the smaller (either 64 or 65cc) chambers and had roughly 10:1 compression ratio. I also ran a 2500 stall with the 270 cam, and had 3.55:1 rear gears back then.
Last edited by cooper9811; 10-24-2017 at 01:29 PM.
10-24-2017, 01:59 PM
#6
Burning Brakes
10-24-2017, 02:44 PM
#7
You say you want to use the stock converter and I am guessing stock gear of 308? That will load up the engine at low speed wont this increase the chance of knock with the compression looking to be around 10+:1? Forged get my vote as they can handle any knock better than hypers (broken piston skirt caused my engine to lose oil pressure). If keeping the stock converter for sure the smaller cam would work better.
Pistons... as far as I have learned here hypers are still ok for this level of HP/torque.
Although, the forged pistons cost 100$ more, so they are an option as well if we conclude they are needed.
Not sure yet which gasket exactly, but it should be ~0.02 to have recommended piston-to-head clearance of ~0.04 .
Last edited by Corto; 10-24-2017 at 02:50 PM.