I have a 383 my dad built with a scat stroker kit and hyper H600P .030 flat top pistons with 4 valve reliefs. It has word products SR heads and a small 218/224 110 lobe flat tappet cam. He also had some new scoggin dickey modified vortec heads with spring upgrades and a professional products crosswind dual plane air gap style intake on the shelf for a 355 build (the block is trash now). I was going to put the vortec heads on the 383 with some porting and the crosswind to boost the 383 HP numbers. I'm now looking at collecting the parts and have everything but the head gaskets. Since I don't have the heads off I can't check for it being decked but I can still see the stamped numbers on the front pass side head/block area. I assume it hasn't been decked.

I looked around to see about compression as the pistons are about 7cc and the chambers are 62-64 cc I heard. If the deck isn't blocked and assume .020-.025" I'm looking for good quench but also keeping the engine pump gas friendly (I would rather not have to run 93). I also have a torqstorm supercharger and brackets that I was thinking of putting it on as well so trying to keep compression in mind (and quench) with boost probably about 8psi (made 10psi on a 5.3LS).

You will likely ask... why vortec and aluminum with bigger chambers.... I have all the parts minus the head gaskets so its free!

 

Sounds like some great parts to throw at it and a good bit done already to boost the hp & torque. Interested to see how you put it all together and what your outcome will be. Sounds like it will be nasteeee! Hope you can dyno and show. Any driveline beefup stuff by dad, or planned by you, that will support? Missing the old days of chasing tenths in the quarter as my current one is slated to be a cruiser/turd (if an LT1 is a turd), so love seeing/hearing of such stuff.

 

the car is fully built and currently driving it (today to work). It’s got a 5.3 LS with a stage 1 high lift cam and an LS6 intake and GTO vararam cold air system. Estimated HP is about 350-360 at the crank. Exhaust is 1 7/8” long tubes dual 3” flowmaster 200cel high flow cats into a 3” stainless xpipe and dual 3” out the back to some dynomax super turbos. Trans is a built 700r4 good for about 550hp, dennys driveshaft and a brand new rebuilt 80-82 aluminum rear with 3.73s and stock 15s on 255 cooper master craft tires. I was told the rear can handle about 450hp with an auto which now has abiut 300miles since I got it a month ago so it’s about broken in now.

I pulled the 383 out to do the LS swap and it drives pretty good honestly. The 383 could go back in with the upgrades which I’ve heard will be around 380ish HP due to the tiny cam but should have at least 50ftlbs over the 5.3.

what’s nice about the 5.3 is while it doesn’t have the tq a 383 would have it’s 87 octane and basically bulletproof. Originally I wanted to supercharge it which I got the torqstorm bolted in but the belt hit the upper arm and shock bolt, then the waterneck got in the way. Supercharging the 5.3 is like 600-650hp which is likely too much for the 700r4 and the rebuilt rear and would require 93 pump at minimum. The 383 could be used for another project down the road or it’s going back in the vette with an ACES 650hp TBI EFI kit.

 

I have the 350 (.030) version of the same pistons in my 355 build and I used them with both 64cc iron and 64cc aluminum heads with .015 steel shim gaskets on my non decked block for a better quench no issues and I always ran 89 or better octane with the 10.2:1 compression but I might have been able to get away with 87.
Are you dead set on the small cam? the reason I ask is the specs of the cam matter a lot here. some build more compression and some bleed off more and this dramatically effects your dynamic compression and what you can get away with. This is where dyno software or free online calculators can help.

 

yea, I was waiting for you to reply in my other thread. You ran 89 with the 64cc iron heads too? The calculations I did in the first post pic are with my cam specs. This came would be a tame street cam peaking by like 5500 which I feel is likely all the vortecs would flow too anyways on a 383. To pull the cam means new lifters and all that which I really don’t want to do. 380hp ish and 450+ ftlbs sounds like a decent 383 and if I throw alittle boost at it no need for a bigger cam. Also in order to get into the 10.2:1 range with the 64cc and untouched deck I’m looking at a minimum .040” gasket which puts quench at like 0.065 if you add in a .025 deck and .040 gasket. The .015 would net me almost 11:1.

 

I did run 89 with the iron heads too... my quench was like .039 And yes I understand your dilemma but again the cam shaft choice directly effects dynamic compression and dynamic compression is more important than static when it comes to detonation resistance. Im not telling you to run a .015 shim gasket. but .065 quench is not going to do you any favors with resisting detonation.68cc or even the 76 cc heads your dad installed may be a better fit for lower octane pump gas and boost.

I understand the choice to go with the small cam too... I am going with a fairly mild cam on my 406 build. the desktop dyno software estimates 487hp and 502lbs of torque potentially according to the math which means I wont hit those numbers but Im actually happy to have anything over 400hp and close to 500lbs of torque.
BTW I had the choice to go with those same pistons in my 406 and opted for the KB -18cc D dished pistons instead to avoid this very thing.

 

I understand. I still don't know if a cam swap will provide me with enough cylinder pressure release to help enough with the dynamic compression. So my options are pull the heads and see how far the pistons are in the hole, figure head gasket for .40 quench and then I will have my compression. Has anyone taken a grinder to the pistons to add more dish? lol

I wouldn't have thought the pistons would be such an issue but I've been out of the SBC world for like 15 years so Its a learning curve again. I really don't want to pull the pistons. I did look at the summit brand 4-7 swap cams for a hot sec specifically the 1204 which is the stage 5. I'm trying to keep the lift under the .525 mark as thats what the vortec head SDPC modded heads will accept with the 1.6 guided aluminum roller rockers that I have. Cam kit is like $300 which isn't too bad. I do dislike breaking in flat tappets tho. I guess I'll plug the numbers and see what it looks like dynamic compression wise with that cam.
https://www.summitracing.com/parts/s...make/chevrolet

If the piston is in the hole .025" then here are the compressions for the current cam vs the 1204 with the .015 shim head gasket. Calculated at .006 valve timing.
Comp 12-238-2 262/270 .460/.469 110 lobe - 218/224 @ .050
Intake open 25 BTDC/ closed 57 ABDC
exhaust open 69 BBDC/ closed 21 ATDC
Static compression - 10.86:1
Dynamic compression - 9.2:1

Summit 1204 Stage 5 296/302 .495/.510 @1.5 rocker 108 lobe - 236/242 @ .050
Intake open 43 BTDC/ closed 72 ABDC
exhaust open 82 BBDC/ closed 39 ATDC
Static Compression - 10.86:1
Dynamic Compression - 8.21:1

I'm assuming we use the .006 numbers and the summit 1204 cam gives me almost a full point drop in dynamic compression and with 1.6RR i'm looking at .495/.528 lift which should be the max on those springs. I guess I could also look at the stage 4 cam which is a 228/236 and similar lift but the 68 ABDC brings dynamic compression to 8.49:1.

Thoughts?

 

Ok, might pivot here.

I've been looking at head options to help reduce the static compression. I found Skip white offers an aluminum 68cc chamber 200 cc china casting but USA hardware for about $1k. DART SHP has a 72cc chamber 200cc aluminum head for $600 each or $1200 plus tax. Both could be setup for roller and skip can also due a flat tappet. HFT saves some money over a roller which is about $1k to do a retrofit but then I don't have to worry about the break in and wiping a cam lobe. I've only ever done one flat tappet ever and it was not exactly stress free lol.

So basically $2k-$2300 for a roller setup with aluminum heads. The 68 and 72cc will get me into the high 9:1s or low 10:1s and dynamic with a 1204 summit cam puts me at 7.54 - 8.2:1 depending on what head or cam I go with.

So I wonder what the HP would be for the 383 with a dart SHP 200cc head with 9.9-10.1 compression and a 232/242 .587/.587 110LSA roller cam and a performer intake with a ACES EFI (good for 650hp). If I had to guess it would be in the Mid 400s no?

 

skip white sells the NKB heads which are the same type of castings as the enforcers from china. here a link to them bare https://www.ebay.com/itm/40160193868...Bk9SR-aF3KroZA or these https://www.ebay.com/itm/39212729568...Bk9SR-iF3KroZA They claim the enforcers themselves actually measure a bit bigger than 64cc if I remember right. 65?cc these heads are al dart platinum clones btw.
I did my upgrade to the com retro roller cam for about $500 using these lifters https://www.rockauto.com/en/parts/en...ve+lifter,5548 and build my enforcer type aluminum heads for about $700 for the pair after buying my own hardware and loading them so you do have room in that 2k budget

 

I wouldn't do the bare head but they offer the 68cc version which has a -4cc intake valve. I still don't think it is enough and will probably still need the 72cc DART version. What I like about the NKB is that its dual intake and valve cover mounting. The Darts are like $200-300 more for the extra 4cc and I assume a better head casting. I've heard the cheap ebay aka NKB heads don't really flow much more than the iron vortecs (around the 250cfm mark at .5-.6 lift) which is like 10-15cc less than a stock untouched vortec. At minimum I would need to perform some port work and I'm gaining 4cc plus .5 of compression safety. From what I've read the AFR also have different valve guides for a smaller 8mm valve vs the 11/32 standard SBC that everyone else sells. That alone was worth something like 10-15cfm on a flow bench plus the added benefits of the lighter valve. AFRs spec out at the correct 64cc but the ebay style are more like 65cc correct. Its very enticing to get the heads bare to build but I've also read that getting the correct valve height to get them all even is a PITA. for the $250 its nice to have SKIP build them. Something about needing two different valve heights due to casting/machining. Then If I get them I can hog them out but at least all the hard work was done in getting all the parts.

Good find on the rollers... I can't believe everyone sells them for $600!!! Standard rollers are like $200-300 and all these have are a link bar. It looks like just about everyone is out of stock on them.

I'm looking at the overall costs and the benefits. Seems like $2k ish (heads and roller retro) for transplanting a 400ish hp 383 and a bunch of work to fab the new header to existing exhaust and then all the accessories and stuff. So costs are probably closer to $2500-3k. I have a balancer leak on the 5.3 so I will likely pull the timing cover (cheap 2 piece) and put on a used stock replacement and a new balancer seal. Since I'm pulling the timing cover Cam Access is pretty good if I wanted to step it up to a decent stage 2 (i built this with a high lift stage 1 due to the 2.87 rear gear and a torqstorm) so I could get some more peak power. my Stock style 12" 1700-2000 stall converter is limited to like 400-450hp I believe so that might need to get replaced and might increase the stall to 2400-2800. Then I thought.... leave the engine alone after the timing cover replacement and then slap on a single 76/65 or 78/75 turbo and get the best of both worlds. I'm still looking at a very expensive $600+ converter but if I limit boost to less than say 6lbs I should be under that 550hp which is at the crank. The rebuilt 3.73 rear gear should be fine for 450hp on an auto on the street. I have the turbo and basically setup for boost already and even have some block hugger headers to fab it all up. I like the low end driveability with the 209/217 summit cam and I can seriously lock up the converter at 40mph and lug this thing at 1100rpms. A turbo would take care of the top end but I would need to fab it all up and see what I can get to fit. On the turbo I'm looking at probably $500 or so in exhaust parts maybe $750 max if I need to get a cheap A2W to fit down low behind the front pass wheel. I already have IC pumps and some A2W plus lots of intake tubing and couplers, Holley Term X and can put my 2.5bar MAP in it and it will run. I also have the torqstorm supercharger but getting that to fit with the upper control arms will not be easy and clear the stock hood.

I know its annoying lol but the car drives good as is... but adding some power say at least another 50-75hp up top would be nice and equal tq. The issue is my other car is a 87 firebird with a single turbo 5.3 (stage 2 cam and a billet 70/70) which makes 650+hp and its a monster on the street. Then I get into the vette and it feels slow.