Engine builder gurus I have a few SBC technical questions

You may remember my thread about the 383 I'm getting ready to build and hoping to get close to 500HP/500 torque.

I am getting ready to buy all the parts to build my 383 motor. I have some questions
1 if I buy a block already machined with cam bearings and freeze plugs ETC...from Summit or Speedway. The bore is already finished to 4.030 are the piston manufacturers so close that the pistons sized to fit the bore at 4.030 ? So if I went with forged pistons they would be .002- .003 thousandths smaller than hypereutectics?
2 These blocks are the newer roller 1 piece rear seal blocks. Some of the balanced kits say internal/External balance they come with a flex plate but I am going to run a manual trans so would I need to have the flywheel balanced with it or just use the standard 305/350 late style flywheel? Others say internal balance but are still 1 piece rear seal. Or I also notice they make a 1 piece to 2 piece seal adapter to use the 2 piece internal balance crank. Do they work well?Is this a viable option?
3: I can achieve about the same compression ratio by using a dished piston with a 64 cc head or a flat top piston with a 75 cc head which would be better or does it matter? I was thinking I may use the dished with small chambered head in case I wanted to add a blower later I could just swap to a 75 head then to lower the ration for boost. Thanks in advance Mike?

 

1) speaking for myself, I dont like the sound of this at all. Is it sold as honed to finished size? I would hope/assume not, and the end user hones it to size. You assign each piston to a specific bore, and hone that bore accordingly.
2) zero first hand experience with the late blocks, so I wont comment
3) if you are going to get anywhere near your performance goals, you will be running 2.02s or bigger, and will need to lay back the chamber wall around the intake valve to the bore, so you will be picking up somewhere in the area of 3cc-4cc of additional chamber volume. Use the 64's with a flat-top.

 

Every engine I have ever built, not just a hone and re-ring, but a race engine or engine making power, regardless of compression, I have pistons in hand before I bore a cylinder. You have to factor in many things.

After I bore and put the assembly together, the rotating assembly should always be balanced. and of course I blue print......

There will be more to change then just heads if you plan on getting a compression boost from chamber size. Even the cam profile is different.

I would plan on what you want, I wouldnt take it over 10 to 1 for street use. Maybe 9.5 to 1 is better suited. match runners intake/head, and exhaust/ primary tubes accordingly.

I agree with 64 cc and flattops as FG said, adding 2.05 intake valves. but 2.02 will work

 

If you have to ask these questions maybe you shouldn't be building your own high perf engine? Do you really want to take the chance that the bore size is correct for your pistons? How about taking the chance the mail order block has the correct deck height, the main bores are round and on spec and the caps fit tight and there are no cracks?
Find a reputable engine builder who can pick the right parts and make sure everything is correct. To get 500 streetable HP out of a 383 a lot of details have to be right... sure it costs more but I have seen way too many DIY engines come through my shop that ended up costing way more to get right than if they would have just spent the money the first time.

 

Thanks for your concern Ottoman I'm pretty sure I am capable of building my own motor. I have won 2 track championships running motors I built. But I have Zero experience with the new 1 piece seal SBC's. The Block is sold thru Summit it is supposedly finish honed (ready to build) it already has the cam bearings and galley plugs installed how would you be able to clean the grit out if you had to fit the pistons? bTW They are decked to 9.005 and line honed on cam and mains. I don't have a core to start with and I have to drive about an hour to a decent machine shop who is always backed up and busy. (Last year I built a 286 flatty the machine shop only wanted one piston to match to bore size) I asked why not all 8 they said the pistons are machined so good now they just needed to mic up one.

The heads I am planning on running are AFR 195's .

 

" pistons are machined so good now they just needed to mic up one."

A dangerous policy. I always have the pistons in hand when honing. Too many variables, was this a set that had a piston replaced in it? Sometimes sets are broken for another customer and then missing pistons replaced with exact same part no. that is larger/smaller or weighs out different.

Manufacturers tend to make "sets" that are similar sizes. It doesn't take much to screw the system up.

Seal adapters work well. I've sold many and have had no complaints, except for the price.

You will need to take the flywheel and flexplate to a balance shop and they will correct the problem.

You can remove the oil gallery plugs and take the block to a car wash. Blow out all passages and machined/internal surfaces. Quickly dry and/or use WD 40 or similar on machined surfaces. Replace plugs and do normal assembly.

 

Thanks for the replies guys. So are the pistons machined to fit the target bore size minus the recommended piston to wall clearance? A forged piston for a a 4.030 bore would be like 4.027 then?

 

#1 Pistons are typically built with the clearance
#2 When buying new internals ALWAYS balance entire rotating assembly
#3 With a 10cc dish, 75cc head, 0.042 head gasket, 0.023 piston height, you will have 8.95 CR too much for a blower...my $0.02

 

.02 cents
I drive more than an hour to get to a good machine shop and there is no way that I would buy a finished block from anyone and there is no way I would stick a piston in a hole that was not finish honed to fit that particular piston. I have found pistons , from very good companies, that were different sizes. 2 or 3 thou is a lot of/too much clearance with modern pistons.
Porting is a must as well as valves to match the expected flow rates needed to achieve 500 hp.
To build an engine for a blower needs all kinds of different internals. Deep dished forged pistons, total seal rings would be good too, a proper cam designed for the blower and rev range you wish to run. how are the rods, what compression do you want , do you have fuel to feed a 500 hp engine..blown or unblown?
Taking a normally aspirated engine and stuffing a blower on it is not how one would do it..unless of course you want a rattling, detonating, piston burning, head blowing gasket engine that does not make power.
If I were trying to make 500 hp..which is a lot of power..if it is real not brag, then the trip to a really good shop is mandated...and I don't care how many engines you have built.
Other than that sounds like a good idea.
your results may vary.
Good luck.

 

I think that the internal/versus/external balance is if you are using the 383 kit with a aftermarket crank or with an stock 400 crank. If my memory serves my right the internal balance is the one you want so you can run just about any balancer/flywheel/flexplate and not dependant on external componenets to balance. The journal where the rear main seal rides may also be different sizes with a early/late cranks and that is the reason for the adapter on the early block. If you have a choice go with the one peice seal block with roller cam bosses. There may be some useful info in this article

http://www.popularhotrodding.com/en...evrolet/smallblock/0611em_vortec_small_block/

Good on you for building your own engines. Lots of measuring and slow assembly will give you something to be proud of.

 

X2, no way, no how, not a chance in hell would I do it, ESPECIALLY with hypers!!!

 

Thanks, Now that I'm home I can answer better than on my phone. I was finally able to get thru to the tech line, yes the blocks are finished honed @ 4.030 and ready to go. He said they sell a lot of them and have good success with them. They recommend (of course) still checking piston to wall clearance. Which I would do anyway but if they were not right I would still have to have fitted which would mean time off work and probably a few week delay. I am going to run forged pistons, Forged 4340 6" I beam rods (full floating)

These are the heads Im planning on using
http://www.summitracing.com/parts/afr-1034/overview/
They are CNC ported w/2.05 intakes I think they should work well, and should be able to support 500/500 or close to it, with the rest of the components being matched up well (cam intake compression ETC...)


If I go with the Flat tops at +5 cc's and .003 down the hole with 75CC heads Im getting 9.75 If I go with the dished slugs at +16.6 cc's and 64cc heads Im getting 9.71 I am not for sure going to add a blower on to this, its just something I thought if later I wanted to do, with the dished I could swap out to 75 cc heads and drop the compression ratio enough to work. (BTW I have a blown small block now that runs on pump gas at 8.9 compression. I know its tricky but it can be done with a boost referenced timing controller) These heads have heart shaped chambers, If I went with the dished and 64 cc's would there be much of a loss as compared to the Flat tops and 75 cc's Seems like I have read or heard the flat top has better combustion characteristics. Is this true?


The tech guy said the Internal/External balance means I would just have to use the later 1 piece rear seal type flywheel and balancer. (I always thought that was just called external balance?)
Again thanks for the replies and help Mike

EDIT: I had a great Machinst/Friend that used to take care of all this stuff for me, so I always just took the machine work for granted but he was killed in an accident. Now Im left without a machine shop thats neither close or that I trust.

 

OK I was able to find a 4 bolt 1PC RMS roller block that was at a machine shop (same shop that did the machine work on my last Flathead) that a costomer never came back for. I have to pay the bill of 300.00 its still Standard bore and comes with a nice standard crank and rods it will cost about an additional 400 for .030 bore and to zero deck and line hone plus intsall cam bearing/freeze plugs etc... so about the exact same price as the block from Summit and I can try to sell the crank and rods to offset some of the cost. So it might end up even cheaper.

I want to run a mechanical fuel pump but the push rod hole is not drilled all the way through. I have heard of guys just drilling them out the rest of the way is this an issue?

Also any opinions on the flat top/75cc chamber VS dish/64cc chambers is there any real difference Compression ratios would be both about 9.7- 9.8 with the flat tops just a bit more compression.

 

I had a 383 external balanced engine built using all new internals.Everything was balanced and blue printed.I used a new balancer and flywheel.I used a set of power pac heads that were ported and opened up for 2.02 valves.The heads were also shaved and the block decked.I would say the heads are maybe 58cc.I run a tunnel ram with 2 holley 450's.Comp cams extreme energy solid lift cam with .555/.575 lift.I am really impressed with this set up.I don't have any dyno sheets on the engine but it is not lacking power.I drive it on the street.The 4.88 gears make it work on the street.I'm not going to drive it across country but it is fun to drive

 

i would prefer reverse dome piston and 64cc heads
internally balanced means that the flywheel and damper are neutral balanced and all the weight needed is internal (mallory,heavy metal installed in the crank) one pieced flywheel has a smaller bolt circle than the two piece seal crank and if you use it the weight has to be removed if the assembly is internally balanced.

 

Some flat top pistons with a set of Vortec heads and a good cam should get the 383 to 500hp easy. Dont forget to get an Air Gap intake and great carb.

 

flat top pistons and vortec heads will result with too much compression for pump gas

 

bullshit.

 

Let me ‘splain…No, there is too much. Let me sum up. Buttercup is marry’ Humperdinck in a little less than half an hour. So all we have to do is get in, break up the wedding, steal the princess, make our escape… after I kill Count Rugen.

watch out for the book learned ones grapeorfake.

many learn the hard way... I for one, after having thief machine shops,
and (thief's of other peoples equipment after they die,) is nothing but EVEL.

ok I fell off the soap box...

Take your time ( ya ya ya read ) measure and read touch and read.
If I took as much time G L E A N I N G info out of the past 50 years
of hot-rod magazines I too could sound like a KNOWITALL.

I don't have time for all the drama.

good luck


My articulation of how and what to do would take a WALL of TEXT.

I think you have some good experience so far, now, just take it a little further... I may be reading you wrong here ...
I have oh--- 30 years ago felt as if i didn't know what i was doing, so i called around and GOT the answer from several people ... hence
they only CONFIRMED what i had already done( lack of confidence i suppose)... only to find out I was right on the money.

there some real good engine bilders here in the HAMB
goatroper and more ...Traditions Racing here in the HAMB too

let us know how this all turns out.




.

tag for info or subscribed as some say

 

no thats my post ...lol

owner of page 2

 

I ahh, ummm, yea... What was the question??

 

383 blower piston clearance other people doing work for me

ah fooie
<348 ci?was the number of this post

 

best of luck

 

falcongeorge do the math compression comes out at 11:1 a little out of range of pump gas
and twit don't call it bullshit unless you can back up your big mouth

 

You have the right idea using forged pistons. Lost some skirt chunks off the KB hypers running at Norwalk last summer. I'm back together over 3 grand later to fix all the damage caused by a failed retainer clip on the older style Comp lifters. Had to go another .010 on the bores so I guess I now have a 385 Stroker. Used Probes forged this time, nice looking pistons, nice finishing and beefy bosses like the old TRW's. Not dynoed but shoud be around 480-500 hp. Dart Pro1 64cc heads 230/2:08, Eddy Air Gap w/carb shop Holley 750, Comp magnum roller rockers wDart stabilizers, mild Comp .510/520 roller cam, Milodon gear drive, Hookers. Around 11:1 compression, street driven with 93 octane and NOS racing octane boost. '77 010 block, Eagle rotating assembly professionally balanced. Getting ready to install a dual quad 450 setup, new experience for me so hope I can get them synced and tuned properly.
Not a supercharger guru but have run a couple and imho I think going above 8:1 might be a tricky deal to maximize performance safely, but I'd like to hear from someone who's done it successfully. I'd say that heavy breathing heads should help. Anyway, I'm new here so just thought I'd throw you my combo for additional reference. Good luck. Dave

 

Henry J WTF are you talking about ?????

Mcgurk Thanks for your input, if I have to pay for another finish hone, so be it but the pistons were pretty darn close. It wasn't my first choice to buy a pre machined block but thats just how it worked out.

BTW I've had 2 of my racing blocks in the past messed up by local machine shops around here, (1 was ruined) so Im not as afraid of this block as many others might be. As for the blower stuff yes I'm aware of that. I have a blown small block chevy now in another car. Im not planning on a blower on this one I was just thinking if I might try it later i migh t be able to swap to a bigger chamber head to get the compression down.

I now have most of the parts, AFR Eliminator 195 CNC ported heads W/75cc's chambers, Scat balanced rotating assembly: Scat 9000 cast steel crank, 4340 6" I-beam rods with ARP 3/8 cap screw bolts and bushed little ends, forged flat top pistons, all balanced by Scat.
I ended up with the pre machined block, I know its a risk but I have to say it looks like a quality job and Im going to take it to have the bores double checked with a torque plate this week, the pistons all measured out at 4.0265 -4.0268 The spec sheet for the block states bore size is 4.0300-4.0305 (with torque plate) the stroker clearancing looks to be done by CNC. If the block is within spec its supposed to be, the piston to wall clearances will be .0035-.004 thats about right although they could even be a touch looser for a hot street motor and be fine I think the piston manufacture tolerances range from .003 to .008. I want to be about .0035 to .0045 I think. My compression should be about 9.7 according to the piston manufacturer. Im shooting for about .040 quench. Im still undecided on the cam it will be a Hyd Roller probably a custom grind, I talked to both Lunati and Comp they are going to spec out a custom grind with my info and see what it comes out like. but it should be around 240*or so @ .050 and probably 530-550 lift on a 106 IC and 110 LS I bet. Ill keep everybody posted. I appreciate the replies I know this isnt the prefered way with the pre machined block but i didnt see any other choice. I couldnt find a core and the machine shop I was going to use didnt want to clearance the block for the stroker so ontop of all this I'm also building the rest of the car at the same time so bear with me please. Thanks again for everybodys input.

EDIT: BTW the AFR 195 heads are light years better than the vortec heads. I might have the AFRs decked a little if it works out my Compression is too low but as far as I can tell it should come in around 9.7-9.8 Id like to stay under 10. I would rather be a bit low and be able to run a touch more timing than to be too high and have to back timing off and run on 93 all the time.

 

....yw...

 

I was wanting to stay under 10 I'm figuring i should be around 9.8 give or take a bit as i dont know how far down the hole the piston will be yet but a can adjust a little with head gasket if i have to.

BTW I just got back from a local machine shop where I had the pistons mic'ed up. They are all even closer than I had measured them at according to him they had less than .0002 variance. He also said every other time he used these pistons and mic'ed them up he's always found them to be "dead nuts on"

So out of curiosity when you guys are setting these clearances up to such tight tolerances if I were to bring this in to your machine shop with the pistons (short skirt 6" rod forged 4032) how much clearance would I get it back with for a hot street motor,and how much tolerance from cylinder to cylinder?

 

Thought I would post an update:
As far as I can tell all the machine work is actually very good. The pistons all measured out to virtually all the same size and after measuring the cylinders they are all within spec. So they are all between 4.030 and 4.0305 that gives me .0035-.004 piston to wall clearance on all the pistons. The Scat stuff all looked very nice too. The mains all plastigauged just under 0025 the rods were all right at .002. The crank thrust is .006 . The pistons are .011 down the hole the left bank seems a little lower closer to .012. Well so far thats all I have got done on it. But I think the Block from Summit is actually a pretty decent piece. Maybe I just got lucky but it seems to all be in spec and nicely machined and clearanced for the stroker crank.

 

So, would an L-99 crank fit this block???...