'86 350

After fooling with turbo'd Volvos for a few years, i'm trying to get my Camaro back on the road this Christmas break while i'm back from school. The old 355 spun a bearing about 3 years back, and of course what started out as a simple engine swap turned into a much bigger job (rear-end, suspension, etc). Then I got distracted by boosted swedish bricks. Waiting to go into the car right now is a very mild (2 bolt) 406. Stock internals, stock heads, mild cam (made for like a 3,200 stall, I don't have the specs in front of me). Up top i'm running a Performer manifold with a 650cfm 4150 and a proform baseplate, I can't remember why I bought the baseplate.

I'm thinking about picking up a decent set of heads before I even put it all (back) together, are there any (cheapish) recommendations? From what I've read, the heads from that era seem to be garbage, are the cast iron Summit heads any better? What about the Dart SHP aluminum or Dart Iron Eagle heads? Would I want a 180cc intake runner or a 200cc intake runner? Any cam suggestions to go along with this? The car is a manual transmission.

Also, right now i've got the open 1" carb spacer mounted from the old 355, I run that because of clearance issues with a vacuum port near the back of the manifold. I've been out of the game for a little while, but I thought I recalled that the open spacers gave a little more power up top (similar to a single plane manifold I guess), while the 4 hole spacers gave a little more down low. I'm guessing I want to probably switch to the 4 hole since I don't see myself spinning this motor much past 6,000rpm on the stock internals, huh?

-Thanks, Brandon

1gary

Morning Brandon.With today's gas you need to figure out your Static Compression ratio.The choice of which combustion chamber cc means alot.So which piston you used(flat top or dished and what cc it is)if the block was decked,what rod length,what stroke,are factors in the scr.Here is a simple formula to get you started:


http://www.csgnetwork.com/automotiveconverters.html

Click on the engine compression ratio calculator tab.

Compressed head gaskets....use .040 or if you know what it is them plug in that value.

The scr dictates much about parts choices.So you want to plug into the formula different cc chamber sizes.The intake runner sizes you can tailor somewhat where the torque curve comes in where less is in fact more at a cost of top end HP.

cuisinartvette

SHP200s are fairly decent, wouldnt put theri 180s on a motorhome, numbers are horrible

Forget the spacer for now thats just a tuning aid. Play with that once its running tuned and youre looking for a little more.

Figure your cam compression etc first before you buy heads.

'86 350

I didn't build the engine, but here's all the information I can gather on it.

The bore is 4.155" (.030" overbore), and the stroke is stock at 3.75". Rod length is also stock at 5.565". The block is not decked. The pistons are flat topped, I don't know the rest of the info on them, but here is the number on top of them: HP400P 030.

I was planning on choosing heads/cam at the same time hopefully, I'm hoping to maximize the stock 400 bottom end (albeit rebuilt) which as far as I'm aware isn't made to really rev in stock form.

1gary

So realistically we are talking about a .030 over smog engine.Right??.

'86 350

Precisely, the main reason i'm hunting for heads and a cam in the first place. There's a chance I might grab the set of camel humps that are in the market place and have the steam holes drilled (anyone know the rough cost of that at a machine shop?), but i'm undecided for right now.

1gary

My thought is your kind of in a mixed bag.Because of the larger C.I. engine it is more excepting of a wilder cam,but without the SCR and better bottom end........it wouldn't work well.And before I forget,whatever heads you use,you have to drill them out for the steam holes.Was this engine run before??.How does the bores look??.Any chance you would want to do a do over with a quick torque plate hone,fresh rings,bearings,and then deck the block??.You know it wouldn't hurt to straight edge the deck.These 400's do move around.I guess what I am suggesting is before you invest more money,to confirm what you have and take the time to get a decent SCR.

If not,cam it very conservatively like 1500 to 5000.A Iron Eagle head might work well which is closer to the intake runner given the size of the engine than any stock head would.

Orr89RocZ

iTrader: (20)

flat tops with 2 valve relief typically give around 11.5 to 1 comp in a 400 with 64cc heads, depending on gasket. Not decked means pistons in the hole maybe .025". Gasket size i'd keep it around .028" and no more. That should give near 11.3 to 1.

To get that all to live on 93 pump, you'll need to cam it up and keep chambers cool with a few steps colder spark plug. Watch your timing. Definately need aluminum heads.

Those stock parts dont necessarily jive well with high compression/big cam/big heads.

If you can get a 74cc head or something similar to drop compression, I'd do so. Figure around 10.3 to 1 or lower for iron heads but with aluminum, 10 is a great street driving compression rato with milder cams.


DART SHP 200cc look like a great bang for the buck head in aluminum. IMO, sub 6000 rpm with a 400" motor, 195-200 cc heads. Above that, 210-220's. Well over 6500, 220-245's general recommendation.

1gary

Orr with the stock rods alone,he is .010 down in the hole over a 5.7 rod.Then a stock deck..............well even with 64 cc heads,I question that ratio.Maybe you could show the math??.

I looked again and the stock 400's where 8.5's.76-64=12cc's.I question if your going to pick up that many points with only 12cc's.

Orr89RocZ

iTrader: (20)

I was under the impression that the 400 even with stock rods had total rotating height of 9" just like any other sbc. Thats crank centerline + rod length + piston comp height. Block is usually 9.025" tall on deck height if undecked...

If its any lower, then comp will be down further. I just assumed 3.75" stroke, 4.155" bore, 4.200" gasket, .053" of piston to cylinder head (.025" in hole + .028" gasket), -5cc of valve relief commonly found on flat tops (this can vary), and 64cc chambers on heads.

If the block was bored and rebuilt, theres no reason NOT to have the block decked alittle, especially if the pistons are down in the hole that far... atleast resurface the block for best cylinder headgasket seal.

'86 350

The engine was run before. I bought it off a member here quite a while back and had it shipped to me. It has almost zero run time, none of that being in a car. I don't have proof of that, but judging by the look of everything, I believe him. In addition I saw receipts for parts that are dated only a short time before I bought the engine off of him. I have run a straight edge on the deck, that checks out great. I suppose the block could be decked, I don't know. I coming from a world of different engines, I wasn't aware that decking the block on these things was a standard practice, that's why I assumed it wasn't. It's very possible it was decked, but when I talked to the seller years ago on the phone he was very detailed about what he did and I don't remember a mention of that. So, I guess the jury is out on that, sorry. What's the standard that people take off when they deck the block? I guess I could figure out what my compression ratio is within a range.

As for my SCR, I'm only one measurement away from figuring out, and that's the "piston dome volume in CCs." Like I said the pistons are flat tops with 4 valve reliefs and the number on them is H400P 030. Anyone know what that measurement would be?


Like I said, outside of the pistons I believe the bottom end is stock. I seem to remember the previous owner/builder saying he threw it together with ARP bolts too, but I'd imagine that's not worth too much. I was just guessing with the 6,000 rpm limit, that's what I've read in my limited experience with these 400 motors. If I can spin it to 6,200 or 6,500 I'd gladly do that. As of now I just want to get the motor in the car though, so the bottom end is staying together the way it is. I'll keep that in mind for the heads though, i'm gonna go search the internet for flow numbers on those Dart SHP 200cc heads.

See my first response about the block being decked. I used the same measurements as you, but I just went off of some Mr. Gasket measurements on Summit. It has a 4.19" bore and a .038 compressed thickness.

1gary

On purpose on my 383 build I went on the deck .010 down with 5.7 rods and a 67 cc head ending up with a 9.3sh scr.The two standards are .010 or 0.Really easy to check.Bring one piston to tdc and measure from the deck to the top of the piston.

1gary

One of the things with 400's you kind of have to do is hone with torque plates in place to simulate where the bores are when the heads are mounted.

'86 350

I'll try to measure it tomorrow. What should I be measuring with? Either way it's not a huge difference according to the SCR calculator and assuming -20cc for piston dome volume (no idea if that's right but someone mentioned using -5cc for each valve relief). A block that hasn't been decked would give me a compression ratio of 8.55:1 and a block that has been decked .010" would give me a compression ratio of 8.7:1.

Orr89RocZ

iTrader: (20)

2 valve reliefs are commonly 5-7 cc total. 4 valve may be 7-12 depending

'86 350

Alright thanks for clearing that up. Using that SCR calculator then and entering a value of -7 or -12 for "Piston Dome Volume in CCs" my current SCR with supposedly between 9.1:1 and 9.55:1.

I'm looking harder and harder at heads, both aluminum and iron. I was thinking a nice middle ground to go with until I can fork out the cash for a nice new set of aluminum heads would be the camel hump heads that were for sale in the market place. Assuming a 64cc chamber and running a head gasket of around .039" or so, those would put my compression between 10.2:1 and 10.7:1. Is that too much to expect to be able to run on 93 octane?

Also, like I mentioned this is a stock 2 bolt 400 bottom end with the exception of some .030" over pistons and (searching through old PMs) ARP hardware holding it together. Nothing special obviously. Is 6,000rpm the limit I should set for how high I can spin the motor or would it be safer to go up higher toward 6,200 or 6,500 rpm?

Orr89RocZ

iTrader: (20)

6000 would be a comfortable limit for more durability. Under 550hp and 6000 rpm you can get them to live well enough. You definately can stretch 6500 but its starting to put some stress on the bottom end and main caps.

With good aluminum heads, 10.5 to 1 comp, and a decent cam, you'll have 500hp and keep it under 6200. Very potent motor that should live on the street well.

Problem with using iron heads now and going aluminum later is this....compression compromise. Either you run a large chamber iron head for mid high 9's to 1 and then go with a aluminum head with smaller chamber to boost compression back up into the mid 10's, or you just shave the aluminums down and hope there's enough material left.

If you dont get compression back up into the 10's with aluminum you start to hurt power alittle.

You really cant beat those SHP heads with 200cc runners. Good american made castings with decent components from what I hear. Just match the springs to the cam, but they have some spring packages that will handle most mild flat tappet cams

sofakingdom

iTrader: (1)

Don't know; never paid anybody to do something I can do myself in 5 minutes with a hand drill.



Lay a 400 head gasket on the head. Line it up to the dowel pin holes. Center punch each of the steam holes. Use a 3/16" bit. Drill the 3 on the exh side straight down, and drill the 3 on the int side just barely into the surface straight, then angle toward the exh (center of the head) at about a 30° angle, otherwise it will never hit the water jacket, it will stay inside the bolt boss casting that you can see it's right next to.

Incidentally the heads in the pic are Dart IE 200s. No they're not box-stock.

'86 350

Alright, glad to hear that about those heads then. Basically I'm looking to drop about $1,500 or less on a set of heads and a cam to match. The 500hp figure sounds great, higher than I thought, honestly. Do you (or anyone else) have any recommendations for a flat tappet cam and a set of heads for that budget?

Orr89RocZ

iTrader: (20)

You may beable to get a set of Profiler 210's from Chad Speier Racing heads with a nice custom flat tappet that will work for under or at 1500 bucks.

'86 350

It's looking like it might be a little more than that, but I'm loving the work I've seen of theirs so far.

One more small question, what do you guys think I should run for plugs/gap on this car? Like I said, I have the iron heads right now on it, I'll probably break it in with those and then in a month or two and a few more paychecks I'll be able to slap on a nice set of heads/a cam. I've got some shorty Accel 576S off my old 355 that have only 2,000 miles or so on them, think those would be a decent option?

Orr89RocZ

iTrader: (20)

Pro-Filer has them as cast for 500 each for your application. Could easily try those

http://www.profilerperformance.com/r.../sbc-23-degree

Chad just takes those and finishes the chambers, shortside radius, bowl alittle bit, and valve jobs them/etc. Extra 495 bucks or so.

Plug gap? I always stuck around .035" on higher compression motors with good ignition box. You can try .040 but dont think you would gain anything going wider than that.