aaronz28

thinking of shelving the 302 in my Z and building an old school 383 with SHP parts - (LT1 or 461 heads/ LT1 intake)

i would only be interested in using one of the SHP cams - 097/346/178
but winding, in a larger cube motor like 383 - what is the lowest compression it will be happy with.

i've found that a 302 really sucks with anything below 11to1 - and gets snapper as you increase compression.

My goal is to build a 10to1 383 that will happily live on pump gas.

thoughts?

troutster71

Why not just build a 400? Only so much romance with a '383 stroker'.
Forum member DZAuto can walk you thru it.

And yes, I have built a couple 383's, for others. They run great. 10 to one should be manageable w/ iron heads, all builds are different.

For myself, I would go for a .030 over, 5.7 rod 400, hyd roller cam, and I could make it work with those heads, if I already had them. That comes out about a 406. 406 sounds better than 383, doesn't it?

Hope this helps, Gary

DucatiDon

Im building one now, but with modern roller cam and aluminum heads...search for my build threads here and in the C3 forum.

65air_coupe

Just what I did and I love it! DZAuto provided the encouragement and also sold me a nice set of aluminum heads so I'm running 10.7:1 with 93 octane. Modded the lifter valley for OEM roller lifter components and stuck a XE282 cam in it. Idles at 850 and pulls like a beast. So much fun!

6T5RUSH

aaronz28,

Good to hear you're still around/seeing you posting.

Always enjoyed your views on the Z28 makin' her run you posted way back when.

Looking forward to your posting up on your latest build.



Jim
In God We Trust!

DZAUTO

I'm definitely of the old school generation. Bigger displacement is better and too big is just right!
When the engine choice is for a small block, the SB400 is my top choice. UNFORTUNATELY, good rebuildable SB400 cores are becoming increasingly more scarce---------------------but they are out there.
Two specifics about using a SB400 to replace a 265-283-327-350. FIRST, it is a drip-in, bolt-in swap-----------toooooooooo simple.
Second, a STOCK GM SB400 core can easily be opened up to 420 with essentially no worries. I DO NOT CARE how you shake it out, big cubes translates to greater torque! One of the best advantages with this is that it permits going with a high geared rearend ratio, such as a 3.08. A healthy SB400 has NO PROBLEM turning a 3.08 rear with essentially NO feathering of the clutch. That's a big plus. This keeps hiway rpm's down and in town, the 400 produces plenty of torque that makes stop light to stop light performance great.

Now, with all that said, there is ONE down side (as I see it), which can quickly and easily be fixed with a little ingenuity. If it is desired to retain solid, NO-HOLE valve covers, such as the finned Corvette script covers, then some method of crankcase ventilation must be devised because 1967 was the last year for a block with the vent hole in the rear of the block. GENERALLY, this requires a hole be cut in the intake manifold, in the rear of the block, etc, to permit plumbing for a PCV valve. You GOTTA have air in-air out. So for an air inlet source, an oil filler tube (ala mid-60s) with a fitting for a hose or PCV valve can be used at the front of the intake manifold.

Below is one of my favorite methods of installing a hole in the rear of a manifold for a grommet for the PCV plumbing. BUT, when doing this kind of a modification, IT IS IMPERATIVE TO FABRICATE SOME KIND OF BAFFLE OR SHIELD below the hole to prevent oil from being sucked into the PCV valve.






If a good 400 can not be located, OR, if you're one of believers (AND I AM NOT) that SB400s are prone to over heating, then building a healthy 383 is certainly an excellent alternative. Without question, efficient breating is the key to better performance. So if old style heads (ie 461-462-etc) are the desired choice, there are still plenty of experienced head machinists that can greatly improve their flow (ya, ya, ya, ya, ya, ya, I know, a properly flowed early head = $$$). And last, without question, the ultimate benefit will be gained from going to an early style retro roller cam/lifters for the early blocks.
But with nicely flowed early heads, a roller cam, MAX OF 10:1 compression, a 383-SB400 will be a killer, which as I mentioned, is a direct swap for an early SB.

mikem350

Aaron, one thing to consider is rear gearing. As DZ said a big cube motor does not need as high a gear to give good manners with a stick. No need for OD either.

If your Z has a 3:73 or higher you get my drift

aaronz28

hey gang- thanks for the comments - i also started this thread on the C3 forum to see if anyone had experience stroking a 1970LT1 -

anyhow - i have pretty much decided to go for the 406 or larger SBC -
although I still want it to appear mostly stock -

right now, i have a M22 with the Autogear M22w gear set which is basically the wide ratio spread with 2.56 1st gears -

i also have 456 out back, so those will go - and i'll probably drop back down to 3.23 or so with a 400 -

thanks - will report back when i finish

DZAUTO

One of my 400s is opened up to 420 which is REAL EASY using a stock GM block and cast crank. I specifically emphasize STOCK GM BLOCK, because you CAN go with an aftermarket block (such as World), which is better and stronger. BUUUUUUUUUUUUUUUUT, what you will spend for a BARE aftermarket block will immediately put you into the budget catagory of building a 454! So, to keep the budget reasonable, be sensible with a GM block and you can have a very healthy big cube 400 that is within a reasonable budget.
To open up a GM 400 block to 420 (which in my opinion, is the limit for reasonableness------------although, it's possible to take one to 434), bore the block .030 or .040 and offset grind the rod journals to small journal size. Although, stock 66-67 (they're the better ones) 327 rods can be used, it's best to buy a strong set of aftermarket rods. IF THE BLOCK IS NOT DECKED, then flat top pistons can be used for a 400 with 5.7 rod length and you machinist will need to mill .010-.015 off the top of the pistons.
And YES, 6.0in rods can be used. But I DO NOT like a 6in rod in a DRIVER engine. They're fine for a competition engine. WHY??? Because with a 6in rod, the wrist pin hole is into the oil ring groove (I DO NOT like that!!!), and the piston is real short which increases the tendency of the piston to rock in the cylinder. That's really a non issue and is OK for a race engine or an engine that will see very limited duty, but if the plan is for frequent or ocassional distance driving, I much prefer the shorter 5.7in rods.

troutster71

Please let us know what you did to the lifter valley on the 400 block.
As some may know, or not know, the price difference between OEM roller lifter components and retrofit roller lifter stuff is quite significant!

Also, question for Tom, DZAuto, what is the stock 400 rod length, 5.4? I have forgotten, but for real performance, they need to be changed, as I believe they load the side of the cylinder wall.

On a side note, about 1984 I built a 5.7 rod 406 for my boss and put it in his '81 Malibu station wagon! Dont remember what heads, but it ran pretty good. Mild sleeper.

Tom, now that I have your attention, I'd like to thank you for all your invaluable technical info. I always read all of your input, and appreciate your sharing a lifetime of experience! Thank you.

Enough blathering! Cheers! Gary

DZAUTO

Beginning in 55, ALLLLLLLLL SB rods (except the 400) were 5.7in. The SB400 rods were 5.565in (.135in shorter). The SB400 was built to be a "workhorse" SB engine for big cars. A low rpm, low torque band, 2bl engine (until 75). The shorter the rod, the greater the side loading on the piston. But with a low rpm engine, that was not a significant issue because the 400 was not ever intended to be a hi-perf engine.
But, when built and modified by hotrodders, the rules changed. Definitely, a longer rod was a benefit for street/performance use, thus, building a 400 with the longer 350 rod became VERY common. In the earliest days of building a SB400 with the longer 350 rods and more or less stock dished 400 pistons, the outer portion of the piston around the dished area was milled away (in the biginning, no pistons were made for the SB400 with 5.7 rods). Later, some of the piston manufacturers offered (and still do) 400 pistons for both 5.565 and 5.7 rods. The price per either piston today is basically the same.
When building a SB400 with the longer 350 rods and a flat tapped cam/lifters, a VERY slight modification needs to be done to the 350 rod (if stock Chevy rods are used). A slight bevel (at about 45deg) needs to be ground to the head of the rod bolts which face the camshaft for clearance of the cam lobes (below). This is toooooooooo easy to do at home with a die grinder and a medium sanding disc. Takes about 5-10sec per rod. This is not necessary on many aftermarket rods for the 400.


The reason it is necessary to grind this extra clearance on the head of a 350 rod bolt is because the rod bolts on a 400 rod are shorter and more recessed into the rod than they are on a 350 rod. The comparrison is seen below (400 rod on right).

4 Speed Dave

I have to disagree on the rod length. I built a 383 for my 1998 Chevy Z71 truck with all the OEM injection system. This truck was daily driven, towed my car trailer and snow plowed with. I used a 6.0" rod and had zero issues. No oil burning no problems one bit. The truck saw cold temps, hot temps pretty much everything you could use it for it was. I put 40,000 miles on that motor and then sold the truck to someone who offered me some good money for it.

On the 3.75" stroke applications with 6.0" rods there is a oil ring spacer ring that bridges the gap over the wrist pin so the oil scrapper rings are never overhanging by themselves. I wouldn't hesitate to build another 6.0" rod street motor. My opinion is based on my real life experiences not what magazines say.

DZAUTO

Dave,
NOTHING wrong with your approach to building a 3.75 stroke motor.
But you just have more faith than me.

aaronz28

so.... I found a 406 short block for sale locally - guy wants 2k - its got all good parts - 5.7 rods.

comp is 10.25:1 with 64CC heads -

i have a mildly ported set of 186s and the good ole DZ302/LT1 intake and correct 800cfm holley sitting on the shelf all ready to go -

also have a trio of old solid lifter cams - the 178 LT1 clone from Predator although on a 115LSA, a Blueprint 346 L76/Z28 30-30 cam - and an old Comp 294s - which i believe is 248/248 .525/.525 110 LSA

I'd really like to keep it GM but if that Comp is really gonna be better than i'll do it.

Thoughts?

also - this will be hooked up to a wide ratio muncie. its an auto gear M22w gearset which has the 2.56 1st gear - car currently has 4.56s but i'm already on the lookout for a 3.08-3.55 setup.

Any advice now that this project has some direction?

A

65air_coupe

Many years ago, even before I was considering building a 383 or 406, someone created a PDF with drawings, pictures, parts list, everything that was needed to convert an early non-roller block to one that would use OEM components. About the only caveat other than being skilled with hand tools, is that it requires using V6 lifters because the lifter bore is too short for V8 roller lifters.

Unfortunately the file was lost many disk crashes ago but you might still be able to find it out there. It was on different chevy forums and the name as I remember it was hydro roller cam retro.

Essentially, you make the top surface of the lifter bores flat and add recesses into the adjacent wall so that OEM dogbones will drop over the flats on an OEM roller lifter. You also have to drill and tap 3 holes in the oil passageway in the center of the lifter valley to hold the spider that keeps the dogbones in place. It's really quite easy if you're good with hand tools and since a picture's worth many words, here's mine along with a photo that I saved from the original file.

4 Speed Dave

None of those cams are close to being right with a 3.08-3.55 rear gear car no matter what transmission you have. I had the 294S cam in a 355 that was in my Nova I ran 4.56 gears in it and the car at 3400 lbs ran 11.90 at 114 driven to and from the track. That cam makes power but the heads you have will limit your power production. I had Sportsman II heads that were ported.

With that compression, rear gear and heads, stick with a 230-240 at .050 cam with .500 lift as those heads won't flow much more over .500 anyway and a LS of 108-110. I'd stay away from a LS over 110 anything as you already have 10.25-1 compression no need to make anymore cylinder pressure. I personally would spend the money on a modern higher/steeper ramp lobe profile hyd roller over an older slow ramp long duration design. I sore I'd never post on a cam thread again so I'm done after this post. I am sure Mike M is just waiting in the wings.

4 Speed Dave

Why bother with all that crap? There is no need at all. There are many vendors that sell lifter for this retro fit application. Buy the correct lifters and add a cam button to keep the camshaft from moving forward and you are done. The photos above don't address the cam button. As the newer style OEM hyd roller blocks have a cam thrust plate to keep the camshaft from moving forward.

65air_coupe

Too bad you feel that way. There are opinions, and then there are...well, other opinions. I'm sure I speak for many when we read threads like this even if multiple posters have conflicting opinions, we still learn valuable lessons.

MikeM

[QUOTE=

I am sure Mike M is just waiting in the wings.[/QUOTE]

I am not waiting in the wings. Wouldn't even commented on your point of view except to say that if I was going to use a roller cam and thought I needed it's benefits for whatever reason, I'd start out with a factory engine that was already built for the roller cam and the heads that would compliment it and be many horsepower and $$$$ ahead.

Your advice is like telling a 90 year old man he can outperform a 20 year old simply by buying a little blue pill. Ain't gonna' happen and you know it! Unfortunately many here will think you have the hot set up for a street driver.

As an "amen" use the length rods Chevy spec'd for the 400 or the aftermarket 383 they offer and the typical tire squealer here will be more than satisfied. It's a proven fact their specs work because they had to warranty it. What is your warranty?

4 Speed Dave

Well according to a few old farts I know that little blue pill works wonders. Maybe you should try one.

If you read all the posts here I built a 383 with 6.0" rods in my daily driven truck for over 40,000 miles then sold the truck and the guy I sold it to loved it. And wouldn't you know it, it had a higher ramp cam and hyd roller in it. Gee I wonder how many engines Gm replaced under warranty in the late 60's to early 70's. I must have done something wrong with all the engines I build, it is amazing they work.