Anyone ever build an Old School 383?
Im thinking of a 30-30 cammed 383 LT1 head/intake motor

Question would be- what is thr minimum compression that cam or the LT1 cam would like to be happy in a 383 iron head motor?

 

It is more like the max compression. I would warn you that a 30-30 cam is extremely junky when compared to modern solid lifter cams. It would be all show and no go. Back in the day they rated the Lt1 at 375 HP gross which is poor compared to modern 400+ hp 350 ci.

The max compression I would guess trying to use would be sub 10 to be on the safe side

 

I hate to leave any power on the table ,when dumping money into a motor .

 

well - a 406 is a great idea and probably not much more expensive...

as for cams - i'm still not convinced that "modern" cams are an improvement over the original GM designs - WHEN USING STOCK HEADS.

and i'm not willing to give up reliability or valve train noise for a few HP/TORQUE.

not looking for a debate here - but magazine articles are not proof - and no one R&Ds cam design around the 1960's/70s iron heads. If i were using AFR or some trick aluminum head - it would be different - but i want/like old school solid lifters - so i think i'm still gonna go that route - but a LT1 cam, or 30-30 cam in a LT1 headed 10:1 406 would probably be a blast to drive.

 

So, if I'm reading correctly, you don't want to debate the issue, but require convincing that cam and head technology hasn't sat still over the past few decades?

 

i don't need convincing - i will fully admit that head and cam technology has moved forward - but i want to use the old iron heads. Furthermore - i want solid flat tappets - and do not want the noise, maintenance frequency, that is associated with faster ramps/more aggressive profiles.

 

I like the way you think. Old school can be fun. It's the idea of it. It isn't a competition about ET's or gross horsepower. It's a state of mind.

 

I don't think you understand what 30/30 means. It is .030 lash and it just is hard on rockers, push rods, valve tips. it is actually wimpy on lift and duration @.050 and has to use light weight springs to keep from hurting anything.

Modern cams are low lash and run quieter

 

yes exactly - i have owned 4 DZ302 cars -
one of them had a 350 rotating assembly underneath an otherwise DZ302 -

at some point, i put a Comp 292h cam in it and it ran better - but i attribute that partially to the fact that the motor was only about 10.5 to 1 and was not jetted properly for the bigger 30-30 cam.

but most recently, i did a ton of cam swaps in my current 69Z and my 64 L76 car - everything from the LT1 cam, to 30-30 Cam to 140 off road cam, and a handful of others (Lunati, Crower, and one other that escapes me) -

nevertheless - i found that the OE SHP cams were always the best all around performers with the factory Cast Iron Heads - and they were the quietest valve train - and after several hundred miles - always were spot on with lash - where I could tell that the others were showing signs of needing adjustment..

This car - is currently setup as seen in this video - and its an asskicker - for a 302 - but i'm tired of noise - tired of the slow starts -not to mention the fact that this motor (at 12.5:1 is f'n expensive to feed) the car has a wide ratio gear set and 4.56s - if I go to 406 or even 383 - that will change -
i was thinking tko600 - and leaving the 4.56s - but now i'm more thinking i'll just leave the wide ratio muncie and go down to 3.55 - -

for my putting around - and occasional stop light romp - i think more cubes/lower compression will make a ton more sense -

i just don't wanna go through this trouble and find out that i'm too low compression or one of these old cams

here's the Z

 

i know this cam inside and out -
it is easy on parts compared to the new aggressive ramp stuff out there.

thanks

 

OK. Guess I didn't understand the point you were making.

Anyway, given the lower octane available nowadays, you will necessarily have to lower (read, "compromise") your CR as compared to the 11:1 of, say, a 1970 LT1, leaving a noticeable amount of performance on the table across the torque curve.

I've built a few detuned old-school mills in my time, and never been sufficiently satisfied with the performance results. In fact, that's precisely why I'm going with modern heads and cam (SFT) for the 427 BB redux currently on the engine stand for my '78. So, the following advice is from the context of having BTDT...

Despite what you may think of newer aftermarket cams, I'd highly recommend giving consideration to something along the lines of CompCams' Nostalgia Plus N+30-30S with ~10.25:1 max CR, depending on the quality of your local pump gas.

In any event, stick with high quality rocker studs and locks, and you won't have to lash all that often once everything settles in. Hope that's worth $.02

 

yeah i've looked at that cam -
about 3 years ago - my Z dynoed 301 rwhp as a 302 with the 30-30cam, headers, full exhaust. the motor is definitely a firm 11:1 and I could run pump gas all day without overheat or detonation of any kind.

going to 406cubes - i don't think i can get that much squeeze and still run pump gas - but then again, if i did run the 30/30 or LT1 cam - i suspect that adding 50 cubes might help overcome some of the loss of compression if i drop it 1/2 a point?

 

So, in a nutshell, you're basically talking about an LT-1 with a stroker crank. I'm thinking it wouldn't be all that different from an LT-1, except that the extra displacement and stroke would tend to tame the cam a bit. The original LT-1s had 11:1 compression ratio, and they can be driven on pump premium, can't they? I would bet you could get away with 11:1 on your stroker, burning 93 octane gas. You'd have to get some accurate advertised duration numbers and run them through a DCR calculator to get a better idea.

Scott

 

I don't think the displacement has much effect on detonation sensitivity.

Scott

 

really? i know for a fact that i can run an 11 to 1 302 on 93 octane with the 30/30 cam and not detonate.

i don't think the same would be true adding 104 cubes

anyone run a DCR for me?

 

I think a better term for a 30/30 cammed 383 with double hump heads would be a parts bin economy build. And i see your in the mire of all the options for a sbc - combinations are endless. Comp cams 30/30 copy cam & lifters are only 220 bucks - $370 with vlv springs and timing set. Hard to beat that price when even a solid roller & lifters will bust 600 bucks. Stroker cranks under $200. Only set back is the stroker wont pull as many rpm with that cam as the short stroke engines. My self i think that cam was a perfect match for the 302" motor and the 383" stroker needs a tighter lobe separation angle - more like 108 LSA.
But i think anyone can have just as much fun building a parts bin motor and with some careful blueprinting can make good power too.

Sorry i dont do DCR - to many details and something the owner needs to learn for himself. But if u do run the calcs try a few on tighter LSA as most cam companies over their grinds on any LSA for a small fee. And really the way to build a motor is choosing a cam last - to match compression rather than build an entire engine to match a cam.

 

Why not? I'm not arguing with you, I'm actually asking. I don't understand how the extra displacement would have any effect, all else being equal.

Scott

 

adding that many inches will tame that cam down some. i kept my stock L-82 cam advanced 2 degrees and added 1.6 rockers then i added 64 cc chamber 190cc runner aluminum heads which took it to right at 10-1 compression and the difference was remarkable. will i ever change cams? probably , but i would do more headwork. the old cams weren't as lousy as people make out ,but better stuff is available today.

 

so i did a DCR calculation - factoring in 103 as the ATDC closing point - (30-30 cam) -

with a 302, DCR is 5.4:1
with 406, DCR is 5.57:1

honestly, i would have suspected it to be considerably different -

so it sounds like i can probably run a 406 with iron heads at 11 to 1, the 30/30cam and not be detonating on pump gas - as i've done it for years with the 302.

cheers

Aaron

 

.17 is not a huge difference, but it is a difference. How does the extra displacement have any effect? I'm scratching my head over this, can somebody explain it?

Scott