Gents,
Considering the Chevy SP350/357 cam for my carb’d stock rotating assembly & block L03.

Found some ‘059 305 58cc Vortec heads, using a #6210 spd bore mech sec Holley, Performer intake, non–computer HEI, Felpro #1094 .015” head gaskets, Hooker 2055’s with Hooker Aero chamber exhaust.

It’s an ‘88 IROC vert with a 5 speed and a tall 3:08 posi rear end.

The Chevy #12677151 cam is a 215’/223’, .473”/.473” with a 108’ LSA.

Would this cam be a little too soft on the bottom end with the above combo do you think?
Thanks.

 

With that gear, yes.

With 3.42 or 3.73, would be MUCH better.

 

That combo should be a strong runner.

 

So, if I’m not changing the rear end to a 3:42 or 3:73, it might be a less responsive car off idle until the car “gets on the cam” as it were, because of the largish(for a 305) 215’/223’ duration & a tighter 108 LSA.

I kind of like the fact that it’s a factory(read reliable)cam, though priced up there.

Not a DD, but maybe really sluggish on surface streets?

 

Exactly.

 

What's the compression ratio on an L03 anyway?
FWIW, I've lived the 3.08 gear life. I drove everywhere in 2nd to keep the RPMs up in case I needed the space in front of the car in the lane beside me.

 

Get the heck out of my way, Grandma!

 

As Rodney D used to say, “Tough crowd!”

 

I don't know if a 108 LSA would work with power brakes or not...

 

That cam pulls plenty of vacuum for power brakes. It will be a strong runner. Intake duration is only 215° @ 0.050 and it is a roller cam.

I have had a 218/218 grind on a 106 LSA in a 305 and it still had vacuum for the brakes and the headlights.

With the 5spd it will be better than an auto. I doubt you even notice a low torque loss to be honest. With the short duration and tight lsa its going to be a fun cam.

Personally I would grab a Cloyes single roller 3 way adjustable timing set for a factory roller cam small block and advance the cam 4°. That cam is 1° retarded from the factory. 4° advance should put it about 3° advance total.

 

Back to my compression ratio question. Any idea?
I was looking for the advertised specs on the cam. Doesn't come up anyplace I've looked.

EDIT: Maybe 270/280? That would be comparable to a Comp Magnum lobe if it is which makes sense for an OEM spec.
If that's a reasonable guess then the overlap plays out to 59 degrees. Same deal as the XR276 I ran for a long time. No trouble with power brakes whatsoever.

 

Thanks for the input skinny, fast, & everybody.
I understand that 10% ethanol gas would be bad for my #6210 Holley carb.
If I decided to change mid stream & try to keep the TBI using a tweaked 46mm & one of tunedperformance chips, would the vacuum with an 8 1/2 :1 305 be adequate with the above cam?
(I know, sorry, more of a TBI forum question)

 

I can address the compression ratio with respect to the cam part of that question.
These values would have to be confirmed before before anything definitive is determined but that said, if you have a static compression ratio of 8.5:1, that cam will kill any thrill you might otherwise get. Dynamic compression falls to less than 7:1 if you take 270/280 as the advertised values for that cam and install it straight up on 108 ICL. Advancing it as suggested by Fast helps a little but the DCR is still only 7.1:1. (I did the calculations based on a 104 ICL).
Getting your SCR to at least 9:1 would help and the cam installed advanced may work out reasonably well. DCR gets to 7.5.

 

Got it. Thank you skinny.

 

E10 is not a problem for your carb.

 

That brings up an interesting story.
It's been beat to death how today's gasoline doesn't "keep" like it did in the old days. I'm understanding how it's the presence of ethanol and its hydrophilic properties that pollutes the fuel and spoils it's shelf life. Around here gasoline has sold as an E10 for decades.
OK. Fair enough.
Now the interesting part. 2006 Chevy Tahoe. 5.3L. Pronounced dead in the water in the summer of 2016. It sat for 4 years untouched until last month, when, with the same fuel in the tank, it was resurrected and drove as if it hadn't missed a beat in all those years of inactivity.
So much for fuel degradation.
Not scientific I know but it is food for thought.

 

LSA means nothing in terms of vacuum, its overlap you need to know.

And that cam comes nowhere near as much overlap as my custom cam in my GTA which has 66° overlap. Idles terribly, but still enough for power brakes.

 

L03 with L30 heads and 305 rebuilder 0.038" thick head gaskets would put the engine around. I would suggest finding a set of MLS or Steel 3.8" bore, 0.016 or 0.020" thick gaskets. Will get it ​​​​​​up closer to 9.5:1.

 

A Felpro 1094 has a 4.1” gasket bore & .015” compressed.
Is there such a thing as a 3.8” gasket bore .015” compressed?

 

Fast,
I know google is our friend, but couldn’t locate a .015” compressed, 3.8” small bore gasket MLS head gasket for L30 heads from any manufacturer so far.

 

Not sure what Fast knows but I've found nothing at .015" in a small bore.
Best I could find:



This isn't to say that a 4.100" bore diameter gasket hasn't ever been installed on a 305.
I'd be more concerned about the deck and head surface finish and if they meet the surface roughness spec for a steel gasket.

 

My block was zero decked, so I used a ProComp 5210 MLS gasket. 4.065 round bore, .041 thick
I don't know if these are available anymore.

 

OK.
We have a readily available 4.100" diameter gasket in the desired thickness. With a 3.736 standard bore that leaves .182" ((4.100-3.765) /2) of crevice around the entire bore. At .015" thick, how much of a detriment is that to performance? If at all.

 

So, in summation, the ubiquitous Felpro #1094 015”, 4.1” gasket bore will suffice with 059 heads on a ‘88 L03 shortblock with its 8.5:1 wouldn’t have too soggy of bottom end response with Chevy’s #SP350/357 215’/223’ @ .050” 108 LSA cam, for weekend use with a T5 & a 3:08 rear end?

Or, am I off?

I bet Sofa was thinking more of a 205’/215’ @ .050” cam for the smaller L03 because of my 3:08’s instead of having 3:73’s.

 

What do you make of this? Especially the little blurb about compression ratio. The notion that the 1988 L03 had only 8.5:1 didn't sit right with me. And I've never seen proof of what the CR actually was.

L03

Years: 1987–95

The L03 produced 170 hp (127 kW) at 4,400 rpm and 255 lb⋅ft (346 N⋅m) of torque at 2,400 rpm in 1993–1995 GM trucks. This engine used the TBI throttle-body fuel injection. It featured "swirl port" heads and served as the base V8 engine in all C/K 1500 Series GMC/Chevrolet Trucks/Vans. (The LB4 4.3L V6 was the standard engine in these models.).

The L03 used hydraulic roller lifters, which allowed it to recover some of the lost horsepower from its factory design, while further increasing efficiency (reduced rotational drag). Despite downfalls in its aspiration restrictions, the L03 had one thing going for it: reliability (87-90 F-bodies that carry the L03 did not use a rev limiter). They used dished pistons with a 9.3:1 to 9.5:1 compression ratio (thanks to the dished pistons, and varying head gasket thicknesses over the years) that left a lot to be desired. The L03 TBI featured a 3.736" bore and 3.48" stroke, the same as its TPI cousin, the LB9. Performance junkies would bore these engines to 3.766" and stroke to 3.75", which brings the engine to 334 c.i. (5.47L). However it is advised not to overbore these blocks more than 30 thousandths, as the cylinder wall thickness is dangerously decreased beyond that point.

Is the 9.3:1 to 9.5:1 a typo?

 

Trying to reverse engineer the 305 with a 8.5:1 CR. It works with a factory deck of .025, an .040" gasket, 58 cc heads and a 12cc dished piston.
A .015" gasket gets you to 9.0:1.

 

I did some digging. Appears GM no longer offers the steel wafer 305 gaskets.

The 305 TBI has a slight dish, but not as much dish volume as a 350. IIRC they are about 10cc dish. The 305 Vortecs usually have a 56cc chamber.

 

edit...scratch what I found. Just remembered you would have to oring the deck or head surface.

 

So, based on what we might have so far:
.015" x 4.100" gasket (the large crevice volume inside the gasket fire ring hopefully is not an issue)
10 cc piston dish
56 cc head
Typical piston .025" down
You get:


Static Compression Ratio

Dynamic Compression Ratio

The DCR was calculated on an assumed advertised duration of 270/280.
There are a lot of assumptions actually and I suggest measuring before proceeding.
That said, if what has been calculated is close, then the 305 might be a decent performer.

 

Skinny, that would be fantastic if that cam & combo would be a halfway decent performer.
Our older metric family SUV can drill my IROC.

I just have to leave existing 305 short block in the car for now.

I sure appreciate your scienced-out mathematical calculations, they’re very encouraging before I dive in with these changes.

The last thing I need is an engine that can’t pull a hat off the top of my head under 3K RPM because I have delusions of grandeur with a 305’s cam swallowing capabilities lol

 

That would be my bad Mortorq. I'd momentarily lost sight of the 305 platform. The AFR heads wouldn't work with the small bore.
But the L30 heads and Vortec base still comprise a decent start to the build (to hell with the 305 naysayers!).
While the cam you've zeroed in on has it's merits, there may be power available with something more akin to the 305. 108 LSA tends to be 350 territory. This may be an opportunity to look at a modern off the shelf grind with a 110 LSA and an IVC to your liking.

 

Download that Pat Kelley DCR calculator here: https://dcr-calculator.software.informer.com/download/

 

Skinny,

Well, never had & probably never will have AFR heads, the AFR’s were never part of my little 305 plan.

Just replacing the 187 swirlies with 059 58cc Vortec heads I presently have, & MAYBE use Chevy’s SP350/357 215°/ 223° @ 050”, .473”/.473”, 108LSA, no. 12677151 cam.
( The rest of the build specs are at the top of the post )

The impression I’m getting is that cam for a 305 with T5 & 3:08 rear gears is just about 10° I & E too big.

 

My go to DCR calculator.

 

I'm thinking that the spec is off for a 305 as well. What I'd like to see is the cam card for that GM part number. But I haven't been able to find that anywhere.
But as a for for instance, there's COMP's XR258HR.
A member here used it a while back. Seems a good fit but this hardly a recommendation. Just a look around.
https://www.thirdgen.org/forums/tpi/...-good-all.html

 

That cam will work great in a 305. I had it in a 350 in a 6,200 lbs van with a 4L85E and 3.73 gears that I towed a 6,000 lbs trailer with. It will be ALOT stronger in the 305 in your car and I loved it in my 350. 4L85E with a 3.73 gear is like having a 700r4/4L60E with a 2.73 gear.

Th 305 I went fast with had a XFI280 cam and around 10:1 compression. Dynamic compression ratio was lower than the cam you are planning to run could ever think about being and it ran its *** off. DCR is only a small piece of the puzzle. You can have a fire breather of an engine even with a low DCR. Its called airflow.

Tighter LSA is going to build cylinder pressure and torque not take away from it. I calculated the numbers a while back using Vizards formula and a stock bore 305 with a 1.84 valve needs a 107 LSA by his formula.

If you are worried about low-end and still want some decent power get a set of Rhoads Lifters. That cam would have stock like idle and low-end and pull like a freight train upstairs with the Vortec heads.

 

We ran the 059 heads on a 350 in an old pickup once because they were free. That truck with a lil K1104Summit cam IIRC, 059 heads, and otherwise stock L05 engine ran very strong. We also ran a 350 in an old Coupe with 081-305 TPI heads and it was surprisingly strong. CR must have been pretty high but they ran well on the street no problems just needed premium gas as best I remember.

 

Which cam? The GM part in question? I'll agree and say it could work well. I think the lift might exceed the Vortec stock capacity though.

As for DCR, sure it's not the answer but it is part of the answer and should always be considered in a NA build.

Getting to the LSA, you bring up a favourite subject. As you're obviously aware (but the OP may not be) Vizard's approach to LSA is based on intake valve size to CID. The more under valved an engine becomes, the tighter the LSA needs to be, all else being equal (I.E. overlap). Tightening the LSA will move the intake to an earlier closing point and that'll build cylinder pressure and enhance the DCR. Do the L30 heads have a 1.84" valve? If so then it's fair to say it's approaching the earlier mentioned under valved territory. 108 is looking like a better fit in that case. Maybe even 107 although I'd like to know which Vizard program you used to arrive at that. I've used his Torque Master program (and got shot down in flames here by the Vizard haters) but has a minimum bore data entry point of 3.80" . I couldn't design a real 305 with it.

EDIT: Just checked the GM cam lift spec. It'll be close as to whether it'll work with the stock configuration. That's not a game changer necessarily but it would require additional work and expense for the OP.

 

I wanted to touch on this specifically because it pertains to the OP but also to a direction I had been thinking about with a 355, COMP's XR288HR and compression less than ideal.
It has to do with a Vizard project that dealt with exactly that scenario. I'l quote from the text at the risk of being sued for copyright infringement.

A short while back, I got involved with a T&L 383 build to test a set of Edelbrock Performer RPM heads and intake while utilizing a COMP Cams 288/293 Extreme Energy hydraulic roller. This, on premium pump gas, cranked out 484 lb-ft and 482 hp, but from T&L it cost $4,596. This combination, however, was more revealing than just peak numbers. The Performer RPM heads have intake ports of 170cc, which are intended to target 350-inch motors rather than 383-inch ones. Theoretically, the combination should produce good results because the higher port velocity (produced by the smaller-than-expected port for a 383) should allow the use of a bigger cam before low-speed output was impacted. That was just the case here. In spite of using a relatively big cam, the engine was up and making great torque just as far down as T&L's SuperFlow dyno would pull it. This result, plus a comment Lloyd made concerning customers who wanted both increased performance and lower fuel bills, caused some new ideas as to where we might go from here. Instead of running on premium fuel, how about mid-grade or even regular fuel? If we used the Edelbrock heads (at an upgrade cost of $325 for a total of $4,207), which were obviously making good torque, and ran at a compression ratio of 9.7:1 instead of 10.5:1, what might we be giving up?

OK, out comes the calculator, and I determine, all other things being equal, that within the expected power range, the lower compression will cost 6 lb-ft and 6 hp. I figure we can live with this, especially as there is a little room to maneuver to redeem at least the low- and mid-range torque.

Normally, for a 10.5:1 compression stroker like we started with, a set of heads with intake runners between 190 and 200cc would be used to make the best mid-range to top-end output. But by utilizing a smaller runner of about 170cc, we can reasonably expect that some, or all, of the low-speed torque that might have been given up with a lower compression ratio could be regained. This means our slightly lower compression engine would drive on the street just as if it were equipped with bigger port heads and more compression.

This same situation might be applied to Motorq's 305. But the jury, I find, is still out as to whether this is a reasonable path to pursue.

So Fast, what do you think about that?

 

Not sure what the 059 intake runner volume is on those heads.

 

.

 

Here's a screenshot from Crankshaft Coalition and their description of the 059 heads.

 

Here's a screenshot from Crankshaft Coalition and their description of the 059 heads.
(Tried to post this earlier but the images weren't very good hence the blank post above)

 

Skinny,
Thanks for that detailed info on the 059/520 heads.
165cc with a .500” cam should help the little 305 breathe with those heads and Chevy’s 12677151 cam, assuming corrections are made for that kind of valve lift in those 059 heads.

 

Pay attention to the lift and yes, you could get some decent results.
As an aside to that, there's the 108 LSA and the idea that it's too tight for 305 CID. But with the smaller intake valve and lesser port flow of the 059 as compared to the 062 Vortec, you tend to fall into Vizard's approach about an engine that's under-valved requiring a tighter LSA to help it breathe. You just may have slotted yourself into that thinking and the 305 will respond in kind.
Good luck. And post back when you get it completed.

 

skinny,
Thanks, I’ll post back when done.

 

Subscribed, as I recently picked up a set of 059 heads for my L03. I have a much milder cam with 112LSA selected though.

 

way to soft consider going to 1700 cam around that number not exactly 1700 I would go between 1100 and 17

 

I don’t know if you can but try to see if you can put a summit 1787 cam in it. That’s what I would do

 

I think you guys are talking about some newer type of engines so ignore my comment in this one