Mortorq

Greetings SkinnyZ, Sofa, Fast355, et al,
Would like to replace the factory hyd roller in my '88 IROC T5 3:08 posi vert. The 305 shortblock is still great. Would like to stay small with the cam to retain some semblance of low end torque.
Will be carbureted using a #4776 600 cam mech sec Holley & a standard Performer Vortec intake with some added 305 Vortec #520(#059) 58cc reconditioned heads. (Cut down valve guides, beehive springs, etc)
Presently has Hooker 2055's with a complete Aerochamber exhaust.

The Comp XE 252's & XE 258's are not available due to all these new supply chain issues. All of a sudden we're living in Venezuala or something.

Competition Products has this wacky oddball cam in stock, an Elgin #E1231P 202/202, adv 275/275, .457"/.457" with a wacky 104 LSA. RV usage, 1500-400 RPM.
Compared to the factory TBI cam, there's 23 degrees more intake & 8 degrees more exhausting duration @ .050", & 5 degrees tighter LSA.
Thank you for your ideas.

Orr89RocZ

iTrader: (20)

That would be similar to the LB9 cam except a super tight lsa. It would work but its a retrofit hyd roller. Youd need to do different retainer method, like a timing cover with button I guess. It be nicer/easier to keep the oem retainer plate method as it works well

https://www.competitionproducts.com/...nfo/ELGE1136P/

elgin has this. Its a touch bigger tho 210/215. But its oem roller

DynoDave43

iTrader: (11)

Strikes me as an odd cam, or at least out of the ordinary. I don't think I'd be comfortable with a cam that runs out of breath at 4k, when your adding Vortec heads that should be good to 5500rpm??? Seems like quite a mismatch.

That cam might be a nice peanut cam replacement in a TBI motor with the swirl port heads that also run out of breath around 4-4500rpm. But that's not your deal.

I hope you keep us updated on your engine build. Not many folks running the 059s. They're a little hard to come by in my experience. I have set that I'll be putting on my L03 in the (I hope) not too distant future. I'd love to hear the story of your build, and how it runs when you're done.

skinny z

Any idea where you final compression ratio will end up?
With decent heads for the CID a wider LSA than 104 would seem to me the way to go. Most shelf grinds are in the 110 range and that I would think would be suitable.
What is the maximum lift you'll be able to accommodate?

Orr89RocZ

iTrader: (20)

did you just recommend wider lsa? Lol

skinny z

What modifications, if any, will you have done to your 059's?
The typical 062 Vortec often have the guides cut down for positive style seals and this opens up options for more lift. Then a beehive type spring for more RPM.
I went so far as to machine mine for screw-in studs and guide plates but if I were to do it again, I'd probably stick with a guided rocker. It's just that much easier to set up. Not to mention the cost savings.

skinny z

Ha ha! Funny Orr. But yeah, for a 305 and decent heads, you know you can spread it out.
My 357 (yeah, believe it or not, the shortblock is in the building!) with modest heads, will likely end up on a 108. Maybe 107 . .
I'll qualify that by saying I haven't decided if I'm building a track first, street car second or the other way around.

Orr89RocZ

iTrader: (20)

i built a track car that i cant really track legally lol and i hate it on the street

skinny z

Understood.
But then again the difference between your twin turbo BBC and my NA SBC, even in "race" trim, is night and day.
My choices will revolve around the cam. More specifically, how aggressive a lobe I'll go with. And the LSA to some extent.
I've always liked driving the Camaro. Cross country trips were part of the repertoire. But these days, that's not as appealing as it once was. So maybe my direction will be more towards the dragstrip that's 20 minutes down the road rather than my hometown that's 2500 miles the other way.
Still streetable but somewhat less so.
As for the OP, that's part of his decision making process too.

Fast355

iTrader: (2)

305/8/1.84 = 20.72. 108 LSA. Then look at your duration, 305 is 38.125 cubes per cylinder. I like a single pattern cam on a 305 with tight LSA. I have found higher average power. Tight LSA and short duration does not mean it will fall on its face at sone rediculous low rpm when the heads flow well for the CID they are feeding. To get the same VE and thus horsepower per cubic inch from a 350 as the 305 with 305 vortecs flowing ~225 cfm the heads on the 350 would have to flow 258 cfm. For a 305 to make peak hp at ~5,500 you will want something around a 220 @ 0.050. If you want peak power at 5,000 about 215 @ 0.050. For longevity I would probably limit a stock cast iron 2 bolt to 5,500 and maybe brief sprints to 6,000. The 305 in my Tahoe shifted at 6,000, made peak power at 5,500 and had a 221 @ 0.050 duration when the 1.6 rockers where included. My LSA was 110 on my setup but I used a cheap flat tappet cam I had laying around. It would have made more torque with a tighter LSA.

skinny z

You make a very valid point regarding the intake valve size.
I was basing my analysis on the 1.94" valve in the 062's.
With the 1.84 valve, the coefficient of discharge is limited. That generally leads to a tighter LSA. (There you go Orr!).
As for torque, some of that will depend on where the IVC lands. Not to mention the static compression ratio.

Fast355

iTrader: (2)

The LSA is a little wider than I would want to run myself but it would be really streetable in a 305 vortec head setup with a carb and a 5spd. I would run it with 787 retainers and Pac1218s. No cutting needed on most vortec heads. 787 retainer usually gives 0.570 or more clearence. Always measure.

https://www.summitracing.com/parts/c...make/chevrolet


FWIW Vortec 305 heads peak at 0.500-0.525 lift where the common Mexico junk 062 peaks at 0.450 and the 305 head outflows the 350 mexican casting. Despite that the mexican 350 head has been used in alot of ~400 hp 350 builds including the Project Humble pie that had the GM LT4 Hotcam in it. Humble pie made 401 hp and 428 tq. A 305 built to the same HP/ TQ per Cubic inch would end up with about 350 hp and 370 tq.

DynoDave43

iTrader: (11)

All good questions. And things I'm thinking over. They are very low hour marine heads. I bought them as-is, and need to have them looked over. No cracks that I could visually see, but before investing time and money in them, I want to make sure they are crack free. I also want to clean out the cooling passages as much as I can (they are a little skanky being from a marine engine). With those things accomplished, I had thought a nice back cut on the factory intake valve and seat, and "maybe" just a touch of material removed from the area right behind the seat. But no real porting or other work of that sort. It's a mild build, and I'm heeding Mr. Vizard's advice about not changing these too much.

I would like some screw in studs, probably done in the manner that this member did it in the linked video below.


It uses these Pioneer threaded studs.

https://www.summitracing.com/parts/PIO-RM348-16

I like being able to do them myself. But that assumes that I'm NOT running guide plates. And you asked about guided rockers. I think this is my preferred path, but....there's always a but....if I'm doing this work, I'd want a 7/16" stud. Now try to find some roller rockers in 7/16" that are self guiding. Not many choices at all. Non guided? 100s of options (well, dozens anyway). 3/8" stud and guided? Lots of options. But not true for self guided 7/16" that I have found. So I'm undecided on all this yet.

And I am hoping to cut the guides down myself for more lift / safety factor, run bee hive or even conical springs and better seals. Would like to avoid cutting the seat, and I think there are good options that don't require that.

I have the heads, some plans, but no work done yet. I had / have a few more parts to acquire first (finally found a Vortec intake I was comfortable with), but we also had a garage fire shortly after buying these, and I've been rebuilding ever since. So this is a project that at the earliest happens the winter of '23/'24, or about 18 months from now.

skinny z

Not sure of the quality but this came up in a quick search.
​​​​​
https://www.summitracing.com/parts/pqx-0235010#overview

Orr89RocZ

iTrader: (20)

for light spring pressure mild hyd rollers 3/8 stud is more than adequate imo

DynoDave43

iTrader: (11)

Yes, those are on the short list. My policy, I want all American speed parts. The reality, the imports are creeping in. I will admit, I have not read any negative comments / reviews of those PRW pieces.

I'm sort of thinking that too. I have a tendency to over think, and over build. But the cam card calls for a fairly mild spring in the scope of things.




If I go 3/8" stud, then these would be on my radar for rocker arms.

https://www.summitracing.com/parts/cca-1617-16

Digging into this a little more today, since this thread got me thinking about it...I called Summit to see if there was a 3/8" equivalent on that Pioneer stud. Turns out, from a rocker point of view, it IS a 3/8" stud. The 7/16" end is only the part that threads into the head.






Mortorq...sorry to take your thread off course, although I hope you find some of this informative.

Mortorq

No worries Dyno,
Appreciate all the info Fast, Skinny, Orr, Dyno.

Fast came up with a Comp Magnum 215/215 @.050”, 500/.500”, 110 LSA option for the little 305.

Would I possibly have a sluggish bottom end with a 3:08 & T5 rear end & that much duration over 205* @ .050”?

skinny z

I have a couple of questions.
What will be your static compression ratio?
What grade of fuel are you comfortable running? Stop to stoplight.
Are you going to degree the cam yourself? Where will your ICL fall?
I see your rear gear is 3.08. What's first gear in the model of T5 you have? 3.35?

skinny z

Torque output is related to compression.
A higher grade of fuel allows for more compression. The cost may even be offset with fuel better economy.
Torque output is also related to the ICL. There's the premium grade fuel question.
3.08 rear gear times a 3.35 first is 10.32. That's not a bad number. It's like a TH350 with 4.10's.
Either cam could conceivably make the same torque at the same RPM depending on how each is dialed in.

dmccain

iTrader: (2)

I've got a stock #049- L98 cam somewhere around here. Good lil cam for mild build. 207in 213 exh. 117LSA , 415 lift I think.

Mortorq

Skinny,
Stock L03 shortblock, the #520 heads have 58 CC chambers like the 187 swirlies that are being replaced.

Would like to keep using 87 fuel, but if not, oh well.

Was going to say it’s an after work pleasure car, but retiring in August anyway lol.
Wasn’t planning on degreeing the cam. 🤫

Ultimately had wanted a single pattern 205* @ .050”, .500” lift, 106*LSA on 100* ICL.
There are no cam blanks to be found, custom AND off the shelf cams seem to be back ordered up the kazoo.

Fast355

iTrader: (2)

I ran a flat top piston 312 with 081 TPI heads and a Melling regrind of the old L82 cam for about a year dragging around my old G20 van. The old L82 cam was a flat tappet 224/224 @ 0.050, 0.450/0.461 lift and on a 114 LSA. Even it still had decent low-speed torque with a 700r4. The cam in the Tahoe was 221/221 @ 0.50 with the 1.6 rockers. In my experience even the 224 @ 0.050 had good low-speed torque and a fairly smooth idle in a 305. I will not hesitate to say that a 215 @ 0.050 would work extremely well. Alot of LG4s got upgraded to the XE256 which is 212/218 @ 0.050 and I really do not recall many people noticing a lack of torque.

skinny z

Ok. Google says the L03 has 9.3-9.5:1 compression. This has to be confirmed for what you're assembling including things like the head gasket you'll use and actually how far the pistons are below the deck.
If regular grade fuel is the target, I understand that having a dynamic compression of 7.8 is workable. That specific number is lifted from an article that focused on a street engine running 87 octane. Aluminum heads though so keep that in mind.
I tend to work with seat to seat duration values for these experiments. It's a true measure of when the cylinder starts building compression. Let's factor out the dynamics of a engine at high RPM for now.
If using your requested 205° @ .050" as a starting point, a non aggressive lobe profile like a COMP Magnum should be about 260° @ .006".
So, 260/260, 205/205, 106 LSA, 100 ICL is roughly what you were looking for.
Using a 9.3 SCR, the DCR with that cam gets you 8.2:1.
FWIW, I had a problem with my Vortecs at that DCR when trying to run a full and proper timing curve. I'll say here that timing trumps compression if a choice has to be made.
If the LSA is closed up to 108 and the ICL is 104, DCR drops a little to 8:1.
You'll notice the ICL is laid back a little as the 100° ICL bumps the running up quite a bit.

Let's go with that.
215° @ .050" translates to about 273° using a High Energy/Magnum profile.
273/273, 215/215, 108 LSA, 104 ICL. DCR is now 7.7:1

That's looking to be a pretty good spec. It's backed up with real world results from Fast and the numbers line up. It'll probably take all the timing it wants for best output before pinging too.
With your T5 first gear, off idle torque shouldn't be an issue. It'll most certainly be night and day over the stocker.

skinny z

I'm going with a Mike Jones cam for the 357. From what I understand he has American made cores in stock and his selection of profiles covers a lot of territory.

http://jonescams.com/hydraulic-roller-tappet/

An example below.



For a 305 and decent heads: 272/272, 216/216, 108/104. 7.7 DCR. Maybe 110 LSA and a 106 ICL.

On the subject of a single pattern vs a split duration, what do you have for an exhaust system? It may be that the engine could use a little help on the exhaust side.

skinny z

Does that spec look right to you? 288 intake. 284 Exhaust. Must be 294 on the exhaust given the 215 @ .050" value.

Fast355

iTrader: (2)

I agree with most points Skinny makes except timing trumps compression. I go for compression over timing. Output will be similar and part throttle efficiency is higher with more compression. Generally the air fuel mixture will burn more quickly at higher compression because it is more dense requiring less timing and this is even more exaggerated at part throttle cruising and idle. What that means is that the spark plug can fire later on the compression stroke to still achieve peak cylinder pressure at ~15° ATDC. Firing later means less negative work on the crank, lower BSFC and improved efficiency.

My dynamic at lower rpm is 9.6:1 and 9:1 at higher rpm. Its a 6" rod 11:1 383. The cam is 271/284 @ 0.06 on a 108 LSA and 106 ICL but the Rhoads lifters knock 20° off that figure when they bleed down at lower rpm. I have verified this statically with a degree wheel. The math also corresponds to this. My IVC is 51.5° when they are bled down. This 383 runs on 91 octane with 31° total timing. Quench is 0.041" and it has aluminum heads. The cooling system also holds it around 185°F.

Rhoads fully bled down
IVC math 251/2 = 125.5 - 106 = 19.5 + 180 = 199.5. 251-199.5 = 51.5

Actual cam profile
IVC math. 271/2 = 135.5 - 106 = 29.5 + 180 = 209.5. 271-209.5 = 61.5

Below are the DCR calculations using Wallace Racing calculator as well as the measured cranking compression test and leak down test values of the actual engine. The cranking compression test was done with an open intake, all plugs removed and a fully charged battery running a stock PWM Vortec starter.

Fast355

iTrader: (2)

The ElgIn specs are correct the lobes have a different profile intake and exhaust wise. I have used that cam and degreed it into a L31 in a 2000 Escalade.

skinny z

Look closely at the 1136. It's exhaust spec is an oddball compared to the listings above and below. Not to mention the advertised vs .050" number.

Fast355

iTrader: (2)

Skinny, the 215 cam I linked is 270 @ 0.006. 110 LSA and 106 ICL. Could probably peg 8:1 on the nose with 4° advanced if low speed torque was more of a priority.

Fast355

iTrader: (2)

I get that but I trust the degree wheel and what I physically measured. It was very close to what they spec with the degree wheel and the intake lobe is definately larger seat to seat. The intake profile is lazier than the exhaust on that cam for reasons I do not understand. I do not know the reason but the Escalade ran very well with it and had a bit of idle thump.

Mortorq

Skinny & Fast,
Is it your considered opinions that the Elgin 1136 would be a good compromise for an off the shelf available roller cam replacement?

I’m presently using Hooker 2055s and a complete AeroChamber exhaust on the stock L03 with deleted A.I.R. pump.

Like I mentioned earlier, waiting in the wings….
Non-computer HEI, standard low rise Performer intake, #4776 600 CFM mechanical secondary Holley, #520 305 Vortec heads, beehive springs, .030” cut valve guide bosses, offset retainers, positive valve seals, Mallory 4309 FPR.
Just looking to help this thing to be a little more responsive.
Thanks

skinny z

Fair enough.
I'll stick with a lower compression ratio just the same.
I've gone the iron headed route and tried the optimize both the static and dynamic compression. The results required a crippled timing curve and efficiency as well as output went out the window. It just wasn't as responsive despite probably having similar peak cylinder pressures.
That said, just enough is just right. You have to find that median.

skinny z

Are we talking about the Elgin 1136 that Orr posted?
It seems we are. However, something in the listing is messed up. With a 106 ICL and a 114 ECL the LSA is 110. Using 288 and 284 on a 110 gets you 66 degrees of overlap. They spec 68 degrees. What gives?

skinny z

I'd like some clarity on the cam specs.
Although Fast has degreed his cam, there is still something skewed with the catalog listing.

If using the catalog specs of 288/284 and the LSA is 110, with a 9.3:1 compression, the DCR works out to 7.15:1.
To me, that's a little wheezy.

skinny z

The cam that Fast linked earlier, the COMP Magnum 270HR, is 270/270, 215/215, 110 LSA and an assumed 106 ICL if installed straight up. You can dial that in to whatever you want.
That would yield a 7.66:1 DCR.
Much better. And very likely to be 87 octane friendly.

That's very close to the custom Jones cam I posted earlier.
If you can't find the Magnum, or are having trouble in general, try him.
You might even go so far as to submit a cam recommendation form from his website. He has a solid reputation and sells quality parts. These days it's unclear where COMP is manufactured since their being bought up a few years back.

BadSS

Not either of those guys, but I've installed a number of cams in 305s back in the day. No question that the 215/215 Comp would be the better pick - especially if they were the same price. However, if I'm reading between the lines, sounds like you would be OK with a just a nice improvement over what you have. If that's the case that 210/215-110 Elgin wouldn't be a bad choice choice at all for you. It would provide plenty of lift for those heads also with 1.6 rockers..

If you go that route, I'd call to confirm but Competition Products is showing it in stock for $270.
https://www.competitionproducts.com/...nfo/ELGE1136P/

skinny z

I won't disagree although I'd like to get the lowdown on that funky duration split.
The Elgin catalog appears to contradict itself but it could something as simple as the way Elgin measures their advertised numbers. .006" lifter rise is the most common I've found and this how I typically compare cams but I've been caught out before. The 006" could also be at the valve. I think Melling measures theirs that way. Or the movement could be.004". That said, it's spelled out the same wherever you can find it for sale so it is what it I suppose.
And as Fast has mentioned, he's degreed one of them and it all lines up.
It's still weird though.
That said, I'll call it the lesser of the two choices this far. I'd venture to say that the long and lazy intake lobe kills some of the bottom end. That's realized in the low DCR. My XR288HR has a 288 advertised duration but the .050" number is 236!

If Mortorq is truly interested in more torque, he might want to take that into consideration.

Fast355

iTrader: (2)

It has been numerous years since I degreed that Elgin but from memory they are advertising at 0.001 lift so lash point to lash point similar to the way GM does. If you look at GMs little 196/206 marine cam it is advertised at 288/308 seat to seat. As for why their calculated overlap is off I am not sure. The same 288/210/0.462 lobe is used in several of their cams and has the same specs in all. Looks to be used as both an intake and exhaust lobe.

If he really wanted some torque he would put some V-Max lifters on that Comp 270. The V-Max lifters would knock that cam down to a ~195/195 @ 0.050 at low rpm.

Fast355

iTrader: (2)

Oops sorry guys, its actually SAE 0.06 specd. So the E1136 is is an older lazy grind much like I remembered. I put the numbers I measured on that cam at numerous lift points into a cam file on Engine Analyzer years ago. It gives up 20+ ft/lbs @ 1,500 rpm compared to the Comp 270 which gives up very little compared to the stock peanut roller cam down low. The Comp 270 advanced to a 102 ICL almost matches the peanut roller at 1,500, betters the stock cam by 2,000 rpm and runs out to 350 hp @ 5,500. Stock peanut roller with 1.6s and 305 Vortecs cranks out 290 hp @ 5,000.

skinny z

Yeah, I saw that lobe profile over several cams. That said, given that the exhaust and intake lobes are measured similarly, the spec itself for the 1136 is just goofy to me. I'm seeing an IVC of 70° ABDC. That's the same as the relatively large XR288HR. That one has 70° of overlap which is significant. The Elgin has 66° . I'm going to say that's a lot for a 305 to handle. Probably too much. This is why I prefer the COMP 270HR. 50° of overlap and an IVC of 61° .
If the OP is looking for torque, that would my choice. There are other grinds too, but between those two, I'm with the 270HR.

The 270 isn't that aggressive a cam and I'd think tuning and idle quality would be next to stock.

skinny z

Bingo!
The loss of low speed torque was the deal breaker for me and that cam. Considering Mortorq is wanting just that, I'm leaning the towards a different spec.
Availability however may be an issue. I waited two months for pistons but my patience I hope will pay off. As it stands right now I've a more durable and lighter shortblock assembly ready to go.

skinny z

That's the great thing that happens in these forums. Discussion. Back and forth. Conclusions.

Fast355

iTrader: (2)

Agreed, those heads flow well enough on a 305 that they really do not need a huge cam to perforn well. I mean they were designed to make reasonable power with a mild cam for trucks, vans and boats. Just going from the stock Vortec tuck intake to the marine intake and from the 191/196 @ 0.050, 0.414/0 428 lift cam on a 111 LSA to the 395' marine cam which is 196/206 @ 0.050, 0.431/0.451 on a 109 LSA increased the power from 230 hp and 280 tq to 260 hp and 308 tq and both net rated with intake/exhaust and accessories. The way a typical dyno pull is done in magazine or Richard Holdener fantasy land (no accessories, electric water pump, open throttle body, long tubes with collector extensions and tuned for peak output) the marine 305 is over 300 hp.

skinny z

I've been nosing around looking for something similar to the 270HR but the pickings are slim.
I'd suggested earlier that Mortorq give a shout to Mike Jones. I'm pretty sure he has American made cores sitting on the shelf and all of his stuff is ground to your spec. Or his if he recommends one for you. A little pricey compared to the Elgin but you'll get what you want.
Eg. 272/272, 216/216, 108/104 for 56 overlap and 60 IVC or 110/106 for 52 overlap and 62 IVC (or whatever you want really). 7.5-7.7 DCR. That's a gentle profile too.

Mortorq

Thanks for all your detailed insight guys. So appreciated.

If I read it correctly, looks like Mike Jones hyd roller cams require his proprietary lifters too.
Don’t really want to sink that much money into a little 305, you know?

The OEM roller Comp Magnum 215 seems to shake out like a reasonable choice to you all?(If it’s actually available)

Or, should I wait till October when OEM cam blanks MIGHT be available for a single pattern 205@ .050” & a 108 LSA that I desired?

skinny z

I think you'll find that the lifter choice is a recommendation. That's to cover his butt in the event that something goes sideways with what someone may have supplied. He's in the top echelon of racing and supplies top teams across the country. He's also a frequent contributor on Speed-Talk. It'll take a call to clarify. I appreciate what you're saying just the same. Valvetrains are expensive.
But I'm not pushing Jones by the way. It's an example. His catalogue and supply appear to very accessible and there's loads of information there.

As for the 270 Magnum, it looks to be best choice so far.
Let's consider your desired cam spec...the .050" number is only part of the story. That same value of 205 can be spread across twenty or more degrees of seat to seat timing spec. Witness the Elgin cam we discussed when compared to a COMP XR288HR. Seat to seat is the same. The .050" numbers are more than twenty degrees in the difference. Two very different cams albeit two different manufacturers. Maybe.
Where did you find that 205 is a number to go after?

skinny z

I've been noodling around with an .050 number of 205 and found a Magnum lobe that's 206 with 252 seat to seat.
Spec would look like: 252/252, 206/206, 108 LSA, 104 ICL. Overlap of 36 degrees and an IVC of 50 ABDC.
Using your 108 LSA and a typical 4 degrees of advance ground in, the DCR hits 8.2. I believe this was touched on earlier and saw that 8.2:1, iron heads and on the street with 87 octane probably wasn't going to happen.
If you could tame the timing curve, it would be plenty torquey.

Mortorq

Skinny
Do you recall the old single pattern FT Crane 274 H06 218/.450”, 106 LSA?

Back at the beginning of this post, actually all I was trying to do was to duplicate WITH a hyd roller, EXCEPT for a few less degrees of duration allowing for the smaller 305.

The above worked on smog 350’s, off idle the chop went away & there was the low rpm snap.

I’m not overthinking this, & really don’t mean to, it’s just that this stuff isn’t available easily any more.

Lazer used to make a “street rod cam” that would do the same thing with short duration, tight LSA, & early torque.

Off idle it smoothed out & was still responsive.

Your mastery of the degree wheel & associated DCR math is impressive.

Fast355

iTrader: (2)

I actually ran that cam in my old 83 G20 van forever and a day ago. Performed well in the factory flat top piston 305 with 53cc 601 heads, performer rpm q-jet intake, 850 cfm q-jet and thorley tri-ys.

The cam in the Tahoe was a Lunati HE 268. 218/218 @ 0.050, 0.457 lift, 110 LSA and advanced to a 102 ICL. I ran it with Rhoads lifters and 1.6 rockers. It had stock 520 casting Vortec heads with 787 retainers and pac1218s.

Fast355

iTrader: (2)

This was with stock GM hardened foot lifters, 1.5 rockers, stock springs and stock 350 manifolds and cats.

I swapped the lifters for Rhoads even used the same cam, 1.6 rockers and upgraded valve springs, long tubes and dual 2.5" to the muffler with high flow thunderbolt cats and single 3" out. The torque came on noticeably earlier with Rhoads lifters although it also had a S10 converter by this point and electric fans.