[GS470]

I'm hoping to do some upgrades and I'm looking to this group for a reality check. My goal is over 600HP on pump gas and I'm hoping the right head/cam swap will get me there (to control costs, I'm hoping to keep as much of the rest as possible).

This is the current setup in my LeMans. The engine was built by Dave at SD Performance in 2003 and he dynoed it at about 500HP@5200 and 560TQ@4300 (at the engine) w/ one of his Holley 950HP carbs (I'm running a Holley Street Avenger 870).

468 cid
400 block
Eagle stroker crank
4 bolt mains
Dave's 260+cfm 6X heads
Ross forged pistons
approx 9.5:1
Performer RPM intake (w/ 1" spacer)
Holley Street Avenger 870
Comp hydraulic roller cam (236/244 @ .050 .565/.570 lift w/ 1.5 rockers 112 L/C) (Dave's "old faithful?)
HS 1.5 roller rockers
Mallory 140 w/ return style regulator and -8 supply and return lines
sumped tank
Doug's headers
full 3" exhaust w/ X pipe

Car has a mild pro-touring setup and is primarily street driven, but I'd like to do a little drag racing and road racing with it, just for fun. I'm running a Tremec TKO II 5sp manual tranny.

Here are my thoughts for a starting point. I don't care if the power band is bumped up some. If I remember the discussion I had with Dave's correctly, he cautioned me about revving it too high because of the HR lifters, but otherwise he said "the engine will run all day long at 6000RPM".

Heads:
I don't want to replace my headers, so I'm looking at 85cc KRE aluminum D-ports, more specifically, either KRE's 325cfm D-ports or SD Performance's 315-320cfm D-ports (the prices are similar). Are these "too much" for my engine/application? Do you recommend one over the other?

Cam:
I'd like to stick with a hydraulic roller, but am open to a solid roller if that's what it takes. What if I kept my cam with the new heads listed above? Power estimates? Otherwise, is there a bigger hydraulic roller option to get me where I want to be? What about solid roller recommendations? I don't care if the idle is rough, but I do want to be able to cruise down the road at around 2000 RPM. My biggest concern with the solids is I've never adjusted them, so I don't know what kind of trouble I'd be getting myself into. I don't mind turning a wrench and I can learn, but I'm certainly no mechanic.

Sorry for the long post, but I wanted to provide adequate detail.

[issach428]

over 600hp and only 9.5 compression is a very fine tuned task with e's or d's. Kaufman d's (that have been ported) will work fine. I would go with a solid roller. I run a solid roller on the street, i set them once and they never move. I do run a stud girdle so that helps. I had the same goal and have 10:1 compression. my combo is in my sig. i only had it out twice before the track closed for winter. hopefully some engine builders will chime in with more advice.

[tom s]

why not go back to Dave and have him spec it out fr you?Tom

[screamingchief]

The head choices you mention sound good enough for your goals.

I'd go with the SD versions of the KRE D's myself.

I'd use a solid roller cam myself,something that specs much like the venerable 290b6 flat tappet solid cam.

I have specs on a version of that sorta cam using the comps hi-tech .420 SR lobes that I would use for something like this,lemme know if you wanna check them out.

That sorta cam should easily make 600+ hp with that combo and the KRE D heads.

Idle will certainly be noticable,but with the roller it should'nt be too unruly.

It also should be really responsive down low too with the tight LSA and a slightly advanced ICL (say 2° to 4°).

Should also pull strong to 6500 + easily.

This cam would also work fine with the 1.5 HS rollers you got now too.

Should'nt need a lifter brace either,but I would consider running a stud girdle as SOP with that sorta SR cam.

I'd also consider going with a victor intake and a better holley.

That would be my plan.

[Hillard]

Stay tuned.....going to the dyno within a couple weeks with a similar combo. Just received the KRE d-ports from SD...320 cfm CNC port yesterday. A hydraulic roller a little bigger than Dave's "old faithful" but I'm using solid roller lifters, stainless 1.65 roller rockers, Torker II w/ 1" spacer, and a custom built Holley from "Shaker455". I'm waiting on the Smith Bros. pushrods right now. I'll provide complete specs and results after the dyno test.

[Cliff R]

Our engine combo below is right up there, and puts down some good numbers considering how "mild" the engine is. Showing us over 120mph with less than ideal converter and gearing and low 11's shows plenty of top end power, as we're motoring through at a relatively "low" 5100rpm's in high gear at the finish line.

FWIW, I'd keep the "old faithful" cam. Dave even mentioned that going to larger cams shows little if any increased torque production over the 236/245/112 cam, although top end power numbers will increase some.

I would also avoid any tight LSA grinds, we have tested enough cams in 455's to know that the "tight" LSA stuff is not the way to go. We actually just finished testing a 247/254/108 cam in a nearly identical engine as you are using now, except the SCR was up near 12 to 1 instead of 9.5 to 1, and was NOT overly impressed with it anyplace. Without going into great detail, the "big" cam on a "tight" LSA simply makes WAY too much mid-range power, nothing less than BRUTAL. It's nearly impossible to hold the engine in a well set-up street/strip car. It "feels" like it's going to delivery a 10 second run to the driver, but is only able to manage low 12's in a very well set-up car. It simply throws ALL of it's power out immediately, which absolutely ANNIALATES the tires on the starting line, then not enough head flow or cam to give us enough top end charge for good track runs. We also dyno'd the engine, made decent numbers, but really "tight" power curve.

I would go with a set of ported KRE heads, the 290's are more than enough cfm for your goals, keep the same cam. Our heads have pretty small chambers, around 76cc, to get the compression ratio up to 11 to 1. Still no problems anyplace managing 89 octane pump fuel.....Cliff

[Half-Inch Stud]

CLIFF, others, Has anyone got data-opinions on a "Big Cam" (257/268/108) installed in a retarded with Rhoads lifters & 1/5:1 rockers in a 9:1 455+060?

Goal is to restore 60foot power and make more power (then the right-sized "Old Faithful" 236/245/112 cam) at the big end.
=====================================
Seems to me the Dual-Plane intake and super-smart exhaust layout is necessary to make it go.

[71 Ventura II]

FWIW Be leery of changing to a smaller chamber in your new heads unless your freshening the rings or have verified the ring seal. Changing from 9.5 to 11.1 could stress the 6 year old ring seal.

Have you considered running the solid lifters on your HR cam like Cliff? Also you may look into just a rocker ratio change to add a little topend power. Honestly, every builder has what they "feel" are ways to build HP. Application and driveline must be otimized to handle the different engine characteristics. Making statements that tight lsa cams are not the way to go are vanilla and incomplete. When you build a car following the same parameters everytime doesn't provide a diverse learning curve. In your specific application and expectations the wider lsa cams in the 112-114 range would help spread out the power, help with pump gas (overlap involved), and provide driveability. I would not be affraid to go as tight as 110 on the lsa but isn't really necessary. We'll leave the "tight" lsa cams to the racers building BIG HP and having a specific application operating in a narrow power band requiring more gear and converter. JD

[Mr. P-Body]

HIS,

Greg Miller did some extensive dyno testing with Frankenstein (that's "fronken-steen") about 4 years ago. He found, with the 10.2:1 E-headed beast, after 254 intake deg (@.050), power started to drop off. We settled on a solid roller that is 248 @ .050. Car runs 10.30s, 3,400 lbs. (with Greg in it...), 93 octane.

GS470,

We have several guys running in the 10s on 93. Many more running low 11s in "street trim" (honest!). 600 GBHP is plenty "doable" with the right combination. Your shortblock is "there". Don't ignore what Jeff says about rings, though. If you have "low miles" (and/or track "passes"), you should be okay. Increased cylinder pressure CAN alter the wear pattern on the rings. It's not a "given", but it is a risk.

Jim

[i82much]

Originally Posted by Mr. P-Body

HIS,

GS470,

We have several guys running in the 10s on 93. Many more running low 11s in "street trim" (honest!). 600 GBHP is plenty "doable" with the right combination. Your shortblock is "there". Don't ignore what Jeff says about rings, though. If you have "low miles" (and/or track "passes"), you should be okay. Increased cylinder pressure CAN alter the wear pattern on the rings. It's not a "given", but it is a risk.

Jim

I'm personally floored by Pinball Dan's car. I can't get over that car. If I understand correctly, it weighs about 3800 lbs and runs low 11's @ 122 or so with a 236 @ .050 (intake) solid roller? I didn't think a cam that small could mph that fast in such a heavy car.

[Steve C.]

Dans's cam is a Comp Cam XE Solid Roller; 236/242 @.050" .620" lift with Harland Sharp 1.65 rockers. More info on the combo:

http://www.pontiacstreetperformance....uild461DS.html

[grandville455]

WOW THAT IS IMPRESSIVE!!..Good to see ya back onboard Todd!! . I hope that ring seal doesnt effect me going from 9.3 to 10.3 ... 600 passes!!

[Silver Judge]

Hi GS470,
This is a good subject that I"m interested in too, I've thought of doing the same thing.
Yup, 600 HP is the new 500 HP I have the bug too.

We're running nearly identical combos right now, Dave built my entire engine from carb to pan and dynoed it before I took delivery of it. I've thought about how cool it would be to have "just a bit more" even though SD Performance's 500 hp pump gas engines makes a helluva satisfying street strip combo.

Isn't Jim Hand running those KRE D ports now and laying down 11.50's in his wagon?

PY Board member Guidos has a super nice 65 GTO stick car that had a combo like ours, built by SD--he leapfrogged up to Eheads, 320 cfm or so maybe 325 and I think he has those heart shaped chambers that SD's been cranking out. So, even though he jumped to roundports, it's worth keeping in mind as a comparison. I think he went from running low 12's to about mid 11's. He is definitely a street strip car lover, and drives his car all over the place too, from Alberta, Canada to Oregon for Tiger Run.

The thing is, with a head that flows 320 CFM, even a d-port, if you get the bug again, a cam change could get you up to about 640+ HP, and the next thing you know, you're going after 10.70's. It's this sickness thing again, LOL

Cliff R's car is a great example of how good that new KRE Dport can perform I think plus Tom S. is correct, Dave will know what to do and what the tradeoffs are. Let us know what you end up doing!

[Cliff R]

"CLIFF, others, Has anyone got data-opinions on a "Big Cam" (257/268/108) installed in a retarded with Rhoads lifters & 1/5:1 rockers in a 9:1 455+060?"

My opinion, and it's just that, is that retarding a relatively "large" camshaft isn't going to have the effect you are looking for. In almost all cases, those big cams are set up with advanced intake closing points, to give the engine a chance at high rpm's to make great power, even while using a relatively "tight" LSA. The "big" lobes naturally do this for us (create more overlap, etc, and exactly why most cam manufacturers offer them on 108/110LSA's right to start with), as having greater off seat timing (larger advertised numbers), they will tend to make the engine want to make power at high rpm's right to start with. Not to mention "big" cams on "tight" LSA's LOVE high compression ratios, or need them to salvage any sort of low rpm power and decent idle/off idle engine characteristics.

Any time I've played around with retarding camshafts, we quickly find the engine getting extremely "lazy" past about 111-112ICL and that's with smaller cams than we are talking about here, and Rhoad's lifters we being used as part of the testing......Cliff

[Skip Fix]

How about a flat tappet hydraulic 239/247 @ 0.050 in a 455 pushing a 3750 lber to 10.9s @ 124?

[pinballDan]

I thought the same thing about the cam Jim AKA mrpbdy was selling me . 236 -242 ,what is this but it will have enough vacuum for the power brakes . Than after tuning the engine and finding the mph of 120.6 and being able to drive the car to work and to the store and every where with out the need for stud girdles or worrying about valve train failures from high spring pressure . I'm very happy .With over 8000 miles and quite a few passes on it and still no leaks or problems it just gets faster . Oh ya it weighs with my fat ass in the seat at 3950 and that was confirmed at 2 scales . Here is it's last run . I'm still looking for some secret mods on the torker ll or should I start experimenting my self to help it out some .

[i82much]

Originally Posted by Skip Fix

How about a flat tappet hydraulic 239/247 @ 0.050 in a 455 pushing a 3750 lber to 10.9s @ 124?

Uh, yeah. I would say that qualifies as bad-(|).

[i82much]

Originally Posted by pinballDan

I thought the same thing about the cam Jim AKA mrpbdy was selling me . 236 -242 ,what is this but it will have enough vacuum for the power brakes . Than after tuning the engine and finding the mph of 120.6 and being able to drive the car to work and to the store and every where with out the need for stud girdles or worrying about valve train failures from high spring pressure . I'm very happy .With over 8000 miles and quite a few passes on it and still no leaks or problems it just gets faster . Oh ya it weighs with my fat ass in the seat at 3950 and that was confirmed at 2 scales . Here is it's last run . I'm still looking for some secret mods on the torker ll or should I start experimenting my self to help it out some .

Awesome. My 505 has a similar flat-tappet cam and a lot of folks told me it was too small. Then I see your car come out with a CVMS motor and say hmm ... seems like Jim has got these 600 hp jobs with smaller XE cams pretty well scienced out.

[Half-Inch Stud]

Here's my TECH BASIS:

I assume the bigger cam will get awee more power in the 4000-5400RPM, with the goal of the fancy crap below to recover (say -200HP) the 60foot capability that the "Big Cam" threw away.

Seems the PMD Valves do not need 1.65:1 Rockers. Rather Valve curtain is achieved well enough with 1.5:1, so the "other way" to sustain that lift is the higher duration lobe.

Reflecting on thoughts: Seems we all have become accustomed to 1.65:1 as a given when actually it is a significant cam spec parameter. Yea, I sold both sets of 1.65 Roller rockers, and am left with the Yellow Crane 1.5:1 Roller rockers (that don;t hit the keepers). So, seems I keep comming up with the "Big Cam" duration & narrowed LSA when coupled to genuine Rhoads to EQUAL the 235/245/112 cam, with a final analysis that I need to retard it if not straight-up.

This is a sort of plea for help because GEEZ, nobody else has said good things about this approach with my kind of 38cc dish compression with Ram III D-Ports.

[Cliff R]

HIS, to get a better idea you may want to take a closer look at the cam cards for both camshafts, and see how much later in the cycle the intake valve closes with the larger camshaft?

Some cams will use assymetrical lobe profiles, and short seat timing events, etc. They can actually compare closer to a smaller cam with traditional lobe profiles in actual off seat valve events.

Even so, retarding a "hefty" cam in a relatively "low" compression ratio engine will do NOTHING to improve power production anyplace in the power range, even at relatively high rpms. The events simply happen too late, the cylinder filling capabilities just continue to get worse, at least that's what I've seen from the little bit of cam moving around we've done on the dyno and at the track......Cliff