455HO build up - lets hear it
 

Ok so doing a 455HO which presently is still stock bore and stock virgin heads. Just want a fun street motor. Have all the power I need in other cars.

Wish to go roller cam though and will not be touching the 108cc 7F6 heads other than new valves and rocker arms etc. Compression should stay under 9:1 with flat top pistons.

Keeping stock crank but getting forged Molnar stock length Pontiac rods.

What roller cam specs will work best? Been leaning towards around a 230/236 at .050 with a 112LSA.

What roller rockers would you recommend?

Does the stock intake and heat shroud assembly work with the tomahawk style valley pan needed to clear roller lifters?

Stock exhaust manifolds.

Lets hear it.

Thanks.

Sounds fun,

Crower Endro RR, they are pricy, but you get what you pay for and like those connecting rods you picked, this is no place to cheap out.

Maybe push the compression a tad.....9.3to 1 if possable,, but not a deal breaker. Deck the block and heads untill there FLAT!
Your cam (roller) numbers are definitely in the range of a fun street engine.
Might I suggest a tad more on the exhaust side......(240*-242*) to help out the use of stock manifolds &
full exhaust. I think a Bullet/UltraDyne grind HR14 Intake 284* adv 230* @.050" .530" valve lift w/1.5 rocker
HR16 Exhaust 296* adv 242* @.050" .530" valve lift...... LSA 112*/113*
Happy Building

Mine is close in spirit to a 455HO, just as a stroker and with more compression (9.5:1). Butler recommended a 230/236, but the crew here talked me into a 236/242. I'm really happy with it.

I'm using a Tomahawk valley pan with a repro RAIV intake so I would imagine you'll be fine. I believe those are patterned off a 455HO intake?

IIRC, the machinist did have to mill a little off the spring seats to get the pressures where they needed to be for the roller so you might not get away without touching the heads.

I have Harland Sharp diamond series rollers. So far so good.

Bore it .030, get an accurate valve job. You'll have about 8.5:1 to run cheap gas...like 87 octane. Run a slightly smaller duration (226/232°) cam on a 114LSA, at about .575-.585 lift. Run HS 1.5s (or Crower enduro if you have the $$). Bring the advance in right away at 1000rpm, and have it all in by 2000-2200rpm. You don't need a Tomahawk valley pan unless you have no pan....if you have a stock 68-72 pan, just massage it.

These SS rockers along with the Crower short polylocks almost always allow you to run the '67 and later stock valve covers.

What trans and rear gearing does the car have?

Harland Sharp 1.5 rockers fit under 67 and up valve covers - I have them with an HR that has .567/.570 lift.

Trans may most likely end up being a TKX with still 3.08 rear gears.

I have and am running H&S 1.65s a 400 lobe lift with late style valve covers with the 5/16th gaskets.FWIW,Tom

My brother Dan has built many 455HO’s for the Pure Stock Drags and stock, they are easy 400 hp/500 lbft engines with 8.5 to 1 compression and 068 style cams (Summit 2801). He built a nice ’71 455HO with good forged rods and small dome forged pistons to get 9.5 to compression and a HR cam with 230/242/112 at .550” lift (custom CC roller) with HS 1.5 RR’s. The ports were stock, the manifolds were stock (intake and exhaust) and it was a beast. It made 485 hp/575 lbft torque. This HO wasn't built for the Pure Stock Drags btw...

Dennis

Wow! If he could pull that out of a 455HO with stock manifolds, it makes me wonder what I left on the table with my build.

man .575 sounds like a lot of lift for a 226 cam with 1.5 rockers? Is that a typo or do you know of a lobe with that kind of lobe lift?

To answer your question, I'll tell you a little story.....

Back in the 90's when I would occasionally drag race my street car, I got a lot of help from an older guy that was into racing Pontiacs. We talked quite a few times about Pontiacs in general and my car in particular. He even helped to port a set of iron heads of mine.

He taught me a lot about head flow and cam choice, and introduced me to the CompCams Master Lobe Catalog. https://edelbrock-files-v1.s3-us-wes...be-Catalog.pdf

Been using the catalog to order custom cams since. If you go to page 26, you'll find the QNI lobes. 13540/13542 are the lobes I'd have put on a 114LSA for the OP.

The helpful older Pontiac racer guy was Pete McCarthy.

My point is you can find just about any lobe you'd ever want to run if you browse the catalog.

Having had a couple cams now in a 455, I would go slightly bigger than the 230/236 cam. The first cam I had was a 232/238 on 112 that utilized XFI lobes. Even at altitude here in Colorado, that cam was vary tame. It made 15" of vacuum (again at altitude) with a smooth idle, but also had a broad powerband. That was on a set of as cast KRE D-ports. I'm not entirely sure if stock D-ports are going to change much in that regard.

For stock manifolds, I would put the LSA out on a 114. That is going to help make some power there, but again will further tame the engine and should bring vacuum up a bit.

I currently run a 240/248 on 112 with the QNI lobes that Lamnas mentioned above. With the KRE 310 cfm dports, its a beast. You can plod around in the car all day long, but as soon as you put your foot into it, things can get stupid real fast. Point being, don't be afraid to put some duration into that 455. You won't kill the low-end on this type of deal. I really think 232-236 is a sweet spot on the intake for a mild performance application.

Thanks! Any thoughts on longevity of the valvetrain with those lobes instead of something softer?

I don't consider the QNI lobes to be all that "aggressive" to be overly concerned about longevity. But I'm also assuming a person running a cam like this isn't going to "cheap out" on other valve train hardware like a good quality spring package, and thick wall pushrods, etc.

If you read the literature on the Q series lobes, they're designed to actually be more stable than previous lobe profiles. I changed lifter brands with my current build, but I can tell you that my curren valvetrain setup at just shy of .6" of lift with .398 QNI lobes is much quieter than my old setup with XFI lobes at .545" gross lift.

I have no issues with valvetrain stability on these at 6000rpm where I shift the engine. I'll reiterate though, I changed from the old design morel (lunati branded) lifter to Johnson short travel lifters. There may be a combination of things there that are working better, not just the lobe design.

I think you were one of the folks that encouraged me to go bigger with my build. Glad I listened :)

The specs of the cam Dennis mentioned above has less duration on the intake side - 230 vs. 236 with the same 242 on the exhaust side. Wondering if that had to do with the unported nature of the heads? Maybe this is a dumb question, but can you give up power by having too much duration in the intake without the airflow to make use of it?

There's always going to be a point of diminishing returns, and the exhaust to intake flow ratio will have some bearing on what works well on the intake side. For simplicity sake though, if a port flows X amount of air for a given valve lift, you can't force it to flow more air by adding duration. However, even at that same maximum flow, keeping the valve open longer does increase the amount of air that has been consumed.

That's obviously a really bad over-simplification because things like atmospheric pressure, scavenging effects, reversion all will have an effect on that. I have pretty rudimentary but observation based knowledge and my general understanding is that increasing the exhaust duration is beneficial specifically in situations where you don't have a high flowing exhaust. That's done for the same reason. If the exhaust straw is small and restrictive, keeping the valve opened a bit longer can help evacuate a bit more exhaust gas, making room for the fresh fuel/air charge. An engine using the stock manifolds isn't going to have a lot of scavenging going on, nor does it flow well. Keeping that exhaust valve open longer while the piston is pushing the spent charge out seems logical.

Why are you guys pushing him into far more cam then he needs to meet his goals for his motor?

Did you folks read his first paragraph?

* heads will obviously get new springs to match cam though in addition to roller rockers and valves

I'm not, and I did.

65MG,
This article might help with your cam selection if you haven't seen it yet.
https://www.hotrod.com/how-to/hppp-1...ller-cam-swap/
Glenn

What are friends for? ;)

With all said and read, with stock heads, is the ram air iv roller cam 232/241 on a 113 too much?

What roller cam specs will work best? Been leaning towards around a 230/236 at .050 with a 112LSA.

He literally asked for recommendations and stated what he is leaning towards. My opinion of that is a cam with an intake duration on either side of about 234 degrees. Others opinions may differ.

I'd use it with a little more compression...like 9.5 to 1.

Dennis

Thanks for sharing that article. I wrote that article for High Performance Pontiac magazine using the 455 HO in my '76 Trans Am as the basis.

We also wrote a similar article about the 455 HO in my dad's '72 Trans Am. You can read about that here.

https://www.hotrod.com/how-to/mildly...-gross-rating/

Hi Rocky. Yes love that article.

Just trying to pick the best cam for a stock set of 108cc heads.

I can't say anything bad about the hydraulic roller that's in my dad's HO engine. We bumped his compression, but at 224/236, it works very well with the TH-400, stock stall, and 3.08 axle.

You could certainly go a little more aggressive if you have a manual, but depending upon the lobe, duration and lift jumps pretty well around the 230 mark. Without port work, there's not much advantage to lifting the valve past .500-inch or so.

What Rocky got out of the 455HO build on the Mustang chassis dyno in that first article is almost exact to the number to what my car put out on a local Mustang chassis dyno. That's cool to see. Very similar builds, I just started with a 400 block.

I am doing the same exact thing right now but with 197 heads, stock 71 intake, etc. I am going with the ram air roller from Butler. Heads are 106cc.

Ram Air IV roller cam from them?

I have a 467 with the Butler 236/242 cam on a 112LSA. I like it. I get around 15" vacuum with a slightly choppy idle and tons of power with really good driving manners with a factory intake and tuned Qjet.

What heads though and flow of them?

Dang that sounds good.

GT

Like many here, I typically dont use less than 230 @ .050 cams in 455 builds, but I also like a little compression with it. At least 9.5 or 10:1

The last 72 455ho I did with it's factory round ports had a slight dome piston for 9.98:1 and that one had Paul's custom 236/242 hydraulic roller on a 112. Worked nice, plenty of vacuum even at 5000 feet elevation to work the brakes, ran the AC fine, and made over 500hp on the dyno on 91 octane.

With less compression id probably look at the butler raiv hydraulic roller for a really tame street engine and 400-450hp.

To be honest these 455's soak up cams with 230 or less like it's not even there.

Edelbrock D port. Bowls cleaned up but no porting, stock flow.

Im building a 455HO block with a set of E Dports,stock crank,SCAT rods and Autotec pistons.Will be a 10-1 CR engine.Dont have the Comp hyd roller cam memorized,will post.Will use the Evolution lifters.Tom

236-242 on a 112.Lobes 3017B-3038B..363-361 lobe lift with 1.65s.Tom

Thanks Tom

getting up to .600 at the valve, what springs are you using? any reason to use a smaller lobe with a high ratio rocker instead of something like the OF lobes with a 1.5?

I did not order the cam,bought it from a friend that had it.I usually try to get closer to 400 lobe lift and run 1.65 rockers.We will use what ever springs necessary for the cam and get me 150 on the seats.Tom

Yes.

Thanks. Going to roll the dice and likely get the Ram Air IV roller cam. Bullet is 6 weeks out so a custom grind not happening.

Keep you posted.... thanks all.

65madgoat,

It must be 455 HO season, I'm pretty much doing the same thing you are. I'm using the stock HO intake, heads, and exhaust manifolds. I have a 71 455 HO, 4 spd, 3:55 rear GTO. I have been messaging Butler about a cam and pistons, and other items. The cam Butler picked out was there Hi-Torq Street Performance Billet Roller Cam. 282/288, 230/236, .510/.521, LS 112. Comp Cams HR Lifters CCA-85701-16. For pistons I'm looking at DDS with -7cc valve reliefs. They also recommended the 80 psi oil pump, which I'm not sure about.

What are the specs on the RAIV cam? What are you doing for pistons? edit: (I found the specs, pretty close to the one they recommended for me)

Yes it is their spec'd Ram Air IV roller on a 113.

Just looking ahead as someday may want more power and would swap my Edelbrock heads on this block that would really put this cam to use.

Went with Ross pistons - DSS or Autotec could be made in a week though I found out.

I went with their 60/70lb pump. May run it at 70lbs.

Good luck on your build. Fun stuff staying stock-ish. Something I have not done in 20+ years.

That's the oil pump I'm looking at as well.

What are you using for a valley cover?

It’s pretty tough to beat the RA IV cam in a 455 but for those who want to experiment here’s one of the best threads on the subject IMO

https://forums.maxperformanceinc.com...hlight=455+cam