Different cam? Chain? Car should be faster
 

Seeking opinions:

My oil pan and rear main seal are leaking. So, I was going to pull the engine. I’ll need a new pan, one piece gasket and was going to do the one piece rear main seal.

While the engine is out, I was curious about making upgrades. Personally, I feel like the car is a dog for the size of the engine and the combination of parts and drivetrain. I understand that this is subjective. On my little quarter mile test tool, it will do mid 14 seconds. I feel like the car should be quite a bit faster.

I’m curious if a different cam would give me more power, without sacrificing street manners? The car currently has perfect street manners. It drives like any modern car. But, when I punch it, I’d like it to be faster. I don’t have a big desire to switch to a roller cam.

The springs are pretty old and I was thinking of going to the Crower 68404.

Also, the last time the engine was out, I feel like the timing chain had quite a bit of slack in it. Seeing as how the block has been line honed at least once, I was thinking maybe I should run one of the undersized chains?

Looking for any advice on cam, lifters, pushrods, timing chain, if there is more power to be had, without sacrificing street manners.


The car is a 67 Firebird convertible.

The engine is a 1970 455, bored .060. It’s been line honed as well.

It has a factory crank ground .010 on rods and mains.

Forged pistons and rods.

The heads are 1971 Pontiac 400 heads, Code 96. Mildly ported, stainless valves. I’ve got Comp Cams roller rockers, ration 1.52. I think they are Magnum. The springs are some tired Comp 988 springs. I was thinking of switching to the Crower 68404.

Compression Ratio should be 9.53:1.

Intake is Edlebrock Performer, port matched.

Car is a Holley 750 with vacuum secondary.

Distributer is Performance Distributors HEI, custom curved.

Trans is a 700R4 with a 2600 stall lock up converter.

Rear end is 3.73 Chevy 12 bolt.

It’s got headers and dual exhaust.

The cam is a Summit 2802.
Cam Style:Hydraulic flat tappet
Basic Operating RPM Range:2,200-5,500
Intake Duration at 050 inch Lift:224
Exhaust Duration at 050 inch Lift:234
Duration at 050 inch Lift:224 int./234 exh.
Advertised Intake Duration:298
Advertised Exhaust Duration:303
Advertised Duration:298 int./303 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.466 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.488 in.
Valve Lift with Factory Rocker Arm Ratio:0.466 int./0.488 exh.
Lobe Separation (degrees):114

Thanks in advance

Cam is too small. The experts here will give you some solid advice.

Thank you. Starting to think maybe a Ram Air 4 cam and switch to a Performer RPM intake might wake up my combo. I'm worried about this 50% failure rate on new flat tappet cams though. I really hadn't considered switching to a roller.

The 455 with 96 heads was a real popular combo in the past. Maybe search for some similar combos here. I would lean toward something like a copy of an ultradyne 288/296 cam.

is a 750 too small for that combo?

Definitely cam is to small. On the 50% failure rate. Any new hyd cam has to be checked before installing to make sure the lifters and cam has the proper taper. Because that has been a big issue.

A larger cam should let it RPM higher but the torque should be there in current form and with that crankshaft with 3.73 gears and extra low first in the trans 2600 stall .. it should be impressive at some point..
basics...check for full throttle maybe secondary vac spring is a black RV spring jetting all kinds of things

i have a 462 slightly larger solid cam 6X-8 heads th400 2.73 gears that pulled a 13.6 at 5800 DA .. so somethig is amiss if your description is accurate

This is cam you want to go with Crower 60919 cam, its basically the Ram Air 1V cam. But much better then old Ram-IV. It’ll wake that baby right up.

Here’s a few things I see.

That carb is too small for that cid motor and with that intake especially!

That intake itself might be the choke depending on how well the porting work turned out.

Keep that cam and when you get the motor back in the car add 1.65 rockers to the intakes only.

To make that work right the springs need to be changed as you have already talked about and the intake needs to be changed out to a performer rpm.

While the engine is on the stand be sure to check and see if the usage of 1.65 rockers calls for different length push rods.

And yes, even 3 degrees of unnecessary cam retard can knock 25 to 30 hp off a motor above 5000 rpm in terms of your CID.

Listen to Gach

How was the existing cam installed? Was it degreed, or was it crammed-in "dot to dot"? What is the cranking compression pressure for all eight cylinders?

That 750 carb and intake is not too small for a 455...at low RPM. If that car doesn't launch hard, it's something else. I don't know how a 700 trans can take the torque of a properly-running 455 even with "billet everything".

What is the fuel pressure after several seconds of WFO?

On my 455, I switched from the 3.73's I had in the rear to 3.36's and the car tended to pick up some. If your current combo is throwing all the torque at you very early and falling on it's face without many revs, those 3.73's are just helping you blow past the torque the engine is making. Taller gears can help you spend more time in the engine's power band, turning it into speed.

I also agree that the intake and carb are likely too small. I would switch to either a factory intake manifold or to a torker ii. It's unlikely that the Performer RPM will fit underneath the hood of your 67 firebird. It's a big engine, the single plane manifold isn't going to kill the torque.

If you're set on changing the cam while you're in there, I think pretty much everyone would lean towards that crower 60919. If you need more manners out of it, you can pair it with a set of Rhoads lifters. Just make sure that the cam and lifters are checked specifically for proper taper, runout and hardness. There's been a lot of testing on these through 2023 and hardness doesn't appear to be an issue, but cams ground with no, or improper amounts of taper as well as lifters with out of spec face machining.

If the engine has been line bored, do you know how much it took to get everything straight? If not, you may need to contact the builder and try to determine, otherwise you're guessing. Either way, try to get a timing set that uses an IWIS chain.

It doesn't. Ask torqhead about it.

Lots of good tips here. Schurkey, it was crammed in dot to dot and like I said, the chain was pretty sloppy. I'm figuring I'll instal one of those undersized ones. I run an Edelbrock electric fuel pump, the higher pressure one with a regulator, so fuel pressure shouldn't really be an issue. It should have plenty of flow.

I'm seeing recommendations for the Performer RPM intake, that my Performer might be the choke and a Crower 60919 would be better than my current Summit 2802.


I really don't want to lose street manners, but would like more power when I punch it. Also, trying to keep the budget relatively low. I've already put so much money into this car.

Its not that 750 is to small, that Holley 750 vacuum secondary crab, Sucks !! Big time. Forgive me because I’m doing this for memory I’ve had to modify those crabs. Here’s why The secondaries are limited jetting wise. Been a while since I’ve done one, but out of memory The metering block Has to be changed in order to get the proper Jetting. When you put your foot into it its just not getting enough fuel and its going to feel like a dog. I would still definitely go with more cam though.

I would ditch that Holly, or get someone who knows how to modify them. Your much better off with a good 750 Q’jet.

Nope to perform RPMs not the choke point. Trust me. Another thing as far as timing chain goes. The Crower 60919 cam. Dot to Dot usually comes in at 106, thay say installed at 108. It’s actually 4 degrees advanced here’s why with chain stretch you’ll end up at 112. So if it cam in dot-dot at 106, you’ll end up at 110. Which makes that cam perfectly street able . So Crower when they design that cam anticipated chain stretch. So they really want it to end up around 110-112. So I wouldn’t worry about running a shorter timing set. Just put in a good Cloys timing gear set, I think they go for 150.00. Don’t buy the cheapet set.

So, my Performer is fine, don't need an RPM, do the 60919, lifters, and 60404 springs and put the cam in dot to dot with a new chain and it'll wake it up some?

Even going by Edelbrock’s own recommendations your darn close to what the Performer can handle in terms of CID and cam.
The Performer is incapable of producing more then 430 Hp unless you lower the plenum divider 3/4” all the way across the plenum or run a open 1” spacer and at that point your better served by the Performer RPM or the T2 depending on your gearing and converter.

I too am surprised you have not torn your 700R up yet!

This is for now a happy accident showing you how down on torque your 469 motor combo is.

I agree, once you get the motor making the power that it should your 3.73 gears will then really show you that there too much .

Thanks Steve. The 700R4 isn't stock. It was built for strength. So you're recommending the RPM intake? The 60919 cam? Crower Cam Saver Lifters? 68404 springs? That's a good combo that will wake it up?

Can you describe how the car responds from a standstill and floored?

Yes, I've got the same combo other then mine is only .030 over @ 9:50:1
Runs super strong and I run a 3:73 gear with a 350-turbo trans 700r4
coming later. I run a 750 vac sedary holley but with the rear metering
block so I can jet the rear of the carb too. I run 72 front and 78 rear jets.
I run the RPM intake also but the torkerII will work as well. The RPM will
fit under the hood of the 67-firebird at least it did on my friends firebird.
Hope this helps and thanks to Gach for his info. I run 38-40 degree timing too.

GT

Sure, perfect street manners, like a modern car. If I let off the gas and accelerate like normal, its like a normal car. If I straight up floor it, the tires will spin. Controlled flooring it, it gets up and goes, but like a locomotive. It's like it builds up speed, instead of all right now.

I just feel like it should be faster/quicker. It acts like it has power, but is overly heavy. For comparison, my Solstice GXP with a manual "feels" like it accelerates MUCH faster, but in reality are probably close in a quarter mile.

Sweet! Nice to find someone with the same combo. So how does it run? Any idea on HP or torque or quarter mile? What's it like when you floor it? How's the street manners?

[QUOTE=General Z ]

I know your running The 96 there a good heads, but let me give you example of a combo. And why the Crower 60919 cam is such a good cam. For must Street cruiser guys. Here’s the combo, 461 ci. 400 block .060 over. With 455 crank. E-heads out of the box, perform RPM intake Q’jet ( Cliff R Q’jet ) Crower 60919 cam, 3.73 gear, in his 67 GTO which weighs 3600 lbs. he ran at Norwalk 11.60 its on video here some where. That works out to 500 hp.

Yes his heads flow 270-280 and yours are probably around 220-250 cfm not sure? So there’s no doubt with your heads a good carburetor you’ll be in 400+ range. Either way the killer for you is definitely 2 things the cam and the carburetor. Is the rpm a better intake yes definitely. So my suggestion to you and it depends on weather or not you want to go with rpm a intake. Is definitely make cam change and definitely carburetor, you to get your Holly reworked like Blue Ghost did so you can jet The secondaries. Or go Q’jet. Trust me you won’t be disappointed.

[QUOTE=Gach;6478930]
Thanks for the feedback. I'm starting to wonder if I'd be better with the 60243 perhaps.

[QUOTE=Gach;6478930]I would follow these guide lines and then try changes like intake and carb.
My motor is iron headed and probibly 400-450 HP and maybe close to
500LBS of torqe. it does pull hard and is a blast to drive.

GT

[QUOTE=General Z;6478934]Personally I wouldn’t but thats up to you. Tell you why thats on a 112, you get timing chain stretch you’ll be at 114, not good for a automatic.

I think something is off with your current tune. The current combo even though not optimum the car should hit hard and rev fast up to 5000 rpm. What is your exhaust? A slushy torque convertor can also kill power. How is your timing set? Is your vacuum secondary carb tuned? Was the current cam degreed?

Thank Gach and blueghoast, great feedback. Much appreciated.

Current 2802 cam was not degreed. Installed dot to dot and I was surprised at the amount of slack in the chain. Exhaust is Hedman headers true duals with Magnaflow mufflers and an H pipe. The torque converter is supposedly extreme duty and probably only has 1500 miles on it. I've tuned the carb to the best of my ability. I put the bigger accelerator pump and power valve on it. Bigger front jets. Haven't changed the rear jets. Have the lightest spring, I think for the vacuum secondary too.

The car pulls, but it feels like a locomotive building up steam and just doesn't pull as hard as I think it could/should.

Z, are your throttle blades straight up when you floor it? One of my buds had a hard time getting this right with his OD trans and when he got it right said it was like a new car.

I would also agree cam is too small . But I'm like TA man and wondering about you tune. I'm curious about your timing. Do you know what it's set at for initial, mechanical advance and total timing and at what rpm? Also from my experience with the 60243 cam in a 455 that was not degree ed was like you mentioned. Like a locomotive off the line.
Even though the cam is too small for the size of cubes, shouldn't this thing just scream when hitting the throttle off the line? I realize it will run out of power sooner than if the cam was property matched to the heads. I'm thinking timing chain (degree cam) and tune.

I put the bigger accelerator pump and power valve on it. Bigger front jets. Haven't changed the rear jets. Have the lightest spring, I think for the vacuum secondary too. I'm also wondering about this carb. Have you tune it with an air fuel ratio gauge or are you just winging it so to speak? Are the secondaries actually opening up?

Yes, the throttle blades are vertical when floored. TV cable is set correctly to trans as well.

As for carb tuning, I'm winging it like you said and using a vacuum gauge for the idle screws. Besides that, seat of the pants meter and sound.

My timing is total around 38. Not sure initial. I've always thought total was much more important and let initial be whatever. I've got no ping on a hot day, floored with 89 octane. We also have 91 or even 93 readily available here too.

If you have not pulled the motor yet you really should do a cranking compression test, just for the sake of curiosity and for your records that you should be keeping.
Your cam isn’t necessarily too small unless your cranking compression is too high.

Also keep in mind these two things , it’s 100% always better to be slightly under Cam’ed then over Cam’ed , and top end MPH is a great thing once you get there!

Good idea. Thanks. It's still in the car. I really should do a cranking compression test. Top end mph isn't really a concern for me. It's a street driven convertible. I'd take mpg over mph. LOL.

The Performer intake is a "turd" on a 455 build, get a factory intake or the RPM if you have room to get it all under the hood.'

Below is a dyno sheet comparing a 224/230 @ .050" on a 110LSA HR cam with a 236/245 @ .050"/114LSA HR cam in a build very close to yours. 455, 9.3 to 1 compression, #96 heads flowing 250cfm. Back to back cam swap with no other changes.

You simply do not have nearly enough cam in it to make big power and the intake is a choke point in the recipe to get there.......IMHO

http://forums.maxperformanceinc.com/...1&d=1705586775

At 9.5 Compression, I would run the Crower 60243 with 1.65 Rockers, or the Crower 60919 with Rhoads lifters. Make sure to degree the camshaft, as every Crower camshaft we have used, both the 60243 and 60919, came in at around 112° Intake Centerline when installed "Dot to Dot". They don't seem to have any advance ground into them. I would install it at 108-109° Intake Centerline. In any case, MAKE SURE you use good USA Lifters such as Hylift Johnson from Topline Automotive, Rhoads uses Hylift Johnson for their lifter, if you opt to go with the 60919/Rhodes route. I would definitly use the Crower 68404 Springs with either camshaft, set up at 1.600" Installed Height. Make sure to run a good timing set, that is tight when installed, we use the Cloyes street Billet sets. Switch the Intake to either a Performer RPM if you have the hood clearance, or a stock iron intake. The regular Performer intake is a choke on the big 455, as it atctually has smaller runners than a factory iron manifold. I would do away with the Holley carb, and find a good late 70's pontiac Quadrajet, contact Cliff Ruggles with the carb number, and have him provide you with his HP rebuild kit, parts. and recipe he recommends for your engine combination. Nothing beats a good running Q-Jet on the street, when they are correctly setup for the engine. They provide the best Throttle Response, driveability, and mileage when calibrated correctly..

Thanks Cliff and Trans Am474. Much appreciated.

Thanks for the information. How crucial is using the Rhodes lifters with the 60919? I was going to use the Crower cam saver lifters. Do I need the Rhodes for vacuum or is it another reason? With my current setup I have 16" of vacuum at idle?

That's a mistake.

There's no telling how many manufacturing errors--never mind assembly errors--are in the various machined parts that affect cam timing unless you look for them with a dial indicator and a degree wheel.

At 9.5 Compression, I would run the Rhoads lifter if using the 60919 camshaft, IF you want to retain as much Idle vacuum as possible, however, it probably still wouldn't produce 16" that you have now. I would estimate maybe around 12-13" if Rhoads are used on the 60919 at your compression. If you had 10-10.5 Compression, you probably wouldn't need the Rhoads lifter at all, to produce roughly the same Idle vacuum as the 60919/Rhoads will at 9.5 Compression. Another thing to keep in mind, is the Standard Rhoads lifter produces a sewing machine tick at Idle, some people doesn't care for that, others it doesn't bother. We have used the Crower CamSaver lifter in the past with success, but I'm not sure if they are a USA lifter, they could be an offshore lifter, which could be a toss up. Now, with all of that said, at 9.5 Compression in a 455, it would be fine to use the Standard USA made HyLift Johnson lifter from Topline Automotive and the 60919 camshaft, it will result in a little more attitude at Idle, and won't produce as much Idle Vacuum, but still should produce enough to run Power Brakes without a problem.

Fantastic. Thanks for the info. You guys are rockstars.

I run the 2802 in a 69 400 with 62 heads, RPM and headers. Idles at 850 with 13"-14" of vacuum, has a pretty good lope. Powerband is 1500-5400. 16* BTDC, 35* all in. It's too small for a 9.5:1 455 if you're wanting to revv it over 5100 RPM.

The thing that stands out to me is the light spring in the vacuum secondaries. That will let the secondaries come open too fast and result in lazy acceleration. If you floor it and it seems lazy, just slowly lift your foot a bit and see if it picks up. If it does, the secondaries are opening too fast. Since a vacuum secondary doesn't have a secondary shooter, you'll get a lean bog until the secondary airflow velocity starts pulling fuel.

I have a 390cfm vacuum secondary on a chevy 235 six cylinder. When I was tuning it, I tried a light secondary spring. As I rolled into the throttle, I could feel the engine sag at a certain point. Raising my foot magically gave more power. If I kept my foot in it, eventually the engine "caught up" with the throttle opening. I then increased secondary spring tension until that sensation went away. You'll likely need to convert from metering plate to metering block so you can change the secondary jetting. I think that requires the 4160 to 4150 conversion kit.

I have an 8.9:1 CR 462 with a RAIV cam and Rhoads lifters in my '72 convertible with RA manifolds, 7K3 heads, an HO intake and Qjet. I think it's a great combination and has very good street manners and has gone 13.4 in the 1/4 with a stock converter.

Does the performance meter you have show MPH times? That maybe would be the better indicator of what HP the engine is making. Mid 14s on the street could be mid 13s on a prepped track.

A 2802 in a 455 is a small cam, so, if the cam timing was retarded, my guess is the engine would actually like it. So I rather doubt cam timing is your issue.. As is I think the 750VAC that has the metering blocks on the secondaries is your biggest issue for your combo, not the performer intake or the cam. Pretty limited on tuning with that carb. If the timing chain was loose when it was installed, was most certainly retarded some. But the 2802 comes with 5* of advance built into it, it has room for some retarding.

Maybe he will comment, but Dennis Jensen on here dyno’d his 70 455 with small valve heads and 9.8 SCR, all stock, no headers, and I think it made 390HP@4800. Best I recall anyway, I think it runs in the 13s in his stock A body. I think he later swapped over to stock round ports with the same short block and it made around 420 HP @5200. The current 112 LSA 60919 with that same set up peaks a few hundred rpm higher, if you are looking for big gains, I think you would be disappointed. I have ran in the high 12s with a completely stock Oldsmobile 455 and headers with the smaller 2801. No question there are better cams for a 455, but it seems like there is something going on more than just the small cam.

Just leaving the 1.52 and swapping from the 2802 to the 60919 is not going to be a big improvement. Both those need 1.65 rockers. The 60919’s that had 112LSA’s I have had do not need Rhoads lifters in 455s. Bigger rockers require the intake pushrod to be clearanced, So if your stuck with 1.52s, i would pick a cam that has more lift, like a Lunati voodoo 704. There are some Bullet grinds that are similar to the Lunati also that provide a lot more lift without a rocker change.

Thanks Chiphead...this helps me a lot...would you recommend a different spring or a cliff type rebuild for a q-jet if the carb is from an unknown origin?

[QUOTE=chiphead;6479047]I run the 2802 in a 69 400 with 62 heads, RPM and headers. Idles at 850 with 13"-14" of vacuum, has a pretty good lope. Powerband is 1500-5400. 16* BTDC, 35* all in. It's too small for a 9.5:1 455 if you're wanting to revv it over 5100 RPM

We have 96 heads in a 71 T37. The 96 heads often start out close to 98 cc, and some get toward 100cc after a valve job. The compression can be in the lower 9s with some 455s and 96 heads, with that cam and the fuel octane it currently likes, my guess is it may be a little lower on compression than mid 9s. Likely it is several things adding up to not meet expectations.

I agree with Jay on the Lunati 704 VooDoo camshaft being a good choice for a 455 as well. We used one is a 467 using Butlers stroker rotating assembly in a 1979 W72 400 build. The customer wanted to retain the stock, numbers matching look, so it retained the stone stock 6X-4 heads, other than adding the 68404 springs and Ferrea Stainless Valves. It came out with 9.3 Compression, and we used the Crower CamSaver lifter in it. It was a 4-Speed car with 3.23 gears and 275/40/17 tires, and it absolutley screamed for having NO porting on the heads, not even port matched. It also retained the stock W72 Iron Intake. We installed that camshaft at 104° Intake Centerline. At a 20mph roll, in 1st gear, it would absolutley start screaming the tires off, without a clutch dump, and pulled really hard at the same time. We were really impressed for having stock heads on it. It idled realtivly mild, just a tiny hint of attitude, and if memory serves, it produced 14" of Idle Vacuum at 800 RPM. The customer was extremely pleased. This is a 100% street car, so no track times....

[QUOTE=kingbuzzo;6479053]Thanks Chiphead...this helps me a lot...would you recommend a different spring or a cliff type rebuild for a q-jet if the carb is from an unknown origin?

Not sure if you're running a vacuum secondary holley or a Qjet? Either way, they're both vacuum secondary carbs. The holley would need a stronger spring in the secondary dashpot to keep it from opening too soon. The Q-jet may need a secondary flap spring/cam/pulloff rebuild. For a Qjet, I think the baseline on the spring was 3/4" turn past where the doors shut. Pulloff release time of 1.5-3 seconds depending on converter and gearing.

The OP should likely re-baseline the tune with a stronger secondary spring. 02 sensor AFR and vacuum gauge really tell you what the carb is doing. Low vacuum and lean AFR dip going to heavy throttle would indicate too-fast secondary opening. The other thing that I wonder about is the converter. Is it flashing to a high RPM, or is it coupled pretty well to the engine? A 455 with a 2802 should pull pretty hard to 4000 RPM or so. If the converter is flashing really high, that may keep the engine from doing its best work. I've seen converters so loose, that the car has to catch up to engine RPM.

Now that where full off the rails with this thread let me try to get the train running again.

Starting with Cliff's post as to why the Cam can make such a difference here's how the Manifold relates to the power band seen.

Here are the flow numbers I took @ 28" on a stock Performer back in 2019.

Runner
2 231 cfm

4 222

6. 225

8. 231

1. 216

3. 247

5. 232

7. 220

Average = 228

The worst flowing runner is capable of making 55hp, and the best can make 63 hp .

This will never happen with this Manifold since number 1 , the plenum is just far to small, and number 2 , the runner area is too small to make 55 hp per cylinder but for running the Intake on 350 cid or less, because there is just too high a level of port velocity.

So running this type of Intake on any iron headed D port motor , and especially if a well done bowl port job was done will limit peak hp to no more then 444 hp at the very best just going by the numbers.

Cliffs findings in his post goes to show full well why you should never overpower any Intake with better flowing heads.

The result will always be less hp being produced then your head air flow numbers would suggest and also the motor will have a far narrower power band then it otherwise would.

All of you folks running 290+ cfm aftermarket heads and a stock tripower have bought yourselves a expensive ticket on this misfit Boat .