Need help with 455 power increase
 

What are some ways to add horsepower to my setup? 1972 Luxury Lemans, 455 bored 0.030 over, #96 heads 3 angle valves, flat TRW pistons, 9.3:1 compression estimate, Melling 26308 cam was set at zero, iron intake, quadrajet by Cliff, curved ac delco hei(sun machine reading attached, not sure what it means), ram air manifolds, 2.5" dual exhaust, 3.73 gears with Eaton posi, 200r4 transmission, 10" billet 2800 stall. Downside, I am not sure if my rods are forged. The paperwork says 496453 crankshaft, polished standard sized rods and mains, rods resized with ARP Bolts.

Not looking to rebuild my motor as it has about 3k miles, but it's not as fast as I was hoping when I put it together. What would be the best way to get rid of the laziness on the line?

My ideas and questions.

1. Advance cam to 109, 4 degrees or
2. Boost compression by adding kre heads if it really would make a noticeable difference over the 96 heads. I was thinking the 74cc heads maybe at 290 or 310cfm ported.
3. Have my 96 heads reworked.

How are you measuring, "Not as fast as I was hoping?"

Do you have disappointing track times or low dyno numbers? Im wondering if you just have a really well-sorted out combo that's running smooth and doesn't feel fast. If you just want it to feel more violent, put a manual in it. It will feel faster. If you are comfortable with the money for new heads you arent that far off of a TKX kit.

If on the other hand you have disappointing measurables, like the track times, then I would pull the trigger on the heads and go with a bigger cam. All the other stuff is likely going to be small gains (if any) that you wont be able to discernably notice. You could probably make some numbers with exhaust, longtubes and 3" exhaust. Maybe more depending on your mufflers, but even if you made an extra 25 Hp I don't think you would feel it.

Im all for people getting faster, I just want to make sure you are having an honest assessment with yourself about what you are disappointed in. If you don't have track times, go make a pass. You might surprise yourself.

It's just in daily driving and getting on it, it doesn't feel fast off the line. I chatted with cliff today and he said that the cam I have is doggish when it's at zero, and recommended advancing it. I am not sure if the shop who did my sun machine curve/timing set it incorrectly, or if I just need to tweak my combo a bit. I just want launch to be better.

Ah, RAIV style copy camshaft. Rhodes lifters would provide some additional low end torque. The best way to increase power everywhere for a given cam and engine size is to increase compression to the limit of the available octane. Rhodes lifters would increase dynamic compression at lower RPMs due to earlier intake closing provided by the fast bleed down. It would pull about the same at high RPM.

Increasing static compression to the mid 10s with high flowing aluminum heads is the nuclear option.

3.73 and 2004R's 2.74 first gear and a 2800 stall should let it spin up. It should blow the tires off. Surprised it feels lazy. How much timing at idle? Did you and cliff discuss secondary opening speeds?

Knowing base timing, compression test and vacuum at idle would help us understand what it's doing now.

I guess a bad timing curve could be a culprit. I would also be surprised that its not blowing the tires off.

Whats your initial timing set at? What are you getting all in without the vacuum advance plugged in? I might put a light on it and see before I started spending money. You might be able to wake it up just with some more timing advance.

Thanks, I do not know the timing as i had a shop do it for me. The shop is a well known gto restoration shop, so I am guessing they would know how to set it. Are you talking about cylinder compression? The builder provided me with those details.

Regarding Rhoads lifters would replacing that now cause a risk to my cam as everything is running smooth and broken in? I have sealed power lifters right now.

I would agree with what some are saying with checking the basics first or have someone knowledgeable help you. Check that the throttle is actually getting pulled all the way open, make sure the choke isn't staying on or the secondaries being otherwise prevented from opening or opening all the way, and check your timing situation.

This is actually a good point. I recently had a deal where my air cleaner was interfering with choke linkage on a quadrajet. Made it run terribly. Make sure your throttle is opening all the way when the fun pedal goes all the way down and make sure your choke isn’t hanging closed.

As far as the timing goes, that’s something you could verify pretty easy. There isn’t much to it. Buy a cheap timing light, plug off the vacuum advance temporarily and just see where you are at. It’s not that the shop doesn’t know how to do it, but if they weren’t given specific instructions on where to set it who knows what they did.

First and foremost what is the motors hot cranking compression?

Larger port higher flowing heads will not help at all in terms of better acceleration below 4000 to 4500 rpm so strip that notion out of your mind.

Your leaving too much in hands of so called experts when it come to distributor timing, and not being able to check it yourself is leaving you behind the 8 ball .


You car set up right and with those rear gears should anniilate the rear tires at will!.

Here’s how your HEI should be set up.

Your total mech advance, if I'm reading it right, is only 12 degrees total. I would try making your initial timing around 16-18 as long as it cranks over ok. Then see if it's an improvement.

If so, you need to have the distributor recurved to have about 16-18 total mech advance with 16 degrees initial advance.


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Thank you, I plan on taking it to another shop once it warms up in the spring to get it looked at once again. I am hoping that timing adjustment livens up the motor a bit.

When you are asking about cranking compression, do you mean per cylinder. If so, they all measured between 159-166psi. The only reason I started thinking about heads is because that is what I was being told by people more knowledgeable than me. Butler, KRE, and Cliff all said that changing my heads would give me more air that the motor needs and generate the power I was lacking. I was told that the 96 heads do not flow great ( I only have the 3 angle and milled a little) and that I want to increase my compression for my cam. 2 of those three mentioned that the cam needs to be put 4 degree forward to 109, and that on center, it will be sluggish. I asked the builder about my concerns and he sent me videos of the same build in a Firebird and it seemed very lively.

I will be honest, I do not know what moving the cam will do to my driveability etc, I am just disappointed in my current setup and for the spring, I would like to wake up my setup or get it set properly if it is not. I am happy to save money wherever I can obviously as I would prefer not to spend 5k on heads/rockers etc. My vehicle prior to this was a 1980 z28 with a 350 crate motor, reverse valve body TH400, 373 gears, that was feel it in your pants way faster

should melt your face for sure.

Even in stock form those 96 heads will make an easy 400 Hp with that cam.

Your issue is not air flow in terms of that motor making good power up to 5200 rpm .
Even with reworked stock rods you do not want to spin that motor passed 5500 which is something you would need to do to make good use of a aftermarket head.

Getting your needed timing right will bring in a added 25 Hp and 30 ft lbs of needed Torque.

I broke out the calculator on that distributor setup. Since the dist turns half as fast as the crank, you double the degrees and RPM stated on the Sun sheet to calculate the timing at the crankshaft.

I get
16 degrees advance at 2000 RPM
20 degrees at 2600
24 degrees at 3400

Assuming the typical Pontiac engine wants total timing to be 36 degrees (which includes base timing) you subtract 36 from the 24 degrees of dist advance to get 12 degrees at idle. So the base timing would have to be set at 12 degrees BTDC to give 36 degrees at 3400 RPM. Base timing (which you set) plus dist advance curve (calculated above) gives the total timing the piston will see at a given RPM.

The total timing at those RPMs with 12* base would be
28* at 2000 RPM
32 at 2600 RPM
36* at 3400 RPM

So take a timing light and verify you have 12* of base timing. This is your starting point for tuning. What's interesting to me is that there is a decent amount of timing from 2000-2600 RPM, but it takes another 800 RPM for the curve to come all in. I assume they did this to provide a safe tuning window that won't rattle the bearings due to too much timing too early.

At low 9s static compression, on 93 octane gas, I would think it safe to quicken the second half of that curve. Basically have all the timing in at 2900-3000 may increase some power in that range. Maybe 15-30 HP depending on what the engine likes.

But that's not going to provide a world of difference unless the actual timing is vastly different from what I estimated above. For comparison, my 400 motors tend to like 14-16* of base timing and 34-36* at 3200. So shoot the timing with a light and report back.

Cranking compression is a decent estimator of how an engine will behave, if engine size, compression and camshaft is known. Manifold vacuum at idle will help tell if an engine is tuned properly, at least at idle. You put the two together to estimate an engine's power potential and if the tune is in the ballpark.

Edit- I just saw that your cranking PSI is in the 160s. That's not bad. My 400 with 2802 and 9.7:1 compression pumps 165 and it's no slouch. I'd look at ignition timing and carb settings first. How about shift points? How long does the 2004R hold 1st gear at heavy throttle?

I do think that the biggest gains would be heads. Its not just airflow. Going from 9.3 to 10.3 compression is going to pick up power everywhere. The power production above 4500 is going to benefit from headers and 3" exhaust, but down low, cylinder pressure rules.

Ok I see the hand written notes now.


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Fuel supply could be an issue. Read your spark plugs. Are they too clean (lean mixture) ? Setup a temporary fuel pressure gage (tape it to the windshield). Do you get a pressure drop when accelerating ? A wide band A/F gage can help, or putting the car on a chassis or hub dyno. I just did the overkill approach with the Tanks INC electric fuel pump setup. Car runs strong now and I will put in on a hub dyno in the spring.

Also make sure when you put the go pedal to the floor you’re getting full throttle at the carb.

If you did heads, do I go edelbrock or kre? Also I was thinking either 72 or 74cc.

How do you find a good shop to tune everything and dial everything in? I spent a good chunk already at the other shop that got everything running smoothly to where I can drive anywhere with zero hesitation, only problem is it's feels sluggish.

Where are you located? There are old school tuners everywhere. Sounds like you just need the timing gone over. Its not hard to do it yourself, with help from this forum and the amount of youtube videos out there.
Your car should blow the tires off with 373's..may just be something simple. I would figure out what is wrong now before you start throwing money at it.

I am in Northern Illinois near the Illinois /wisconsin border.

I took out some spark plugs and stuck a bore scope in to take some photos. Do these look like TRW forged pistons? Also photo of spark plug



https://ibb.co/g3GvZdG
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https://ibb.co/RzXN6HD
https://ibb.co/WtcTRQt
https://ibb.co/ZHdPHBF
https://ibb.co/wRNDQ67
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https://ibb.co/zR8WNJ2

My quadrajet has 29268wf 0779 on it. It's also leaking from here from that gasket I believe or sprayover, it's also all on the top of the intake.

Laziness off the line with a 455, 200-4R, 3.73 rear combo means one of three things: (1) carb, (2) ignition timing, or (3) dead torque converter.

My money goes to timing curve, very easy to experiment with less than fifty bucks. Make sure the vacuum and mechanical advance are working properly.

do a stall speed test to see where converter rpm goes up to... as well. not sure if that is documented. unless its been mentioned.

Cliff has mentioned your cam needs to be degreed. This is your issue with laziness off the line.
My first engine build 455 with 6X heads and a qjet. It was built without the cam being degreed. It was exactly like you say, lazy off the line.

I had the engine redone because of bearing failure and this time the builder made sure the cam was degreed. Completely different engine off the line. Yes, also your timing has to be setup correctly. I believe my initial was at 16 degrees.

I see a blocked off vacuum port in that photo of your Carb.
Do you even have the vacuum advance hooked up, because it needs to be to maximize part throttle performance no less other details like helping the motor run cooler and aiding gas mileage.

Some photos

More photos

I think everyone has stated the same 3 things you are looking at. That cam needs some advance to work. You definitely need to check your timing. I personally fear that the 9.3:1 CR is/could be the detrimental factor here. With #96 heads having 96 ish cc's would give you the 9:1 ish compression ONLY if the slugs are all the up to the DECK. Typical aftermarket slugs are made at varying compression heights/pin height. which in turn changes things ALOT. My ROSS dish pistons the CH was 1.480....THATS .020 in the HOLE! On a STOCK engine. The ICONs ch are 1.490...original stuff is 1.500. The 041 cam is really going to like some compression to work.
With all that said ...even a lazy 400 with 9:1 and 041 cam with a 2800 convertor and 3.73 gears ...would should and could blow the tires off almost at will during launch.

i dunno, man. even with a cam that isn't installed perfectly, low compression, and a bad timing curve .... a 455 with 3.73 gears and a 2.74 first gear ought to rip your face off in first gear.

What sparkplug and what octane fuel is being used?

How much vacuum at idle, and what is idle RPM? Base timing? Without knowing that, we're at the point of guessing. The vacuum can under the brake booster points at low vacuum.

It does look like the carb may be leaking a bit. Without checking float height and knowing if castings are warped it's hard to say why it's seeping. Who did the carb?

What happens when you stomp the gas from a dead stop?

Others have mentioned advancing the cam or timing curve & Im sure that needs to be checked... but on an old 455 6X-4 heads ~9-9.5:1 comp I had in the 90's on a very tight budget build with a mild comp magnum 280 cam and cheap 2300ish converter... that cam was installed straight up due to lack of experience using a stock timing curve HEI... that car would smolder the tires off the line even with 2.56 gears & a TH400, I changed to 3.73 gears & you could barely do half throttle launches without the tires going up in smoke. Even a totally stock 455 has more than enough low end torque to smoke the tires at will from a stop.
I also have a 400 9:1 in a 78 TA with smaller comp XE cam that I installed straight up and using stock timing curve, that car also smokes the tires easily with 3.42 gears and runs mid 13's at 103+mph taking it easy on crappy hard street tires.

Many of todays modern cars, even V6 smaller cars feel super quick from a stop or 25-30mph roll, but that can be deceiving compared to a big heavy car with a slower revving big V8. Hope you can figure out the issue with some of the suggestions above, but dont throw a bunch of money at it from a shop that charges 100+/hour labor, if you have basic tools & mechanical ability you can check or do most the things yourself with some help here or other interweb sources.

Maybe consider a shop with a wheel dyno that can do some tuning or changes without getting inside the engine for cam work etc?

I would confirm that the harmonic balancer hasn't slipped. Timing can be way off.

Is this vacuum line going to the distributor?

https://forums.maxperformanceinc.com...7&d=1734020738

If so, move the distributor advance to here.

https://forums.maxperformanceinc.com...8&d=1734020752

I thought I read somewhere, probably on this forum, that vacuum from an intake runner is unsteady, pulsed.

Those more knowledgeable than I will correct me if I'm wrong.

Yes it goes to the distributor. It was initially on the carb but they could not get it running properly.

The 1st pic is manifold vac source that some prefer, the 2nd pic at the carb vac tree would still be a full manifold vac source... if ported vac is desired it would be one of the small front carb ports above the base plate that are plugged off in OP's pics.

Thanks, I am going to a shop today near me to discuss the cost of getting the cam degreed. Would you do anything to the heads, intake or carb? I have the opportunity to swap my quadrajet which is is 750cfm with a fully rebuilt 800cfm with electric choke. He said he can modify it to my iron intake choke system if needed. I do not know about quadrajets at all, so I am not sure. I was thinking maybe degree the cam, get a RPM manifold and a holley that I can adjust myself.

OK that's interesting.

The purpose of vacuum advance is to add timing at light load (high vacuum) and reduce timing at high load (low vacuum). When the throttle is opened, vacuum drops and vacuum timing goes to 0. This reduces the chance of detonation/pinging at heavy throttle. When throttle is reduced for cruising, the vacuum advance adds timing at light load to improve MPG and light throttle response.

Typically I like Ported vacuum from a carb source, so the vacuum advance only works above idle. This results in a more stable idle, because vacuum fluctuations at idle do not impact idle timing. Having to run manifold vacuum to the vacuum advance to get the engine to idle, indicates either a lack of base mechanical timing, or too-lean idle fuel mixture, or a cam that is entirely too large for the engine size and/or compression. The cam is marginally too big at 9.3 compression. This can be mitigated by increasing compression, advancing the cam 4* and/or using Rhodes lifters. The rest of the issue is tuning, adding base timing, adding idle fuel by modifying the Q-jet's idle feed circuits..

I would not recommend throwing another carb on it, unless there is something specifically wrong with your carb. The '77-80 electric choke and APT Q-jets are easier to tune, but not required. A good Q-jet tuner could make any '70s era Q-jet work well. Q-jets are notorious for being lean in the idle circuit, so the vacuum advance could be a crutch for lean idle mixture. Going from 750 to 800 CFM isn't going to do much on a mild street motor. Be aware that if you get the TV cable adjustment wrong, the 2004R transmission can fail due to low line pressure. So pay close attention to any throttle linkage changes.

Tune, tune tune. Throwing parts at it is not a shortcut.

Here are all the specs I can locate on my motor and setup right now. This is probably all the information I currently have.

• 455 YW 485428 E174, block from 1974 bored 0.030 over, 9.3:1 CR. Block is 0.015” deck height to top of piston, compression between 159-166 on all cylinders
• 496453 Crankshaft
• Polished standard size rods and mains, resized rods with ARP bolts
• TRW Forged pistons, mahle rings
• #96 heads E171, 3 angle valve grind, milled, screw in rocker studs, new integral valve guides, new valve seals, valves ground and cut 3 angle
• Melling 26308 cam
• HT-951 Lifters
• 224-43364S oil pump
• R.A.R.E. Ram Air Manifolds, 2.5” downpipes, 2.5” exhaust, Spintech 9000 mufflers
• 1555cpa copper lead rod bearings
• Tin Indian Performance Viton rear main seal
• 160-degree thermostat
• 9799068 iron intake manifold
• 29268WF 0779 Quadrajet Carburetor
• Carter fuel pump
• GMB 13-1280 water pump
• Cold Case Radiator
• Powermaster mini high torque starter
AC Delco HEI Distributor
• Rebuilt AC Delco Alternator
• 200R4 SSR non lockup, Billet servo 2nd gear, Dual feed with new 3-2 control system, Competition Valve Body, Alto race red clutches for 3rd and 4th, 2nd reverse boost valve 0.300, line pressure boost valve 0.500, line pressure regulator spring, 10 vain rotor pump, Wide Alto red lined band, shift kit, HDS hardened stator, bearings replacing thrust washers, 4130 steel band anchor, 0.500 booster valve, triple 3rd pressure and clamping force, steel input shaft forward drum, pan spacer and 700 4R filter, long transmission cooler
• 9.5” Tri Shield performance Billet Torque Converter 2700-3000 stall
• Eaton Posi, Motive 3.73 gears

Looking at the compression pumping numbers advancing the cam from straight up too 109 would help some. But I don’t know that it is actually your problem, 160 lbs should be enough, especially with a 2800 stall converter and that deep gear combo. You already have to much stall for Rhaods lifters to help with bottom end.

I have done more 96 d port head Pontiac combo’s than any there Pontiac combination, both stock and ported that flow in the 280s. That should run in the 13s pretty easy as it is, could nearly make it into the 12s with a sticky tire. The cam timing would be worth a few tenths, assuming it is correct that it is straight up now. Which judging by the pumping numbers, I don’t have any reason to question it isn’t straight up.

Maybe I will tow it someplace to get tuned this winter. Couple questions.

1. Should I keep the iron intake?

2. I reached out to my carb builder and he will swap out my current quadrajet for a 800cfm carb for not too much money, he can even provide an electric choke but my manifold is setup different. Do I stay quadrajet, do I upgrade to 800cfm, or do I ditch and go edelbrock/holley?

3. Do I spend the cash to degree the cam, is the return worth it? The only benefit would be I can change the timing chain at that time as I believe its not a double roller chain.

I am just looking for the most economical way to get this engine competing with my friends. We plan on renting a drag strip this spring and they have quick street cars with a mopar 408 stroker, and some BBC builds in the mix.

With the pumping numbers you have, I don’t think it is worth the return unless your goal is to pick up a few tenths.

Another q jet would be worth a try to see if it wakes it up. It won’t be any quicker than a well tuned 750 though if your is working correctly. The only way I would consider switching to a holley is if you changed intakes, to a single plane. A single plan trades some low end for upper end power, it sounds like your looking for power everywhere yet. The stock intake should not be close holding it back yet. Fuel pressure gauge, AFR meter, and read the plugs are the basic tuning tools you could do without taking it to a shop. Could also try a DUI distributer if the carb doesn’t help, they are usually home runs right out of the box.

How does your car do coming up on the converter? Is it tight, and moves the car with light pedal feel?

Its a very tight converter. When Continental stopped, this is the converter Cliff recommended to me to buy. Another option is to do more head work, port the 96 heads and add roller rockers.

A friend has that same converter in his GTO, they are nice converters.

It sounds like you’re pretty serious about making your car quicker if you have plans to go to the strip.

If you just have 1.5 rockers, you about have to take the heads off to clearance the heads for 1.65 roller rockers. Just switching to roller rockers won’t make it quicker, you have to run a larger ratio too. So at that point you may as well have someone port them and clearance the pushrods. We have 96 heads yet on our 71 T37 on a 455, started out stock and worked there way to were they are at now. They flowed in the 280s after the last time I worked on them. Which is enough flow to support 550+HP in a street engine pretty easily. Certainly easier to buy aftermarket aluminum though, but probably 3X the money if someone has already been through your heads. Around 500 HP is about the limit on a RA4 cam for a street engine no matter how good the heads are, it hard to get enough lift go much beyond that.

I will be stopping at the local racing shop in town here in about 2 hours to chat with the owner to see what he would charge for porting vs just buying new heads. Also, I do not have anyone around me that knows or will work on a quadrajet making it hard to stick with one. I want to ask him his familiarity with them and then make a decision on the intake/carb combo. Having a quadrajet is nice, but when issues arise, I do not have the expertise to troubleshoot them which makes it then a requirement to ship back and forth to the builder.

I really think you could be making a mountain out of a molehill here. These threads tend to get out of hand, and Im not even saying any of it is bad advice, but I just think you should slow down and try a couple of baby steps.

Before you blow half of your fresh engine apart, I think you should just check and make sure more timing advance doesn't wake the car up some. You can get a cheap timing light for next to nothing. I know you've said you arent an expert, but I promise this is something you can do yourself. Heck you could facetime me or another member and I will walk you through it.

Alternatively I also think simply going to a chassis dyno for a tuning session is a very good idea. For one it will give you some tangible evidence of if it actually is underperforming. And those guys will easily be able to do some of the simple adjustments like timing, and seeing if your throttle is opening all the way.

I agree on that. The issue is I attempted to get someplace by me for a dyno tune last year and was turned away because of the quadrajet. They didn't have anyone familiar with them which seems to be a common scenario.