454 has no power. Help!

bigblocktroubles · Jul 19, 2002

What I have is a '91 GM Mark IV 454 crate engine. Less than 300 miles on it. Edelbrock Torquer intake, Holley 750 vacuum secondary carb (model 4160), stock everything else. It has oval port heads.

I don't know what hp this engine was rated at. The engine sounds really good. Little bit of a lope at idle. When driving the car, there is no power. Can only spin the tires in 1st gear (TH350 tranny). If you backpedal to get it to hook, it will dog out after it hooks up. Never has any power in 2nd or 3rd gear. I mean this thing is really slow. I could beat it with a stock chevy pickup!

It was fouling spark plugs big time (within 20 miles they would be fouled). The carb was used in a different car before and was jetted way too big, it had #77 jets in it. I rejetted it to #66's. Doesn't foul the plugs as quick now but still might be a little rich. I am reluctant to go any leaner because I wouldn't think they would need to go leaner than that.
Timing is set at 12 deg. initial. The distributor is an HEI from a sb 350. Tried advancing a few degrees and retarding it a few. Only made it worse. Do I need to recurve it? If so, what do I need to buy? springs, ect?
I don't have a tach, but at about 3000 rpm, the engine will miss fire badly. When revving up through the range, it will struggle to get beyond that rpm, then will get a little better above it.

I was using an edelbrock 600cfm carb. The car was even worse with that. I found that there was a vacuum leak in the edel. carb. The Holley was a known good pulled from a car that ran well (just liked a LOT of fuel, thats why the #77 jets).
I put new plugs in, new plug wires, new dist. cap,
Could a bad tranny cause any of this? How would I tell? Sorry for the long post, but I'm getting really frustrated with this one.

1 2RUN · Jul 19, 2002

According to Holley the original primary jet size for that carb is 72. 66's might be a little on the small side. I don't know what car this is in but if you have the HEI hooked up to the resistor wire for a points type ignition that'll give you a weak spark. You should run a 14 gauge wire from the IGN terminal on the fuseblock to the HEI.

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'69 RS Camaro
355 5-speed 4.11

67rat · Jul 19, 2002

Bad cam lobe(s)??

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67 RS 427,700R4

bigblocktroubles · Jul 21, 2002

A bigger problem became evident recently.
I noticed that while driving, If i hit the brakes the oil pressure will drop to around 20psi. If I slam the brakes, the oil pressure goes to 0. Not Good! The engine needs about 6 quarts of oil in order to build pressure. I originally thought that it was just a big pan. I'm not too familiar with BBC's. Now it looks more like the sump fell off or is pushed up. Is there anything else that causes this before I pull the pan? Not going to drive the car anymore till the oil pressure problem is found and fixed.
That stunk because I just got the car running a little better by cleaning up the plugs and messing with the timing. It still had a little hesitation when I punched it, but it would cough a little then really wake up. It seemed about right, all I needed was a better gear ratio and it would have been haulin'. I'm thinking about going to 3.55's or 3.73's. The car currently is geared REALLY tall. 2.??:1 i believe. It was on that test drive that I noticed the oil pressure problem.

Milan · Jul 22, 2002

If your [plugs were fouled Its likely that your oil is diluted with gas also that may account for some oil press. prob. And 66 is WAY too lean You likely have other Carb problems. That engine should bake the hides at request. Check your oil and change it. After you fix your oil prob have some one who is good with carbs lend you a hand or get a carb book and spend some time understanding why thing happen. You wont be sorry.

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67 prostreet BB Camaro
80 z28 Camaro 355ci
71 BB SS Chevelle (clone)
2002 35th anniv SS Z28 conv.

J early · Jul 22, 2002

Yes you should fix that oil pressure problem fIrst. Sounds to me like your engine is sluggish in part due to parts that just don't perform together. Like you said, rear end gears too low, torque converter to low a stall speed?, stock HEI with advance that comes on way to fast, carb way too small. All these things on a big block with a moderate cam spells DOG. Lumpy cams like RPM's to perform well and all your parts are not up to the task. Driving on the street you would be happier with a 750-850 cfm carb, converter with 2500-3000 stall, recuved distributor and 3.5 - 3.75 gears out back.

Milan · Jul 22, 2002

SLOW DOWN. I would be reluctant to say that all those are problems. First off even with a stock TQ conv and low gears a smaller carb ought to atomize fuel better. any way Find/fix oil prob have carb tuned/checked I think from there you can spend money as you wish. I would do the Dist and the carb LAST! BB chevys like "lumpy cams" due to their superior valve configuration. My opinion there is nothing wrong with your combo!!!!!! can it be improved upon? Sure! But dont freakout and think you gotta reinvent the wheel!!! My advice to fellas is, and has been in the past, get a couple of how to hotrod Big block books. I mean a COUPLE atleast. Read them and learn the value of your stock components and their limitations and then choose your upgrades carefully. Again Only my opinion!! Good luck Milan. Oh Use the search function It is very helpful !!

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67 prostreet BB Camaro
80 z28 Camaro 355ci
71 BB SS Chevelle (clone)
2002 35th anniv SS Z28 conv.

J early · Jul 23, 2002

Freaking out is not exactly what I would call it. It is all to common to hear about a motor that just doesn't have the power it should because it is a "Big Block" or has "Speed parts". Correct choice of individual components is crucial in allowing an engine to perform optimally. This idea is hardly reinventing the wheel, it is hotrodding 101. As was said, there are primary issues to address first to allow the engine to survive and be tuned properly, but if one asks what can be done to improve performance, they will get an answer on this forum like mine, which is correct. All hotrodding takes time and money, we all know that. Yes a 600CFM will atomize fuel and keep good air speed, but in this application it will run out of breath fast, and it sounds like the cam being run does not produce power at low RPM's. Nuff said.

Milan · Jul 23, 2002

J I was telling The author to calm down. It is a crate engine and I don't think he should throw any performance parts at it till he gets His basic running problem cured. Thats all i was trying to say. I see too many times people hav fundamental engine problems then only complicate the situation be adding new parts to the mix. The 750 carb he started with will be just fine for now. The cam I believe he said is what the engine came with. I believe that there is a possibility thet the heads are the oval peanut ports . If thats the case He should be carefull on cam selection. NOW "nuff said" .

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67 prostreet BB Camaro
80 z28 Camaro 355ci
71 BB SS Chevelle (clone)
2002 35th anniv SS Z28 conv.

J early · Jul 23, 2002

Milan,
Agreed!

J

drpm · Jul 23, 2002

also you said you used a small block dist. I didn't know you could do that!!! bb use 36 degrees of total timeing and small blocks use as much as 42 degrees I think the problem lies in the distributor and the oil problem is any bodies gess, bearings, oil pump releaf spring or just gas in the oil i've had problems with the edelbrock carbs. as far as the power have you checked compression, fouled spark a lot of times can't be cleaned if their fouled just replace them it't hard to tell over the computer with out here it do basic checks and make sure the not a biger problem good luck

bigblocktroubles · Jul 23, 2002

let me start by saying that I am not trying to start a riot. i would also like to say thank you for all your assistance. This is what keeps our hobby going.

I agree that this thing should bake the hides at request, but it cannot.

I used the distributor from a small block because it was the only one I have for chevy.

Yes it is the stock cam that came in the crate engine. Or at least that is what I am told from the original owner of the engine. I don't plan on throwing performance parts at it. I don't think I said anything about selecting a different camshaft at this point. That would be one of the worst things to do right now. Whatever GM put in there should work with the heads and c.r. ect... GM knows what they are doing. I just want it to run without stumbling over itself when I hit the gas. One thing I learned in hot rodding 101 is not to change cams and other engine components until you know exactly what is in the engine, ie, what heads, static c.r., rear gear ratio, converter stall speed, ect..., and what you want out of the engine. I don't know anything about this engine at this point, but I do know that i want it to scare the crap out of any unsuspecting passengers. The only thing I may do for sure is change the rear gear because my current gearing is defineatly too tall.

what do I need to in order to adjust the total timing of my dist. so that it is more favorable for a big block? I do not have a timing light with an advance dial on it. I will get either that or some timing tape, otherwise it will be impossible to measure the total timing. I just need help with how to make the changes to the dist. and what parts I may need to get it done.

The 750 holley carb is a known good, that is why i put it on. I will rejet to the 72's and see what happens.

all of that will of course wait until the oil pressure problem is fixed. I have drained and strained the oil. the good news is that there were not any metal shavings or bearing parts in the oil. I put new oil in. Still same pressure problem and still needs 6 quarts. I even put 4 quarts in and jacked the front of the car up on jack stands. Still no pressure, absolutely 0 psi. It seems that the oil level has to be really high to get picked up. When the oil level is high enough, then there is plenty of oil pressure (40psi at idle and over 60psi at anything above idle.) only deceleration of the car affects the pressure then, when the oil runs to the front of the pan.
It would seem to me that the crankshaft would be sitting in the oil also since teh level is so high. That would be a definite source of parasitic loss. The engine used to be in a t-bucket the previous owner had. He said at one point, he dented the oil pan when loading the car on a trailer. He replaced the pan. he did not mention replacing or even looking at the oil pump. Maybe that knocked the sump loose or pushed it up. The owner didn't drive the t-bucket very much so probably didn't notice the problem. It sounds like it was more of a trailer queen.

long story short: I need to fix the oil pressure problem, rejet the carb, new plugs and re-curve the distributor. Hopefully that will solve the hesitation problem. I will at some point change the rear gear. Of these things, the one I don't know how to do is change the total timing on the dist.

Timberwolf · Jul 23, 2002

What are you using for an air cleaner? And hood clearance?

Reason I ask is my 69 Coupe with athe flat hood had absolutely minimal room for an air cleaner with it's 454 and a high rise GM intake topped by a q jet. I put a 2" thick edelbrock air cleaner on it, and I couldn't close the hood with the lid on. I could make it work without the lid, so I covered the top of the filter with UNI filter foam. The hood closed, and it kept things clean, but the car made NO power when the secondaries opened. It would pull ok till the vacuum opened the back burners, and then it was as if someone hit the brakes.
Pulling off the air cleaner, I made a pass down the side street and she ran like a raped ape.
Bottomline, is air getting into your motor? It is enough? Not enough air means you will be running rich, even with jets that by number seem too lean, thus fouled plugs.

[This message has been edited by Timberwolf (edited 07-23-2002).]

Milan · Jul 23, 2002

The total timing issue can be put on the back burner. I never checked total advance on a sb and I didnt know there was a difference either way if there is a diff you will be getting more adv and I doubt that is contributing to your prob. I'd bet the oil pickup got smacked up 1st off. The I say that you have a carb prob. those jets would not foul the plugs in 20 miles! Id check float height and powervalve

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67 prostreet BB Camaro
80 z28 Camaro 355ci
71 BB SS Chevelle (clone)
2002 35th anniv SS Z28 conv.

jski67 · Jul 24, 2002

I had the same problem when I installed my 454 years ago. The pickup had fallen out of the oil pump. Apparently this is especially common with high volume oil pumps and pressed in pickups. After I reinstalled the pickup, I spot welded it to the pump. I figured if I ever needed a new pump, I could afford a new pickup too...

Hope this helps

Jason Kalinoski

67 Camaro 454/TH350

J early · Jul 24, 2002

When I installed my 454 I had to get a cowl hood so I could run the K and N filter that would give me the CFM I needed. I do use an Extreme filter lid too. I run a stealth intake and a Holly 750. Last thing I wanted to do after all the engine work was to snuff off the air at the top!

gheatly · Jul 24, 2002

I would pull the pan and check the oil pickup. The tube could have twisted and lost most of its interference fit when the previous owner hit the pan. Now that you've jostled it around installing it into another car, the pickup could have fallen out.

I agree with you, it's a crate motor that should already run well, esp if it ran well for the previous owner. Fix the oil problem first and then move on to the timing. Unless it's dumping gas into the engine, the carb is low priority - everyone runs a little rich.

bigblocktroubles · Jul 26, 2002

Thanks for all your help guys.
I did try the car without the air cleaner on and it acted no different. that was a good idea to check it.
I'm going to get the pan off today after work. i'm gonna fix the timing and check the carb out. The gaskets I put in (summit racing rubber ones) needed modification in order to be installed. I had to cut holes in them to make them like the old gaskets that I took out. It is possible that they are not lining up or the whole is not uniform enough. I am going to get the paper set of gaskets and install them on everything except the primary fuel bowl. Since there are no secondary jets on the other fuel bowl (uses a metering plate), I don't need to be removing and reinstalling that bowl to rejet anyway. If I knew that particular carb didn't have secondary jets I wouldn't have removed that bowl in the first place. The Haynes book said that there could be jets there for that carb series so I had to check.

Thanks again for all the help.

454 has no power. Help!

bigblocktroubles

1 2RUN

67rat

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Milan

J early

Milan

J early

Milan

J early

drpm

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Timberwolf

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J early

gheatly

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