hectre13

iTrader: (4)

Hey All,

I am finally getting back into building my Camaro again. I have owned the car for like 8 years now.. and we have put a lot of work into it... unfortunatly my friend and I didn't know what we were doing when we were building the engine, and now need to fix it haha. we were having constant issues with vacuum/carb/timing with it, I figured that at least to get a better start this time.. different heads may be the way to go?

I have had the worst time trying to get this thing running right, and one big thing people were telling me is that my heads are kinda jacking up my build.. what are your thoughts?

What do you think the best (budget friendly) advice you can give me to make my engine build ideal.. new heads? if so, what kind? would I need to replace the rockers and such? I don't even know where to start.. my friend who was helping me kinda bailed and am on my own now.. I work on motorcycles a lot and am confident I can build this engine, just don't know the best combo on this kind of stuff.

this is what my setups is currently:

-Stock LO5 short block out of an 88 Chevy Suburban (.040 over flat top hypereutectic pistons, .010 under crank journals, moly rings, bimetal bearings, high volume oil pump, and all ARP fasteners, stock rods/crank)
-Stock LO5 (193) swirl port TBI heads, rebuilt and milled slightly, with Crane Valve Springs.
-Comp Cams Thumpr Cam (279 and 297 duration, 0.479 and 0.465 lift (with 1.5 rockers), and 107 degree lobe seperation, flat tappet hydraulic 279TH7 )
-Comp Cams Lifters that came in the Thumpr Cam kit
-Proform gear drive
-Summit One piece forged chromemoly pushrods.
-Crane Gold Race Full Roller Rocker Arms (1.5, non self aligning, narrow body).
-Crane Springs
-Summit Racing Street & Strip Stage 1 Intake Manifolds SUM-226016
-MSD Pro-Billet HEI Distributor 8365
-Holley 670cfm Street Avenger Carburetor vacuum secondaries
-Hedman Elite HTC headers

DiabolicalRS

a lot of people are going to tell you try and find a set of vortec heads, but if those are still a lil too pricey try and get some L98 heads.

NagleMac

iTrader: (1)

Different heads wont fix your vacuum, carb, and timing problems.

Ozz1967

iTrader: (4)

check ALL vacuum lines in the engine bay, then block off all of the ports on the intake/carb. This ensures a solid vacuum condition. If you still have a vacuum issue, Pull the heads and intake and reinstall, make sure of a solid seal. Since you're running a carb, pull it, re-install ensuring good seal.

This should eliminate any potential vacuum leaks.

Reset the timing (never done a non computer car so not sure what base timing should be...)

TreeFiddy

Unless the heads are damaged in some way, it should at least run right. Vacuum, carb, timing problems - pretty vague - In what way is it misbehaving?

89rs454

It's a Carb engine it's simple really, You don't have 15 sensors nor a computer. Get a good dizzy dial it in make sure it has good Fuel pressure and a breather. Done.

Damon

TBI heads with a Thumpr cam? I wouldn't. They don't make much vacuum to begin with, and that might be part of your "vacuum issue."

JaBoT

What kind of vacuum problems does it have? Low, bouncy? If it's bouncy, is it still bouncy holding rpms at 2000? If it is just low keep in mind that's what that cam is designed to do.
While yes you need a set of heads with that cam it should still run right. It just wont make any power.
What is you timing at?

Edwardgp

Its great that you are getting back into it again. You will get it right this time. Edward.

hectre13

iTrader: (4)

Hey Everyone, thanks for the responses.. the vacuum issues from what I understand is because of the cam.. the engine runs, it just has never ran all that great (under load). I was having hesitation issues off idle, and inconsistent idle, and was having a weird issue of when the gear was in park that it would idle way high.. and then when in gear it would drop to almost dying.. that is probably a trans issue though.

I haven't looked at the engine closely in years, so off hand I can't tell you where the timing is set, fuel pressure from what I remember was strong. my biggest concern is that my heads are holding my setup back big time.

would it make sense trying to get my car to run right on those heads? or would it make more sense trying to pick up a different set of heads? I know it sounds like I am stuck on the whole heads thing.. but I know they are very restrictive, and that they probably the weak part of my setup.

Damon

If you're going to keep the cam, then yeah, I'd change the heads. Or vice versa. They're just not a good match for eachother. Since there aren't many performance cylinder heads available in the oddball 87-up bolt pattern you'll either need to buy an earlier bolt pattern head and slightly modify the 2 center bolt holes on your intake (or buy an 86-down bolt pattern intake) or step up to a Vortec-style cylinder head and get a matching Vortec intake.

The big drop when you throw it in gear is NOT likely to be a trans issue. With that cam unless you're running a significantly higher stall converter than stock, it's not going to be happy. ALSO, these issues can be compounded if that RPM drop causes the timing to back down- this can be both because of the centrifugal OR the vacuum advance OR both! You want nice stable timing both in Park and in gear. No change.

JaBoT

The hesitation is probably a combination of the street avenger carb (they are know for this issue) and the timing.
Put the light springs or 1 light and one med spring in the distributor then set the timing to 36 at 3000. Make sure the timing is correct before you even touch the carb. I would even sugest double checking tdc with a piston stop as inexpensive balancers have a tendency to be off by quite a bit.
Next take the carb off and set the idle screw so the primary transition slots looks like this
Idle_transition_slots_setting_zps7bcc767a.jpg?t=1378700924
next turn the secondary blade stop screw upside down like this so you can access it from the top and use this screw to adjust idle speed. Sometimes its a little loose in the threads when turned upside down. Try a little threadlock or silicone to hold it.


Put the carb back on and adjust the a/f screws and use the secondary stop to adjust the idle speed.

Should run like a different car, but you will probably still have a bog from the street avenger carb

89rs454

You see this is why i like my FI knock sesor. map sensor and fuel injection and opti.Your computer will tell you whats wrong 90% of the time.

hectre13

iTrader: (4)

JaBoT,

I will give your instructions a try.

knowing that my heads are not what is causing my issues here and it is more of a tuning problem. I DO know that my heads are a bottleneck. if I change them out at some point, what heads would you guys recommend? (this car has a pretty small budget).. I'm assuming vortec heads? is there a specific set I should be looking for?

also, would it make more sense to change out the street avenger carb for a different type?

-Jeremy

JaBoT

Vortec heads are not really an inexpensive option as everyone thinks. Right off the bat you need a new manifold. So to match the cam you need a performer rpm so thats $200.
Then you can get a set or promax vortec heads assembles ready for .575 lift from summit for $764/ Now you are over 950. Not really budget any more.
Also I would recommend changing the intake to a rpm 1500 - 6500 style as your cam surpassed the power range of the intake you have.

I don't like the street avenger carbs at all. There is a bunch of issues with them, but see if you can get it to work right first.

hectre13

iTrader: (4)

JaBoT.. now assuming that my build doesn't change besides my head/intake to the ones that you recommend (proMaxx vortec heads and the different intake) what do you think my engine setup would be outputting power wise? I know the cam/carb are probably going to lose me a little.. but just curious.

JaBoT

Probably mid to high 300s for hp.
Personally I would recommend spending another 50 or 100 and just get a set of profiler 23 degree 185cc heads instead of the vortec heads and manifold.
http://www.profilerperformance.com/r.../sbc-23-degree
It will make more power. And maybe if you have the money now or in the future an rpm manifold instead of the idle to 5500 one.
But in the mean time set up the distributor and carb the way I said. It will run much better and you still have to set it like that for the other heads anyway.
Just curious. Any reason you are running a gear drive? and chose the thumper cam?

hectre13

iTrader: (4)

my friend who built the engine kind of sold me on the idea of it being cool (this was like 5 years ago) since then I had lost interest in the car and started working on motorcycles.. now that I have my own place to work on it.. I have a lot more interest in getting my setup right more than trying to make it cool.. thus the reason I have a polished aluminum holley street avenger.. probably money better spent else where.. but at the time.. I just took his word for everything.. and since then have realized he didn't know what he was doing either haha

hectre13

iTrader: (4)

Hey JaBoT, if I were to sell my street avenger and pick up and double pumper of some sorts.. what would you recommend.. my car is going to be converted to a manual trans so no worries about kickdown or anything like that.. I was looking into Holley again, or Demon, or Quick Fuel.. any recommendations?

JaBoT

I personally like the proform street series. For the price you can't beat it. I have probably tuned over 20 of them and never had a problem. Quickfuel is nice also. They are basically the same carbs.
Did you ever set the timing and carb the way I said? getting another carb with those heads is kinda a waste of money. The street avenger should work. Plus you should get everything working the way it is now before trying to make more power. If there is a problem now it may still be there later after the parts swap.

hectre13

iTrader: (4)

I am actually going to start tearing my stuff down.. I'm going to be pulling the engine and cleaning it up and replacing things that I probably should have in the first place (oil pump, oil pan, etc) and then going to replace the heads and intake.. I'm selling a bunch of old parts which is going to help fund my project.. I have been contemplating a cam swap too, but not sure on that yet. I'm going with the vortech heads you had suggested.. it will be an on going project, and will probably be asking you all sorts of questions. I figure if I am doing all this.. might as well look into a new carb while I am at it.. I should be able to get some decent money back from the polished aluminum street avenger.