i just help a friend of mine replace the heads on his 350 with a set of edelbrock e-street heads. the engine is from a 1978 chevy c10 stock cam/ bottomend, long tube headers 2" true dual exhaust, edelbrock eps intake, edelbrock 1405 600 cfm carb, open element filter.

all we did was replace heads and now it has absolutely no power we got it up to about 85 after about a solid 2 minutes of WOT and it cant even do a brake stand burnout, where as it had no problem going 120+ and could do a mild burnout before the heads. the engine sounds healthy enough and has great driveability absolutely no stuttering or bogging of any kind. the only thing i have noticed is it kind of sounds like the engine is breaking up in the upper rpms.


so far we have replace carb, replaced cap/rotor, wires, spark plugs, mechanical fuel pump, added fuel pump regulator set at 6 psi, set initial timing to 8 degrees, replaced intake manifold gaskets again, and tuned carb with a vac gauge. it still has no power at all but has pretty much perfect driveability

any ideas?

 

Timing set too low... Try 14 btdc

Also check your valve adjustment, sounds like you may have a few too tight.

Oh and what spark plugs did you use?
The E street heads needs 3/4" reach, gasket washer seat plugs...
Not the 5/8" reach taper seat plugs like the stock heads you removed

 

okay will reset timing and yeah we just got some O.E replacements from advance where would you get those plugs? should the autoparts house carry them?

and it is extremely possible we didn't set the valves correctly it was both of our first times ever touching a set and we just did a 5 min google search before attempting it.

 

The spark plugs is your biggest prob. Using std. plugs the firing tip is not even sticking out of the hole in those heads

Plugs that you need are these. (I run the autolite 3924 in mine)
AUTOLITE 3924
CHAMPION 71 RC12YC
NGK 2441 BCPR5EY-11 V-Power Plug
AC Delco 41-610
AC Delco FR3LS

Here is the way I have always adjusted the valves. http://www.centuryperformance.com/va...procedure.html

ENGINE OFF Valve Adjustment Procedure - The Quick and Accurate Way:
First, view this simple chart below for Small and Big Block Chevy Engines. Do you understand what it describes? A more detailed explanation follows below the chart. For other engines you will use the firing order that matches your engine to create a similar chart. This chart is based upon "opposite" cylinders of your firing order. (see below)

Intake Valve Adjustment: ENGINE OFF!
with #1 cylinder Intake Valve at full valve lift .... Adjust #6 Intake Valve
with #8 cylinder Intake Valve at full valve lift .... Adjust #5 Intake Valve
with #4 cylinder Intake Valve at full valve lift .... Adjust #7 Intake Valve
with #3 cylinder Intake Valve at full valve lift .... Adjust #2 Intake Valve
with #6 cylinder Intake Valve at full valve lift .... Adjust #1 Intake Valve
with #5 cylinder Intake Valve at full valve lift .... Adjust #8 Intake Valve
with #7 cylinder Intake Valve at full valve lift .... Adjust #4 Intake Valve
with #2 cylinder Intake Valve at full valve lift .... Adjust #3 Intake Valve

Exhaust Valve Adjustment: ENGINE OFF!

You will notice that this is the same procedure and sequence as the intake valves listed above. Only now you are adjusting ONLY the exhaust valves the same way.
with #1 cylinder Exhaust Valve at full valve lift .... Adjust #6 Exhaust Valve
with #8 cylinder Exhaust Valve at full valve lift .... Adjust #5 Exhaust Valve
with #4 cylinder Exhaust Valve at full valve lift .... Adjust #7 Exhaust Valve
with #3 cylinder Exhaust Valve at full valve lift .... Adjust #2 Exhaust Valve
with #6 cylinder Exhaust Valve at full valve lift .... Adjust #1 Exhaust Valve
with #5 cylinder Exhaust Valve at full valve lift .... Adjust #8 Exhaust Valve
with #7 cylinder Exhaust Valve at full valve lift .... Adjust #4 Exhaust Valve
with #2 cylinder Exhaust Valve at full valve lift .... Adjust #3 Exhaust Valve

 

oh and you will see this when you read the above link... But 0 lash is NOT when the pushrod stops turning. It is the very monument when you feel the slightest resistance while spinning the pushrod

 

i've never purchased a set of aftermarket aluminum heads, but being they are Edelbrocks i bet they came with pretty thorough instructions on how to install them, how to adjust the valves, which spark plugs to use, and how to tune it when it's running..

 

okay yeah we adjusted the valves WAAAYYYYY to tight then, i swore i read somewhere zero lash was where the push rod stops spinning and we tightened down either 1/4 or 1/2 turn past that hopefully we didn't hurt anything too much.

So new spark plugs, adjust valves the right way and set timing to 14 btdc. next day off is saturday so will report back with results


ive done alot of work on ohc 4 and 6 cyl engines, so i figured we wouldn't even need to look at any instructions or anything to slap some heads on an old carb'd sbc. i guess thats what i get for rushing into it. to my credit though everything else has went smoothly

 

okay update. we adjusted valves correctly, changed spark plugs to CHAMPION RC12YC and upped the timing to 14 btdc. and it diffidently helped smooth everything out and picked up some power we can now burnout slightly but i would be very surprised if this thing ran faster then a very high 15 second 1/4 mile.

its also running a pretty small exhaust true dual 1 5/8 - 2" exhaust piping and stock cam. could it be one of those that are holding it back this much? it runs pretty much 100% perfect at this point, but is for sure putting down less then 200 hp to the wheels

 

Is the carb adjusted properly?
Was timing set with the vacuum advance disconnected, the port plugged on carb?
Is the throttle cable set up correctly? The PO on my current 3rd gen project did a hack of a V8 swap and didn't set the linkages right. When floored, the throttle cable wouldn't open up the secondaries.
Don't know your level of experience with carbs or anything, but trying to help.

 

yes carb is adjusted with a vacuum gauge as per edelbrocks instructions and yes timing was set with port plugged and thorttle is opening and throttle cable is set up perfectly.

 

Awesome. I figured, but you never know. I'm sure if people checked their fuses and relays before hand, 90% off the electrical forum would be gone.

Were those the 64cc or 70cc heads? On a 78 low compression 350 the 70cc heads would suck.

 

i have no idea honestly but id have to assume they are the 70cc my friend doesn't know much about engines and probably assumed since 70cc would be better since you know biggers always better lol

 

No problem, I've done similar previously. Just throw a turbo on there to boost the compression.

 

Besides torquing everything down correctly, using the proper gaskets, etc, the most important thing is to match your parts to your goal. Heads, intake, cam and carb need to be all matched together. On my current car, it's not though. It's a drastic improvement that from what the PO put on. I just threw on parts that I happened to have sitting on a shelf at home. The thing that sucks about engine building is that learning experiences cost a lot of money.

 

Sorry but kind of sounds about right now man. That engine (well cam, and compression) was not a power house. Stock 160-170 HP

Your heads, intake, headers might have added 75 HP at best. So 240 HP at crank.. Take 15-18% off for drivetrain loss and you have 197 HP at the wheels.

Tiny exhaust pipes don't help. 1-5/8" is WAY too small. 2" true duals would be ok, 2-1/4" dual would be better.

What is the rear gear ratio? Gears like 2.73, 3.08 suck. 3.23 to 3.73 is what you want with 3.42 being a great all around gear

 

I think the 1-5/8" was for the headers, and he did say a 2" true dual exhaust. I do agree on the rear end gears. If not at least 3.23 replace them.

I almost forgot, you asked if changing the cam will help. Yes, it would. I'm sure some members here could give you good advice for your setup.