[jv628]

I have a 400 motor that does not have any power.I am looking for some suggestions on what to do. What I have is a 400 that has been recently rebuilt, was bored .030 over ,stock crank and pistons , a 2802 Summit cam , I have a set of 15 heads and a edelbrock performer pontiac manifold with a Q-jet carb, 3 tube headers. I have 3.36 gears and a rebuilt 400 trans with stock converter. This is in a 69 GTO, wont even spin tires from dead stop and I only ran 17's at the track . As far as normal everyday driving it runs pretty descent, Is there a better combination of heads and or intake or carb I should try. Any help or advice would be greatly appreciated.

[WDCreech]

I think that your biggest problem is the stock converter, and if those #15 heads are 1970 heads, they are small valve, but that wouldn't hurt your bottom end.

[guccieng]

how well did you tune the combo? parts sound fine, but they must be dialed in. did you degree the cam? what timing are you running (poncho's seem to very sensitve to timing)? how much and how soon is your mechanical advance? are you using vacuum advance? are you getting full throttle on the carb? fuel pump keeping up? i think you have plenty of potential in that combo and should be able to light up the rear, even with a stock converter. how many rpms do you drop when you put it in gear?

[screamingchief]

Stock pistons...

I hope you dont mean those "one size fits all" 8 valve relief cast pistons that sit way down in the bore as SOP,and have like twice the valve relief volume as a "good" piston has???

Well,the bad news is your compression may be waaayyy lower than you thought it was.

Also,there are two different #15 head castings out there.

One is 72cc "nominal" spec. ('68 290hp & 340hp 400's)
The other is 89cc "nominal". ('70 360hp 455)

And often the chambers on "virgin" heads will CC a bit larger than the nominal specs suggest.

So that too could be playing into this as well...

We would need to know the date codes on the heads to settle that deal.

Honestly,worst case scenario,the CR could easily be less than 8.0:1 here.

Couple that sorta low CR with a fairly big cam for the given "mild" combo,and I'm not surprised it seems a bit "lazy".

But all that takes a lot of things for granted,we would need much more specific info to be certain that is the problem here.

Terms like "stock" really wont cut it in terms of dissecting a combos good & bad points.

FWIW

Bret P.

[hal101]

i would say you need a 3000 stall converter at least 10-1 comp (72 cc heads)

and i never had good luck with the performer i would change to RPM or back to the cast iron

[geeteeohguy]

I'm running the same basic combo you are: original '67 400 bored 030 in my '67 convertible, with an 068 cam, stock log manifolds, stock original carb, stock original points distributor, 1970 #15 heads which cc'd at 87cc and have the small valves (I did upgrade the studs/nuts), TH400 with a stock converter and a 2.56 posi....and my car fries the tires when you stand on it from a stop, and runs very well going down the road. My short block was rebuilt by me with forged pistons back in 1988 and has about 68,000 miles on it. Something is wrong with your combo: the cam might be off, your compression is too low, etc. It should run better.

[mikeb]

Sounds like maybe you're not getting enough mechanical ignition advance. Hook up a timing light and see if the timing mark moves when you rev the engine.

[jv628]

Mikeb, I just checked and yes when I rev up the motor the timing mark moves down about an inch below the timing marks.My timing is at about the 12 mark. And the date codes on my heads are g028 andf258,so would those be from 68. Tomorrow I will be going to talk to the guy who built the shortblock to see exactly what pistons he used and to see if he did degree the cam and I reall appreciate all of the help I am getting from you Guys to help me get this thing figured out here soon,Thanks Jeff

[Kyflier]

You could have carb problems as well. I had a 71 400 that was very lazy as well. Car had been parked for a long time. I pulled the carb and went through it, it wouldfry the tires after I got through with it. Might check to make sure it's all functiong righ there as well. (my power piston was stuck in my carb)

[1967Tempest]

Had the same issue. Thought that the combo was correct. Got ticked off and found that the rebuilder had used the "one size fits all" NP411 piston. Coupled with a BIG quench area, my 9:1 compression engine turned out to be 7.5:1.this car was a TURD in town.

No big as I got a better set of heads and milled them to boost SCR to 8.2. Swapped cam to a smaller one and now, fries the tires with 2.56s and a 4 speed.

[mikeb]

I just thought of another thing. Are you sure that your throttle is opening all of the way? And if you are running a qjet - does the choke disengage and allow the air flaps to open?

[jv628]

I talked to the guy who built the motor and he did not degree the cam and also said used stock replacement cast pistons.

[geeteeohguy]

Before I installed the 068 cam in mine, I originally got a repro 067 grind from one of the vendors back then. The car was a complete slug, and this was was with #12 Ram Air heads I was using at the time! I checked it out, and the keyway was off-set....it was waaaay retarded. It does happen sometimes......