[462ta]

old motor
400,5C heads,8/1 comp,2801cam,stock intake,quadrajet,ram air man 2 1/2 exh,3.23 gears th350 stock stall.

new motor
406,13 heads,9.5/1 comp,60916cam,stock intake,quadrajet,ram air man 2 1/2 exh,3.23 gears,th350 2500 stall.

old motor on G tech would pull low 14's new motor will not even come close,usually hi 15's.
new motor has about 1000 miles on it now and just doesn't seem to pull hard like it should any ideas.this is a fresh rebuild with forged pistons and rods,zero decked and balanced.heads rebuilt with new springs and stamped 1.5 rockers.

[71 Ventura II]

Originally Posted by 462ta

old motor
400,5C heads,8/1 comp,2801cam,stock intake,quadrajet,ram air man 2 1/2 exh,3.23 gears th350 stock stall.

new motor
406,13 heads,9.5/1 comp,60916cam,stock intake,quadrajet,ram air man 2 1/2 exh,3.23 gears,th350 2500 stall.

old motor on G tech would pull low 14's new motor will not even come close,usually hi 15's.
new motor has about 1000 miles on it now and just doesn't seem to pull hard like it should any ideas.this is a fresh rebuild with forged pistons and rods,zero decked and balanced.heads rebuilt with new springs and stamped 1.5 rockers.

How are you leaving, ie standing start? If so are you loosing time spinning the tires? What's your shift point? Whats the total timing of the engine and at what rpm? Have you limited the advance to not retard/advance the timing above 4500 rpm's? Also have you verified the secondaries are opening all the way with the new setup? I'm biased as I ran a similar setup into the 12's so I feel it should be getting your car in the 13's minimum. JD

[mchell]

a couple thoughts....

looks like all you did was change heads, cam and a tiny bit more stall........the head change is moot in my mind as the 5c's are a good head for a 400 to begin with.....the 13's are also a good 400 head but you will gain little in the way of power between the two....the cam choice with the gear and stall is probably whats dogging it.....

You probably had a pretty good "match" with the first setup, as in,compression, cam, gear and stall

Your new setup is a little short on gear, a little short on compression and a little short on stall to be optimized for the cam you have chosen.......

[mchell]

forgot to ask.....what car is the engine in???

Hard to compare engine performance with light weight cars such as 71 Ventura's and heavy chasis cars such as GTO's and T/A's at near 4000lb's.......

[PunchT37]

Are you running an adjustable valve train? Did you degree the cam?

[462ta]

car is 72 formula
adjustable valve train,leaving from dead stop,no tire spin to speak of,shifting at about 5000,leaving tranny in drive,secondarys are opening,
12 deg tim

[65nss4spdGTO]

Did you CC the heads? How did you come up with the compression? number 13 heads should give you more compression and more power. What pistons did you use? the head swap alone should be worth 10hp, did you check compression to see if yopu are leaking, how do the plugs look?

[67cruiser]

May i ask, you stated stock intake, what year intake?? 67 thru71 are the good ones only for stock set-ups, never mentioned where your timing is set either?? I to fill car should be in the 13,s without any trouble to.What size headers are you running??? tri y headers or a true 4 tube header?? Yes please check to see if your sec. are opening to a full 90 degree,s by all means. What combo carb. are you running?? Also does the car bog?? Whats your fuel system like?? WE NEED MORE DETIALS TO HELP YOU OUT!!

[71 Ventura II]

Originally Posted by 462ta

car is 72 formula
adjustable valve train,leaving from dead stop,no tire spin to speak of,shifting at about 5000,leaving tranny in drive,secondarys are opening,
12 deg tim

Agreed the weight of the vehicle will make a big difference! Those Formulas are a little heavy most likely pushing 3800 lbs.

1. You need to identify/validate your Total timing consisting of the Initial (you stated 12 degrees) combined with the mechanical advance in the distributor. You'll need to know both the Total and at what rpm it's reached.

2. With that cam and combo I recommend an initial timing between 14-16 degrees and a total of 34-36 degrees to start.

3. The cam you selected doesn't even hit the Peak HP until 5400 rpm's and will need to be shifted 300-500 rpm's above the peak. Shift point that worked well for me was between 5500-5600 rpm's. 5000 rpm's is to low.

4. If your running regular "Street" radial tires and not blowing them away on the launch I'm betting your in need of a good advance curve in the distributor for one thing.

Try tuning the engine and increasing the shift points and check back. Good luck! JD

[screamingchief]

I agree I would like to know if the cam was degreed when installed.

Did you use a new timing chainset?

If so what brand?

Also like to know what brand & part number for the valvesprings and converter,those are two items that buying per cost can get a fella in trouble.

Also agree when problems arise,it's time for basic diagnostics,check the cranking compression,check the engine vacuum readings,check for vacuum leaks,and in the really tough cases,leak that thing down to find any serious issues.

What changes were made to the carb tuning on this?

Often something as simple as adjusting the valves too tight are the culprit,but till you work out those bugs,it's hard to say for sure.

[tempest455]

Tuning is everything!

[Will]

Same carb with no changes? New combo will want a lot more fuel, carb may need tweaking.

Not sure how mchell figures 8:1 compression is as good as 9.5:1 or higher. In terms of flow the 5C are as good as the 13s on the intake side, but the extra compression should definitely help and the extra exhaust flow should also help.

[95ramairformula]

With the 13# heads on the 400 and the Crower 60916, the engine should be a monster for performance. I am figuring close to 10.1.1 compression with that set up.

I don't trust the GTechs at all. Not a good measuring tool as compared to a local dragstrip. A buddy of mine ran 14.01-14.20 with a gtech on a flat 1/4 mile road.
Mph was in the 102-104 range. He then went to the dragstrip and ran consistent
14.5-14.7's at 97 mph. This was with the old style GTech as the new ones may be better. I have heard they were more accurate.

Keep tuning on the new motor. You have the right combo for sure. While the 60916 may like little more gear than the 3.23 it should still be a very strong performer. The difference between the two setups in performance should be night and day difference with the higher compression motor way on top.

[mchell]

not trying to be picky, but I did not say the extra compression was not worth anything....I said it was worth little...........and I mean little......most would not notice a gain by raising compression 1 point with all else being equal......and basically, all else is about equal here.....in my mind other upgrades needed to take place to optimize the cam.......if the 5c heads he was running were the 350ci heads they should have around 93cc chambers, which would yield about 8.5 to 1........8.5 to 9.5 is not earth shattering...

once again, I think his combo is SLIGHTLY mismatched, possibly causing a reversion in performance.......

[carguy1959]

I have a 64 GP w/ a 68 400/400 auto. I recently swapped the 68 #15 heads for a set of 68 #16 heads that I ported and polished. I put in a 2801 cam and a 2000 stall converter. I have stock hwy gears. After the swap it ran crappy with the original 68 q-jet, that worked well with the original setup. I got a 79 olds 800 cfm q-jet, rebuilt it, set the timing to 16 degrees initial advance, 40 degrees with vacuum. Now the cars runs great. I also have 1.65 roller rockers. I would suggest a carb swap and play with your timing till you get the best results.
Steve

[mchell]

not sure where all the "get a big carb" stuff is coming from.....as a comparison.....I have been running the same 71 qjet on my engine combo for 10 years.....my combo's have ranged from a bone stock 400 running in the high 14's to a 455 combo running flat 12's......never had a need to do much to the carb other than address the idle bypass airflow to get better idle with more cam......the qjet is a wonderful carb as it only flows what the engine combo wants.....I currently race and travel with 3 qjets that I have prepped myself, NONE outperform the other........I am confident that you have not "outgrown" your qjet.......... yet

[grandville455]

I have to agree with mike there on the carb deal.. I have my original 74 q-jet off my grandville that i tweaked.. And A friend borrowed it once when his well prepped carb wasnt up to snuff was full of rust cause of a bad tank.. anyway my carb ran dead even with what his did before the rust got into it!..... Carbs arent that finicky.. that carb now wont idle as good as my own 77 q-jet ,but like mike said idle fuel etc.. there but WOT its right there!... I would tune tune tune.....

[462ta]

thanks for all the replies.
heads were 76cc,14 cc dished pistons and zero decked
68 stock intake
hughes gm25 convertor
12 deg with 34 total in by 3000
83 olds carb that i went thru using cliffs book,73 jets 44 rods AU sec rods on H hanger
ram air man to X over thru dynamax ultra flows all 2 1/2
cam was installed straight up not degreed

[hal101]

i think the AU sec rods are a litle lean i have CE sec rods in mine and it runs great

[Tiberius]

With your #13 Heads, and now good compression and hot cam. Your car should Launch hard.

Your gears are okay...( Maybe could use 3.73's and a highier stall. ) and get the carb recalibrated by a good carb builder.. Set timing properly.. and I think that'll change your impression.

Something is amiss. and no-way should you be doing 15secs with that combo.. more like solid 13's