Matching your camshaft to your compression - Dyno a testing 1970 GTO Pontiac 400 - Quadrajet Tuning

This video concludes the testing after increasing the compression pressure from 140 to 170PSI.
The subject engine is a 406 Pontiac with #13 heads and a Crower 60916 camshaft, stock 977068 cast iron intake and 750CFM Rochester Quadrajet the compression ratio is now 9.88:1 increased from 9.1:1.

[@Christopher-re2hl]

I'm glad you're experimenting with the Pontiac 400. I have one just like it with 6X4 heads and a sum-2800. I have another block I am going to build later and will have #13 heads ported with 10.5:1 compression and either a competition cams 270 or 280H. I can't run an Edelbrock performer RPM because of hood clearance but maybe a torquer two small open plane or cut the plenum divider down on the stock. I will be running the same ram air three reproduction manifolds and like you am faced with trying to figure out how to get the best out of those manifolds. The 280H might be a tad too big for those manifolds and the 270 might be just right. What you did so far is working great I might just duplicate what you did thanks again 👍

[@goldsgarage8236]

Thanks for the info Chris. AG

[@alexvendrig9205]

Great having Austin's experience with the carb-

[@goldsgarage8236]

Austin as an accomplished engine builder and drag racer. I am amazed at the power he make with Stock and SS engines. AG

[@battletrak4392]

Storing the metering rods in a piece of cardboard is genius! Always good to see a Pontiac V8.

[@goldsgarage8236]

Thanks Battle, sorry i missed your question until now. We were lucky to have Austin to help us. AG

[@davenkaren2572]

I LOVE that you give clear explanations!!! Great vids!!! THANKS!!

[@goldsgarage8236]

Thanks very much for the nice compliment Dave. You are inspiring me! AG

[@adammcilmoyl4278]

Those Qjets are highly under appreciated. Those carbs, along with the early Holley 3310 with the dogleg boosters, were the best street performance carbs ever made IMO. I've got a late 70s 454 Qjet I'm going to be using for a 427 Chevy build, and a late 70s Pontiac W72 Qjet for a 400ci Pontiac build as well. Both are the larger 800cfm units.

[@goldsgarage8236]

Thanks Adam, I would agree. this was also an 800. AG

[@realazliving]

Good work. I'm glad you got what you wanted out of it.

[@goldsgarage8236]

Thanks Robert, it was a bit of an experiment but we were happy with the results. AG

[@The340king]

The only thing better than a water brake dyno is God's dyno, the racetrack. I used to use Engine Jr/ Engine Pro to determine the optimal duration for my race engines. It becomes more subjective when you apply it to a street engine. Good work!

[@goldsgarage8236]

Thanks for your comment Brad. AG

[@PatandDoopypoopy]

Hi. Just a thought. Great changes. We have done similiar with very positive results. So we did a few more changes. We advance in 2degree increments until peek comp reached.(sometime 6 degrees total) We did 1 additional step for low end torque (especially if a stock_near stock stall speed). We use true blue name brand Rhoads lifters. Yep they make noise of course (its ok, they sing to you,). We liked the improvement all the way around.

[@goldsgarage8236]

Thanks for sharing your knowledge and experience Patrick. AG

[@alleyoop1234]

I find it interesting that AX rods were used. I had a factory 1980 Monte Carlo Turbo Coupe that had a draw through turbo setup with a Q Jet. When I took it to the drag strip I ended up using AX rods also. But I do not remember what hanger I used, it was 30 years ago. With a few mods and 18PSI & 2.56 rear gears I got it to run 13.9's at the Eagle Motorplex

[@kensnyder2340]

AX metering rods were pretty common in some 454CI chevies. A lot of the 500 CI Cadillac's had CZ rods. These were great for a big block with high flowing heads, large cam & headers. 😁

[@goldsgarage8236]

Thanks for your input Ken. AG

[@robertwest3093]

Only 20 hp difference between manifolds and headers at that power level is impressive by any standards. Some exhaust manifold designs are good but the majority are bad. When it comes to nice manifolds the 1960s and early 1970s Mopar manifolds come to mind. I would have liked to see the gains with just the compression increase. 21 lb/ft gain for less than 3/4 point compression increase and 4 degree cam advance is impressive!

[@goldsgarage8236]

Thanks Robert, the Ram Air Manifolds are actually pretty good. They have a divider cast between the center cylinders that share the same exhaust port.

[@mikeing3924]

Great video. Pontiac engines are awesome. How does one reach this quadrajet expert Austin for advice or carburetor replacement?

[@goldsgarage8236]

Thanks Mike, Austin's cell # is 519-670-1897. He said you are welcome to call him. Please leave a message if he doesn't answer. Good luck.

[@tonysingleton8340]

So what was the difference in horsepower with the headers vs the Ram air manifolds?

[@goldsgarage8236]

Thanks for the question. On the previous dyno session we got about 20HP more with the headers, however in this session we focused on the tune with the manifolds because that is how it will be in the car. If you notice how the Pontiac heads are made, the center 2 cylinders share the same port and so the headers only have 3 pipes. The manifolds however have a divider between the cylinders which I would expect will help.

[@jimdandy849]

Great explanation of what was done. I have advanced cams for the same reason and also to good effect. Were the #13 heads bone stock, or was any porting done? Thanks.

[@goldsgarage8236]

Thanks Jim, there was some mild porting on the heads. AG

[@scottsienkiewicz8371]

Still curious as to what size jets were in the Quadrajet?

[@goldsgarage8236]

Thanks Scott. I will try to find out for you. AG

[@yarrdayarrdayarrda]

Quadrajets, so easy to tune WOT, biggest pain in the arse to tune the primaries. (also rods, but also jets. Pulling the lid off of one of those, with the choke linkage, is a job.)

[@goldsgarage8236]

Thanks Yarda, please keep watching. AG

[@dadalebreton184]

1 year after... How much mileage, what kind of driver was he? The compression is now 170psi but could have been a little more and more lift if the camshaft wasn't worn a couple of thousands. People tend to complain about Carters or Rochesters but they where engineered to drive and street race occasionaly. Delorean wanted to win on sundays. Thats why he put these engines in GTO first of all. Great content.

[@goldsgarage8236]

Thanks for the comment Dada. DeLorean was a visionary for sure.

[@joe-hp4nk]

Correct me if I'm wrong, but advancing the cam will increase the overlap thus tightening the LSA, which is a good thing.

[@scotthatch4548]

Incorrect... Lobe center angle and overlap is ground into the camshaft ... Advancing the camshaft moves the whole cam

[@goldsgarage8236]

Thanks Scott, you are correct.

[@joe-hp4nk]

@@scotthatch4548 ok, thanks

[@keithiverson6687]

Advancing the cam will close the intake valve earlier, which will trap more air at lower rpm. This usually makes more torque, but hp will drop off faster past peak.

[@scotthatch4548]

@@keithiverson6687 actually torque is more about fill at 75 degrees after tdc and advance gives you more fill because of lower center line angle on intake valve... Closing early can help with pump back but that is less of a concern ...I have done videos on these camshaft events

[@WesternReloader]

Making 160 psi warm cranking compression at 5100’. Puts me around 190 at sea level. Run a 500cfm carb at elevation and 600 at sea level . 10:1 331 sbf

[@goldsgarage8236]

Interesting approach, thank you for sharing Piercer. AG

[@robertwest3093]

Also, anyone that chooses the Quadrajet carburetor are alright by me! It's all I ever use. If more people would learn how to tune them I believe more people would be using them.

[@goldsgarage8236]

Thanks Robert, you are correct. We have tested engines with Quadrajet vs. Holley carbs and they do well. The Stock and SS drag racing guys like Austin Ward (who was in this video) make awesome power with Quadrajets.

[@kensnyder2340]

@@goldsgarage8236 , There are also front metering rods& spring that can be tuned on the Q-Jet. If I remember correctly they are called vacuum pistons. I used to have good luck matching the spring controlling the front metering rods to the engine vacuum. Really affects the mileage as well. I'm sure Austin knows all this. I always like the Q - Jet, very tune able carburetor. So many people in the 60's & 70's removed these in favor of the Holley. I enjoyed the video.

[@jimmyjimbo61]

I sure would be interested in the dynamic (not static) compression of both builds. 140 psi on the first build was pathetic! And... I would want a tad bit more than 170 psi than the second build provided. But, thats just my two cents worth.

[@goldsgarage8236]

Thanks Jimmy, I will ask Mike to reply to this question as he has these numbers in his head. For info, we did detect a little detonation as we advanced the timing.

[@mkimble21]

Dynamic was 7.35:1 and 7.98:1

[@scotthatch4548]

You need to probably watch my videos on what makes HP because it doesn't work like you think... I have a whole series of them at the chalkboard explaining engines

[@goldsgarage8236]

Thanks Scott, and sorry for the late reply. Yes I have watched your videos, very informative. Thanks AG.

[@jimclarke1108]

Here again

[@goldsgarage8236]

Thanks for watching my channel and commenting Jim. AG

[@marknowakowski6590]

Hmmmmmm to my understanding 69 was the last yr for the GTO. 70 yr split up into the Pontiac tempest and the lemans due to insurance and government regulations.

[@goldsgarage8236]

Thanks Mark. I will have the owner respond to this one. AG

[@mkimble21]

71 was the last year. 72/73 is was an option on the Lemans and 74 an option on the Ventura.

[@larryw5429]

If they are going to run premium fuel why not have compression up 10.5:1 Its free basic hp gains everywhere! Most 60s-70 year muscle cars had at least 10:1 compression and 70 gtos had 10.5:1 and made 370 hp with manifolds on with a old cam profiles. so at sub 10;1 compression you went backwards.. Modern camshaft profiles and stock compression that motor should of been made 400 hp easy! You you did all that work and took motor out heads off ect to gain only 10 hp? No reason you can't have a 400 pontiac 1 hp per cubic inch and still have it very streeable with todays camshafts!

[@davidmitchell7183]

With cast iron heads, I think most builders stay 9.5 to 1 or under but what do I know. Back in the 60's higher octane leaded gasoline was available. We stopped using it after seeing the long term effects on Boomers decision making.

[@timsprojectcar1875]

@@davidmitchell7183 I agree with the strategy of using cranking compression to match cam to the C.R. of the engine. It makes sense.

[@goldsgarage8236]

Thanks Tims

[@goldsgarage8236]

Thanks for your comment David, being a boomer myself, I would have to agree with you

[@goldsgarage8236]

Thanks for your input Larry.

[@Rick-O-Shay60]

WTF No dyno pulls? What were the gains with carb adj? You build engines, yet don't know how to set up a carb? 👎

[@goldsgarage8236]

Thanks for your comment Ricky. We did make video of the dyno pulls, however we lost some footage through technical difficulties. There are other video's on my channel of the same engine on the dyno so please feel free to check them out. As for the carb tune, since I had access to the expertise of Austin Ward, I think it was smart to use it. I hope you continue to watch my channel and make your comments. Allan Gold