#21  
Old 10-28-2020, 05:14 PM
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As a comparison I have a stock ‘68 350HO 4 speed w/3:36 saf-T-trac in my Lemans convertible and I don’t think the HO engine is really anything more than what your rebuilt HP/TQ numbers should be although the 18 heads do yield a higher compression.
What I can tell you is that it gets up and goes (factory rating 320HP) so something is off with your tuning I would suspect. I thought my 350 HO came factory as a 068 cam with the 4 speed (evidently ‘69 HO Lemans did) but I was told it should be an 067 (you can hear it idle in my signature). While a Summit 2800 might be a good choice I would have at least chosen the 2801 (with my drivetrain combination).
Maybe have one of our resident experts go through your distributor curve and carb after you resolve bad lifter issues (as mentioned possibly dropping those cylinder down on power)? If that doesn’t liven it up maybe the cam timing is off?
Let us know what you find.

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  #22  
Old 10-28-2020, 05:20 PM
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You didn't mention a vacuum advance system, are you using one, or just initial and mechanical?

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Old 10-28-2020, 05:36 PM
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I would also suspect a flat cam, that car should easily be able to break the tires loose with a 3.23 gear.

There may be a host of tuning issues that could be adding to the lack of performance from a standstill. If everything is as it should be you are correct in assuming that the performance is substandard.

I'm curious if the cam timing was checked upon install for a mistake in timing components. Trusting the manufacturers to not have any variances in the cam components is a blind leap of faith.

Many possibilities in hunting down why performance has suffered in this build, it may take a qualified detective to track down all the possibilities.

Two cross threaded studs would be a red flag in my opinion, to suspect the whole build. That is however my opinion, and you asked for advice, and opinions.

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  #24  
Old 10-28-2020, 06:35 PM
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Quote:
Originally Posted by dataway View Post
You didn't mention a vacuum advance system, are you using one, or just initial and mechanical?
Vacuum advance. No clue what the range is. Whatever comes standard on the Pertronix "Plug and Play" distributor, would be my best guess.

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  #25  
Old 10-28-2020, 06:38 PM
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Quote:
Originally Posted by Stan Weiss View Post
Please do a cranking compression test and post up the numbers.

Stan
Measured with an OTC tester.

1 = 180
3= 170
5 = 170
7 = 180
2 = 170
4 = 170
6 = 150
8 = 165

The intake lifter/push rod on #8 has partial oil flow. Intake lifter/push rod on #6 has no oil flow.

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  #26  
Old 10-28-2020, 07:47 PM
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Quote:
Originally Posted by FlyJS41 View Post
Measured with an OTC tester.

1 = 180
3= 170
5 = 170
7 = 180
2 = 170
4 = 170
6 = 150
8 = 165

The intake lifter/push rod on #8 has partial oil flow. Intake lifter/push rod on #6 has no oil flow.
Unless your cam is installed really far advanced you have close to the CR you were told. What octane gas are you running?

Stan

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  #27  
Old 10-28-2020, 07:53 PM
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Quote:
Originally Posted by Stan Weiss View Post
Unless your cam is installed really far advanced you have close to the CR you were told. What octane gas are you running?

Stan
Shell and Chevron 93. Engine temp never gets over 185*, FWIW.

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  #28  
Old 10-28-2020, 08:00 PM
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When you put the new lifters in, I would put a dial indicator on each individual one and make sure they are all opening to the advertised lift. If a lobe or two is really flat, it might even be noticeable visually.

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  #29  
Old 10-28-2020, 08:06 PM
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My feeling is you have to must cylinder pressure. You can lower you CR or or put a bigger cam in it. If it was mine I would put a 2802 cam in it.

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Old 10-28-2020, 08:09 PM
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Quote:
Originally Posted by RocktimusPryme View Post
When you put the new lifters in, I would put a dial indicator on each individual one and make sure they are all opening to the advertised lift. If a lobe or two is really flat, it might even be noticeable visually.
Makes sense. Hopefully, I can find someone to help as I don't have a dial indicator or experience using one.

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Old 10-28-2020, 08:17 PM
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Quote:
Originally Posted by Stan Weiss View Post
My feeling is you have to must cylinder pressure. You can lower you CR or or put a bigger cam in it. If it was mine I would put a 2802 cam in it.

Stan
Interesting thought. I happen to be messing around with one of those online, dynamic compression ratio calculators. This was just for my own edumacation trying to understand the concept. When I plugged in numbers for my combo, it showed me on the high side of DC. When I plugged in the numbers with the Voodoo 256/262 cam, the DC was significantly lower. I have to wonder if there's something to that?

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  #32  
Old 10-28-2020, 08:34 PM
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Quote:
Originally Posted by FlyJS41 View Post
Makes sense. Hopefully, I can find someone to help as I don't have a dial indicator or experience using one.
You can buy a cheap one off amazon with a magnetic base. No need to go nuts. Summit also sells individual solid lifters, which help with checking lift without a hydraulic plunger messing up your readings. I have a couple solids in my tool box for that purpose.

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  #33  
Old 10-28-2020, 09:46 PM
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My buddy is a big time tuner in the late model world. He’s seen lots of ping issues with shell gas. Apples to apples proven - shell sucks. Chevron ok. A out of town guy at track this weekend has a 69 lemans bracket car with 350P. Runs 8.10’s 1/8th! Dude is from Abilene, Texas. Maybe he’s on here. Pretty damn quick with traditional Pontiac 350

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  #34  
Old 10-28-2020, 10:07 PM
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I used to run a P350. Stock internals, cast rebuilder pistons down in the holes, XE256 cam, #17 heads. Performer and Q-jet. I had about 36-38* of timing in it to get some low-end back. Made about 12-14" of vacuum. Compression in high 8s.

It was in my 67 Lemans with stock converter, TH350 and 3.23s. It would smoke the tires pretty good. It would chirp 2nd at WOT and run right with a stock 60s Thunderbird on a top end run one day on the interstate. Ran mid 9s in the 1/8th, which is mid 14s in the quarter. I ran a set of 670s and headers on it, but it didn't pick up too much. It did act like it wanted a bit of stall, it didn't really wake up till 1800 RPM. But it was a lot of fun for the cheap. I've posted about it before on here, you may be able to fi nd old posts of mine.

The 2800 is 204/214. The XE256 was 212/218 on 110LSA. I do think you could use a 212-215* cam, especially since you have a stall. Don't use a XE, use a Crower or Lunati on a 112-114 LSA if you have detonation issues. The pistons down in the hole aren't helping.

If you think a lifter is bad, go ahead and change the cam. No sense doing it twice.

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  #35  
Old 10-28-2020, 10:09 PM
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I'd ensure the mixture on the carb is correct at all rpms. you need to install an O2 sensor to really know what's going on. once that is set, you should be able to raise the timing to the normal 36ish total. you also don't want the timing coming in to quick. I would not have it come in any faster then 3,500 rpm initially.

the low compression on 6 and 8 are troublesome. are you sure you let it pump up enough to give a good reading? i normally let it pump around 5 times per cylinder just to be sure.

if your cam flattened a couple lobes that is not good either. that fine metal running around the engine doesn't do anything good for it. ask me how i know...

that should be a strong little 350.

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  #36  
Old 10-28-2020, 10:10 PM
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Upon further review, it seems I was referring to the wrong timing curve notes. Currently, I'm running 14* initial and 34* total. Sorry for any confusion.

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Old 10-28-2020, 10:36 PM
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Quote:
Originally Posted by FlyJS41 View Post
Measured with an OTC tester.

1 = 180
3= 170
5 = 170
7 = 180
2 = 170
4 = 170
6 = 150
8 = 165

The intake lifter/push rod on #8 has partial oil flow. Intake lifter/push rod on #6 has no oil flow.
Try backing off the rocker arm nut with the engine running so you can see if the oil begins to flow. Had this experience, and the pushrod was not spinning as it should. Backed off the nut (poly lock) and oil began to flow - problem solved.

  #38  
Old 10-28-2020, 10:51 PM
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Quote:
Originally Posted by 74Grandville View Post
I'd ensure the mixture on the carb is correct at all rpms. you need to install an O2 sensor to really know what's going on. once that is set, you should be able to raise the timing to the normal 36ish total. you also don't want the timing coming in to quick. I would not have it come in any faster then 3,500 rpm initially.

the low compression on 6 and 8 are troublesome. are you sure you let it pump up enough to give a good reading? i normally let it pump around 5 times per cylinder just to be sure.

if your cam flattened a couple lobes that is not good either. that fine metal running around the engine doesn't do anything good for it. ask me how i know...

that should be a strong little 350.
Yes sir, I believe I gave it sufficient cranking time. Out of curiosity, I did a wet test on 6 and 8. Came up with 165 and 170 respectively. She doesn't burn any oil that I'm aware of.

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  #39  
Old 10-28-2020, 10:58 PM
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Quote:
Originally Posted by PontiacJim1959 View Post
Try backing off the rocker arm nut with the engine running so you can see if the oil begins to flow. Had this experience, and the pushrod was not spinning as it should. Backed off the nut (poly lock) and oil began to flow - problem solved.
Thanks Jim. Should I back it off until it ticks, then re-lash or just loosen 1/8-1/4 turn and see what I get?

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  #40  
Old 10-28-2020, 11:04 PM
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Quote:
Originally Posted by Sirrotica View Post
I'm curious if the cam timing was checked upon install for a mistake in timing components. Trusting the manufacturers to not have any variances in the cam components is a blind leap of faith.
Of course I have no proof, but I'm guessing it was simply installed dot-to-dot.

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