Looking for 20+ More HP - Page 4 - Vintage Mustang Forums
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post #46 of 91 (permalink) Old 05-09-2019, 11:17 PM Thread Starter
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Here's the plan I'm going with.....

Getting the BUNG and O2 sensor/gauge installed. Going to monitor the AFR and tune carb/recheck timing...maybe new wires. After its dialed in - hopefully it gets the higher RPM issue sorted. If that doesn't get it - going to have a look @ that valve float possibility but I suspect the previous steps will fix whatever is going on there. I imagine I'll get that problem fixed somewhere in the process. I still want to figure out the compression ratio. Is there a way to figure out ratio w/o using one those calculators? I just don't know enough about the pistons to convince myself I'm going to accurate. Is there relationship between cylinder compression and the compression ratio? I certainly can come up with the cylinder compression pretty easily.

If not - throwing caution to the wind and front end is coming off - slapping a CAM/lifter/spring combo (maybe roller conversion) that will pull through 6500 RPM and power on through life like Rick Flair.

Side note: throwing some 3 point seat belts in front and back next week. Was driving with my 9 year old in the back seat and "maybe" pulled out of the neighborhood a bit vigorously. She slid across the back seat laughing and giggling. I asked if she had her lap belt on and she did. She then replied that she didn't believe the seat belts in that "old" car were very effective so yeah - she's smart and I bought some new belts.

If anyone thinks this is a dumb plan - feel free to let me know, I'm always open to feedback.

Thanks and have a great night.

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post #47 of 91 (permalink) Old 05-09-2019, 11:42 PM Thread Starter
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Quote:
Originally Posted by 2nd 66 View Post
ditch the power steering and a add phenolic carb spacer and a Filter top.......
.

So whats the carb spacer bring to the table. Only cooler fuel. Had one one years ago but now its sitting on my desk. Unsure I understand the principle behind them. Any science behind the size of them (1/2'' versus 1") besides hood clearance? Just wondering. Might have to hit up Alexa and see what she has to say about it.

Thanks
-J

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post #48 of 91 (permalink) Old 05-10-2019, 02:02 AM
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Carb spacers are a tuning tool. Sometimes they can improve your top end by a few horses, sometimes not. It's all about harmonics. Pulses running through the manifold, and whether the fuel stays properly in suspension, how well it pulls air and fuel through your carb. Cooler carburetor is nice too, if you have to do a hot start. How tall should it be? Well, start with one size, see if the engine likes it, and then try another size. That seems kind of basic, because it is, and that's really exactly how a tuner finds out what the engine wants.

Open spacer vs 4-hole vs tapered? Well, with your carb, running a dual-plane, you're going to want all the signal you can get, I'm thinking. 4-hole makes more sense to me, because you separate the vacuum signal instead of sharing it from side to side like an open or even tapered spacer would. However, on the top end, the open spacer might (again) give you some extra power - probably at the expense of some low to midrange torque and driveability.

Flat tappet hydraulic lifters might be able to spin to 7k if your valvesprings will take it, and the lifters are not pumping up. Hydraulic roller lifters are heavier, and require more valvespring to control them. They don't do well past about 6500 RPMs, so you need to decide if this quest for power requires more RPMs, or if you can find a way to build more torque and keep your revs down at a more reasonable level. If you really want to sing past 7k, start thinking about solid lifters. As you gain in RPMs, you really start to stress other parts too, like your rods, pistons, and bearings. Having a high quality balance job, damper, and flywheel (along with maybe a safer bellhousing?) become pretty important.

IMHO, knowing that you don't want to redo all the guts of your engine in order to support this quest for 300, making more revs is probably not the direction you want to go with this. Finding more torque instead of just making it farther up in RPMS is probably better for your stated goals.
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post #49 of 91 (permalink) Old 05-10-2019, 06:25 AM
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Assuming your RPM heads has 60cc combustion chambers, I’d estimate your static compression ratio to be about 9.3:1. That’s just using generic dimensions common to most 302 engines.

Something that no one has mentioned is switching to 1.7 ratio rocker arms. But you may want to get the valve springs sorted out first.

I’m a believer in using carb spacers and I’ve almost always used a 1” open spacer.
Spacers add a little more plenum volume to the intake manifold. Which helps the engine breath at higher rpm.
General rule of thumb is open spacers for dual plane (split plenum) manifolds and 4-hole spacer for single plane (open plenum) manifolds. But every engine build is a little different so try each one to see which works best.

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post #50 of 91 (permalink) Old 05-10-2019, 09:12 AM
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Here are some of my thoughts;


A global thought process, you can "tune" your car to build numbers and I can "tune" my car for performance and I'll bet shaved eyebrows I will beat you. This is why people say use the dyno to get the best baseline you can then go to the track with a tool box and truck full o parts. Performance is not just about numbers, performance and winning is about being fast in the type of driving you choose.



Carb: People think big is about HP, big carbs will give big HP numbers BUT throttle response suffers. THis is no big deal if you stomp at the red light and lift off the red button at the green light - leaving your foot on the floor till you go through the gates. For track and autocross work, your car needs to snap when you want it to, this may not show up on a dyno since your "snap" on your dyno run happened about 2500 rpm when you floored it in 4th gear. Its all about mid-range velocities and bigger carbs have smaller velocities as they are designed to move big air for motors need big air. So when the air flows slow, the impulse from WOT to cylinder head is lethargic, no snap and there is a penalty as fast moving air atomizes fuel better.



Flywheel: unless you want to drag race, your neck will feel an aluminum flywheel everywhere on an autocross or track but it may not show up on your dyno numbers except that the curve will rise slightly quicker but the top number may not change one bit. Again, throttle response with an aluminum or light flywheel is an amazing seat-of-the-pants experience.


I have the Performer RPM system on my 351 and it doesn't roll off like yours, check your cam specs against the cam engineered for your heads and intake to see how close it is. Mix and Match is always a crap shoot and more a reflection of the competence of the builder than anything else.



Before I did anything, I would send your Dizzy out for a rebuild and correct curve. That may give you a big difference for a reasonable price giving you the upper RPM range. I would change the MSD box only after everything else including the purity of the power source at high RPM is investigated.



Finally, before I went back to get the shaft up your tail pipe, I would add a bung and install a AFR gauge, then you can tune to your heart's content...




Good Luck
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post #51 of 91 (permalink) Old 05-10-2019, 12:07 PM
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Really? You've just changed your argument with "properly chosen off-the-shelf cam," but it may not exist in the first place.
The off-the-shelf cam for a 300rwhp 302 exists and it's not rocket science to choose it.

A cam was recommended to me by a member of this forum and I went out and found it used for $150. If you look at the specs, it's pretty standard stuff. Lift and duration close to what TFS calls a "stage 2" cam. You can find similar cams from various manufacturers. My static compression was on the high side cause I was originally building a 289 and so I thought the lazier LSA of my cam would help deal with that. If you understand cam specs it's not hard to choose one for your standard, run-of-the-mill SBF. Building a stroker with nitrous? Maybe you need call someone to optimize for your nitrous window. Building a 302 that has been built a million times before = don't need to call anyone.

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post #52 of 91 (permalink) Old 05-10-2019, 01:01 PM
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One last thing, you might look at a large diameter cap with a converter. MSD pumps and the big cap is supposed to give the extra gap for hi-rpms and big energy. I bet MSD calls for one... I JB weld my plastic converter to the screw so its solid to the dizzy.

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post #53 of 91 (permalink) Old 05-10-2019, 02:24 PM
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Originally Posted by jdub View Post
The off-the-shelf cam for a 300rwhp 302 exists and it's not rocket science to choose it.

A cam was recommended to me by a member of this forum and I went out and found it used for $150. If you look at the specs, it's pretty standard stuff. Lift and duration close to what TFS calls a "stage 2" cam. You can find similar cams from various manufacturers. My static compression was on the high side cause I was originally building a 289 and so I thought the lazier LSA of my cam would help deal with that. If you understand cam specs it's not hard to choose one for your standard, run-of-the-mill SBF. Building a stroker with nitrous? Maybe you need call someone to optimize for your nitrous window. Building a 302 that has been built a million times before = don't need to call anyone.
I always recommend Anderson cams on these cookie cutter builds. They make great power
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post #54 of 91 (permalink) Old 05-10-2019, 02:25 PM
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Quote:
Originally Posted by dobrostang View Post
Here are some of my thoughts;


A global thought process, you can "tune" your car to build numbers and I can "tune" my car for performance and I'll bet shaved eyebrows I will beat you. This is why people say use the dyno to get the best baseline you can then go to the track with a tool box and truck full o parts. Performance is not just about numbers, performance and winning is about being fast in the type of driving you choose.



Carb: People think big is about HP, big carbs will give big HP numbers BUT throttle response suffers. THis is no big deal if you stomp at the red light and lift off the red button at the green light - leaving your foot on the floor till you go through the gates. For track and autocross work, your car needs to snap when you want it to, this may not show up on a dyno since your "snap" on your dyno run happened about 2500 rpm when you floored it in 4th gear. Its all about mid-range velocities and bigger carbs have smaller velocities as they are designed to move big air for motors need big air. So when the air flows slow, the impulse from WOT to cylinder head is lethargic, no snap and there is a penalty as fast moving air atomizes fuel better.










Good Luck
Exactly what I was saying.....
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post #55 of 91 (permalink) Old 05-10-2019, 02:39 PM
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Im not sure if you mentioned this or not in a previous post, but what are you running for a fan set up? Engine Masters on motortrend did a dyno shoot out where they ran a small block with out a fan and then with a fan and it lost almost 30 horsepower due to parasitic losses of running the fan. If you have an electric fan, then disregard this post. but this is just my 2 cents.
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post #56 of 91 (permalink) Old 05-10-2019, 04:20 PM
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Originally Posted by jdub View Post
The off-the-shelf cam for a 300rwhp 302 exists and it's not rocket science to choose it.

A cam was recommended to me by a member of this forum and I went out and found it used for $150. If you look at the specs, it's pretty standard stuff. Lift and duration close to what TFS calls a "stage 2" cam. You can find similar cams from various manufacturers. My static compression was on the high side cause I was originally building a 289 and so I thought the lazier LSA of my cam would help deal with that. If you understand cam specs it's not hard to choose one for your standard, run-of-the-mill SBF. Building a stroker with nitrous? Maybe you need call someone to optimize for your nitrous window. Building a 302 that has been built a million times before = don't need to call anyone.

What works in one situation, doesn't always apply to others. When people give share information and results based on their singular experience like it's written in stone, it's not always helpful to the OP. Especially when it is inaccurate.

I am glad you're pleased with your choices

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post #57 of 91 (permalink) Old 05-10-2019, 04:40 PM
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Originally Posted by bbmach View Post
What works in one situation, doesn't always apply to others. When people give share information and results based on their singular experience like it's written in stone, it's not always helpful to the OP. Especially when it is inaccurate.

I am glad you're pleased with your choices
You leave me no choice

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post #58 of 91 (permalink) Old 05-10-2019, 04:43 PM
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What works in one situation, doesn't always apply to others. When people give share information and results based on their singular experience like it's written in stone, it's not always helpful to the OP.
What I find unhelpful is when people add ambiguity and mystery where there is none. You're making building a 300rwhp more complicated and expensive than it has to be. How is that helpful?

Honestly a lot of the advice in this thread is pretty bad. Maybe there is actually some mystery in building a 300rwhp 302, because a lot of people don't seem to have a clue.

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post #59 of 91 (permalink) Old 05-10-2019, 05:06 PM
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What I find unhelpful is when people add ambiguity and mystery where there is none. You're making building a 300rwhp more complicated and expensive than it has to be. How is that helpful?

Honestly a lot of the advice in this thread is pretty bad. Maybe there is actually some mystery in building a 300rwhp 302, because a lot of people don't seem to have a clue.
Because you took the easier route doesn't mean you should discount other experiences. Not everyone thinks good enough is good enough. If making a phone call nets you (more HP, better driveability characteristics, idle quality, etc) with a particular camshaft grind your combination calls for, why would you discourage that?

The OP stated he was looking for 20 hp. Once he dials in his combination, he still may be 15 hp short. IF he decides to go the new camshaft route, getting the recommendation from a camshaft company isn't complicated nor more expensive than this thread. :-)

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post #60 of 91 (permalink) Old 05-10-2019, 05:58 PM
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Spoke with the shop who ran the Dyno. They require an O2 bung installed on my exhaust (which I do not have). They did no put an O2 wand in the tailpipe. I assuming they did not because they work solely on late model mustangs. (best guess or I could be making sh*t up - no idea) I should have asked the question upfront - now I know. So no AFR. Need to figure out how to get that O2 reading.
Start with the easy stuff...
1. Verify your throttle linkage is opening your carb all the way. I've heard of a number of instances where 'full throttle' was not yielding full throttle. When a friend sorted that out on his Pantera, it unleashed the beast!
2. Send the distributor out to be rebuilt and properly curved.
3. Get a proper Dyno Tune - Go back to your tuner, have him install an O2 bung so you know what's actually going on in the engine with your A/F ratio, and properly tune the car and carb on the chassis dyno. You should do that regardless of anything else, and do it again if you make any other changes to the engine (intake, exhaust, cam, valve springs, etc.).

That's my advice, and it's only worth what you paid for it!
Good luck!

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