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Cant get full throttle Engine wont rev up past 3,500 without bogging down
Date: September 12, 2020 06:25PM

I just picked up this decent buggy at a good price and it idles great FIRES RIGHT UP but wont rev up past 3,500 or so..
SO..
I checked everything points,distributor,fuel pressure,rebuilt carbs,checked valve adjustment everything is great....the only thing odd is when i do rev it up a little i get a slight pop or backfire from the 1,3,5 side of the engine on deceleration. all the valve adjustments are correct.
engine has headers and it's in a buggy and and the engine rotation is clockwise for the vw trans....
i will be checking compression tomorrow...
WHAT THE HELL MAN...!!

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: MattNall ()
Date: September 12, 2020 06:40PM

While holding the Trottle WIDE open, and revs to 3500 rpm, advance the. dist buy hand to seee if it will rev to 5,000 rpm. Back to idle and check what base timing is.

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: alphasud ()
Date: September 12, 2020 10:20PM

Good tip Matt I was thinking timing was late as well. Popping also could be exhaust leaks.

David North Idaho
1965 Corsa Turbo converted to 140
1971 Super Beetle with 2.5L Subaru engine
1965 Corsa mid engine project
1973 Mercedes 280 project

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: 66vairman ()
Date: September 13, 2020 11:22AM

While unusual --- A restricted exhaust can cause the problem you mention. Critters or collapsed muffler baffles can do it.

I'm sure you checked it, but plugged up air filters will also cause problems.

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: FLSteve ()
Date: September 13, 2020 02:06PM

Are you sure you are getting full travel of the throttle linkage?

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: junkman ()
Date: September 13, 2020 08:11PM

My 1963 Spyder had the same problem when new, and when the dealer pulled the engine apart, they found that it had the wrong cam installed at the factory, or at least that is what they told me. I didn't see it apart, and I believe them to have been an honest dealer, so I have no reason to doubt them. It drove great after that, and I never blew a head gasket, like some friends that had Spyders were doing regularly.

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Woodstock CT... Located on the Connecticut / Massachusetts border, approximately 6 miles from the center of Southbridge MA. About 45 minutes from Hartford CT. 1 1/2 hours West of Boston MA. Woodstock CT to Los Angeles CA 2,937.1 miles. 1 Mile as the crow flies to Big Bird's nest.

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: RobertC ()
Date: September 13, 2020 11:44PM

Did you get bored again - and try to run your dune buggy?

You posted basically the same problem 3 years ago?

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: JimBrandberg ()
Date: September 14, 2020 05:41AM

Is the distributor mechanical advance working? With the vacuum advance disconnected can you see the advance with a timing light when you rev it up?

Sometimes the harmonic balancer rubber slips so The timing notch on the pulley is not accurate. Usually there's an index line on both sides of the rubber in line with the notch.

Verify full throttle by looking into the carburetors with the engine off.

I don't know if I'm brave enough to run the engine at full throttle while messing around with the distributor timing rotation.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: roger65180 ()
Date: September 14, 2020 05:51AM

A hot coil that is weak could cause that issue , I had a 61 Impalla 283 that ran and one a test drive it just got slower and slower till it would not go 10 mph , new hot coil and off it went.

Roger R
Madison Wi
62 ct pg turbo
65intercooled 180 4sp,autocrosser
62 Rampy

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: TerribleTed ()
Date: September 14, 2020 08:27AM

Restricted fuel flow could also cause this issue. If the fuel can not flow fast enough to keep up with demand the engine will not accelerate past this point.

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Avid Corvair hobbiest since 1984.
I have personally performed ground up restoration on over 20 Corvairs.
I currently work full time at restoring and repairing Corvairs.
Located in the Atlanta Georgia area.
[www.facebook.com]

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Date: September 14, 2020 12:38PM

It's a new buggy i just picked up for cheap and its doing the same thing mine was years ago and i can't remember what i did to fix it ...

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Date: September 14, 2020 12:52PM

I FOUND THE PROBLEM !!
it has the high rise carb adapter on it so two carbs into one.
And the carb that was on it was a holly 350 CFM and i had an extra 600 CFM carb
So i put that on it and now it screams like a scalded cat with no hesitation
and only a little puff of black smoke on acceleration none at idle or cruising.
fires right up and runs like it should...
IT RUNS GREAT JUST LIKE MY OTHER BUGGY..
Now my daughter has one of her own and we can go ride in the desert ...
THANKS FOR ALL THE COMMENTS....
It got the old ass rusted wheels in my head turning again....

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: TerribleTed ()
Date: September 14, 2020 01:04PM

A 600 is quite large for this application. Most people using a center mount carb setup have found that a carb around 350-390 CFM is ideal. The carb you removed might be ideal if it wasn't screwed upsmiling smiley

---------------------------------------------------------------------------------------------------------

Avid Corvair hobbiest since 1984.
I have personally performed ground up restoration on over 20 Corvairs.
I currently work full time at restoring and repairing Corvairs.
Located in the Atlanta Georgia area.
[www.facebook.com]

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Date: September 14, 2020 03:45PM

It was a brand new holly 2 barrel carb from holly mfg that the previous owner put on when she took off the two single carbs and it had no stutter or hesitation with the two singles...
With the new carb it stuttered and had hesitation so she had put bigger jets in it and it still did the same thing.
Stuttering and hesitation at 3,500 rpm or so..
So i put on a bigger cfm 2 barrel carb from a 65 ford mustang and it worked great no stutter,no hesitation and it's not running to lean it has just a little puff of black smoke when you accelerate from a stop..
i checked the jets in the new carb and my other one and they are the same size..
So i guess it was not getting the right amount of airflow on acceleration because not it runs like a scalded cat..

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Re: Cant get full throttle Engine wont rev up past 3,500 without bogging down
Posted by: Wagon Master ()
Date: September 14, 2020 05:19PM

You found a 600cfm 2 barrel on a Mustang? Interesting!

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