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Old 07-04-2005, 13:36   #1 (permalink)
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rpm loss problem.. help!

i was running a cleveland with 2v oc heads heavely ported,weiand x-cel, a hyd tapped cam .560 lift and 245 duration, my valve springs are 337lbs the car would twist to 7000rpms and reliably built power to 6500+rpm.

i just recently converted to oc 4v heads, new stainles valves same valve springs and edelbrock torker intake and portplates on the exhaust side only. same cam, same everything. all ports are portmatched for best flow. problem is
it only twists to 5600rpms and then cuts out like its hitting a rev limiter. i played with them timing some but i live in a residential neighborhood and cant scream up and down the street and the track to too far away to go if evrything is not working well.
anyone have any ideas? also, i have a msd pro-billet dist. if anyone else has a msd dist. and a relatively close set up could you tell me what spring combos you use and what color over-all advance bushing.
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Old 07-04-2005, 15:08   #2 (permalink)
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Re: rpm loss problem.. help!

dyno tune time, it was the best money i spent in my car
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Old 07-04-2005, 15:18   #3 (permalink)
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Re: rpm loss problem.. help!

i agree but i want to atleast figure out a close baseline and have my rpm's back.

i would really like to try someone elses spring and bushing set-up for the distributor that has a cleveland.
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Old 07-04-2005, 16:32   #4 (permalink)
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The last time i had rpm drop off like that is when i wiped a cam real bad. Instead of swinging to 7000 rpm, it would drop off at about 5800.
Also, check you're accelerator linkage, to make sure full throttle is there.
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Old 07-04-2005, 18:13   #5 (permalink)
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Re: rpm loss problem.. help!

thanks, i just had the cam out and everything was ok on it, and i had to build a new bracket for the throttle cable so i know it opens full too. but thanks for your suggestions.

do you think that it has to be a fuel or ignition problem, or am i completely overlooking something. like is there going to be a need for more or less total advance with this head change?
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Old 07-05-2005, 00:58   #6 (permalink)
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Re: rpm loss problem.. help!

Quote:
Originally Posted by musclemustang8
it only twists to 5600rpms and then cuts out like its hitting a rev limiter. i played with them timing some but i live in a residential neighborhood and cant scream up and down the street and the track to too far away to go if evrything is not working well.
anyone have any ideas?
If it acts like its hitting a rev limiter, its not the timing. Its probably valve spring related, ignition related, or fuel related.
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Old 07-05-2005, 01:24   #7 (permalink)
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Re: rpm loss problem.. help!

4V valves are larger and heavier than 2V items. My bet is you need to up spring pressure to accomodate for the large valves.

[edit] A set of Isky 8005a's will more than like stop your valve bounce.
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Old 07-05-2005, 02:02   #8 (permalink)
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Re: rpm loss problem.. help!

What is the spring installed height? Did you recheck the installed height when swapping into the new heads?
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Old 07-05-2005, 02:36   #9 (permalink)
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Re: rpm loss problem.. help!

Quote:
Originally Posted by musclemustang8
but i live in a residential neighborhood and cant scream up and down the street.
I'm enjoying living in the country now Nothing but cows and sheep to annoy.

From the video evidence I've seen............xdclevo doesn't worry about houses either!!
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Old 07-05-2005, 03:12   #10 (permalink)
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Re: rpm loss problem.. help!

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Originally Posted by TruBlu351
From the video evidence I've seen............xdclevo doesn't worry about houses either!!
houses, what houses? iv'e seen no houses!! You been on that smoke again??
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