468 BB dynos at only 266 at wheel. what to do? - Page 5 - Chevelle Tech
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post #61 of 145 (permalink) Old Jan 22nd, 19, 11:45 AM
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Tom
 
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Re: 468 BB dynos at only 266 at wheel. what to do?

Oh... forgot to mention about my friend’s ‘68. His engine expert did his distributor curve for him also. 18° initial and 65° total!!!

SIXTY FIVE DEGREES!!! I fixed that for him before the first dyno run. A grenade waiting for the pin to fall out....

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post #62 of 145 (permalink) Old Jan 22nd, 19, 11:50 AM
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Re: 468 BB dynos at only 266 at wheel. what to do?

I'd say that the cam you have will work. It probably won't be ideal, something a bit smaller would work better, but I wouldn't necessarily go to the trouble to change it.
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post #63 of 145 (permalink) Old Jan 22nd, 19, 1:14 PM
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Re: 468 BB dynos at only 266 at wheel. what to do?

Quote:
Originally Posted by v8440 View Post
I'd say that the cam you have will work. It probably won't be ideal, something a bit smaller would work better, but I wouldn't necessarily go to the trouble to change it.
Especially if cam in engine is broke in and made it past the break in stage. Flat tappet cams are so risky to use anymore, even with the proper break in procedures.
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post #64 of 145 (permalink) Old Jan 22nd, 19, 2:13 PM
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Re: 468 BB dynos at only 266 at wheel. what to do?

Flat tappet cams are fine. The only risk is in the owner of the vehicle driven.

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post #65 of 145 (permalink) Old Jan 22nd, 19, 3:33 PM
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Re: 468 BB dynos at only 266 at wheel. what to do?

Well, they're FINER after they're well broken in.
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post #66 of 145 (permalink) Old Jan 22nd, 19, 6:17 PM
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Re: 468 BB dynos at only 266 at wheel. what to do?

Quote:
Originally Posted by any4xx View Post
Oh... forgot to mention about my friend’s ‘68. His engine expert did his distributor curve for him also. 18° initial and 65° total!!!

SIXTY FIVE DEGREES!!! I fixed that for him before the first dyno run. A grenade waiting for the pin to fall out....

Experts are everywhere....

Bigger is better right

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post #67 of 145 (permalink) Old Jan 22nd, 19, 7:20 PM
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Re: 468 BB dynos at only 266 at wheel. what to do?

If you are willing to spend money on heads, a head and intake swap would transform the engine. But, you will also need pushrods. As far as which head would work best with that cam, Chris and some others should be able to tell you.
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post #68 of 145 (permalink) Old Jan 23rd, 19, 8:41 AM
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Re: 468 BB dynos at only 266 at wheel. what to do?

IMO leave the heads and cam alone for this year if your static compression ratio is really 10:1. You need to at least verify this and also where the cam has been indexed. Can do all of that without taking engine apart. If cam installed right and compression checks out then I would change
Out the intake manifold and tune the engine.
Just for example .. I've run way bigger heads ( only cause I had them laying around ) Brodix 360 cc on a 468 spinning only to 6,000 and made good HP. Was it optimized NO - would still roast radial slicks and turn mid 11s. automatic trans.
Just my 2 cents. Enjoy the car!

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post #69 of 145 (permalink) Old Jan 23rd, 19, 9:45 AM
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Re: 468 BB dynos at only 266 at wheel. what to do?

I'm with Gerry; bought some really ****ty 990s from a member here ( all the gear was toast), paid too much, and they sucked poorly down low, AND up high. But I left the boat anchors on there until I got a set of homemade 781s done up. WORLDS of difference. HOWEVER, it was still a 427, just down on TQ and HP across the board. If it wasnt a tripower atop, I likely would have fattened up the jets to counter the weaker signals to optimize it , and let it be. But I changed the "fluid dynamics" instead, by putting heads on that will maintain better charge velocity.

Oddly, and to the OP's point, had to run a rectangular port tripower atop oval port oem 781s. Now, from a fluid dynamics POV, when you constrict a passage, the flow's speed and psi rise at that point - which entering the cylinder heads isnt a bad thing, and maybe why this old "racers trick" works oddly well. The flow hits a friggin' wall, but then sucks through a smaller hole. Velocity + . It goofed me that it worked, even at low speeds.

Your flow doesn't hit a wall, but simply pukes out into a bigger pipe, a pipe that is frankly too big to begin with. The worst possible scenario before it hits the valve bowls. Velocity - + another - for the too big intake ports. so velocity --

Get the right intake on; it ought be a much better matched system. Recall that all the old timers call these nothing but "air pumps". Your's may be losing much intake velocity and flow, due to a port mismatch.

$300 to swap it out. Easy job. Hardest thing is to wait for the coolant to drain. you may net up to 30 ponies tho, and more importantly, it'll make "seats of the pants' lite a small fire under your azz! _

And also with Gerry on cam timing. Do the quick and dirty method, only need to remove valve covers and ignition + to roll it over w/o firing. You are looking to ensure the #1 intake valve is open more than the #1 exhaust valve at #6 TDC, if that makes any sense. Its EASY to check. Measure the relative heights of the #1 valves when the engine is in #6 TDC ( one revolution out on the balancer). If intake is open more than exhust is ( literally valve retainer to head surface measurement - crude) , its advanced. Pretty much where you want it. If they are even heights. the cam is "straight up". ANd if the intake hasnt cleared the ex height yet, its retarded.

PS: Another Pro story, I told a pro engine shop that was freshening up my 427 to put my Ultradyne in +4 minimum. Well, i couldnt get the thing to idle at all hardly,. 1200 rpms, 7" Hg, etc, so I called the cam designer Harold Brookshire, and he 'splained the QnD method. Well LO and Behold, wasnt the cam in -7 degrees, as the exhaust was still more open than the intake valve. ( which I found after the QnD said it was retarded by using a degree wheel. ). The pros had put the offset cam pin bushing in backwards. Literally. WTF? Pros, eh? I did the engine myself in my garage next time, with machine work farmed out and checked with my crude dials, calipers and plastiguage. Anyway Harold's QnD saved me a ton of anguish.
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post #70 of 145 (permalink) Old Jan 23rd, 19, 12:34 PM
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Re: 468 BB dynos at only 266 at wheel. what to do?

Here , I went on Ebay to look for a Qjet oval port dual flange for my next rat ( truly pro built as my "handjob" 427 only made 510HP or so) !) during lunch and found this. Good deal on one that has never been mounted, imho. Not a steal,. but a good deal.

https://www.ebay.com/itm/GM-Chevy-RE...e3g:rk:19:pf:0

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post #71 of 145 (permalink) Old Jan 24th, 19, 2:42 AM
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Re: 468 BB dynos at only 266 at wheel. what to do?

The method for checking if the cam is adv/ret in post 69 is not going to be reliable for this cam that has hyd lifters, due to the lifters bleeding down. It is also a dual pattern cam, which affects the reading.
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post #72 of 145 (permalink) Old Jan 28th, 19, 6:56 AM
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Re: 468 BB dynos at only 266 at wheel. what to do?

jeeze guys. cabin fever already?

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post #73 of 145 (permalink) Old Jan 28th, 19, 7:05 AM
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Re: 468 BB dynos at only 266 at wheel. what to do?

a little clean-up seemed to be in order.

it's a long time till summer

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post #74 of 145 (permalink) Old Jan 28th, 19, 7:29 AM
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Re: 468 BB dynos at only 266 at wheel. what to do?

Baby steps, grasshopper. Dual plane rectangular port intake first, see what that does, then go on to the next...
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post #75 of 145 (permalink) Old Jan 28th, 19, 9:57 AM Thread Starter
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Re: 468 BB dynos at only 266 at wheel. what to do?

Intake is actively being shopped for.
probably getting this one unless anyone has any other thoughts
https://www.edelbrock.com/rpm-air-ga...UaAh-EEALw_wcB

But, just so that there are no surprises, i want to confirm the heads are indeed what I was told they were.

Where can I look for the serial number/part number on the ProComp heads?

I would hate to buy a rectangular port intake only to find that the heads are oval.

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