I’d pass on the quadrajet, the TQ is a much better carburetor. You’ll end up going down the rabbit hole and talking to a bunch of chivvie guys and what do they know? Nothing,otherwise they’d own mopars.
road car cam for my 318
- Thread starter str12-340
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A quadraJet is a good carb, when done right. Problem is it takes more work than a TQ and isn't designed as well. But when done right it will run 10 sec quarters and in another application, get 20 mpg on a 350 engine. You could always count on Chevy to snatch defeat from the jaws of victory. Bean counters ruled the roost, not engineers.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I see I'm late to the party and unwilling to read all three pages. So if someone has already mentioned this, my apologies. Your cam is;
272/272/110/52* overlap. In at split-overlap of 110, the Ica is 66, Compression is 114 and power is also 114. With headers, running at 65=1800 rpm, that's a lousy economy cam.
Advanced to 106, the compression becomes 118, and the Power to 110. which is way better. Overlap is still 52, but the exhaust is now closing 4* sooner. Put some log manifolds on that to kill the overlap and watch what happens. Then, at the other end cruizing at 65=1800 with that cam, even advanced, with a factory type distributor is a bad recipe. That combo will want Cruize-timing to be up around 45 degrees, or more. Have you tried getting there? IDK where you have the Base-Timing set at, but if your mixture screws are not centered in their range, to slightly lean, I'd be willing to bet she's running fat....... all the time; the Idle mixture screws are for idling on, whereas the transfers are your Primary cruizing fuel supply.
If you run a LOT of Idle-timing, then the Power-timing has to be limited and slowed down, to not detonate at PT never mind WOT. If the throttle is nearly closed while cruizing, the VA cannot work.
Here's an example.
Let say you are running 20s at idle.. Thus the Distributor cannot bring in more than 15/16 for power, and say that happens at 3400.
Firstly, the throttles will have to be nearly closed to run that 20* which means the transfers will be nearly closed, which means that the mixture screws will have to be cranked open to supply idle-fuel. As a result, as soon as you open the throttles, and the Transfers come on line, the AFR will go rich.
The second thing that happens with 20* of idle-timing is that the the Vcan gets no signal from the sparkport, until you open the throttle a long ways then it comes in ok but when you get to ^5@1800, you back off to cruise, and anything can happen at the spark port. Maybe you lose all signal/ maybe 50%. But here's the thing, typically the Vcan is only good for say 10 to 13 degrees. Losing even half of it is a very big deal.
Suppose your Distributor starts advancing at 1000 rpm and all 16* are in at 3400. Thus the rate of advance is .67 degrees per 100 rom. so then, at 1800 cruise, the D is supplying ~5 degrees. thus your all-in timing is 25, IF your vcan is bringing in 15*, this comes to 40*. What if your engine wants 56*, or more, like mine does? Guess what, if that is true, your cruise-timing is 16* retarded! So she NEVER develops peak combustion pressure, and what there is of it, is chasing after the piston that is running away from it.
And so, those expanding gasses may enter the headers still burning and for sure still expanding. Which totally disrupts scavenging. Which in your case, while cruising, is probably a good thing, lol.
Now;
Your cam has Compression plus Power duration of 228* and overlap of 52*
My former cam had Compression plus Power of 227*, and overlap of 53 * it was spec'd as 223/230/110@050, which I later learned was 270/276 advertised. I tuned that beast to over 30 mpgUS, running at 65= 2100, running the cam 2* RETARDED, because she already had 11.3 to 1 Scr. It liked up to 63* of cruize-timing in certain situations but most of the time I ran 56*, now at 65=2240 (different trans, different rear gears.).
Now I gotta tell ya, my cylinder pressure with that cam, easily ran to 195psi in at the recommended plus 4*.
Now I'm not saying that you need to run your cruize timing up to 63*, lol. What I am saying is that cruise-timing for best economy is nearly critical.
To find the window, I installed a dash-mounted, adjustable timing module, with a range of 15degrees, and in the coming weeks before the gas-mileage run, I got intimately acquainted with what my engine wanted and changed the distributor dozens of times, to make it happen. And changed the low-speed fuel delivery nearly as many times.
and then it happened, I found a shortcut. And I'll give to you for free.
Warm up your engine, I run 207*F.. Rev up your engine to cruise rpm and maintain it there. Next, without regard to reading the timing, just pull in some timing, little by little, keeping the rpm steady. Keep advancing it until more advance produces no more rpm. Now read the timing@cruise-rpm. What you read is what the engine wants, at that rpm, with no load. From that number I subtract 3 degrees for load-compensation, and then I go build my advance curve to make that final number happen. Had I known this when I started, I couldda saved myself a lotta time.
From this starting point I just leaned it out until it was too lean, signaled by misfires and such, then put a lil fuel back in. Then road-tested with the dial back, looking for the perfect cruise-timing. My window was 56>60 @2240rpm, , sometimes as much as 63 degrees.
Just so you know, My combo likes
14* Idle timing plus
14* by 2800 distributor; 20* in by 3400/plus
22* in the Vcan, asap, plus
whatever more I can add with the dial-back, usually at least 6*
I liked that Hughes cam. I was very sad when it dropped lobes.
For pure economy, yeah, I'd look for a cam like the big guns here have already recommended. and or, run the one you got a lil faster to get it out of reversion.
cookietruck
Well-Known Member
That grind is the same as a comp 268-xe
I would try something a step or two smaller and on a 112 lsa
That was my recommendation, but as usual, it got buried.
cookietruck
Well-Known Member
Yeah i saw that. And it says it’s in stock which might be a big deciding factor.
junkyardhero
Well-Known Member
meh. let people make recs on cams they've never used on motors they've never built. it makes it more interesting.
Yup. Plus, typically, Summit uses American manufacturers for their products a LOT. Crane used to grind all their cams, for instance. I don't know who does now, but they are decent quality, or we'd be hearin about it. lol
Exactly. Yeah screw it. LOL
junkyardhero
Well-Known Member
*shrugs*
everybody gets so wound up on numbers and squeezing every last ounce of performance or whatever out while gargling the balls of some math nerd and jerking off to dyno sheets. meanwhile they totally disregard that ma-fuggin-mopar wrote the book, literally, on how to do it in the damn 70's.
it's like some stupid ego thing: oh, i can't possibly run a cam that small! i might as well run a stock one then!
Yup.
as the OP here... not buried - currently down to 3 possibilities and your recommendation is on the list. At the risk of pissing somebody off, part of the art of navigating FABO is separating the wheat from the chaff... or perhaps the golden nuggets from the gravel.
Don't worry about pissin me off. I would say I don't care which you choose, but I do, otherwise I wouldn't have made a recommendation. It won't bother me a bit if you choose something else. Just remember no matter what you choose, there's always something left on the table, so don't run yourself crazy over it. This hobby is supposed to be fun.
Rusty - I was counting you among the wheat, that's why that cam is still one that I am researching. I like the comment about this being fun!
It's kinda like sex. If you ain't havin fun, find a new partner. Same with hobbies.
junkyardhero
Well-Known Member
^^^ this.
cam selection is always a compromise, you just have to decide where, how and what you want to compromise.
the duality of a low comp motor and relatively low rpm operation means that the "wrong" choice won't have far reaching implications like, say leaving 50hp on the table. but the "right" cam will make that little motor shine like a crazy diamond.
junkyardhero
Well-Known Member
some of us are masochists, rob.
Yeah, that would not be me. lol
Still feel it’s a tune issue.
Here is the cam I run in my 5.9.
And I have an 800 AVS , RPM intake , 9.1 comp, and 1.7 HS rockers, Dougs headers ,2.73s , 205/70-14s . 18 mpg running rich (hwy mpg) . Vacuum at idle is around 14.
I feel 22 is doable if I rejet some. And I might need a little more ting .
Here is the cam I run in my 5.9.
And I have an 800 AVS , RPM intake , 9.1 comp, and 1.7 HS rockers, Dougs headers ,2.73s , 205/70-14s . 18 mpg running rich (hwy mpg) . Vacuum at idle is around 14.
I feel 22 is doable if I rejet some. And I might need a little more ting .
From D. Vizard, who tested 19,000+ cam combinations for Crane cams. You do NOT widen the LSA for a lower range, you reduce duration. He has another saying.....the right cam costs the same as the wrong cam.
remytherat
Well-Known Member
Today as I sat in inner city traffic and contemplated the absurdity of life, picking a small cam was something to appreciate.
I then retroactively slapped myself for wanting a duggada duggada cam.
Either way, running enough timing at idle and cruise is essential. With 214* at 50 and 110LSA, my motor sounds stock with 12 base and the can pulling in 20 at idle.
I then retroactively slapped myself for wanting a duggada duggada cam.
Either way, running enough timing at idle and cruise is essential. With 214* at 50 and 110LSA, my motor sounds stock with 12 base and the can pulling in 20 at idle.
Yeah and my foot up his *** costs nothing. Cept maybe hosing my foot off.
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