AFR angle plug heads and block hugger header clearance?

[pparaska]

Supposedly, some angle plug heads won't have a problem with having the sparkplugs/wires clear block hugger headers. I have the usual hooker 1-5/8" block hugger headers.

 

Anybody tried putting block hugger headers on AFR SBC heads and checking spark plug/wire clearance?

[nullbound]

granted you asked for info on AFR... i had the standard hooker block hugger headers on my 350. when changing to the 377 with angle-plug canfields, the hookers had no way of clearing the spark plugs. i could not even start the end bolts, as the spark plugs interfered with the outer tubes.

 

i had to go from this style header:

 

to this style from zigs street rods:

 

the center primaries dumping on the block side of the collector made the difference for the canfields. i am assuming it would be about the same for afr's.

[Mike kZ]

The Zig ones are what I have on my angle plug Trick Flows. I did have steering shaft interferance with them, and added a U joint on the shaft.

[Mike C]

I posted this in the Exhaust forum a few weeks ago, but go to Jegs site and check out the Patriot headers.

 

They make block huggers in round as well as D port that will clear angle plugs. They also have a cone type connector that doesn't use collector gaskets $229 for the coated ones seemed like a fine deal.

 

No guarantee they'll fit, but they look like other block huggers FWIW...

[Zoldman]

Here's a probably really dumb question:

 

Why angle plug heads? I have straight plug AFR heads on my '79 Vette and love them, so I was going to use the same ones on the 383 I'm building for the Z.

 

Do the angle plug heads go on late model engines or something like that? Both of my engines are 70's vintage, so straight plug was what was recommended.

 

I hope there aren't any header clearance issues with straight plug heads. I've been looking at the Sanderson Q series headers; they are unique and don't look to interfere with the steering shaft at all. Pricey though...

 

Bill

[Mike C]

Angle plugs are supposedly more efficient. Lighting the fire nearer the exhaust valve for optimum spark placement high in the chamber. Most likely, straight plug would be fine. LT1 with aluminum heads have angled plugs, but the iron heads have straight plugs. Stock the iron flow slightly better, and with bowl work, work awesome.

[John Scott]

AFR disputes the angle plug theory. I asked them the question and was told their heads make the same hp angle or straight. More relevent to the old style factory heads. I have straight plug 195s, Rewarder headers with plenty of room for wires and plug r&r. I understand your wanting to wring every bit of power, but block huggers are already a compromise. Going racing for titles and trophies, then maybe those couple of ponies will matter. I accepted the fact and went for fewer headaches and better ground clearance with my 1 3/4 rewarders. From the looks of your engine design, you're going to have more power than you know what to do with so, bolt them babies on and enjoy the ride!

John

[Mike C]

I agree with John 100% on that. The 2 1/2" collector on the headers hurt power way more than any that MIGHT be gained with angle plugs.

[John Scott]

I agree with John 100% on that. The 2 1/2" collector on the headers hurt power way more than any that MIGHT be gained with angle plugs.

Then again if you are running 2 1/2 exhaust, then you want the 2 1/2 collector. Better to flow into the same size pipe. Not many will fit dual 3s under a Z. Running a block hugger through a muffled exhaust will minimize any losses compared to a tuned full length exhaust with a muffler, so again we make concessions unless a full race applications. I think too many of us beat ourselves up trying to make the perfect beast. I've found a healthy V8 will rarely, if ever have any competition on the street. Yes there is always someone faster, but you'll find they usually live on trailers or spend most of the time in a garage.

John

[Mike C]

There are benefits into necking down the collector and then re-expanding it. There are some patented headers that neck down at the tube juncture but expand right after. Just like with an intakes plenum volume, collector volume can help even out pulses and improve flow. If you could get a shorty with 3" collectors and run 3" 90 manderel bends and then neck down to 2 1/2" to run down the tunnel, the shorty headers wouldn't pay the big a penalty compared to long tubes. But no doubt about it IME, that 2 1/2" collector hurts power output.

[pparaska]

No doubt, between the 1-5/8" primary block huggers with 2.5" secondaries, 2.5" duals and mufflers, I'm probably killing 25 or more horsepower over good open headers. The 700 cfm TBI is also a bottleneck. With large tube headers and large exhaust, and a 900 cfm TBI or carb, I'd probably gain 30+ hp over what I'll be running.

But I think this will be more streetable, and cheaper to put together.

If I feel the need for more top end, I'll go to MPI with a 1000cfm

TB and larger tube headers.

 

Straight plug it will be.

[Mike C]

This is going to be a 406, correct? With all of that taken into account, I think it leads you back to the straight plug AFR 190s and then optimizing camshaft for your combination. This seems to be a perfect application for a split pattern cam. Obviously not to crutch a poor exhaust port, but for exhaust compromises. I would try and keep .050 duration of the intake in the 220 deg range and 230 for the exhaust on 106 LSA. Definitely a custom order. Still running 1.6 ratio intake rockers and 1.5 exhaust. What intake is the TBI based on? If raised runner, do the 195's, if standard runner the 190's.

[pparaska]

Doesn't it make sense to run a bit larger port volume (although 5ccs isn't much) for a 406, even if it doesn't get spun much above 6200 or so rpm?

 

Also, I'm starting out with grumpyvette's recommendded Crane solid flat cam 114681 (http://dab7.cranecams.com/SpecCard/DisplayCatalogCard.asp?PN=114681&B1=Display+Card), that has a good bit more 0.050 duration but a 112 LSA. Quite a bit more cam than you're suggesting. Not to worry, I have a 236/242@.050 110LSA solid flat tappet cam in the 327 I can use, as well as a 224/224@.050 LSA solid flat tappet cam in the wings. If the 114681 (244/252 @.050, but only 280/288 seat duration) is too much, I can always back down. Grumpyvette assures me I'll like the 114681 I'm thinking with 406 cubes, compression, etc. it should be have a good bit more low end torque and throttle response than the 327, especially with the TBI.

 

With that cam and the 10.5:1 compression I should get, the DCR is over 8:1, so I should be in pretty good shape.

 

The TBI is just a Holley Pro-jection unit bolted on either a Holley 300-36 dual plane or Victor Jr manifold.

[Mudge]

Stock the iron flow slightly better, and with bowl work, work awesome.

 

They are still going to weigh more and are lower compression. Since they are the same casting, I'd rather have the aluminum head. The 1997 Fbody has the same flow as the Impy iron heads, the 93 however has the most raw material to remove for the ultimate in LT1 flow, without getting LT4/AFR or adapting SBC heads.

[Mike C]

Pete, I see no reason to add port volume since flow is higher on the smaller port head. Just base the decision on your intake. The 195 for a raised runner intake, the 190 for a standard runner intake. If you stick with the 300-36, run the 190's if you are going to buy a Victor Jr. AND heads, get the raised runner 195's and corresponding intake.

 

What is the thinking in over 240 deg at .050 on a sub 6500rpm engine? I think your cam choice is way too big.The one in your 327 is WAY too big IME. My 331 hated lots of duration, especially on wide lobe centers. One of your reasons for doing the bigger engine was low speed performance, and I think that cam choice is equivalent to a bullet in the foot... Just for grins, you should stick that smaller 224/224 cam into your 327 and see how much faster the car is. My current 355 was in a '79 Z/28 that weighed the same as my '69 with the same gear ratio and same trans ran 13.70's with a Comp 292 244@.050 and .500 lift cam. It's a full SECOND faster with the smaller 236/236 (admittedly a roller, but the increased lift is slightly offset by significantly reduced overall duration so curve area should be similar.)

 

I think the best choice in cam for you motor is the Isky 280 Mega Cam. There is no gain for running a solid cam in this street type environment. Only in above 6500 rpm operation for extended periods of time is their any real gains. Just adds to the noise and complexity. I would rather run shorter cam timing with a narrower LSA for the same idle but better power delivery. Besides, Vizard points out that 400ci motors make the most power at something like 104 LSA. Add 1.6 rockers to the intake, maybe figure out a way to get a 3" collector attached to the shorty headers and some 3" mandrel 90's into 3 to 2 reducers then use your existing exhaust out the back.

 

Grind No./Type: 280-MEGA, HYDRAULIC High performance use/bracket racing. Lopey idle. 2500 Stall. 9.5-10.5:1 compr. 3.90-4.11 axle ratio. Up to 780 CFM Carb. RPM-Range: 2500-6800 Valve Lift - INT: .485 EXT: .485 Valve Lash Hot - INT: .000 EXT: .000 ADV Duration - INT: 280° EXT: 280° .050 Duration - INT: 232° EXT: 232° Lobe Center: 108°

 

This cam is real close to the Joe Sherman grind that made 600 hp in his 365 ci motor. Just a flat tappet version. I'd put my money where my mouth is, too, running this cam most likely for my next motor. The reduced LSA shouldn't be a big concern with your FI setup since the overlap of the smaller cam/narrower LSA shouldn't be anymore than the larger cam/wider LSA.

 

http://www.iskycams.com/productdisplay.php?sku=1322&hdwt=31101&loc=101&dealer=no

[pparaska]

Mike, consider that Joe's cam, as described on PH's website and in their mag is described as:

" The camshaft was ground by Isky (PN 201282-08). It carries .565-inch of valve lift (with a 1.6:1 rocker) on the intake side, and .530-inch of lift on the exhaust (with a 1.5:1 rocker). The lobes were the same, and both were originally designed for intake use. Joe ordered it with the intake lobe on both sides, with a .234@.050 duration, and a 108-degree lobe separation angle. Advertised total duration was 282 degrees. It's a trick cam, but we've seen much bigger cams run on the street without worry. "

 

And if Vizard and others are correct and that you need to delete 5-8 degrees off of a solid flat tappet's 0.050" duration to compare it to a hyd. flat tappet cam, the Crane 114681 (244/252@.050) is not that far off Joe's (intake anyway). Although it does have more exhaust timing. With dual exhaust and maybe restrictive exhaust for this engine, I'm thinking that may not be a bad idea. Same deal for my 327's 236/242 @.050" cam - it's more like a 228-231/234-237 @ .050 hydraulic. But the solid throws the valve open (initially) faster and gets into the .100 and up flow region of the port/valve sooner, even sooner than a roller. After that the roller is quicker.

 

BTW, I know it's hard to compare lobe intensity between a solid cam and a hydraulic, but the Crane 114681 numbers are 280adv-244=36 deg and the Isky 280 is 280adv-232=48 deg. And the 280adv of the Crane intake lobe is after lash is accounted for as well. Subtracting 5-8 degrees from the 114681's intake .050 duration to be able to compare, you get 280adv-(236-239)=41 to 44 degs. To me the Isky seems a bit slow opening initially, but it's hard to compare without resorting to using a Cam Doctor on both grinds.

 

I'm leaning toward the Vic Jr (have it) so the it'll probably be the 195 heads. Remember, this is a 406, not a 350 or 383. So the general advice for port port volume, which is typically for a 350 or 383 would be a bit conservative, in my thinking.

 

When the carb is in good tune (recently), my 331 comes on strong at about 2200 and keeps pulling past 6200. Yes, it's a bit lumpy below 2000, but it's not bad - it'll lug down to 1600 around the side streets without complaint. I imagine that TBI will improve that as well. To me, a 2200-6200 powerband is just fine for a light street car. And with 75 more cubes and much better heads, I doubt that another 6 degrees of adv duration and 8 degrees of .050 duration will hurt. If so, the 236/242 cam can go in. I picked the 244/252 based on it being the MOST I'd ever run in this app (thanks to grumpyvette and Crane's tech line) and I wanted the rods clearanced for the most cam I'd be likely to install. I have no problem going down a step in cam if that's what's called for. But with the kind of traction problems these cars have, I'm not sure what will be best.

[Mike C]

Sherman's cam was a hydraulic roller, but other than that compares nicely with the flat tappet. Your reason for switching to the large displacement engine was smooth, linear powerband and IME, that's just too much cam. My 331 with 9.8:1, LT-1 intake and 780 Holley had a 2800-6800 rpm powerband with the Cam Dynamics 284 .480 cam. It never really was as fast as I thought it should be. 14 teens at 100 mph in 3500# car. 13.4 with a 75 horse Marvin Miller N20 system. This was circa 1985 which says something about the durability of the little motor! It has an Energizer 266 in it now and resides in my Jimmy. 1200-4500 powerband. Does an admirable job of accelerating two plus tons with the new cam. If you are going to go with the mechanical cam still, I would seriously consider having an eqaul duration intake/exhasut cam ground on a sub 110 LSA.

 

It's going to run fine regardless, but hey, I've got to get my 2c in!

[pparaska]

Mike, no doubt a custom cam would be optimal. And I'm beginning to think that a tighter LSA and single pattern would be better. Dual pattern eats into the overlap budget too much, especially when you have a tight LSA.

 

Oh well, nothing on this build/exhaust is really optimized. Lots of compromises. At least I have a few cams to slide in there to play around with.

[Mike C]

You seem to be a prime candidate for a two piece timing cover!

 

Your exhaust restriction is the primary reason I would be reducing the profile of the cam. If you can optimize power below 6000 rpm, exhaust restrictions will have a more minimal effect on power. I hate to beat a dead horse... But if you spend more $ up front on the roller, you can reduce overall duration while increasing area under the curve. The broader powerband characteristics of the roller will allow you to reduce advertised duration while maintaining the same power band. Then (most likely) you won't have to swap cams all of the time! If you didn't already have a warehouse of cams, this would be cheaper, too!

 

My mechanical roller is NOISY and my next cam will be a hydraulic roller, but with that said, CAT has mechanical roller lifters for $105 a set! Not much more than a set of Crane or Comp flat tappets. They get $240 for hydraulics, not such a smokin' deal.

 

http://www.catpep.com/Products/ProductDetail.asp?Part_Category_ID=17

 

And I think it is Herbert who will custom grind mechanical rollers for $199. If you run a street roller type grind, you can use mechanical flat tappet springs for the most part. My street roller specified 145# seat springs. That being the case, you can have a mechanical roller for just a little over $300 rather than the $900 mentioned earlier. Something in the neighborhood of 280 degrees advertised duration, 235 at .050 and .560 gross lift would be awesome on a 108 deg LSA.

 

Do you already have rockers? I've got a set of brand new 11752 Cranes that I would like to combine with a set of 11755 to have a 1.6/1.5 set if you want to buy a set of 11755 and swap half Harland SHarp is probably the best bang for the $, but cheaper rockers than the 11752 hit the retainers on my heads. They say they will clear 1.63 springs, but I think they would have trouble with 1.55 on my motor. My current springs are 1.437.

[pparaska]

Yep - I have the Edelbrock 2 pc AL timing cover .

 

I'll check with the guy doing my short block, but I have a feeling that if that Crane 114681 solid flat tappet cam was used to clearance the rods, a roller won't clear.

 

I agree on the merit's of a roller - and thanks for the tips on cheaper versions and the possible use of my solid flat tappet valve springs.

 

I have CC Pro Magnum 1.52:1 roller rockers now. Not looking to spend more money there either, especially if it's just 5-10 hp, like I've heard.