[Bronco Logic]

I've searched for about an hour and haven't found any definitive answers. I more or less want to know what size rockers I should go with and the pros and cons of each size. This is the first (and probably last) engine I've ever built. Here are some specs and if you guys would chime in and let me know what you think I would appreciate it. Any suggestions or upgrades you think I left off or should include is wanted as well. Specs are as follows:

1993 w/speed density

-351w block bored .30 over w/ bigger pistons
-comp cam that fireguy's thread suggested
-gt40 heads
-edelbrock upper/lower intake
-bbk 56mm TB
-jba headers
-msd dizzy
-9mm wires
-3'' exhaust w/ hooker aerochamber

Also, with these upgrades, should I choose a better spark plug or stick w/ autolite copper's?

 

[Bronco Logic]

anybody?

 

[SigEpBlue]

You waited a whole two hours before bumping? :rofl:

What do you mean "what size"? Ratio? Stud size?

 

[Bronco Logic]

What do you mean "what size"? Ratio? Stud size?[/QUOTE]

Yeah. 1.6's or 1.7's. What is the difference in performance?


As far as bumping is concerned, I didn't know there was a minimum time limit restriction.

 

[BigBlue 94]

1.6

 

[SigEpBlue]

The performance difference is virtually nil. I'd go with whatever is less-expensive at the time if I had to go with roller rockers. I just don't see them benefiting a slow-turning engine that much.

These truck engines never see over 5500 rpm, and even up there it's not usually for very long, unless you have a penchant for manually shifting it and bouncing off the rev limiter; other parts will probably limit you before the rockers, is what I'm saying. Contrast that with a Mustang with a 6250 rpm rev cap and a 5-speed with 3.73s you can keep up there in the 4500+ zone for a much longer time, and the benefits of the roller rockers become more clear. High-speed operation is much more intense upon the valve train, and friction losses pile up quickly. You're only really 'gaining' if the roller rockers have significantly lower friction at the trunnions and tips than the stock stamped rockers. In my experience, they don't. At least on a roller lifter setup.

From personal experience, I have never EVER seen a factory stamped rocker and fulcrum fail. I've seen them scored and scraped due to long oil drain intervals clogging the pushrods and oil holes in the rockers, but never really fail. Contrariwise, I've pulled chunks of rollers from exploded trunnions out of a couple of oil pans. I could argue that poor valve train geometry was to blame, but a few others have had similar experiences. I suppose above all else, they get noisy with time and use.

However, if you're rebuilding and you need new rockers anyway, you might as well. I guess.

I have 'pros and cons' for each 1.6 and 1.7 ratio rockers:

1.6:1
Pros: Factory ratio, no goofy geometry (usually; always check), less power required to operate valve train, cam profile will act as the manufacturer/grinder intended it to (yes, I'm aware there are grinds made for 1.7s, but those aren't as popular), lower stress on pushrods and lifters.
Cons: If you're going to be spending money on roller rockers...

1.7:1
Pros: higher total lift, more 'area under the curve', better vacuum potentially at low speed, possibly more power (something on the order of 10 horsepower, maybe on a good day).
Cons: higher potential for geometry to be wrong (requiring push rod change, shims, etc.), higher load on camshaft, lifter, and pushrod, increased power required to turn valve train.

Hope that helps.

 

[seawalkersee]

Get the 1.73s for the cobra and there is not a problem with geometry.

Chris

 

[Bronco Logic]

The performance difference is virtually nil. I'd go with whatever is less-expensive at the time if I had to go with roller rockers. I just don't see them benefiting a slow-turning engine that much.

These truck engines never see over 5500 rpm, and even up there it's not usually for very long, unless you have a penchant for manually shifting it and bouncing off the rev limiter; other parts will probably limit you before the rockers, is what I'm saying. Contrast that with a Mustang with a 6250 rpm rev cap and a 5-speed with 3.73s you can keep up there in the 4500+ zone for a much longer time, and the benefits of the roller rockers become more clear. High-speed operation is much more intense upon the valve train, and friction losses pile up quickly. You're only really 'gaining' if the roller rockers have significantly lower friction at the trunnions and tips than the stock stamped rockers. In my experience, they don't. At least on a roller lifter setup.

From personal experience, I have never EVER seen a factory stamped rocker and fulcrum fail. I've seen them scored and scraped due to long oil drain intervals clogging the pushrods and oil holes in the rockers, but never really fail. Contrariwise, I've pulled chunks of rollers from exploded trunnions out of a couple of oil pans. I could argue that poor valve train geometry was to blame, but a few others have had similar experiences. I suppose above all else, they get noisy with time and use.

However, if you're rebuilding and you need new rockers anyway, you might as well. I guess.

I have 'pros and cons' for each 1.6 and 1.7 ratio rockers:

1.6:1
Pros: Factory ratio, no goofy geometry (usually; always check), less power required to operate valve train, cam profile will act as the manufacturer/grinder intended it to (yes, I'm aware there are grinds made for 1.7s, but those aren't as popular), lower stress on pushrods and lifters.
Cons: If you're going to be spending money on roller rockers...

1.7:1
Pros: higher total lift, more 'area under the curve', better vacuum potentially at low speed, possibly more power (something on the order of 10 horsepower, maybe on a good day).
Cons: higher potential for geometry to be wrong (requiring push rod change, shims, etc.), higher load on camshaft, lifter, and pushrod, increased power required to turn valve train.

Hope that helps.

Wow....Beautiful....How much do I owe you?

Which would you buy? I have a buddy who has some scorpion 1.7's that he wants to get rid of. I know these are probably too much for my application but he only wants $150 for them. I was on summit last night searching and for their "summit brand" they're asking $160. The gt40's have over 100k miles on them so I figured I need to do everything while the motor is out.

 

[SigEpBlue]

Wow....Beautiful....How much do I owe you?

A favor. I'll let you know when I need it. :histerica

Which would you buy? I have a buddy who has some scorpion 1.7's that he wants to get rid of. I know these are probably too much for my application but he only wants $150 for them. I was on summit last night searching and for their "summit brand" they're asking $160.

Meh, those are too cheap. Personally, I like Harland Sharp rockers, although I wouldn't buy that brand through Summit; their website is too confusing when you start to narrow down the type you want.

If you're looking for 5/16-inch pedestal mount bolt-ons, then yes, as suggested, the Cobra M-6564-A50 rockers are probably the best 1.7 solution. Those or Crane's WG3070 1.6s are a great middle-ground on price vs. quality. The CompCams 1052-16 rockers are another nice pedestal-mount option.

HOWEVER if you went with 1.7 rockers, that's going to put you over 0.500 valve lift. You'd end up with 0.508 / 0.515 inch lift, instead of the specified 0.478 / 0.485, which is also going to put more load onto the cam lobes. Comp would NOT be happy about covering damage under warranty should anything happen. Also, any lift above 0.500-inch is wasting power, since the GT40s stop flowing around that point, IIRC.

Does your 1993 model have an F4TE block? If so, you could install a roller cam and lifters with no modification. That would be the absolute best valvetrain upgrade, IMHO.

The gt40's have over 100k miles on them so I figured I need to do everything while the motor is out.

Yup, including new valves, springs, keepers, and recutting the seats. Valvetrain components are relatively VERY cheap compared to other engine parts. If you do your research and shop around, I bet you could get all of the valves and springs for less than $150. THIS is where I think you should be spending your money, not rocker arms. Without an excellent seal, all of that increased airflow into the cylinder is wasted, blowing past the valve seats. With 100k on them, I wouldn't depend on them without rebuilding.

Keep in mind, Summit Racing is not the end-all stop for parts. In fact, they've ruined it for a lot of us that were used to going down to the local speed shop and getting good deals on parts. Now, they CAN'T sell below Summit's prices because of the direct-to-retail channels Summit has. Also keep in mind that racing parts are not made to last, so the more OE stuff you can use, the better for the longevity of the engine.

 

[bossind]

I'm a big fan of doing all my lift with the cam and sticking with a 1.6 rocker.

 

[Swat]

1.6

Comp cams magnum roller tip rockers: http://store.summitracing.com/egnsearch.asp?N=700+300350+115+4294908331

 

[Bronco Logic]

Sig, I don't have a roller block. I have another 351w block thats been bored .30 over and has the comp cam already installed so that is what I'm going to stick with.

I'm wandering if I should shell out the money to rebuild the gt40's b/c i already have $350 in them the way they sit. Another $150 or more would put them at $500. I have a another friend who has some aluminum pro comp heads. I'm pretty sure the specs are:

210 runners
54cc chambers
2.02 intake
1.6 exhaust

I have no idea if this is too much. Feel free to laugh and flame. I know very little about this. I have always been under the impression that aluminum heads are much better than cast iron b/c their stronger and lighter. In the meantime, I'll try and find specs on gt40's.

 

[SigEpBlue]

Sig, I don't have a roller block. I have another 351w block thats been bored .30 over and has the comp cam already installed so that is what I'm going to stick with.

Bummer, but that's all right. :thumbup

I'm wandering if I should shell out the money to rebuild the gt40's b/c i already have $350 in them the way they sit. Another $150 or more would put them at $500. I have a another friend who has some aluminum pro comp heads. I'm pretty sure the specs are:

210 runners
54cc chambers
2.02 intake
1.6 exhaust

Those would...really kill your low end torque and driveability. The 210cc runners are a bit on the large side, and by 'a bit,' I mean 'a lot.' Velocity will be very low under 3000 rpm or so, and would not be well-matched to the rest of your setup. The 54cc chambers would probably push your compression ratio higher than you want to go if you still want to run pump gas. Consider the fact that a 58cc chamber gives you a 9.66:1 ratio with a NON-overbored cylinder. A 54cc chamber with a 4.030-inch bore would push it well over 10:1...if my mental calcamalator is working today. :toothless The higher compression would help make up for the loss in velocity a little, but that much compression is really pushing it.

I have no idea if this is too much. Feel free to laugh and flame. I know very little about this. I have always been under the impression that aluminum heads are much better than cast iron b/c their stronger and lighter. In the meantime, I'll try and find specs on gt40's.

I wouldn't say necessarily aluminum heads are better than cast iron. It really depends upon what you're trying to do. Shedding about 40 pounds isn't really a factor on a 5000-pound toolshed, but it can mean another 0.05 second in the ¼-mile. That's what those heads you're looking at are made for, and for screaming up into the upper rpm ranges required in drag racing.

Just a little FYI while you're looking for the GT40 specs: use Federal-Mogul's web site once you know the dimensions and specifications of valves you're looking for. Federal-Mogul is the parent company of Speed Pro, btw, and that's the company I went with because frankly, their documentation is the best and most-easily found. Anyhow, at their site, you can enter ranges of values for things like valve and spring dimensions, spring pressure values, etc. It makes finding 'alternative' part numbers easy. Go here first, then click "Click here for Specification Look-up," then at the top click "Specification." They really bury it, I know, but that's the kind of investigating and research ya have to do to find less-costly and higher-quality parts.

 

[Swat]

I'd run the big heads if I could get them for cheap. Sure they will make a little less on the low end torque, but you will get considerably more top end out of it. It will produce more power and allow the engine to spin-up a bit higher. I have compared the large heads I run to GT40s and stock heads. I see at most a lost of 10 ftlbs of torque at 2,000 rpm but a gain of over twice that much on the top end! I run a Crane cam for low end grunt and World products Windsor Seniors with 200 cc intake 1.60 Exh. and 2.02 intake valves. I have run these heads on NA 302, 347, boosted 347, and now a 393 stroker.

 

[79BlueMule]

I have a set of the 1.72 ford racing rollers that are pedestal mount. they are brand new in the box. i'll take 200 shipped. i can send you some pics if you like. let me know, thanks

 

[Bronco Logic]

Anyone else care to vote? gt40 or aluminum.

 

[Bronco Logic]

sig, can you comment these http://cgi.ebay.com/ebaymotors/ws/e...m=280244408819&ssPageName=STRK:MEWA:IT&ih=018

After searching for 2 hours I don't know the exact specs for what I'm building. I know its a bronco and not a mustang and I got a cam that is for low end grunt. I just want the most bang for the buck, best power( for a bronco) and reliability.

 

[SigEpBlue]

This is gonna be a LONG ass post. opc1:

The advertisement is a lie, assuming Coast High Performance's website is accurate. In the eBay ad, it is stated:

PRO COMP 3037 SMALL BLOCK FORD BARE ALUMINUM ALLOY HEADS 60CC/190CC. GREAT STREET/ STRIP HEAD DESIGNED FOR USE WITH STOCK OR STROKED SMALL BLOCK SIZES LIKE:302/331/347/351W/393/408/418/427
HEADS ARE SUPER AFFORDABLE AND ARE DESIGNED WITH MUCH BETTER FLOW FOR LOW END TORQUE. NEW MUCH IMPROVED HEADS FROM EARLIER MODELS SOLD CHEAPER ON E-BAY. HAS A LOT THICKER DECK FOR IMPROVED SEALING. USED BY COAST HIGH PERFORMANCE (CHP), FOR THE BUDGET MINDED ENTHUSIASTS ON THEIR "STREET FIGHTER GT" 306/347/393 SERIES CRATE ENGINES.

According to CHP's website, even their 'budget' GT and Street Fighter series use AFR and Edelbrock heads, respectively. The ad makes yet another mistake; he can't even get the names of CHP's crate engines right! They don't even have a "street fighter GT." It's either a GT or a Street Fighter, not both. He's trying to confuse people into believing this horse shit. If you don't believe me, check out CHP's site for yourself. I even downloaded their catalog and searched for these heads. They're nowhere to be found.

But wait, it gets better:

NOTES:* WHEN USING POP UP PISTONS, CHAMBER TO DOME CLEARANCE MUST BE CHECKED.
* WHEN USING HIGH LIFT CAMS, VALVE TO PISTON CLEARANCE MUST BE CHECKED.
* MAY NEED TO PORT ALIGN INTAKE MANIFOLD TO HEAD, VERY HIGH HEAD INTAKE RUNNER.
* BEST USED WITH FPP 1262-R INTAKE GASKET AND FELPRO 1487 HEADER GASKET.
* USES FLAT SEAT NOT TAPERED SPARK PLUGS.

If it was a quality casting, the intake runners would be dead-on or very close to it. I understand the need to gasket-match, but they're probably high so the Chinese company that cast them could screw up the deck bad enough, mill them down, enlarge the combustion chamber, and there wouldn't be a problem with the intake ports being too low. Just an assumption, but probably accurate.

Which leads me to my next itch to scratch about these: where the F*CK are these things made? Canada? Chile? No, wait...let's take a look at the casting numbers:

Here's a link to a LARGE picture, to let you get a closer look at the horror. Just to clarify, look immediately to the right of the exhaust port. Are they serious? They let crap like that out their doors? I would be too embarrassed to sell anything that looked like a 6-year-old Chinese kid stamped it with random numbers. In the same picture, look at the scribe and machining marks. These are NOT of any decent quality whatsoever, IMHO.

Bottom line: would they work? Sure. Maybe for a little while, but I sure wouldn't depend on them for anything. They are most likely Chinese castings, because any quality aluminum heads, even used, are about $1000. According to the ad, they're bare heads. It'd be another $80 for the valves and springs, but who knows what the specs are on those components?!?

My recommendation: keep those GT40 heads, shop around the local engine rebuilders and machine shops in your area for prices on seat cutting, valve job, how much they'd want for valves and springs, etc. You might be able to keep your valves and retainer sleeves if the valves can be machined and the seats recut to match. This is where the touch of an experienced head builder can really help you. You'll be paying more for labor than parts, probably, but that's better IMO because if you have questions or anything bad happens, you can come back and ask or get service.

With those eBay heads, if something goes wrong, you're screwed. No warranty, no service place, nothing. Welcome to Boned Creek, Population: you!

If you need head parts, look up a 1993-1995 Lightning for them, since the GT40s came stock on those. I'm having a helluva time getting into Federal Mogul's website right now to list the factory valve specs for you, but just going off of RockAuto's prices for 1994 Lightning parts:

Springs: #VS718 & VS733 are $1.20 and $1.37 each, respectively.
Keepers: #VK115 are $0.15 each.
Exhaust Rotators (roto caps): #RC140 are $3.67 each, and you might not even need them.
Valve stem seals: Get anywhere, about $15-20 a box for Viton, and a box is good for one head.

I won't list valves for you since Federal Mogul's site isn't working now, but for comparison, I ordered valve numbers V1961 and V3926, and they're $4.78 and $4.67 each, respectively. That's a grand total of $75.60 for all new valves. I think you can do the math for new springs and keepers.

See what I meant about this being cheaper than it seems? Getting the seats cut will be the rest of the cost. It's going to be a toss-up as to whether getting your valves machined or getting new ones will be cheaper.