Tom 400 CFI

I have some issues with it. I'll first list the combo, then thell you what I think is wrong with it.

*'91 350, 4 bolt, 1 pc rear main
*Trickflow heads
*Dished pistons (~8.6:1<-[edited 7/14] Compression ratio)
*Roller Rockers
*Edelbrock Performer RPM Cam 308*/318*(advertised) 234*/244*@.050"......488"/.510"
*Edelbrock Performer RPM intake
*Edelbrock Performer 1411 Carb (750 CFM)
*H.O. air cleaner, w/proper ducting
*Edelbrock TES headers
*LB9 dual-cat Y-pipe (stock, with stock cats)
*LB9 intermediate pipe
*Flowmaster Muffler
*2" tail pipes.

I think this thing has too much cam and carb for the compression, and exhaust.

I also think the cam too much seat to seat duration for the amount of @ .050" lift.

Lastly Talk to me about the TES headers, and LB9 exhaust. What is the HP/flow limit of these parts.

RB83L69

It all looks OK, except the cam and the carb. That's WAY too much seat timing for the CR, and just a generally lame cam; and not the best carb choice for the application at hand.

I'd look for a symmetrical roller grind in the 220-224° range, around .500" lift. Something like the Comp "Magnum" 276HR. A better carb would help too; maybe a Holley or Demon 650 man sec dbl-pump.

I think you should see 360-375 HP with that combo. The exhaust won't go too much past that I don't think. As long as you stay with that, don't get too carried away trying to get high-RPM HP out of it; work on getting good velocity and strong mid-range, with peak HP at around 5600-5800 RPM.

89gta383

iTrader: (5)

That looks like the performer rpm combo minus the heads and headers and roller cam. Should still make the 420hp that they advertise with the parts listed. Might be able to do better with the cam and headers though.

Stekman

I agree with the above. The edel cam is old technology. Lose the edel cam.

I believe the 280HR is the grind RB is referring to (276hr is a popular Extreme Energy grind). IIRC the 280hr runs about 224 with low to mid 500's in lift on a 110 LSA. Should wake things up over that edel cam.

Tom 400 CFI

RB,
The cam you recomended, the Comp "Magnum" 276HR, isn't that a hydraulic roller? This engine is a flat tappet I believe. I don't know if it is worth the money to convert it to a roller... though I wonder if the '91 block would accomodate the factory roller parts, which should make going roller pretty economical.

Why did you recommend the Magnum over an XE?? I was thinking an XE274H might be a good choice. (?) It's got a little more lift for the same duration. Lastly (for the cam), why do you recommend a symetrical grind when my exhaust is probably the weakest llink here? Thanks.

89gta383, you are correct, this was/is a Performer RPM package, minus the heads.

You guys don't think the stock dual cat "Y" and 2" tail pipes are hurting anything?

Edit: I was planing on going with a ~600 CFM Road Demon carb.

Stekman

Was this 91 block from a passenger vehicle (car) or a truck? If from a car, it should have provisions for the factory roller. I don't believe trucks recieved roller blocks until the Vortec days in 96.

Tom 400 CFI

It was from a 3500 Van. Hence the 4 bolt mains and steel crank. So you are correct, no roller cam, but I didn't and don't know if the block has provisions for a factory roller cam. I don't THINK it does, but I'm not sure....

-Tom

Streetiron85

I have an 88 truck engine and it came with roller cam provisions, but it had a flat tappet cam installed.
I don't have any pics.
But if you've gotten used to seeing non roller blocks, the roller blocks are clearly different. They have 3 bolt bosses cast into the center of the lifter valley that are about an inch high, and a few other changes as well.
It's easy to spot the difference if you have one.

89RsPower!

a 91 truck block should be exactly like 88 StreetIrons is talking about, it should have the three bosses for the spider tray but they arn't tapped since it came with a flat tappet installed, very easy conversion if you have the factory roller parts, all you really need to do is tap the bosses for the spider tray.

BadSS

Your problem is the cam is too large for the exhaust system. Plus by you saying tailpipeS,, it leads me to believe you have the single inlet dual outlet Flowmaster. That is their worst flowing muffler,, I think somewhere along the lines of 480 cfm (??), which isn't much better than stock. While the muffler is large,,, the actual baffled part of the muffler has less volume than their smallest 2 chamber muffler. If you notice,, for the Flowmasters, the larger mufflers are considered better performers. Plus,, the dual outlets are suppose to be 2.5”,, and 2” pipes can only make things worse. So,, yes,, I'd think the exhaust is a problem as well as the cam.


I’d check those stock cats and consider custom mandrel bent 2.25” pipes to new high-flow 2.25”cats if they're bad, or deleting them if it’s an option,, or maybe rigging it up so you can swap out Y-pipes, with and without cats??? At anyrate continue by using at least a 3.0” intermediate pipe to either one of the larger single in, single out Flowmasters (if want to stay with a Flowmaster). If you want dual outlets,, DynoMax makes a race series muffler that I believe to be best flowing single inlet, dual outlet muffler available (965 cfm?? -- at least it was the best back in 2002 when I research mufflers before buying one). At a minimum, I’d go with a 3” cat-back and change the muffler.

The cam is old school, and you would see improvement by going to one of the smaller duration, fast rate cams with no change in the exhaust (assuming the cats are OK). I’d recommend the Comp X-Treme 4x4 cams. They have a few more degrees added to the exhaust duration and are cut on a 111 spread. I’d go with the X4262H 218/226 – 111 to be conservative (if you didn't want to do a lot with the exhaust), but the X4270H 226/234 – 111 would not be too much cam,,, especially if you went with high-flow cats,,, or could delete the cats.

As far as carbs, I don’t particularly care for the Edelebrock carbs, but if nothing is wrong with it and it’s properly tuned,,, you’re not going to see any difference and could slow down moving to a 600 carb. Spend that money towards at least a new muffler and different cam and I believe you’ll be a lot happier than with just a carb swap.

F-BIRD'88

Tom talk is cheap. Why not uncork the exhaust and take it for a ride? you'll see what you're missing.

No high perf cam and carb can breath through that mess.

Fix the compression ratio too. based on your info I'd say its about 8.8:1

Pull the heads. Shave .060" off them and reinstall with a felpro shim gasket .015" thick. This will get you 10.0:1.
if your block has been decked some use a .028" gasket.

that "old school" cam is good for over 400hp (in a 400hp engine. With a 400hp exhaust.) It has to breath.
you'll need a custom 2.5" into 3.5" Y pipe with a 3.5 to 4" intermediate pipe into a flowmaster Deltaflow or a Magnaflow muffler. Intergrate twin hi-flow 2.5" carsound cats
into the system by making the Y pipe join behind the transmission instead of crossing under the engine.
Like in a 4th gen fbird. you cannot buy this system it has to be custom fabricated. But the components are readily available. Most all of the bolt on 3rd gen exhaust systems are junk and not work the $$$. they are designed for 250 and 300hp engines.

Tom 400 CFI

88 Fbird, I don't know WHY I didn't think of unhooking the exhaust! Duh! Thanks for that "reminder".

FYI for all of you...I didn't put this wacky combo together! I just bought this car:
https://www.thirdgen.org/techbb2/sho...hreadid=199928

...and now I want to "fix" what I believe are flaws in the combination of parts.

Also, I definitely intend on changing the cam. Absolutely. I don't desire to make the combo work around that cam at all. Therefore, a gigantic exhaust may not be necessary, but I did suspect that there are issues with that exhaust no matter what my goals are. I was also hoping that by going with a smaller cam (I had the XE274H in mind) I would increase cylinder pressure (less leakage) and improve the torque, which is pretty damn soft right now. Information about specific components though (such as the flow of the flow master muffler that BadSS posted) are great to hear. So thanks for that type of stuff.

What I need now: Track times with and without exhaust: To happen this week now, and specific info on the pistons, and deck height so I know exactly what compression I have. If I really have less than 9.0:1, then I wouold agree that the heads need to come off and be cut.

Thanks for the input so far.

BadSS

Do you know for sure the dish size on the pistons? If not do you think the guy might still have the receipt for them? KB makes three for your application, 12cc (KB193), 18cc (KB142), and 22cc (KB101 / KB118).

Based on your approximation of 9.5:1,,, hopefully you have the 12cc dish pistons. However, KB rates their advertised ratios based on 0 deck height, so it’ll be lower than advertised with a standard deck height. 64cc heads, .038” gasket, .025" deck,,, you're looking at compression with -12cc to be about 9.1:1, -18cc would be around 8.6:1, and the -22cc would be near 8.3:1.

Tom 400 CFI

O.K. I have some bad new, IMO. Here is an email I got from Mark (the previous owner) this AM:

Tom,

The Keith Black Pistons that are in the SUPER"Z" are part # UEM - KB142030 from Summit.

also I found the Cam Spec Card:

Duration at .006" Lift: Intake 308deg Exhaust318deg
Duration at .050 Lift: Intake 234deg Exhaust244deg

Lift at cam: Intake .325" Exhaust .340"
Lift at valve Intake .488" Exhaust .510"

Timing at .050 Lift: Open Close
Intake 10deg BTDC 44deg ABDC
Exhaust 59deg BBDC 5deg ATDC

Centerlines:
Lobe Seperation: 112deg Intake Centerline: 107deg

The UEM-KB142030 is the 18cc piston, so according to what you said, BadSS, I'm looking at ~8.6:1, which is terrible...even worse at this elevation! Man, I do NOT want to change the pistons. Grrr.

-Tom

ME Leigh

Supercharger time, oh wait those are hypers. Time to look for some 58cc heads. Or mill the crap out of those.

Stekman

That's a lot of duration for not so much compression.

RB83L69

That's even worse!!!! Who in his right mind would build a motor like that, except for a blower application? (which it would be good for, except for the cam)

With that little compression, it's not going to make much power, period. And with that clunker of a cam in it, it's not going to have any leave whatsoever, it'll be a total 60' pig. Just an all-around terrible mismatch.

IIRC those heads have a fairly favorable E/I flow ratio, which is why I suggested the symmetrical cam. With the lower compression, you might want to keep it symmetrical anyway, just to get as much energy out of the hot gas and turned into mechanical work before the exh valve opens as possible.

What's the situation here? Did you just buy this or something?

Tom 400 CFI

And you are dead on right about that. Even with a 3.73 rear, the thing requires a lot of clutch slipping to get going. It is an out-of-the-hole-pig. Not much happens until about 3k, and I'd say the exhaust probably starts shutting things down around 5k, though it *seems* to pull to 65k pretty well. The more I learn about it, the worse it gets! But I pretty much have all the info now, so I know pretty well what all needs to be addressed.

Thanks for that explaination. I was definitely wondering about that recomondation above, so I appreciate the additional input.

Yes. The situation can be found here:

https://www.thirdgen.org/techbb2/sho...hreadid=199928

and here:

https://www.thirdgen.org/techbb2/sho...hreadid=233877

But the "short story" is that I bought it and drove it from Mass to UT, thinking a cam would improve it tremendously. Then (after driving it 2300 miles), I decided that the carb HAD to go (for a Demon), and at the same time I began to wonder about the current exhaust. So I started this thread.

This engine needs to be fixed. I think the most economical way out of it is milling the heads, cam, carb, and custom exhaust, like BadSS suggested about (mimicking the LS1 F-bod exhaust). I have an appointment for the exhaust on Friday down in SLC.

This engine has a bunch of GREAT parts...it's just that none of them go together! What blows my mind is that the friggin' thing turned 20 mpg on all but two tanks for the entire 2300 mile drive out here! and I made that trip in 38 hrs, total...i.e., I wasn't going slow. Crazy.

Thanks for all the input.

-Tom

leeperryracing

You answered your own question Tom, you got way too much cam for that for low CR...but on the other hand, if you want to run a solid shot of nitrous or a blower depending on how strong the bottom-end is, that CR is perfect. With the NOS or SC bumping up up the CR when applied you will be able to feel the wrath of that cam.

Tom 400 CFI

LPR,

Thanks for the input. I don't want to do any N2O or Forced induction, as the money that would require would completely blow my whole mission w/this car. If I DID do something, it'd be Turbo(s) because of the altitude compensating nature of the way they work. Up here in Park City, we are all missing 1/4 of our power and torque do to the thin air. Turbo's would fix that (for the most part).

My plan at this point is to run it at the track next friday night for a base line(it rained here last night ), do a cam, exhaust, and carb and put it up for sale. If it doesn't sell this summer, this winter, I'll pull the engine and replace the pistons with something much more appropriate. This is a much better solution, IMO, than chopping the hell out of a perfectly great set of TFS heads.

BadSS, if your still following this, I brought the car down to SLC to have an exhaust shop look at it and allow me to explain what I was after. I think I'll be making an appointment Monday for next Friday at that place, to get the work done. What I'm looking at is a 2.5" Y going from the current Edelbrock TES "headers" down past the trans and joining just after the trans ala LS1 style as you had recommended. Then into a 3" back to the stock muffler location. A dynomax, SLP, or Magnaflow muffler, into two 2.5" tail pipes.

Does this sound sufficient? Are the headers "adaquate"? I loike the look of tail pipes on either side, but I THINK that both pipes on the same side would flow better (SLP style). Any comment there. Thanks again to everyon that has lent their input.

BadSS

The DynoMax that I have has a 3" inlet, and a large center free-flow pipe, but It's "Y" shaped inside. So,,, the majority of flow looks like it should go out the driver's side, but the exhaust pulses at idle feel about the same, judging by hand.

I wanted the dual outlet look to give the car more of a stock / sleeper look. It has run 12.3s on the engine with the DynoMax muffler (330rwhp) in cool weather and 11teens on the button (200 shot) in 90 degree heat. It hisses (actually it's more like "FFFFFFFFFFFF") going down the track on the button though,,, which indicates its not flowing all that good,, but it's not flowing all that bad either. Last track outing I had two people come by to ask what muffler I had on it, They couldn't believe how quiet the car was (running low 11s) going down the track.

Anyway,, here's some part numbers to make things easy on you if you go this route - taken from an early post of mine:

you can get the true 3" pipe separately as 2 part numbers – intermediate pipe #44063 (with the 3" converter flange) and the "over the axle" 3" pipe #43248 - and you could run what ever muffler you want. I went with the Race Series Dyno max #17227 - 3" inlet with two 2.5" opposite exit tail pipes. Dynomax claims this muffler flows 940cfm,, but it's over $100. You can also buy the 2.5" tail pipes from Dynomax as part numbers 43243(RH) and 43244(LH) from Summit.

Like I said earlier,,, I was going for the the stock look at that time - I was building it for my wife and never thought it would see 12 second quarter miles though. It's a good exhaust that probably won't hurt much time for cars running high 11s on the motor. If you think you'll go any faster than that,,, I think I probably would bone up for a 3.5" exhuast and a single inlet/outlet 3.5" Borla or MagnaFlow.

Good luck!

Tom 400 CFI

Thanks for the reply. From what you said, the exhaust I'm looking at is going to be sufficient. I'm definitely not looking to go 11's, that's for sure. That post was good info though, so thank you.

-Tom