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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
I've got a carb-swapped L98 that I want to add more fun to... Looking to change heads, intake and cam. Mostly street/daily use. I'd like great off-idle responsiveness w/stock converter, while pulling harder and farther into the RPM range.
I'm considering (but would really like your input);
Edelbrock performer EPS intake
Flotek 102-205 heads or similar w/ smaller intake runners (I'd really like to keep my stock center bolt covers, and I don't see any Brodix, AFR, or Dart offerings w/ center bolt config)
Comp Cams XR258, or XR 264
Thanks in advance for your input!
- Maker
Last edited by Maker-Wright; Jan 23, 2025 at 11:14 AM.
Reason: add pic
Who is Flotek? Where do they make their products? Can you trust them? You sure they'll be around however long you have the product? Any idea how to get tech support if you need it? How's their quality control?
From my limited understanding, cylinder head manufacturing and facility ownership has changed dramatically in recent years. Some well-known brand product lines may have been outsourced and/or acquired by private equity (read, decimated in the name of profit). Meanwhile, foreign-made, lesser-known heads have come a long way in regard to quality. Flotek states their heads are "Assembled in the USA", and they seem to get good customer feedback, sometimes equal/better than some product lines of more well-known brands...
I was going to post the same Weingartner video.
Seems the Floteks might be lumped in with other Chinese castings. Which other than the source of origin, can result in some decent heads. Anything like that, that you would buy should be disassembled and checked out for QC because I can't say I know of a quality assurance job that exists in China. But I'm biased there.
Post up some data on the Floteks if you can find it. Port cc. Valve sizes. Chamber volume. Flow bench data if there's any independent source. (Maybe Stan Weiss' head data website has something). http://users.erols.com/srweiss/tablehdc.htm
The Vortecs have a long and stable history including performance expectations and limitations. Data is available in the link above.
Then decide.
I'd like to Buy American too... I checked into the GM- made Vortec heads last year. Seemed like the rave reviews were matched by other's reports of castings cracking. Summit's assembled version of the Vortecs seem to have quite a few customer reports of terrible casting quality, missing rocker studs, weak springs, etc. Don't know if the Edelbrock version of the Vortec heads, the E-Tec's, are American made, but they're drilled for center-bolt covers, at over twice the price of the Flotek heads. Helluva thing if the Eddies were made in Taiwaniastan, right next to the Flotek factory. I was a CNC programmer/operator for many years. Seems like it wouldn't be that tough for AFR, Brodix, and Dart to drill and tap 4 holes for center-bolt valve covers, and possibly expand their customer base (or maybe I'm just too damned hung up on keeping my center-bolt covers :-)
I would get AFR Enforcers. They are drilled for perimeter and centerbolt....but you will have to grind the inner rail lip a little on your covers to clear the perimeter bosses. That's what I did.
The price of the Enforcers is too good.
Cam in the 224 degree intake range.
It looks like you're not in a thirdgen, so hood clearance looks good. I'd grab a performer RPM.
The heads are a little restrictive but will flow fine up to 5500rpm or more. Hell, I built a real healty 355 years ago and ran reworked 305 (416) castings on it.......that sucker ran like stink up to about 6200rpm! The Vortec is just a better head all the way around. It's designed differently to flow much better. If you just want to buy heads then go for it, but for anything less than a true 350hp it's really not necessary. Your compression in stock form is around 9.5:1 which is just right on todays crap fuels running though a carb. The "Performer" intake is fine for daily street driving, it's just not enough intake volume for a performance 350. A dual plane high rise is my go-to, specifically the old style Weiand 8016. That thing absolutely rips on a 350hp 350! Your Edelbrock 600 also is a GREAT carb for putting around the streets. They idle awesome, get decent mileage, and just work pretty well right out of the box........for putting around. I bolted on and ran an Edelbrock 600, then a Holley 670 "Street Avenger" (both right out of the box) on that 355sbc I mentioned earlier. It was like the Edelbrock just threw 100hp right out the window!! It really was that big a difference! Your headers and exhaust will also be fine. Make sure your distributer has a nice hot coil, performance module, and performance curve kit installed. On the camshaft.....with your setup.....I'd look for something dual pattern with an advertised duration of 265-272 and lift in the 440-470 range. It will still have very good street manners. So, get 'er fixed up right and then blame me later for costing you a pair of rear tires
Considering this engine will operate at lower RPM's, from idle to the occasional 5k romp, would I really gain much with the RPM manifold vs a Performer EPS?
Wouldn't I need more than OEM stall for a 224 degree cam to work well at/from idle?
Considering this engine will operate at lower RPM's, from idle to the occasional 5k romp, would I really gain much with the RPM manifold vs a Performer EPS?
Wouldn't I need more than OEM stall for a 224 degree cam to work well at/from idle?
Take into consideration how much weight you have to move vs. the gearing.
Of all the the suggestions posted, you might find a properly spec'd torque converter will give you more of what you're looking for. Combine that with an upgraded top end retrofit and you're golden.
Anything posted previously, while a good combination in their own right, will suffer if the gearing/tire size/converter aren't optimized.
This is taking into consideration that you said "stock converter". I found one of the biggest game changers with an engine of this spec was a converter upgrade. You don't want to lumber through the first few couple of thousand RPM waiting to get into the meaty part of the torque curve.
To qualify that a little further: I built a 350 with Vortec heads (although the brand of head here is not relevant). Cam with 276 (adv) intake duration and .510" lift (hyd roller). While it was a solid performer it wasn't until an off the shelf TCI converter (advertised as being 1000 RPM over stock) that did the entire package come alive. Not just dragstrip results but the overall feel on the street as well. A thousand or so RPM while accelerating can make a big seat of the pants difference.
What is the vehicle weight?
Last edited by skinny z; Jan 25, 2025 at 06:38 PM.
Take into consideration how much weight you have to move vs. the gearing.
Of all the the suggestions posted, you might find a properly spec'd torque converter will give you more of what you're looking for. Combine that with an upgraded top end retrofit and you're golden.
Anything posted previously, while a good combination in their own right, will suffer if the gearing/tire size/converter aren't optimized.
This is taking into consideration that you said "stock converter". I found one of the biggest game changers with an engine of this spec was a converter upgrade. You don't want to lumber through the first few couple of thousand RPM waiting to get into the meaty part of the torque curve.
To qualify that a little further: I built a 350 with Vortec heads (although the brand of head here is not relevant). Cam with 276 (adv) intake duration and .510" lift (hyd roller). While it was a solid performer it wasn't until an off the shelf TCI converter (advertised as being 1000 RPM over stock) that did the entire package come alive. Not just dragstrip results but the overall feel on the street as well. A thousand or so RPM while accelerating can make a big seat of the pants difference.
What is the vehicle weight?
I'm guessing around 3,500 lbs,1957 Chevy 3100 truck w/2nd gen camaro ft. clip
Cool ride. Love those trucks.
3500 lbs is about the same as a 3rd gen Camaro. Or at least mine is anyway.
One thing you've got going for you is the numerically high overall 1st gear. The 3.06 ratio in the 4L60/700R4 combined with the 3.73 rear gear makes for some tidy acceleration in it's own right. This is also my combination and while not spectacular, it did yield some decent 60' times when it was spec'd with an engine with about the same performance level as you're targeting.
While I went with Vortecs way back then (as they were the hot and budget friendly ticket 25 years ago), there are similar performers in the aftermarket aluminum game as has been suggested.
Poking around a little bit and I see the AFR 180cc SBC Eliminator Street Heads (not the Enforcers) have the centre bolt valve cover option you're looking for. Not sure if they've been mentioned or not. At 180 cc it's a decent size for a 350. Said to be entirely manufactured in the US including the casting which, as far I know, can't be said for the Enforcers. Cast in China and machined in the States.
A flat top 5 cc piston with a .040" piston to head clearance and a 64 cc combustion chamber lands you right around 11.5:1 which in my estimation is a little steep with a short cam like the 276.
75 cc gets a 9.2:1 which is OK although I tend to build towards something slightly higher. 10.5:1 is good target with aluminum heads. In my opinion that is but also the opinion of several builders I've worked with or talked to.
Not sure what your particular engine dimensions are. I see it's a L98 and the internet says that it would have a 12 cc dished piston. In that case a 65 cc head gets a 9.5:1 CR. 75 cc is 8.6.
You have to consider too how far the piston is below deck. If it's a stock block about .025-.030" down is the norm so the gasket has to be picked to suit.
The above I think would work with your performer intake. A 1" open spacer is said to be a real benefit on that dual plane with it's solid divider. The other intake of choice (but not the only one obviously) is the RPM Air Gap.
I think the EPS might be a step backwards. Especially if the rest of the top end is improved.
HP peak RPM would be below 6k. Something like 5500-5700 but would take you past 6000 no problem as mine regularly hung out there when racing. Primarily on the 1-2 shift as that shift ratio drop is pretty steep (in the 700) and my converter didn't do much with respect to shift recovery.
Last edited by skinny z; Jan 26, 2025 at 11:44 AM.
Considering this engine will operate at lower RPM's, from idle to the occasional 5k romp, would I really gain much with the RPM manifold vs a Performer EPS?
Wouldn't I need more than OEM stall for a 224 degree cam to work well at/from idle?
No, not the EPS. A mild 305 runs GREAT with those style intakes. The 350 needs to breathe more and really likes the taller dual plane. Keep your duration under 220. I've always liked the Crane 262 or 266H cams. Maybe check out those specs then find something in your brand of choice that's similar. The 3:73 gears are AWESOME with the short 1st gear of the 700r4. Let me give you some real world experience numbers..........I daily drove my 2wd '88 S10 Blazer with 305 swap for 16 years! That thing weighs 3900# with me sitting in it. I ran stock (as cast) 416 heads, 9.5:1 Keith Black pistons, old school Blue Racer 265 cam, roller rockers, Weiand Action Plus intake, Holley 570 Street Avenger, Shorty swap headers, 700r4 (stock 4.3 Astro van converter), 3.42 gears, and dual 2 1/4" exhaust. That thing would run consistent 2.0 second 60ft times and dip into the 14's in the quarter at around 98mph..........and then I'd drive about 90 miles back home LOL!! It's all about the combo matching up.
No, not the EPS. A mild 305 runs GREAT with those style intakes. The 350 needs to breathe more and really likes the taller dual plane. Keep your duration under 220. I've always liked the Crane 262 or 266H cams. Maybe check out those specs then find something in your brand of choice that's similar. The 3:73 gears are AWESOME with the short 1st gear of the 700r4. Let me give you some real world experience numbers..........I daily drove my 2wd '88 S10 Blazer with 305 swap for 16 years! That thing weighs 3900# with me sitting in it. I ran stock (as cast) 416 heads, 9.5:1 Keith Black pistons, old school Blue Racer 265 cam, roller rockers, Weiand Action Plus intake, Holley 570 Street Avenger, Shorty swap headers, 700r4 (stock 4.3 Astro van converter), 3.42 gears, and dual 2 1/4" exhaust. That thing would run consistent 2.0 second 60ft times and dip into the 14's in the quarter at around 98mph..........and then I'd drive about 90 miles back home LOL!! It's all about the combo matching up.
From what I've gathered, if I want brute off-idle go-now from a 350, I need primarily to be mindful of port velocity, as well flow rate, all the way from carb base to exhaust. Hence the quest for smaller intake runner heads rather than 195's, sticking to the 1-5/8" headers, etc.. Cam I'm considering has a somewhat tight LSA of 110, 212/218, .487/.495. That's what made me wonder if the EPS' smaller port size would be more conducive to my goal. I really don't care to run much above 5,000 rpm, but I'd like it to pull hard off-idle all the way to 5k. I'd rather give up a few HP/hundred RPM up top rather than sacrifice anything down low. I'd imagine my current set-up as-is might make 200HP/crank at the elevation I live at. Back end is light enough that It'll pretty easily break traction from idle and often chirps when I hit 2nd. I really can't imagine why I'd want a stall converter without adding a whole host of additional mods to make the thing stick. With all that in mind, still sound like the RPM would be a better choice for me? I have no experience with either the EPS or RPM. Just going from what I've read. Your 305 swap sounds very intriguing to me!
Cool ride. Love those trucks.
3500 lbs is about the same as a 3rd gen Camaro. Or at least mine is anyway.
One thing you've got going for you is the numerically high overall 1st gear. The 3.06 ratio in the 4L60/700R4 combined with the 3.73 rear gear makes for some tidy acceleration in it's own right. This is also my combination and while not spectacular, it did yield some decent 60' times when it was spec'd with an engine with about the same performance level as you're targeting.
While I went with Vortecs way back then (as they were the hot and budget friendly ticket 25 years ago), there are similar performers in the aftermarket aluminum game as has been suggested.
Poking around a little bit and I see the AFR 180cc SBC Eliminator Street Heads (not the Enforcers) have the centre bolt valve cover option you're looking for. Not sure if they've been mentioned or not. At 180 cc it's a decent size for a 350. Said to be entirely manufactured in the US including the casting which, as far I know, can't be said for the Enforcers. Cast in China and machined in the States.
A flat top 5 cc piston with a .040" piston to head clearance and a 64 cc combustion chamber lands you right around 11.5:1 which in my estimation is a little steep with a short cam like the 276.
75 cc gets a 9.2:1 which is OK although I tend to build towards something slightly higher. 10.5:1 is good target with aluminum heads. In my opinion that is but also the opinion of several builders I've worked with or talked to.
Not sure what your particular engine dimensions are. I see it's a L98 and the internet says that it would have a 12 cc dished piston. In that case a 65 cc head gets a 9.5:1 CR. 75 cc is 8.6.
You have to consider too how far the piston is below deck. If it's a stock block about .025-.030" down is the norm so the gasket has to be picked to suit.
The above I think would work with your performer intake. A 1" open spacer is said to be a real benefit on that dual plane with it's solid divider. The other intake of choice (but not the only one obviously) is the RPM Air Gap.
I think the EPS might be a step backwards. Especially if the rest of the top end is improved.
HP peak RPM would be below 6k. Something like 5500-5700 but would take you past 6000 no problem as mine regularly hung out there when racing. Primarily on the 1-2 shift as that shift ratio drop is pretty steep (in the 700) and my converter didn't do much with respect to shift recovery.
Would I lose a couple points of compression going with the AFR's 65cc chamber, opposed to Brodix or dart's 64cc chamber? would it be too negligible to make any difference? I believe the AFR Eliminator's have better flow #'s (CNC'd), but I'm also trying to keep the ports fairly small to keep the velocity up.
The biggest issue I see is that you don't exactly what your working regarding the shortblock. Ultimately you need to be able to determine the possible compression ratios from whatever stackup of piston dish, piston deck, head gasket and of course the heads.
If torque is what you're after, and that's down low in the rev range, then you want to get the compression up.
With any head you pick for that snappy throttle response, targeting 10:1 or better will help in that regard. Once the CR is determined then a cam can be picked to compliment that CR and RPM .
As for port velocity, 180 cc should give you what you want. There are 170 cc heads (Vortec for example) but if you check out CFM vs size, the word is that the AFR 180's hold their own.
But the cam selection will make or break this deal more than anything.
The biggest issue I see is that you don't exactly what your working regarding the shortblock. Ultimately you need to be able to determine the possible compression ratios from whatever stackup of piston dish, piston deck, head gasket and of course the heads.
If torque is what you're after, and that's down low in the rev range, then you want to get the compression up.
With any head you pick for that snappy throttle response, targeting 10:1 or better will help in that regard. Once the CR is determined then a cam can be picked to compliment that CR and RPM .
As for port velocity, 180 cc should give you what you want. There are 170 cc heads (Vortec for example) but if you check out CFM vs size, the word is that the AFR 180's hold their own.
But the cam selection will make or break this deal more than anything.
I don't have anything definitive yet, but I'm really expecting the typical 9.3:1. I did a compression test on Thursday. Hi- 135, Lo- 128, Avg- 131.6, Dev- 5%. Took a look down the plug holes with inspection camera. Pistons look to be original iron-head L98-type, shallow dish w/valve reliefs. I'm planning on using Fel-Pro 1003's @ .041" compressed. I'm getting ready to pull the engine here in the next week or two.
Last edited by Maker-Wright; Jan 27, 2025 at 09:27 AM.
Looking at it from the way I put a 350 together, I think the biggest struggle will be building enough compression. It's not just about horsepower as you've stated that you want that pull from off idle. That's torque. And to build torque, you need compression. Low static compression can be aided somewhat with a short cam so as to get the intake valve closed sooner. So while that will trap more air, there's going to be less time to actually fill the cylinder. This is where power output goes down. And this is where the difficulty lies.
A cylinder with a smaller chamber will give a boost. There are 60 cc options. A thinner head gasket will help too. I'm sure you'll find that the pistons are at least .025" down at TDC. Maybe closer to 30 thou. An .026" gasket (which I've used countless times) will restore some of that. (There are thinner shim gaskets but I've no experience with them).
There are other ways to get the compression up but that's far removed from a heads and cam swap.
Anyway, which ever direction you go, I'm sure it'll be a step function improvement over what you have now.
One thing I meant to add was the option of using the L98 Corvette heads. GM 10088113. With a 58 cc combustion, a 12 cc piston, .025" deck and a .026 gasket it gets close to 10:1 (9.87 give or take).
Centre bolt compatible and I believe they also have early style centre intake bolt angles but don't quote me on that.
One thing I meant to add was the option of using the L98 Corvette heads. GM 10088113. With a 58 cc combustion, a 12 cc piston, .025" deck and a .026 gasket it gets close to 10:1 (9.87 give or take).
Centre bolt compatible and I believe they also have early style centre intake bolt angles but don't quote me on that.
I greatly appreciate the suggestion...
One thing I forgot to mention in the OP was that I really want to keep using cheap pump gas, which is 85 octane around here. If there was one, I'd go for a simple fix to add a few more points to the CR, to~ 9.5, but I'm worried going higher than that would necessitate more $$ at the pump. I'd like to keep some squish in the head gaskets in case of any minor discrepancies in mating surfaces, and I believe .041" is already on the thinnish side. Also, I really don't want to spend any money at a machine shop to shave heads, block, or to change pistons or rods if the ones I have are found to be in good shape at tear-down. Right now I'm leaning hard towards saying adios to my center-bolt covers, going with Brodix IK 180's/64cc, and the Comp Cams XR264 Roller. I know these are pretty benign mods compared to what many do, but I'm thinking that'll be a big change from what I have, and enough to put a smile on this 'ol non-racer boy's face, whilst keeping fuel costs low and MPG on the higher side.
This is the engine I did for my previous daily-driver. A 1967 Bobbed Deuce and a half. 478 cubes, engine weighing literally a ton, with a whopping 145 HP.
330 HP and 420' lbs in a vehicle weighing 3,500 instead of 10,500, should be quite a change for me :-)
Last edited by Maker-Wright; Feb 1, 2025 at 07:21 PM.
I greatly appreciate the suggestion...
One thing I forgot to mention in the OP was that I really want to keep using cheap pump gas, which is 85 octane around here. If there was one, I'd go for a simple fix to add a few more points to the CR, to~ 9.5, but I'm worried going higher than that would necessitate more $$ at the pump. I'd like to keep some squish in the head gaskets in case of any minor discrepancies in mating surfaces, and I believe .041" is already on the thinnish side. Also, I really don't want to spend any money at a machine shop to shave heads, block, or to change pistons or rods if the ones I have are found to be in good shape at tear-down. Right now I'm leaning hard towards saying adios to my center-bolt covers, going with Brodix IK 180's/64cc, and the Comp Cams XR264 Roller. I know these are pretty benign mods compared to what many do, but I'm thinking that'll be a big change from what I have, and enough to put a smile on this 'ol non-racer boy's face, whilst keeping fuel costs low and MPG on the higher side.
I think the Brodix are an excellent choice. They were at the top of my list but didn't include them because of the perimeter bolts. Remember too that your cam choice will be a big player regarding eventual compression pressures and fuel requirements.
With a 64 cc combustion chamber, a 12 cc piston, .025" deck and a .040 gasket it gets close to 9:1. (8.89). Make it an .026 gasket and you're at 9.3:1.
As for the the head gasket, in the twenty or so that I've used, with CR from 9.5:1 to 11:1, iron or aluminum heads, decked or undecked block surface, not one failure ever. And thousands of miles of service too. Mahle 5746. The resellers listings are all over the map but in Mahle's catalog it comes in at .026". Just throwing that out there. Remember that getting the piston to head clearance to at most .040" pays dividends. It elevates the detonation threshold for one. It also aids combustion efficiency. Keep in mind that compression also helps in the MPG department.
As for the cam, the XR264 has an IVC of 58°. As a measure of pump gas grade suitability, some folks like to refer to the effective compression ratio or DCR. I can reference it because I'm dealing with only one engine platform (Gen 1 SBC) and a general region of engine output so I've learned what works for my builds.
That cam, installed on it spec'd centerline, yields a 7.8:1 DCR. That should produce about a 190 PSI cranking compression (at sea level). Aluminum heads will provide some greater tolerance to low grade fuel although I'd be remiss if I didn't say that 85 octane might be pushing it. Inlet air temperature, coolant temperature and timing will be key.
This is the engine I did for my previous daily-driver. A 1967 Bobbed Deuce and a half. 478 cubes, engine weighing literally a ton, with a whopping 145 HP.
330 HP and 420' lbs in a vehicle weighing 3,500 instead of 10,500, should be quite a change for me :-)
Having driven a deuce and a half (as a civilian DND employee) I have to say that that engine is like jewelry (Ours were olive green IIRC). Well crafted and well done!
I think the Brodix are an excellent choice. They were at the top of my list but didn't include them because of the perimeter bolts. Remember too that your cam choice will be a big player regarding eventual compression pressures and fuel requirements.
With a 64 cc combustion chamber, a 12 cc piston, .025" deck and a .040 gasket it gets close to 9:1. (8.89). Make it an .026 gasket and you're at 9.3:1.
As for the the head gasket, in the twenty or so that I've used, with CR from 9.5:1 to 11:1, iron or aluminum heads, decked or undecked block surface, not one failure ever. And thousands of miles of service too. Mahle 5746. The resellers listings are all over the map but in Mahle's catalog it comes in at .026". Just throwing that out there. Remember that getting the piston to head clearance to at most .040" pays dividends. It elevates the detonation threshold for one. It also aids combustion efficiency. Keep in mind that compression also helps in the MPG department.
As for the cam, the XR264 has an IVC of 58°. As a measure of pump gas grade suitability, some folks like to refer to the effective compression ratio or DCR. I can reference it because I'm dealing with only one engine platform (Gen 1 SBC) and a general region of engine output so I've learned what works for my builds.
That cam, installed on it spec'd centerline, yields a 7.8:1 DCR. That should produce about a 190 PSI cranking compression (at sea level). Aluminum heads will provide some greater tolerance to low grade fuel although I'd be remiss if I didn't say that 85 octane might be pushing it. Inlet air temperature, coolant temperature and timing will be key.
