7A-G(T)E build questions

[Rogue-AE95]

I've been searching & reading through older posts, but not finding anyone asking quite the same thing. I've been emailing Matrix Garage with questions and about his 7A-GE & other parts, and have appreciated the time he's taken to answer my questions. I just wanted to get some more input & opinions here before finalizing my decisions and making purchases. Anyways, what I want to do is build a moderate-NA 7A-GE with the "room" for turbo in probably a year or so after the build is finished & engine is broken in.

I have:
• 7A longblock
• 16v smallport head with stock intake & exhaust (head will need to be cut -- was stupidly cut .006" by a shop I brought to for cleaning & inspection)
• 4A-GE stock head gasket
• 81.5mm late/smallport GZE 8.9:1 pistons
• 116 tooth timing belt
• brand new 4A-GE oil pump (need to check the gear thicknesses)
• ARP everything (want to get the updated set of head studs though)
• adjustable cam gears (one set from T3 with timing marks, one set without)
• both sets of stock cams (earlier BP & later BP/GZE/SP)
• HKS springs
• 2 sets of used stock springs
• 2 sets of used stock valves
• Supertech standard size valves

Soon to get:
• MG custom 7A rods (brings 4A-GE pistons back up to the deck)
• MG broached 7A timing cog
• piston skirt coatings (probably from Swain Tech)
• OST ported head
• aftermarket engine management (was thinking MegaSquirt 3 or Hondata S300 ECU)

Might get:
• CPS/COP setup eventually
• Tomei PonCams or MG's 262 cams?
• TRD .8mm head gasket?
• new OEM springs?

The engine build is all about reliability & power (to get my wagon's fat ass moving from a stop), with decent gas mileage as a secondary. Engine is going into an AE95 (AWD) wagon. It'll be used for occasional daily driving, and less often, longer road trips. I may track it once, just to see how it does. I decided on a 7A for the extra displacement, power, and torque. I can't keep driving the 4A-FE with its 100 HP any more... and I'm not even getting the decent mileage they're supposed to get.

I know that using 4A-GE pistons in a 7A brings up the compression ratio. Along with those MG rods, the cut head, and TRD gasket, I should be in the mid-10:1 range? I was thinking about keeping the comp just under 11:1 if possible. With a turbo later on, would I be able to turn it up closer to 250-300HP? The NA stage's HP isn't as important for the first year or so of this engine. Anything will be an improvement over the 4A-FE!

I want to stay shim over bucket. I have no problem buying aftermarket cams, but should I, with turbo & higher power goals in mind for later? I have springs for either option. Is my piston choice reasonable? I know a custom piston is always better, but these GZE pistons are brand new & I trust their reliability -- especially after the skirt coatings.

[oldeskewltoy]

stock chamber, stock gasket, zero deck 2nd gen 4AGZE piston, 7A stroke - I got just over 10 to 1

.008" cut head w stock chamber(35.4cc), TRD gasket, zero deck, 2nd gen 4AGZE piston, 7A stroke - I get just over 10.5

head with 34cc chamber volume(1.1mm/.043" cut), TRD gasket, zero deck, 2nd gen 4AGZE piston, 7A stroke - I get just about 10.8 - will need adjustable cam pulleys to correct timing.

As to management... 4/7AGE is not overly complicated, get a management system that is easily understood, and tune-able. Look in your immediate area at tuning shops, and see what they know how to tune.

As to camshafts... another option would be a set of Cat Cams 252 8.5mm lift cams. Reason is when they are matched together they have only 2 degrees of overlap, also with an earlier intake valve closing event, you build more cylinder pressure with less chance of that pressure escaping out the exhaust valve.

[yoshimitsuspeed]

As to camshafts... another option would be a set of Cat Cams 252 8.5mm lift cams. Reason is when they are matched together they have only 2 degrees of overlap, also with an earlier intake valve closing event, you build more cylinder pressure with less chance of that pressure escaping out the exhaust valve.

You are thinking about supercharged motors.
A well setup turbo motor will have about 1:1 boost to pre turbine backpressure ratio. In this case you can size your cams and overlap much like you would an NA motor.
If your turbo is too small your pre turbine backpressure will be much higher than boost. On a turbo the risk of too much overlap is not intake charge blowing into the exhaust but exhaust gases being blown into the intake. If this happens there are many solutions. One could be to run less overlap. Another could be to run a better flowing turbine side or otherwise reduce restriction on the exhaust side. Even something like running a bigger cam and lower boost could bring the turbo into a better ratio improving scavenging with more overlap.
SC or turbo just like NA overlap isn't inherantly bad. Running too much or too little is. Ideal is running the proper amount of overlap. In a well setup turbo that could in fact be quite a lot. Cam makers just tend to make boost cams low overlap to be safe in various setups and often for both SC and turbo which have completely opposite concerns in regards to overlap.

[oldeskewltoy]

You are thinking about supercharged motors.

actually, I was thinking more of his application... this engine is going into his AE95 All-Trac wagon. The E5x Corolla all-trac transaxle has a final drive down @ 3.7, and the car weighs 2700#s. In the short term this is without boost. So based on his unique situation I felt a "shorter duration" cam would benefit. The other cams are not without their merit, but I happen to understand his circumstances owning an All-Trac myself.

[Rogue-AE95]

Thanks guys. Tuning an aftermarket ECU, I will have to talk to tuners and see. There's a big Honda scene in the Tampa Bay area, that's why I figured on trying a chipped Honda ECU (and it's been done before on 4A-GEs). I do know one Honda ECU / wiring master who doesn't like the Megasquirt ECUs. Cams are now the one thing I haven't made up my mind about just yet. I was curious:

As to camshafts... another option would be a set of Cat Cams 252 8.5mm lift cams. Reason is when they are matched together they have only 2 degrees of overlap, also with an earlier intake valve closing event, you build more cylinder pressure with less chance of that pressure escaping out the exhaust valve.

I can't seem to find those anywhere, and it seems the 252 ex cam was sold in a pair with another duration intake cam. Is it possible to get a pair of just that 252 ex cam? Are there any alternatives other than custom cams?

[oldeskewltoy]

I can't seem to find those anywhere, and it seems the 252 ex cam was sold in a pair with another duration intake cam. Is it possible to get a pair of just that 252 ex cam? Are there any alternatives other than custom cams?

http://www.catcams.com/products/camshaf ... TUP_id=827 - intake cam

http://www.catcams.com/products/camshaf ... TUP_id=828 - exhaust cam.


Why I recommend this.... I spent the day yesterday driving my All-Trac around.... excluding all out acceleration, I spent most of my time between 2500, and 4500. The lower you can make your peak torque, the easier it'll be to utilize the power.

Rogue.... you drive around and watch where your rpm range is.... look at where you want the power....

[Rogue-AE95]

I'll check next time I drive it to work (bit of a commute, mostly hwy driving). Just guessing, I'd say I'm at about that same range, depending on what roads I'm on. Those RPMs equate to cruising at about 50-90 MPH, which sounds almost right for hwy driving. More like 60-80 MPH on the hwy for me. I do want low end torque as much as possible. That's one of the reasons I chose to go 7A instead of 4A. I'm not planning to scream into 6k+ RPMs all the time (but I will do that occasionally), so I'm not trying to make all the usable power higher up in the RPMs.

What I meant about the Cat Cams is that I can't seem to find anyplace online selling them. Though I found one ended ebay listing, it was for the matched pair that Cat Cams sold them as (262 in / 252 ex, I think).

[yoshimitsuspeed]

I can see if my cam making still has his 250ish patterns. Like he doesn't already make enough fun of me for mostly moving 264s and 272s.
Personally I do agree with him on this. I wouldn't waste my money on anything smaller than a 264. At this point it's the rare case I'd even run that. My car is all about maintaining low end and quick spool. He is making me a slightly modified version of my 272 that has a little more lift and a little more duration at .050/1mm. I will be able to report back very soon but he says that it should have very minimal effect on low end and MPG which is also important to me. On this car more out of principal than necessity. I will also be able to fine tune cam timing which will allow me to move my power curve and effect MPG.
Running a bigger cam will allow me to make more power per PSI which means I can also run a smaller turbo per hp goal which means quicker spool and more low end.
If I want more top end it will be easier to swap out turbos and much cheaper if I stay with the junk yard dogs I tend to run.

And on to the final point, you should choose your cam for your ultimate goals. Picking a tiny NA cam now might leave you missing out on your long term oppertunity making you wish you went another direction or making you think about buying a second set of cams. Buying cams for your ultimate goals may leave your interim setup lacking a little more but it will just be more motivation to complete your build. Even if you stayed NA I would still go with my 272 personally but I don't mind reving an A series motor. I think going with the 7A to gain that low end is a great idea but for me weight doesn't matter. Gear ratios only matter in that I would make sure I have enough power curve to span the gears. If I had to drop to fourth at 4200 RPM to pull that hill in exchange for 6500 RPM that will allow me to get around a semi with a quickness then that definitely works for me. RPM is how small motors get their go. Adding displacement is how you get around that. You have already added some displacement so that will help across the board but it's still a little motor with limited power till you put a turbo on it. At that point you can have more than enough wherever you want it.
The other thing to remember is that a cam will tend to feel smaller on a longer stroke motor. This is not a fixed rule but a general rule of thumb.
So if you are set on going smaller let me know and I am sure I can find you something. I would really urge to go bigger though. One thing to remember is that advertised duration is not the whole picture. For example my 262 cam has 230 deg duration at .050". My 272 has 230 deg. People talk about advertised duration and think a 262 must behave massively different than a 272 but it is only a tiny part of the story. My 265 cam has 234. It has more duration at .050 than my 272. In certain situations it could feel like a slightly bigger cam.
With that said, my cam company has a couple smaller cams on their old list that I could look into. For example they show a 264 designed for turbo applications with 9.2mm lift and 224 deg at .050". And a couple others between that one and my 272.
Personally I would go bigger though.
If you have some time I hope to have my 272 with 9.7 lift and 235@.050 installed on my BT soon.

[oldeskewltoy]

What I meant about the Cat Cams is that I can't seem to find anyplace online selling them.

http://www.catcams.com/dealers/list.aspx?title=dealers You can also email Catcams directly.


oh.... and yoshi makes a good point which I've always danced around, there is a LOT to comprehend... and MANY options.... (Because most peoples eyes glaze over when you begin to discuss camshaft specifics...) total, or gross duration is an absolute waste of time for anything other than guesstimating ramp rates.... duration @ 1mm (.040") or .050" is far better to figure out what the camshaft will do for you.....

Stock early cams are 240 gross duration, 204 @ 1mm, later cams were 232 gross, 198 @ 1mm. Note the early cam has 2 degrees more duration between gross duration and 1mm. Also the later cams are not "matched", they are off set. Matched in this case mean the exhaust is a mirror of the intake, while the later cams are each unique. Both of these cams pull to 6500-6600 before they go flat, they also provide peak torque around 4800. Most 256 type cams have 214-218 durations @ either .040, or .050. and that is another point... most of the Japanese market cams use 1mm(.040") of lift to measure durations, while many of the cam makers from other parts of the world use .050" as the measure. Those extra .010" can mean a lot.

[jinx]

I know of a street ca18 done over 500hp using Tomei 260 hydraulics (and stock intake mani).
He said he 'felt' no need to wring out the motor past 8000 rpm, seeing as it was a street ride
With smaller '300hp' turbos, those 1.8s (with 260 Tomei, HKS 264s etc) make excellent midrange torque
would "smaller than 264s" really be a 'waste' ? ....or the advertised duration almost neglegible among brands ?

I'd think, with a porky chasis, you'd stay conservative on the cam, and run the biggest turbo "sized" to give you the desired torque curve (spin up early enough)

[yoshimitsuspeed]

I know of a street ca18 done over 500hp using Tomei 260 hydraulics (and stock intake mani).
He said he 'felt' no need to wring out the motor past 8000 rpm, seeing as it was a street ride
With smaller '300hp' turbos, those 1.8s (with 260 Tomei, HKS 264s etc) make excellent midrange torque
would "smaller than 264s" really be a 'waste' ? ....or the advertised duration almost neglegible among brands ?

I'd think, with a porky chasis, you'd stay conservative on the cam, and run the biggest turbo "sized" to give you the desired torque curve (spin up early enough)

See I don't think I would ever do it that way. I would much rather run a cam on the bigger side then size my turbo to get my desired power curve.

[Rogue-AE95]

Thanks again guys. I hate to say I'm still clouded about which set to go with. But I figure on having the bottom end done before the head, so I'm not in a hurry. I need to read up more on cams and turbos. Two areas I know little about.

Edit: I asked earlier but haven't seen a direct answer... should I bother with shim UNDER bucket? I wanted to stay shim over bucket if possible. I know it's going to add more expense to the build, and I wasn't looking forward to that after factoring in new cams and head work. At least I can sell off the 40/20 rods I never used and recoup some of these costs.

[yoshimitsuspeed]

Even with a turbo build it would still be best to first set your power goal, second pick your cam and then third pick your piston. If you are still trying to decide between two similar cams it wouldn't be the end of the world to proceed with the bottom end but i would still prefer to have the top end figured out first.

You definitely don't need shim under bucket in the range you are looking. Around 10mm is where you would really want to start thinking about that.

[oldeskewltoy]

You definitely don't need shim under bucket in the range you are looking.

agree.....

[Rogue-AE95]

OK, thanks. From searching online / elsewhere, it seemed that the shim over bucket setup had its limits lower than 10mm of lift. I also saw somewhere (Toymods maybe) that with proper clearances set for the shims, that you would be fine with seemingly higher lifts. And in the same regard, you could see major problems with improper clearances but using milder cams.