Question about air flow on near stock B16A head: Will it work for a race 1000cc “B” motor, or will it be a wheezing pig? How about the same question if I went to 750cc?



I am rebuilding the engine for my Bonneville Land Speed 1990 Honda CRX.



I didn’t build the existing motor, but last summer, I set a new H/GC record at Bonneville of near 147 mph, breaking a 25 year old record by 12 mph. I could only pull 8500 rpm, when I was told max power was at 9400 rpm. “H” engine class is 1523cc maximum displacement. The engine did this while in horrible condition: Post race inspection showed compression pressure measured 120psi, 40psi, 60psi, 140psi in the cylinders, and the exhaust cam had spun on the adjustable cam sprocket, so I was running a full 10 degrees retarded. The head gasket was NOT blown like one would suspect from compression pressure: Long term coolant/head gasket leak had caused so much corrosion in the cylinders, that 3 of the 4 sets of piston rings were so frozen solid in the pistons, I had to break them out.



Needless to say, there is a lot of room for improvement. A properly built 1500cc engine should have me pushing that record above 170mph.



However, here is my thought:



In order to have a max HP high RPM 1500cc class Honda "B" series motor, I think I would need a very well ported head. I have already paid a lot of money to have the existing head properly rebuilt, and kind of don’t want to tear it apart to re-port it.



The current motor parts are a Type R block cut to B16 deck height, stock 81mm bore, stock crank offset ground to 73mm stroke to make it about 1508cc, CP pistons that ended up blueprinting to about 10.7:1 compression, Skunk2 Tuner 2 cams, Nearly stock B16A head, and dual Weber 48mm carbs.



I was thinking of building a new motor, using these parts, and running in the “I” engine class, or just over 1000cc displacement.



Engine would be same Type R block, about 81.1mm bore, new Scat crank destroked to about 1.95 inches to make about 1000cc, same Skunk2 Tuner 2 cams, same nearly stock B16A head, (existing Skunk2 valves, titanium retainers, new Pro series springs), CP custom pistons to get compression up to 14 to15:1. I am looking for max power at 9500-10,000 rpm, occasionally going to 10,500 rpm if I undershoot gearing for conditions. I don’t need power until 7000 rpm, and I manually activate the VTEC at about 6000 rpm.



My whiz-bang computer, using Desk Top Dyno 5, says such an engine combination, with stock “B” engine head typical airflow, will make right at 200hp at 10,000 rpm. I was hoping for 180-200hp.



My thoughts are that a stock head/airflow, while great for a high performance 1600-1800cc street/strip engine, would be a killer, all-out race head for 1000cc displacement size engine.



Or would this head make a 1000cc Honda “B” based engine a wheezing pig?



Thank you for any thoughts,



Jeff

 

wow... interesting idea you got there and I'd love to hear other experts chime in on this one. My thoughts are in line with you... the B16 head flows VERY well so on a 1000cc engine it should be a "killer" race head! I would think a destroked 1000cc setup like that should turn 12000rpm easily with good parts, 1 liter bikes do it all day.

Would it possibly be more cost effective for you to use a 1000cc sport bike engine to start with? You have to have a small fortune wrapped up in that B series block just trying to destroke it.

 

Based on a super sixteen race engine I've designed stock c5 CFM + 10 CFM valve job stockish intake port vol, C space work, 12:1 static, de-stroked 81.5 x 71, makes nice shape of power up top peak rpm 9700, piston speed and loads better than the b16. head flows more than enough to make 220-230 peak with nice shape.

RE 1000cc motor:

The fmeps on a such a High rpm motor + pumping make me think this is a bad idea, it would need a dry sump setup for sure to keep rings happy.

My super sixteen race engine is in the 247-250 Bhp range modeled about 10bhp more. head CFM limit is not the real problem, burn speed, shape, and limiting short circuiting of fuel out the ex port.

Stick with the CC with such a nice R/S peak piston speed, flow demand is great, peak piston G are good, MPS nice as well, so will not have to over spin and lose even more fmeps in the valve train.

all the best

p

 

Originally, I was going to compete using motorcycle engines in a CRX. Then I found a perfect example of a CRX with most of the work done.

In addition, to run in the production class, you need to have an engine representative of what came stock.

And now for the really sharp readers with trivia: How is it that I can run a 1990 Honda CRX in the Gas Coupe and Sedan class (4 seat cars, not 2 seat) and use a Honda "B" series engine as a PRODUCTION engine???

Jeff

 

The reason I want to use this funky bore/stroke combo is I want to use a Honda "B" engine to race for the "Production" record. I can't really make the bore smaller, as now there are head/valve issues. I have to destroke that much to make displacement of 1000cc.

Jeff

 

Jdm rear seats and a b16 came in the japanese models.

 

It will be pain to get the compression ratio properly high. But as long as you are above 12:1 it should be possible to make some serious power.

What compression ratio did you use in your calculations?

Remember a 1000cc bike engine/gearbox weighs a LOT less, so unless the class i weight restricted you will have a big disadvantage there.

 

Weight isnt too important for bonneville salt flats land speed racing. A lot of people use weight to gain an advantage since using aero downforce increases drag. Weight=acceleration. Lsr has more emphasis on power and not acceleration so im sure the weight difference between a bike engine and car engine wouldnt be a problem. If anything the heavy car engine will help with traction

 

That is a very interesting concept.Imho i would go with a GSR Head, I'd reduce bore size as far as valves allow and then i'd shorten stroke as necessary. Lighter piston will benefit you at the RPM you will be shooting for. Also since head flow isn't an issue I'd go with the GSR just for the combustion chamber superiority, which now that i think about it you will have to modify anyway.

 

Excellent answer. I didn't think someone would get it that fast! I get a lot of funny looks with the car, as I have it set up as a JDM car for production, but switch to domestic body parts, and run it in Gas Coupe class as a stock car with an engine swap.

Also correct about weight not being a #1 priority in LSR. My first interest was using a Honda B engine to be able to run production, and then if it made enough power, run in all of the other classes.


Thanks,

Jeff

 

My compression ratio used for calculations was 14 to 1. Yes, very hard to do. I think chamber volume needs to be about 18cc. As in very tall dome. I am actually going to try for closer to 15 to 1.

I was going to degree the cams, figure out the closest the valves come to the piston with appropriate clearance, and then hold the valves at that distance, and make a silicone mold of the combustion chamber, and take it to CP, and see what they can do.

Anyone have any recommendations on changes I should make to the combustion chambers for flame travel if the chamber is this small? I can fill the chamber with clay on areas to enlarge before I make the mold.

Which brings me to another question: What would a reasonable safe clearance distance be for valves to piston, and piston to head? Assuming aftermarket rods and 10,000 rpm.

Jeff